Category 6™

Severe Weather to Ramp Down This Weekend, Temporarily

By: Bob Henson , 5:29 PM GMT on March 30, 2017

A brief break in our multi-day spate of U.S. severe weather appears to be forthcoming, but not until one more day of widespread severe storms. In its Day 1 outlook issued at 11:30 am CDT Thursday, the NOAA/NWS Storm Prediction Center placed a large swath from the Ohio Valley to the Gulf Coast under a slight risk of severe weather through Thursday night, with a pocket of enhanced risk over the lower Ohio Valley.

Thursday’s setup is looking less potent than its counterparts earlier this week, largely because of widespread clouds, showers, and thunderstorms already ongoing late Thursday morning. The weaker storms now covering much of Illinois and neighboring areas will tamp down on daytime heating toward the north end of the risk area. Meanwhile, a large thunderstorm complex centered in southeast Louisiana will impede Gulf moisture from flowing toward the enhanced risk area. Even though a compact, energetic upper-level trough is approaching the Mississippi Valley, there will be only limited instability for the trough to work with, given the factors above.

Figure 1. A GOES-16 infrared satellite image from 11:21 am CDT Thursday, March 30, 2017, shows the upper-level low centered near the KS/MO border, with extensive clouds and thunderstorms stretching ahead of it from the Great Lakes to the Gulf of Mexico. A small pocket of relatively clear air may allow for storm redevelopment on Thursday afternoon over the lower Ohio Valley. GOES-16 data are preliminary, non-operational, and still being tested. Image credit: NEXLAB/College of Dupage.

Figure 2. NOAA/SPC’s Day 1 outlook issued at 11:50 am CDT Thursday, March 30, 2017, includes an enhanced risk of severe weather for parts of southern Illinois and Indiana, western Kentucky, and far northwest Tennessee, surrounded by a much broader region of slight risk.

Tornado tallies for 2017: Still at a record clip
This week’s much-anticipated severe weather has produced plenty of large hail and high wind but thankfully, few tornadoes. SPC logged 7 preliminary tornado reports on Monday from Mississippi to Kentucky. A total of 17 reports came in from west Texas on Tuesday, with 4 reports from southeast Texas and central Arkansas on Wednesday. None of this week’s tornadoes thus far have been especially intense or destructive.

As of Thursday morning, the year to date had seen a total of 24 tornado-related fatalities in the U.S., all in January and February. The preliminary "inflation-adjusted" total of 349 tornadoes through Wednesday keeps 2017 at record levels for the largest number of tornadoes up to this point in the year in records going back to 1954.

Figure 3. Tara Shadoan takes her belongings before the insurance company tows her car damaged by a hailstorm the night before in Highland Village, Texas, on Monday, March 27, 2017. Image credit: Jae S. Lee/The Dallas Morning News via AP.

A pause, and then another burst next week?
Pockets of severe weather may continue through the weekend, but the fast pace of upper-level lows and troughs will make it difficult for adequate instability to get into the right place for a major outbreak. SPC is calling for a marginal risk of severe weather across parts of the mid-Atlantic on Friday, in association with the upper low now traversing the Ohio Valley, as well as a marginal risk over the southern High Plains ahead of the next system. This strong upper-level trough will become a cut-off low over the Southern Rockies late Friday into Saturday, then accelerate eastward across the Gulf Coast states from Sunday through Tuesday. It’s a safe bet that large clusters of intense storms will develop ahead of this trough, but these clusters may set up just offshore in the northern Gulf, reducing the risk of severe weather inland.

Yet another strong upper-level trough will enter the Plains by late Tuesday. This will be one to watch, as models project it to generate a very strong surface low, with powerful flow through the lowest few miles of the atmosphere leading to ample wind shear from the Southern Plains to the Midwest. The main question mark is how quickly moisture will return to the area.

Figure 4. March is often Colorado’s snowiest month. The snowstorm of March 17 - 19, 2003, was the most intense to strike the Denver area in over 80 years. In some parts of the Rocky Mountain foothills west of Boulder, more than 80 inches (2 meters) of snow fell. Image credit: UCAR, photo by Carlye Calvin.

End-of-month snow blitz for the Rockies
The upper low cutting off over the Southern Rockies on Friday and Saturday is on track to bring plenty of welcome precipitation to the Wyoming/Colorado mountains (as much as 1 to 2 feet of snow in favored areas) and on the adjacent high plains. Temperatures may be just cold enough for a wet snow along most of the Colorado Front Range, including Denver and Boulder, although periods of rain could cut back on the totals at some of the lower urban elevations.

Both Denver and Boulder have measured just a trace of snow in March thus far. That’s a notably meager total in what’s typically one of the snowiest months of the year. In Denver records going back to 1882, only two other Marches—2012 and 1995—got only a trace of snow for the entire month. It’s quite possible Denver will see measurable flakes by midnight Friday night. Boulder may have a better shot than Denver at a trace-only March, since its March 31 observation will be taken at the local COOP site at 6:00 pm. Friday.

Figure 5. The SREF ensemble-based modeling system projects a wide range of potential snowfall for Broomfield, CO (between Boulder and Denver). The big spread isn’t a surprise given that snow totals will hinge in large part on a very small temperature range. The ensemble average of around 12” by Saturday night (solid black line) seems plausible if temperatures get cold enough. Image credit: NOAA/SPC.

Three storm chasers killed on Tuesday in Texas
Three storm chasers died on Tuesday afternoon in a collision near the town of Spur, TX, east of Lubbock. Killed were Kelley Williamson and Randy Yarnall, contractors for the Weather Channel, and Corbin Jaeger, an Arizona-based chaser who filed reports on the website MadWX Chasing. Williamson and Yarnall were featured on TWC’s series “Storm Wranglers,” which debuted last fall. The Texas Department of Public Safety reported that Williamson and Yarnall were traveling north on a farm-to-market road on assignment with TWC when they ran a stop sign and collided with Jaeger’s vehicle, which was traveling west on another farm-to-market road.

“Kelley and Randy were beloved members of the weather community as well as true weather fans. We will miss them. Our thoughts and prayers are with the families and friends of all three victims as they mourn this loss,” said TWC’s Stephanie Abrams. “Corbin was one-of-a-kind and will be missed deeply,” noted a statement on the MadWx Facebook page. “Our thoughts and prayers go out to Corbin's friends and family, as well as the friends and family of Kelley and Randy, who also passed away in the accident.” For more, see the online video from TWC’s Ari Salsalari and a statement issued by the Weather Channel.

Bob Henson

Trump’s Executive Order Threatens to Wreck Earth as a Livable Planet for Humans

By: Jeff Masters , 1:13 PM GMT on March 29, 2017

Decades of progress on cleaning up our dirty air took a significant hit on Tuesday, along with hopes for a livable future climate, when President Trump issued his Energy Independence Executive Order. Most seriously, the order attacks the U.S. Environmental Protection Agency’s (EPA’s) Clean Power Plan, which requires a 32 percent reduction in CO2 emissions from existing power plants by 2030 (compared to 2005 emission rates.)

Tuesday’s blow was just the latest in a series of attacks that threaten our health and the planet’s health. On March 15, Trump also ordered the EPA to review tough air pollution rules for cars and light trucks that were set to kick in between 2022 and 2025. Trump’s proposed budget for fiscal year 2018, released earlier this month, slashed funding for the EPA by 31%, and eliminated money for renewable energy programs and energy efficiency efforts such as the Energy Star program.

Trump’s war on clean air will potentially kill tens of thousands of people annually and have health costs in the ten of billions of dollars each year. Separate studies done in 2016 by the World Bank and by the Health Effects Institute (a U.S. non-profit corporation funded by the EPA and the auto industry) estimated that air pollution kills between 91,000 and 100,000 Americans each year—nearly double the number of U.S. combat deaths (58,000) in Vietnam, or over 30 times the death toll of the 9/11 terror attacks. The EPA estimated that tough air pollution regulations under the Clean Air Act that began in 1990 saved over 164,000 lives in the year 2010 alone.

Damages from U.S. air pollution are extreme. The World Bank study estimated that in the year 2013 alone, the U.S. suffered $473 billion in health-related damages from air pollution--about 2.9% of the GDP. Health care consumes one-quarter of the $3.7 trillion federal budget, and air pollution is a significant contributor to that bill.

Figure 1. Polling in 2016 by the Yale Program on Climate Change Communication revealed widespread support among Americans for the key provision of the EPA’s Clean Power Plan: setting strict CO2 limits on existing coal-fired power plants. Such limits were supported by 69% of Americans, including majorities in all 50 states and all 435 Congressional Districts; 75% of Americans supported regulating CO2 as a pollutant. Image credit: Yale Climate Opinion Maps.

Power plants are the single largest source of greenhouse gas emissions in the U.S.—about 31 percent of the total, and are also a significant source of deadly air pollution—about 26% of all air pollution deaths in the U.S. according to a 2013 MIT study. The authority for the Clean Power Plan comes from the EPA’s Clean Air Act, along with the Supreme Court’s 2007 decision requiring the EPA to regulate carbon dioxide as a pollutant. The Clean Power Plan is a key component of America’s commitment to reduce global warming under the 2015 Paris Climate Agreement, and there is broad public support for reducing emissions of CO2 from existing coal-fired power plants (69% of Americans, including majorities in all 50 states and all 435 Congressional Districts, see Figure 1.)

Figure 2. Weakening of U.S. air pollution regulations goes against widespread public support for clean air. A January 2017 poll by Reuters found that 39 percent of Americans would like to see the EPA "strengthened or expanded," 22 percent wanted it to "remain the same," and just 19 percent said they would like to see the agency "weakened or eliminated.” The rest said they "don't know." Image credit: John Mashey,

Benefits of the Clean Power Plan far exceed the costs
The EPA estimates that annual costs to industry of the Clean Power Plan will be $1.4 - $2.5 billion in 2020, increasing to $5.1 - $8.4 billion per year in 2030. These estimates factor in the costs of investments in transitioning to lower-carbon electricity options and the savings that result from investments in energy efficiency. Electricity bills are predicted to rise modestly by 2.4 to 2.7 percent in 2020, but then decline by 2.7 to 3.8 percent in 2025, and 7 to 7.7 percent in 2030 as investments in energy efficiency pay off.

The public health and climate benefits of the Clean Power Plan are worth an estimated $34 billion to $54 billion per year in 2030, far outweighing the costs, the EPA estimates. Burning fewer fossil fuels will create less air pollution, and air pollution from the power generation industry will fall about 25% by 2030 if the Clean Power Plan is adopted. The EPA projects that the reduction in pollution will prevent up to 3,600 deaths, 1,700 heart attacks, 90,000 asthma attacks, and 300,000 missed work and school days per year by 2030 (note that a person who dies from air pollution-related causes typically dies about twelve years earlier than they otherwise might have, according to Caiazzo et al., 2013.) For every dollar Americans spend on the Clean Power Plan, $4 worth of health benefits will result, says the EPA. The greatest benefits would come in the upper Ohio Valley and farther downwind, where pollution from power plants is highest: southeast Ohio, northwest West Virginia, and western Pennsylvania—areas Trump carried in the 2016 election, including two swing states that pushed him over the top.  

Figure 3. Levels of the deadliest pollutant, fine particles less than 2.5 microns in diameter (PM 2.5), have fallen by 37 percent and prevented tens of thousands of premature deaths since 2000, thanks to EPA Clean Air Act regulations. A peer-reviewed 1997 EPA Report to Congress reviewed the benefits of the Act from 1970 to 1990, and concluded that in 1990 alone, pollution reductions under the Act prevented 205,000 early deaths—more than three times the number of U.S. combat deaths in Vietnam. However, this progress is now threatened by the pollution-friendly Trump administration. Image credit: U.S. EPA.

Opposition to the Clean Power Plan
As one should expect, lobbying groups who receive money from the fossil fuel industry are unhappy with the Clean Power Plan, and criticize the plan’s complexity and large number of regulations. They have a point—it would have been far simpler and more effective to achieve the plan’s goals through a cap-and-trade system, or through a cap-and-dividend approach, or by having Congress adopt a simple carbon tax of $40 per ton (a version of which was proposed in February by a group of Reagan and Bush-era Republicans called the Climate Leadership Council). However, Congress failed to pass a cap-and-trade bill during Obama’s first term, and he was forced to use the regulatory power of the EPA to bring about the reduction in U.S. greenhouse gas emissions needed for the Paris Climate Agreement.

Critics also dispute EPA’s cost estimates, saying the costs will be much higher. Several of these criticisms state only the costs, not the benefits, and also ignore the huge death toll of air pollution. And at least one study has found that the EPA underestimated the benefits and lives saved by the Clean Power Plan—an independent analysis by Energy Innovation: Policy and Technology LLC,  an energy and environmental policy firm. In a 2017 study, they estimated that the cumulative savings to the U.S. economy (in reduced capital, fuel, and operations and maintenance expenditures) of adopting the Clean Power Plan would exceed $100 billion by 2030, and reach almost $600 billion by 2050, assuming that pollution reductions continue to stay strong after 2030. Failure to adopt the Clean Power Plan would cause more than 40,000 premature deaths annually in 2030, and more than 120,000 per year by 2050. Energy Innovation came up with their estimates using the Energy Policy Simulator (EPS) open-source computer model.

Figure 4. Costs and benefits of the Clean Power Plan as estimated by the U.S. EPA. Image credit: U.S. EPA.

Repealing the Clean Power Plan won’t happen quickly
The Clean Power Plan will be difficult to undo quickly. The plan was finalized by EPA in 2015, and is currently being reviewed in the U.S. Court of Appeals for the District of Columbia Circuit. Under the new executive order, the Department of Justice will ask the court to suspend the case until the EPA can review and write a new version of the rule. (Before that happens, the court may still rule on the Plan as written, which will influence how the EPA can rewrite the rule.) Once the case is removed from the court, the EPA will have to legally withdraw the existing rule and propose a new rule to take its place, a process that could take years, as the new rule will have to be justified in court, and would likely be challenged in court by environmental groups, according to an in-depth analysis by Brad Plumer at In the meantime, nothing prevents states from continuing to reduce emissions by implementing renewable energy standards, efficiency programs, or cap-and-trade programs like exist in California and the Northeast. Thus, some of the benefits of the Clean Power Plan will happen regardless of Trump’s orders, and 31 states are on track to be more than halfway toward their near-term Clean Power Plan emission reduction requirements (Figure 5.)

Figure 5. A 2015 Union of Concerned Scientists (UCS) analysis showed that existing clean energy commitments already place 31 states on track to be more than halfway toward their near-term Clean Power Plan emission reduction requirements, with 21 states set to surpass them. These commitments include carbon caps, mandatory renewable electricity and energy efficiency standards, announced coal plant retirements, and bringing on line nuclear power plants currently under construction.

New executive order attacks the “social cost of carbon” 
The “social cost of carbon” is an estimate of how much human emissions of carbon dioxide cost society via damage to the climate. In 2015, this number was set at $36 per ton of carbon dioxide pollution, and the social cost of carbon underpins at least 150 federal regulations. The “social cost of carbon” tries to answers the question, “how much should we be willing to pay to avert future climate damages?” This number is highly uncertain, but is definitely not zero. Trump’s executive order calls for a reassessment of the social cost of carbon, with the aim of reducing it or entirely circumventing it. has an excellent explainer on the “social cost of carbon”.

Automobile fuel efficiency standards to be reviewed 
President Trump, speaking in Detroit on March 15 to a group of autoworkers, said the U.S. Environmental Protection Agency will take action to potentially relax tough air pollution rules for cars and light trucks that were set to kick in between 2022 and 2025. A review of the rules was completed in 2016, ahead of a deadline in 2018. “It was necessary (to resume the review) because the standards were set far into the future," Trump said. "If the standards threaten auto jobs, then common sense changes could have — and should have — been made." The review opens up the possibility that the strict fuel economy regulations for 2022 - 2025 will be significantly weakened; it is relatively easy for the EPA to undo the regulations, according to a New York Times analysis. Once the 2017 review is finished, the EPA can withdraw the current rule for post-2021 emissions, and put forth an alternative set of standards within a year. The EPA may also withdraw a waiver that allows California (and other states that have joined it) to enforce stricter auto emissions standards than the federal government imposes. Air pollution from vehicles in the U.S. is responsible for about 26% of all U.S. air pollution deaths, so weakening of these regulations will likely result in thousands of premature deaths that would not have occurred otherwise—in addition to the thousands of deaths we can expect from a weakening of the Clean Power Plan.

U.S. Paris Climate Agreement commitments unlikely to be met 
Trump’s executive order and proposed budget make it clear that we can expect most of the efforts to reduce U.S. emissions of greenhouse gases under the Paris Climate Agreement to come under attack, and it is unlikely the U.S. pledge will be met. In that landmark agreement, the U.S. promised a 26 - 28% reduction in U.S. greenhouse gas emissions by 2025, as its fair share of the effort to keep global warming no more than 2°C above preindustrial levels (the generally accepted goal for avoiding dangerous impacts.) According to an excellent analysis by, the Clean Power Plan accounts for roughly one quarter of all the emission reductions promised by the U.S. as part of the 2015 Paris Climate Agreement. The other three-quarters of the reductions were to come primarily from stricter fuel economy stands for vehicles, tighter emission standards for new coal- and gas-fired power plants, new regulations to curtail methane leaks and limit methane from agriculture, energy efficiency measures, and initiatives to curtail hydrofluorocarbons (another potent greenhouse gas.)

Taken altogether, the numbers from these efforts don’t quite add up to the promised 26 - 28% reduction in greenhouse gases by 2025, said a 2015 World Resources Institute analysis—and thus additional actions beyond what Obama proposed would be needed. According to a 2016 paper, ”Assessment of the climate commitments and additional mitigation policies of the United States”, and the web site, current U.S. policies, including the Clean Power Plan, would only reduce emissions by 9% below 2005 levels by 2025. A much more aggressive Clean Power Plan was being counted on, plus a whole host of "TBD" actions needed from President Obama’s successor. An excellent new analysis by the Rhodium Group predicts that Trump’s current executive orders and proposed budget will most likely result in a 14% reduction in U.S. greenhouse gas emissions below 2005 levels by 2025—far below the promised 26 - 28% reduction of the Paris Climate Accord. The Rhodium Group’s worst-case scenario—if further efforts to weaken greenhouse gas regulations occur, such as a rollback of automobile emission standards for the 2022 - 2025 period—was a 9% reduction in U.S. greenhouse gas emissions by 2025; their best-case scenario was a 17% reduction.

Figure 6. U.S. greenhouse gas emissions as projected in 2008 for a "business as usual" scenario (gray dotted line) and under the pledge made as part of the Paris Agreement (orange and green dotted lines). Image credit: Earth Institute/Columbia University.

Assault on methane emission rules 
Methane is also a major greenhouse gas, and Trump’s executive order directs efforts to reconsider and rewrite rules on methane emissions. This follows on the March 2, 2017 directive from the EPA to withdraw a 2016 Information Collection Request which directed existing oil and gas facilities to provide data needed to best reduce methane and other harmful emissions from the oil and natural gas industry. However, new methane rules will take years to rewrite and will have to suffer court challenges, and one state—California—voted on March 23 to approve new methane regulations that are the strictest ever adopted in the U.S.

More serious attacks on clean air and clean water likely coming 
Wunderground’s climate change blogger, Dr. Ricky Rood, in a 2017 editorial in EOS, warns that, “Following Trump’s rhetoric, we must be prepared to face efforts aimed at weakening the Clean Air Act itself. Also in the crosshairs are many other environmental statutes passed in the 1970s, such as the National Environmental Policy Act, the Clean Water Act, the Endangered Species Act, and the Safe Drinking Water Act. In terms of enduring impacts, weakening of these underlying statutes will be more consequential than scuttling the Clean Power Plan.” In an email to me, Dr. Rood said he believes that a rollback of auto emission standards will ultimately end up being more consequential to air pollution and the climate than a rollback of the Clean Power Plan. This will be because market forces are making it likely that the power generation industry will head towards renewable energy sources, but market forces are not acting that way on the auto industry—external regulation is needed to force emission reductions.

The latest assault on climate science by House Republicans happens at 10 am EDT Wednesday, March 29, when the House Committee on Science, Space and Technology holds a 2-hour hearing titled, “Climate Science: Assumptions, Policy Implications, and the Scientific Method.” The Republicans have called three witnesses: Dr. Judith Curry, Dr. John Christy, and Dr. Roger Pielke, Jr., all of whom are unfriendly to climate science. The Democrats got to call one witness, Dr. Michael Mann of climate “hockeystick” fame. The hearing is here:

Brad Plumer of has an excellent explainer on Trump’s executive order.

Follow the Climate Deregulation Tracker website to monitor efforts undertaken by the Trump administration to scale back or wholly eliminate federal climate mitigation and adaptation measures.

March Madness: Trump Proposes 31% Cut to EPA and Big Cuts to Climate Change Programs, my March 16 post

EPA Chief Denies Basic Climate Science
, my March 10 post

"Together we are going to start a new energy revolution," Trump said, upon signing Tuesday’s executive order. However, his order promotes dirty and deadly 19th Century coal technology, instead of clean 21st Century renewable energy solutions like wind and solar power, making his remarks sadly preposterous. The name of his order, the “Energy Independence Executive Order” is also preposterous, since the U.S. doesn’t import coal, and the stated primary aim of the new order is to revive the coal industry (coal miners were on hand for the signing ceremony.)

In his first speech to Congress, Trump promised that his administration would work to “promote clean air and clean water.” This promise has been exposed as a blatant falsehood by his executive orders and proposed budget, which move us sharply in the opposite direction. By itself, a U.S. failure to make its emission reduction targets of the Paris Climate Agreement will not doom the world to a dangerous rise in temperature above the 2°C threshold. However, we’ll be lucky to hold global warming to an extremely dangerous 3°C above pre-industrial levels, even if all of the promises made by the 195 nations that signed the Paris Agreement are met. That agreement counted on strong additional actions and leadership by the biggest emitting nations to force additional cuts in greenhouse gas emissions. Lack of inspirational American leadership, as glaringly evident in Mr. Trump’s latest executive order, will hurt global efforts to meet even the grossly inadequate goal of keeping global warming below 3°C, increasing the odds that humanity will have to resort to desperate geoengineering efforts to keep climate mayhem from wrecking Earth as a livable planet for humans. We must resist and protest Trump’s assault on clean air and a livable climate as if our lives depend upon it—because they do.

Contact your House Representative
Contact your Senator

Jeff Masters

Climate Change Politics

Debbie’s Silver Lining: Cooler Waters and Less Coral Reef Damage

By: Bob Henson and Jeff Masters , 4:46 PM GMT on March 28, 2017

Tropical Cyclone Debbie roared into northern Queensland, Australia, early Tuesday local time, hurling giant waves, fierce winds, and a major storm surge into the sparsely populated coast. Landfall occurred near Airlie Beach at about 12:40 pm local time Tuesday. Debbie’s top sustained winds at landfall, averaged over 1 minute (as is standard practice for Atlantic hurricanes), were estimated at 105 knots (120 mph), near the midpoint of the Category 3 range on the Saffir-Simpson scale. Debbie ranked as a Category 4 on Australia’s tropical cyclone rating scale, which uses different thresholds and 10-minute wind averaging.

An anemometer located near the airport on rugged Hamilton Island, near the south eyewall of Debbie as the cyclone approached the coast, recorded peak sustained winds of 99 knots (114 mph) gusting to 142 knots (163 mph) at 10:30 am Tuesday local time. The anemometer is at an elevation of 59.4 meters (195 feet). One would expect slightly higher gusts at this height than at sea level, as the effects of surface friction would be less and the turbulence produced by the coastal topography could allow for stronger winds to mix down from aloft.

As of midday Tuesday EST, only one serious injury had been reported from Debbie, although the toll could rise as relief crews enter the hardest-hit areas on Wednesday local time. Power was knocked out to some 40,000 homes and business, noted’s Sean Breslin. The cyclone's approach marked the largest pre-deployment ever carried out by the Australian Defense Force ahead of a natural disaster, said Prime Minister Malcolm Turnbull.

Figure 1. Tropical Cyclone Debbie making landfall over Queensland, Australia, as seen by the MODIS instrument at 0342 UTC Tuesday, March 28, 2017 (1:45 pm Tuesday local time). Image credit: NASA.

Figure 2. Storm clouds gather in the town of Ayr in far north Queensland as Cyclone Debbie approaches on March 27, 2017. Image credit: Peter Parks//AFP/Getty Images.

Figure 3. Winds at the airport on Hamilton Island, Queensland, AU, peaked at 142 knots (163 mph) at 10:30 am local time on March 28, 2017, as Tropical Cyclone Debbie approached just to the north. The site experienced sustained winds exceeding hurricane force (65 knots) from 1:00 am to 2:00 pm Tuesday, a span of 13 hours. The anemometer at Hamilton Island is located at a height of 195 feet, which allowed for slightly stronger winds than at sea level. Image credit: Courtesy Michael Theusner.

Debbie’s prolonged storm surge
Debbie’s slow forward motion in the hours prior to landfall allowed surge to pile up from southeast winds pushing water into a concave portion of the coastline about 20-30 miles south of the landfall location. According to storm surge expert Hal Needham, witnesses reported water about one meter (3.3 feet) above ground level In the area near Midge Point. At Laguna Quays, the storm surge was 2.75 meters (9 feet). The surge’s effects were exacerbated by the new moon and by Debbie’s slow forward motion, which allowed at least one meter of storm surge to persist through a full astronomical cycle (12 hours), including a high tide.

Needham reports that the surge from Debbie was the 14th highest on the Queensland coast since 1880, and the highest since Tropical Cyclone Yasi (2011). On top of the storm surge, mammoth waves—again boosted by Debbie’s slow motion—battered the coast. A buoy located about a mile offshore from Hay Point recorded waves exceeding 10 meters (33 feet), topping the previous record at that location of 7 meters in data going back to 1993.

Figure 4. Significant wave height and maximum wave height on March 27-29, 2017, at the Hay Point buoy, located about a mile offshore from Hay Point and about 8 miles southeast of Mackay, Queensland. Image credit: Queensland Government.

Debbie’s heavy rain to swipe New Zealand
Even as it decays, the circulation of Debbie will continue to dump very heavy rain across parts of Queensland, with the help of precipitable water (moisture in a column above the surface) exceeding 2.75” in some spots, according to satellite-based estimates. Later this week, Debbie’s remnants will flow southeastward and merge with a frontal zone, perhaps dumping additional heavy rain onto the mountains of southern New Zealand.

Figure 5. Rainfall for the six-day period starting at 06Z Tuesday (5:00 pm Tuesday local time in Queensland) could exceed 200 mm (8”) over the higher terrain of Queensland, Australia. Storm totals for Debbie could reach 500 mm (20”) in some spots. A swath of moisture associated with Debbie’s remnants may extend to the west coast of New Zealand’s South Island. Projections shown here are from the 06Z Tuesday run of the GFS model. Image credit:

Debbie will slow coral bleaching in portions of the Great Barrier Reef
Though the wave action from Tropical Cyclone Debbie likely caused some destruction of fragile corals along portions of Australia’s Great Barrier Reef, that wondrous natural site is likely to experience a net benefit from the passage of Debbie. The cooling effect of the storm on near record-warm summer waters that were besieging the reef will help reduce coral mortality from the reef’s ongoing coral bleaching event. By raising global temperatures overall, human-produced climate change has led to especially sharp oceanic warming during El Niño events. The result has been three global coral bleaching events: the first in 1998, the second in 2010, and the third beginning in 2015. That event is still under way— the longest, most widespread, and most damaging on record, according to NOAA.

Preliminary satellite data (Figure 5) showed that Debbie’s passage had already cooled waters near the coast of Australia by up to 2°C on Monday, and additional cooling has occurred since that time. This amount of cooling may be enough to stop widespread coral bleaching and die-off along central portions of the Great Barrier Reef.

Figure 6. Departure of sea surface temperature (SST) from average on March 27, 2017. Debbie’s passage had already cooled waters near the coast of Australia by up to 2°C by this time, and additional cooling has occurred since the time of this image. Image credit: NOAA.

Australia’s Great Barrier Reef suffered its greatest coral die-off ever observed in 2016, when about two-thirds of the shallow-water coral on the reef’s previously pristine, 430-mile northern stretch died. The only thing that saved the southern portion of the 1,400-mile long reef was wind, rain and cloud cover from the passage of ex-Cyclone Winston, which churned up the waters and cooled water temperatures by up to 3°C. As discussed in a paper published this month in the journal Nature, ”Global warming and recurrent mass bleaching of corals,” Winston passed over Fiji on February 20, when the southern Great Barrier Reef was only 1 °C cooler than the north. By March 6th, this disparity increased to 4 °C. Corals in the south that had begun to pale in February regained their color in the south in March, whereas bleaching continued to progress in central and northern sectors.

Figure 7. Prior to the arrival of Debbie, the entire Great Barrier Reef was experiencing “Alert Level 2” bleaching stress (associated with widespread coral bleaching and significant mortality), according to the latest four-month forecast from NOAA’s Coral Reef Watch. This is the highest level of thermal stress in NOAA’s warning system for coral reefs.

Hurricanes can alleviate thermal stress on corals by three mechanisms:

1) Hurricanes absorb energy from surface waters through the transfer of latent heat, causing evaporative cooling. The magnitude of the cooling is related to the intensity and extent of the hurricane.

2) Local upwelling brings deeper, cooler water to the surface. The amount of surface cooling resulting from these mixing mechanisms will depend on the hurricane wind speed and how the water temperature varies with depth at each location.

3) Clouds of a hurricane shade the ocean surface from solar heating, allowing the water to cool and reducing light stress.

The benefits of reducing coral reef damage can be economic as well as ecological. Australia relies on the Great Barrier Reef for about 70,000 jobs and billions of dollars annually in tourism revenue, according to a recent New York Times analysis.

We’ll be back with a new post by Wednesday at the latest.

Bob Henson and Jeff Masters

Figure 8. A variety of corals form an outcrop on Flynn Reef, part of the Great Barrier Reef near Cairns, Queensland, Australia. Image credit: Toby Hudson/Wikimedia Commons.

Hurricane Coral Reefs

March Going Out with a Weeklong Roar of Severe Weather

By: Bob Henson , 7:00 PM GMT on March 27, 2017

Severe weather watches may be a daily occurrence into at least the first weekend of April, as upper-level energy continues to stream across the U.S. atop an increasingly rich supply of low-level moisture. Already, 2017 has been a noteworthy year for severe weather. Even after tornado reports for earlier decades are inflation-adjusted (in order to balance the more complete reporting of tornadoes in recent years), the total of 325 preliminary tornado reports through Sunday is the highest for the period Jan. 1 - Mar. 26 in records dating back to 1954.

A hail-strewn Sunday in TX/OK
Moisture from the Gulf of Mexico returned just in time on Sunday to produce a bumper crop of intense thunderstorms ahead of a sharp dry line in Oklahoma and Texas, especially between the Oklahoma City and Dallas-Fort Worth metro areas. Fortunately, the conditions didn’t coalesce to produce many tornadoes—only one was reported, near Ada, OK (see photo at bottom)—but more than 100 reports of severe hail had been compiled by the NOAA/NWS Storm Prediction Center (SPC) as of Monday morning. Just southeast of Denton, TX, the town of Corinth was bombarded by hailstones as large as 4.25” (for comparison, a softball is about 4” wide). Supercells in south-central Oklahoma dropped widespread 2” - 3” hail, with one report of a 3.25” hailstone southeast of Francis, OK. There was considerably less high wind than large hail in Sunday’s storms, although a gust to 65 mph was reported near Anthony, KS.

Figure 1. Rick Smith, warning coordination meteorologist for the National Weather Service office in Norman, OK, took this photo of a supercell in eastern Oklahoma from the National Weather Center offices in Norman around 6:00 pm CDT Sunday, March 26, 2017. Image credit: Rick Smith, used with permission.

Stop in the middle of a highway? Hail, no!
Sunday’s prolific hail producers reignited a problem familiar to those in the Southern Plains: the specter of people parking beneath bridges, right in the middle of highways (even interstates!), in order to protect their vehicles. It goes without saying that this practice not only puts everyone behind the stopped car(s) at risk of hail damage, but it impedes any emergency vehicles from using the roadway. If a tornado were to strike one of these traffic clots, a major disaster could easily result. Dennis Mersereau (@wxdam) included plenty of photographic evidence and food for thought in his 2015 post on this issue: “This is one of those instances where people have to remember that we all live in a society, and that they have to think of the safety of those around them, as well.”

Figure 2. Damage expert Tim Marshall (Haig Engineering) captured this 3” diameter hailstone from the storm that struck Double Oak, Corinth, The Colony, and Frisco, TX, just north of Marshall’s house. “Looks like I’ll be booked evaluating the damage through at least mid-summer,” said Marshall. “Spring has roared in like a lion.” Image credit: (c) Tim Marshall, used with permission.

Figure 3. As of Monday morning, March 27, 2017, the NOAA/NWS Storm Prediction Center had designated “enhanced” risk areas for parts of the Tennessee Valley from KY to MS on Monday and for parts of TX and OK on Tuesday, March 28. Significant risk may also emerge on Wednesday and subsequent days this week.

Day by day through the week ahead
Very large hail was a continuing threat on Monday afternoon, as the pocket of very cold air aloft migrated into the mid-Mississippi Valley. In its outlook issued at 11:30 am CDT Monday (see Figure 2), SPC was highlighting far western TN and northern MS with a risk for significant large hail (2” or more diameter). A preexisting cluster of thunderstorms moving through northeast AR at midday Monday was expected to segue into new supercells toward the southeast. A solid swath of low-level moisture evident in the 12Z Monday sounding from Jackson, TN, will be moving into the area by afternoon, enhancing the severe threat. Late Monday, high winds may become more of a concern as the supercells morph into one or more squall lines further east toward Nashville, TN, and Huntsville, AL. As with Sunday, the tornado threat appears fairly low on Monday afternoon.

The U.S. pattern will recharge on Tuesday as another compact but strong upper-level low swings into the Southern Rockies. Deep low-level moisture will surge into Texas ahead of the upper low, with dew points of 60°F to 70°F likely to be widespread by Tuesday afternoon. Severe thunderstorms may form along a warm front expected to lie near the Red River of west TX/OK, as well as along a dry line in the South Plains of TX. The greatest likelihood of tornadoes will likely be near the intersection of the dry line and warm front (the “triple point”), but upper-level wind shear and instability could be more than adequate for tornadic supercells along either boundary.

Another round of intense storms appears likely on Wednesday from eastern OK and TX into parts of AR and LA, especially if the remnant activity from Tuesday night doesn’t interfere. It’s unclear if low-level wind shear will be as strong on Wednesday as on Tuesday, but conditions still appear ripe for widespread storms dumping heavy rain, hail, and high wind, as well as the possibility of embedded tornadoes.

More severe weather could erupt on Thursday, especially in and near Mississippi, and on Friday as far east as the Carolinas, as the upper low translates across the eastern U.S. Meanwhile, yet another upper low will be diving into the southwest U.S., poised to trigger the next multi-day round of severe storms. This one may begin on Saturday across western TX if moisture returns in time. A better bet for severe weather in TX/OK/LA may be on Sunday, with the upper low expected to stall out as unstable air continues streaming north from the Gulf of Mexico. Patterns like this sometimes evolve into more of a heavy-rain threat than a tornado-favorable setup, but there is still ample time to see how this one evolves.

Both the GFS and ECMWF suggest that the pattern will remain progressive into next week, with at least one more significant upper low traversing the U.S.

We’ll be back with our next post on Tuesday. For more on Tropical Cyclone Debbie, which was approaching the Queensland, Australia, coast early Monday afternoon EST, see Jeff Masters’ post from Monday morning. Please free to discuss Debbie in the comment section of this post!

Bob Henson


Severe Weather

Category 3 Tropical Cyclone Debbie Pounding Queensland, Australia

By: Jeff Masters and Bob Henson , 4:23 PM GMT on March 27, 2017

Tropical Cyclone Debbie is battering Northeast Australia’s Queensland coast with torrential rains and high winds as the storm heads west-southwest at about 5 mph towards an expected landfall near 3 pm EDT (19 UTC) Monday. Debbie intensified into a Category 3 storm with 115 mph winds on Monday morning U.S. time, and satellite images on Monday morning showed an impressive storm with a well-defined eye surrounded by eyewall thunderstorms with very cold cloud tops that were increasing in intensity.

Winds at Hamilton Island in the south eyewall of Debbie were 85 mph (10-minute average), gusting to 113 mph at 2:30 am local time Tuesday (12:30 pm EDT or 16:30 UTC Monday), and winds at Hardy Reef were sustained at 63 mph, gusting to 93 mph at 11 pm local time. According to storm surge expert Dr. Hal Needham, storm surge levels were beginning to build on Monday afternoon (local time) at several sites along the Queensland coast. Laguna Quays, Mackay and Dalrymple Bay all reported storm surge levels exceeding 0.5 m (1.64 ft).  Water levels should increase through the night as Debbie approaches the coastline, with storm surge exceeding 2.5 m (8.2 ft) in localized areas between Bowen and Mackay. Debbie has favorable conditions for intensification, with light wind shear and warm ocean temperatures of 28 - 29°C (82 - 84°F.) However, Debbie does not have much time to intensify before landfall, and will likely be at Category 3 strength then. Recent runs of the HWRF model predict that Debbie will dump a large area of 8+ inches of rain near the coast, which is likely to cause considerable flooding and agricultural damage.

Figure 1. Tropical Cyclone Debbie nearing landfall as seen by radar at 16:00 UTC (12 pm EDT) March 27, 2017. Image credit: Australia Bureau of Meteorology.

Figure 2. Track of Tropical Cyclone Debbie as projected by the Australian Bureau of Meteorology at 12:10 am Tuesday, March 28, 2017 (10:10 am EST Monday). Debbie is a “4” on the Australian tropical cyclone intensity scale, whose 1-to-5 numbering system has lower intensities than the Saffir-Simpson equivalent familiar to Americans, which uses 1-minute sustained winds. According to BOM, Debbie’s top 10-minute sustained winds at 10:10 am EST Monday were 175 km per hour (108 mph), and Debbie’s top 1-minute winds were 115 mph, corresponding to a low-end Category 3 storm on the Saffir-Simpson scale. Image credit: BOM.

Figure 3. Tropical Cyclone Debbie, as seen on Monday afternoon (local time), 03:50 UTC March 27, 2017. At the time, Debbie was an intensifying Category 2 storm with 105 mph winds. Image credit: NASA.

Tropical cyclone history of the Queensland, Australia coast
According to NOAA’s historical Hurricane Tracks tool, Queensland has been hit by nine tropical cyclones of Category 3 or higher strength on the Saffir-Simpson Scale since 1989. Four of these storms have hit since 2011:

Tropical Cyclone Marcia hit central Queensland near Shoalwater Bay as a Category 4 storm with 145 mph winds on February 20, 2015, causing $590 million in damage. No fatalities were reported.

Tropical Cyclone Nathan hit far northern Queensland as a Category 3 storm with 115 mph winds on March 19, 2015, causing $57 million in damage.

Tropical Cyclone Ita hit Cape Flattery, Queensland as a Category 4 storm with 145 mph winds on April 12, 2014, causing over $1 billion in damage to agriculture. Ita killed 40 people in the Solomon Islands while it was forming (thanks go to WU member elioe for this correction.)

Queensland suffered a devastating blow on February 3, 2011, when Tropical Cyclone Yasi made landfall in northern Queensland as a Category 4 storm with 155 mph winds, killing 1 and causing $2.5 billion in damage (2011 dollars.) According to EM-DAT, Yasi was the most damaging tropical cyclone in Australian history.

The Australian Bureau of Meteorology has a nice summary of the major to storms to impact Queensland before 2011.

The Atlantic’s first Invest of 2017, 90L, not likely to develop
A large area of low pressure a few hundred miles east of the Bahamas was designated as the season’s first Atlantic “Invest”—Invest 90L—by NHC on Sunday. 90L is over waters that are near 24°C (75°F)—barely warm enough to support formation of a subtropical depression or subtropical storm. Satellite loops on Monday morning showed that 90L had a vigorous circulation, but little in the way of organized heavy thunderstorm activity. With wind shear a very high 50 - 70 knots, and with the low headed northeastwards over cooler waters, development into a subtropical storm is unlikely. 90L will pass a few hundred miles southeast of Bermuda on Tuesday. According to NOAA’s Historical Hurricane Tracks, the only March tropical cyclone ever recorded in the Atlantic was a Category 2 hurricane that passed through the Lesser Antilles on March 8, 1908.

Hurricanes Matthew and Otto get their names retired
The World Meteorological Organization (WMO) announced on Monday that two major hurricanes in the Atlantic from 2016—Matthew and Otto—will get their names retired from the active list of hurricane names. Matthew and Otto are the 81st and 82nd names to be removed from the Atlantic list. The WMO will replace Matthew with Martin and Otto with Owen when the 2016 lists are used again in 2022.

Bowen Australia radar loop courtesy of Brian McNoldy.

Jeff Masters and Bob Henson


Australia Braces for Debbie; Localized Tornado Outbreak Possible Sunday in TX/OK

By: Jeff Masters and Bob Henson , 5:17 PM GMT on March 26, 2017

Northeast Australia’s Queensland coast is bracing for the arrival of Tropical Cyclone Debbie, which intensified into a Category 1 storm with 80 mph winds on Sunday morning. Debbie is headed west-southwest at about 4 mph, and is expected to make landfall on Tuesday morning local time (Monday evening in the U.S.) The storm has quite favorable conditions for intensification, with light wind shear and warm ocean temperatures of 29 - 30°C (84 - 86°F.) However, satellite images on Sunday morning showed that Debbie had failed to take full advantage of these favorable conditions for intensification, thanks to dry air pulled off the coast of Australia that had wrapped into the core of the storm. There is still time for Debbie to undergo a period of rapid intensification before landfall, and the storm could well be at Category 3 strength by then, as predicted by the Joint Typhoon Warning Center.

According to Australian hurricane expert Bruce Harper, the population of the area expected to receive the brunt of Debbie’s winds is around 15,000. The region is surrounded by flat sugar cane fields, and heavy rains from the storm will likely cause considerable agricultural damage. Debbie is a very moist storm, and a large area of torrential rain in excess of 8 inches will accompany the storm as it make landfall, according to the 06 UTC Sunday run of the HWRF model. A maximum storm surge of about 3 meters (10 feet) and storm tide (height of the surge plus the tide) of about 4 meters (13 feet) can be expected to the left of where the center makes landfall, if Debbie intensifies to Category 3 strength.

Figure 1. Tropical Cyclone Debbie, as seen on Sunday afternoon (local time) March 26, 2017. Image credit: NASA Worldview.

Tropical cyclone history of the Queensland, Australia coast
According to NOAA’s historical Hurricane Tracks tool, Queensland has been hit by nine tropical cyclones of Category 3 or higher strength on the Saffir-Simpson Scale since 1989. Four of these storms have hit since 2011:

Tropical Cyclone Marcia hit central Queensland near Shoalwater Bay as a Category 4 storm with 145 mph winds on February 20, 2015, causing $590 million in damage. No fatalities were reported.

Tropical Cyclone Nathan hit far northern Queensland as a Category 3 storm with 115 mph winds on March 19, 2015, causing $57 million in damage.

Tropical Cyclone Ita hit Cape Flattery, Queensland as a Category 4 storm with 145 mph winds on April 12, 2014, causing over $1 billion in damage to agriculture. Ita killed 40 people in the Solomon Islands while it was forming (thanks go to WU member elioe for this correction.)

Queensland suffered a devastating blow on February 3, 2011, when Tropical Cyclone Yasi made landfall in northern Queensland as a Category 4 storm with 155 mph winds, killing 1 and causing $2.5 billion in damage (2011 dollars.) According to EM-DAT, Yasi was the most damaging tropical cyclone in Australian history.

The Australian Bureau of Meteorology has a nice summary of the major to storms to impact Queensland before 2011.

An early appearance of the Atlantic’s first named storm of 2017 unlikely this week
A large area of low pressure has formed a few hundred miles east of the Bahamas over waters that are near 24°C (75°F)—barely warm enough to support formation of a subtropical depression or subtropical storm. Satellite loops on Sunday morning showed that the low had little in the way of organized heavy thunderstorm activity, and with wind shear a very high 50 - 60 knots, development of this storm into a subtropical storm is unlikely. The low will head north and then northeast, passing a few hundred miles southeast of Bermuda on Tuesday. According to NOAA’s Historical Hurricane Tracks, the only March tropical cyclone ever recorded in the Atlantic was a Category 2 hurricane that passed through the Lesser Antilles on March 8, 1908.

Figure 2. At the center of a compact severe weather threat area highlighted by the NOAA/NWS Storm Prediction Center for Sunday, March 27, as of 11:30 am CDT was a moderate risk across parts of south-central Oklahoma and far north Texas (red). “Moderate” is the second-highest of the risk ratings issued by SPC.

Localized severe weather outbreak expected on Sunday in OK/TX
A couple of intense supercells, possibly bearing tornadoes, may crop up late Sunday in south central Oklahoma, possibly extending into north central Texas. Low-level moisture was quite limited across the area late Sunday morning, with dewpoints mainly between 50°F and 55°F. However, dewpoints in the low- to mid-60s had surged from the Gulf of Mexico to just south of the Dallas-Fort Worth area. As a compact upper-level low swings into the Southern Plains, a surface low centered near the Oklahoma Panhandle on Sunday morning will quickly strengthen, with a sharp dryline and cold front extending southward.

Figure 3. A midlatitude storm wrapping up over the Southern Plains is arriving hard on the heels of another midlatitude storm now centered in northern Illinois, as shown here in a NOAA GOES-16 visible image from 10:52 am CDT Sunday, March 27, 2017. The short distance between these systems has made it difficult for moisture from the Gulf of Mexico to return in time for today’s potential severe weather in OK/TX. Data from GOES-16 are preliminary, undergoing testing, and have not yet been declared operational. Image credit: College of DuPage.

Moisture streaming northward from the Gulf is not quite as deep as it can be this time of year, but it appears richer than it did with Friday’s limited severe weather. If deep moisture does make its way as far north as the corridor between DFW and Oklahoma City, conditions there will be quite favorable for tornadic storms, with substantial instability (perhaps up to 2000 joules per kilogram of CAPE) and ample wind shear (winds will be veering as well as strengthening with height). Although low-level wind shear will not be exceptionally strong, the distinct veering (turning of winds with height) should help lead to well-structured supercells. I wouldn’t expect a widespread tornado outbreak, but the situation definitely bears watching in and near the Interstate 35 corridor between DFW and OKC, especially between about 4:00 and 9:00 pm CDT Sunday.

The NOAA/NWS Storm Prediction Center raised the risk level in this area from enhanced to moderate early Sunday morning, highlighting the chance of tornadoes, significant large hail (larger than 2” in diameter) and very high wind (gusts of at least 74 mph). Short-range computer models indicate that the storms may congeal into a squall line on Sunday from eastern Oklahoma into western Arkansas. Thunderstorms should be somewhat less severe but more widespread across northern Oklahoma and much of Kansas.

We’ll be back on Monday with an update on Debbie and on more possibilities of U.S. severe weather in the upcoming week.

Jeff Masters (tropical) and Bob Henson (severe)

Figure 4. Dewpoint changes between 8:00 and 11:00 am CDT Sunday, March 26, 2017 (increases in green, decreases in tan) atop surface winds at 11:00 am. Dewpoints increased more than 12°F in three hours across parts of north Texas as a surge of moisture arrived from the Gulf of Mexico. Image credit: NOAA/NWS Storm Prediction Center.

Hurricane Tornado Severe Weather

Weird Coastal El Nino Clobbers Peru: 80 Killed, $1.4 Billion in Damage

By: Bob Henson and Jeff Masters , 6:00 PM GMT on March 24, 2017

The world’s costliest flood disaster of 2017 is still unfolding across parts of coastal Peru, where extreme rainfall atop normally dry terrain has led to episodes of major flooding over the last few weeks. More than 110,000 people have been displaced by flooding since December, according to Reuters, and more than 80 deaths have been reported.

The death toll makes the floods of 2017 Peru’s deadliest floods since 2009 - 2010, when 158 people died in flooding between December and March. Preliminary damages from the 2017 rains and flooding in Peru are estimated at $1.4 billion (0.7% of Peru’s GDP), according to insurance broker Aon Benfield. Significant damage has been done to Peru’s infrastructure, with 2,188 kilometers (1,360 miles) of main roads and 928 kilometers (577 miles) of rural roads destroyed, along with 194 bridges. Approximately 671 kilometers (417 miles) of irrigation canals have been destroyed and as many as 23,000 hectares (56,000 acres) of crops damaged or destroyed, including grapes, mangoes, and bananas.

Figure 1. Huachipa district, east of Lima, on March 19, 2017. Flash floods and landslides hit parts of Lima, where most of the water distribution systems have collapsed and people are facing drinking water shortages. Photo credit: ERNESTO BENAVIDES/AFP/Getty Images

According to EM-DAT, the international disaster database, the most expensive natural disaster in Peruvian history occurred during the El Niño rains of 1983, when heavy rains unleashed a landslide that killed 596 people and cost $2.4 billion (2017 dollars.) The Global Facility for Disaster Reduction and Recovery (GFDRR) estimated total damages from the rains and flooding of the 1982 - 1983 El Niño amounted to 8.1% of Peru’s GDP. The El Niño rains of 1997 -1998 also exacted a heavy toll; the GFDRR estimated that Peru suffered nearly $2 billion in losses (5.9% of GDP).

Flooding where it’s been raining—and where it hasn’t
The current Southern Hemisphere summer is Peru’s rainy season, but this year has delivered in a much bigger way than usual. At least two stations in the far northern coastal province of Piura recorded about 10 times their average rainfall for the period from January through March, according to a blog post by NOAA’s Tom Di Liberto. At a desert location like this, it’s to be expected that the wettest years will produce several times the seasonal average. Still, according to Di Liberto, “2017 is already likely one of the wettest years on record for San Miguel in the Piura province.” San Miguel de Piura had racked up 10” by early March, compared to a typical wet-season total of just 2”. On March 3, the town of Partidor reported an all-time daily record of 258.5 mm (10.18”),

While the heaviest rains have deluged the Pacific-facing west side of Peru’s coastal mountains, especially toward the north, the resulting floods and mudslides have affected many areas downstream, between the mountains and coast. This includes Peru’s capital, Lima, where major damage and disruption (including a disabled municipal water system) have occurred despite virtually no rain in the lowest-lying parts of the city. Just 0.7 mm or 0.03” fell at Lima’s airport from Feb. 2 to Mar. 23. Lima is a premier example of a coastal desert city, with a climate dominated by gentle onshore flow atop cool, upwelled Pacific water. The result is a paradoxical blend of high humidity, frequent cloud cover and fog (especially in winter), but very little rain. Lima’s annual average precipitation is a mere 0.6”, and the city’s wettest day on record—January 16, 1970—brought just 17 mm (0.67”).

Figure 2. Sea-surface temperatures have been warmer than average over the past month across most of the southeastern Pacific. The unusual warmth has been especially sharp near the coast of Peru, where the monthly departures from average are greater than 3°C (5.4°F). Image credit: NOAA/NWS Climate Prediction Center.

El Niño’s weird evolution and its impact on Peru
Peru normally gets its heaviest rains during El Niño events. When El Niño is strong, unusually warm waters extend through the eastern tropical Pacific all the way to the coast of South America. The process shuts off the cold, upwelled current that normally keeps coastal Peru air-conditioned and mostly rain-free. The warmer water is typically accompanied by a stronger tendency toward moist, warm westerly winds off the Pacific into Peru. When that flow reaches the mountains, heavy rains are often squeezed out.

This chain of events played out during the super El Niño of 1997-98, when flooding and mudslides took more than 200 lives in Peru and displaced hundreds of thousands in early 1998. The floods of 2017 have been deemed the worst for Peru since 1998. Some locations in the Piura province have received even more seasonal rain and more extreme one-day rainfalls this year than they did in 1998.

What’s puzzling this time is that the 2014-16 El Niño, the strongest since 1997-98, officially ended more than half a year ago, and it didn’t bring exceptional rain to Peru. Weak La Niña conditions then took hold in late 2016, only to quickly dissipate in early 2017. Meanwhile, sea-surface temperatures off Peru—where the concept of El Niño originated—have skyrocketed since the first of the year. The Niño1+2 region has been running more than 2.0°C above average since late February (see Figure 2 above). This warming has been so strong, and the rainy pattern so clear, that Peru’s national agency for El Niño research, ENFEN, issued a coastal El Niño alert that’s been in place since February 15. Meanwhile, the broader-scale Pacific pattern still hasn’t meshed with the standard El Niño criteria used by NOAA and other international agencies.

Why didn’t El Niño bring the expected heavy rains to Peru in early 2016, and what’s going on this year? The answer may lie in El Niño’s geographic flavor, according to Ken Takahashi (@ktakahashig), an expert at ENFEN and the Instituto Geofísico del Perú. Takahashi has analyzed a number of El Niño events by whether the focus of warming is in the central equatorial Pacific (C-type) or eastern equatorial Pacific (E-type). The other two “super” events of recent decades, 1982-83 and 1997-98, were both E-type, but the 2014-16 event, which peaked in 2015-16, ended up as more of a hybrid, leaning toward a C-type (see Figure 3 below).

Figure 3. Each El Niño can be rated according to whether its sea-surface warming is more focused in the central equatorial Pacific (C index) or the eastern equatorial Pacific (E index). Of the three strongest El Niño events since 1950, the 1982-83 and 1997-98 events were dominated by eastern Pacific warming (E-type), whereas the 2015-16 warming was more of a C-type than E-type event.

“For Peru, the pattern mattered for the impacts,” said Takahashi in an email. In 2015-16, he noted, “the drying effect of the central Pacific warming dominated over the rainy effect of the coastal warming. That was quite different from what's going on this year, in which the large-scale atmospheric pattern is still La Niña-ish, which helps the rains associated with the coastal El Niño.” Takahashi sees some parallels between the current event and another “coastal” El Niño in 1925, which he analyzes in a paper now in review.

Will we get a full-blown El Niño this year?
“The current state of the Pacific is a wonderful example of why we need to change the current definition of the El Niño-Southern Oscillation,” said Michael Ventrice (The Weather Company). “We often try to bin all El Niños or La Niñas into the same category, where in reality there is a spectrum. This year nicely illustrates this, as the current configuration of sea-surface temperature anomalies does not nicely fit the current definition of ENSO.”

Ventrice sees the current sea-surface temperature patterns more as a reflection of atmospheric dynamics rather than an ocean-driven process: “Since the current ocean state is likely more of a response to atmospheric wind stress, I suspect it's unsustainable.” He’ll be watching to see if any westerly wind bursts develop over the western Pacific in April or May. If these don’t develop, then we may not get an El Niño at all in 2017, he told me. “I think a weak El Niño or neutral state is the most likely outcome at this point.” Ventrice emphasizes that we’re now in the midst of the well-known spring predictability barrier, which limits our ability to predict ENSO outcomes.

Figure 4. Departures from the seasonal norm in sea-surface temperatures (SST anomalies) since April 2016 across various parts of the equatorial Pacific Ocean. El Niño conditions are associated with SST anomalies of +0.5°C or greater in the Niño3.4 region. The Niño1+2 region has been exceptionally warm since late January even though the Niño3.4 region has been near neutral. Image credit: NOAA/NWS Climate Prediction Center.

An early appearance for the Atlantic’s first named storm of 2017?
The models are predicting the formation of a large area of low pressure a few hundred miles east of the Bahamas on Sunday and Monday, and this low has the potential to acquire characteristics of a subtropical storm as it heads north and then northeast, passing a few hundred miles southeast of Bermuda on Tuesday. Water temperatures in the region are near 24°C (75°F), which is near average, and these waters may be barely warm enough to support formation of a subtropical depression or subtropical storm. According to phase space diagrams from Florida State University, the low will initially have a warm core that will gradually weaken as the storm encounters cooler waters near 21°C (70°F) by Tuesday. We give 5-day odds of 10% of this low becoming a subtropical depression or subtropical storm. According to NOAA’s Historical Hurricane Tracks, the only March tropical cyclone ever recorded in the Atlantic was a Category 2 hurricane that passed through the Lesser Antilles on March 8, 1908.

Bob Henson and Jeff Masters

Figure 5. GOES infrared satellite image showing an elongated frontal system extending from the northwest Atlantic into the eastern Caribbean Sea at 1645Z (12:45 pm EDT) Friday, March 24, 2017. A center of low pressure is expected to form east of the Bahamas near this decaying front. Image credit: NASA MSFC Earth Science Office.

El Niño Flood

A Prolonged Series of Severe Threats—But How Severe?

By: Bob Henson , 4:36 PM GMT on March 23, 2017

As storm systems sweep across the country over the next week in classic late-March fashion, we can expect near-daily doses of severe weather over parts of the south-central and southeast United States. A parade of moderately strong upper-level lows will be pulling in a steady stream of warm and moderately moist air from the Gulf of Mexico. Most of the resulting severe weather will plow through the regions most favored for stormy conditions in early spring, from Texas and Oklahoma across the Mississippi Valley into the Southeast states. Fortunately, no sign of a major tornado outbreak is rearing its head right now.

Figure X. The NOAA/NWS Storm Prediction Center’s convective outlooks issued on Thursday morning, March 23, 2017. Each of the next three days (March 23-25) features a slight-risk area.

A warm Gulf of Mexico, yet a modest supply of moisture
The extended sequence of severe weather will kick off with a line of storms expected to form by around sunset Thursday (see Figure 3 below) along a sharp dry line that will extend from west Texas to central Nebraska. There will be strong dynamics and ample wind shear. However, the low-level flow from the Gulf hasn’t yet been fully recharged with moisture throughout the lowest mile or so of the atmosphere. Even though the western Gulf is much warmer than normal for late March, a condition that typically favors severe weather (see this Capital Weather Gang overview from Wednesday), the atmospheric dynamics in recent days haven’t been optimal for water vapor to evaporate from the toasty sea surface into the atmosphere.

The result is an air mass with fairly high surface dew points but a shallow vertical extent of moisture. Even at Corpus Christi, TX, the 12Z Thursday sounding showed a mere 1.66 cm (0.65”) of precipitable water (moisture in a column above the surface). This is well below the average for the date of about 0.90”. Soundings from Brownsville, TX, and Lake Charles, LA, were also less moist than average for this time of year.

It may take several more days before the Gulf flow will be able to bring a richer supply of moisture into the severe weather belt. Moreover, the upper-level features moving through the country over the next few days aren’t especially cold aloft. This will cut down on the contrast with the warmer, moister air below, which in turn will keep the air from being as unstable as it could be.

Figure 2. Winds at the 250-mb level, about xx miles above the ground, will be howling at more than 100 knots (115 mph) in a pocket approaching the Southern Plains at 6:00 pm CDT Thursday, according to this 12-hour forecast from the 12Z Thursday run of the GFS model. Image credit:

Figure 3. A line of strong thunderstorms was projected by the 12Z Thursday run of the 3-km NAM model to be in place across western TX/OK/KS at 8:00 pm CDT Thursday, with more isolated storms over northwest Kansas and southwest Nebraska. Version 4 of the NAM, with an upgraded horizontal resolution of 3 kilometers (roughly 2 miles) across the entire contiguous U.S., was introduced on March 15, 2017. Image credit:

Day by day
The relatively modest instability on Thursday will favor storms with strong downbursts along the dry line but will make it tougher for intense supercells to consolidate, which greatly reduces the threat of a widespread tornado outbreak. I would expect the best odds for a sustained supercell, perhaps with one or more tornadoes, in northwest Kansas or southwest Nebraska, where the nose of the moist low-level return flow will wrap around a surface low beneath strong upper-level forcing. On the other side of this low, wind-whipped snow may create blizzard conditions by early Friday across parts of eastern Colorado just east of Denver.

Another round of storms is expected on Friday from eastern OK and TX into Arkansas and Louisiana. It remains to be seen how the leftover storms and cloud cover from Thursday night will affect the prospects for Friday. Again, the most likely outcome is a squall line with pockets of high wind and large hail. The best odds for any tornadic supercells may be toward the north end of the risk area, from southeast Kansas into northern Arkansas and southern Missouri, if enough unstable air can make it to this region. Low-level winds will be backing toward a south-southeast direction across this area, which should enhance wind shear. A modest severe threat should again emerge on Saturday, this time across Mississippi and Alabama, as the upper-level low and surface features continue sweeping eastward. As shown in Figure 1, NOAA/SPC’s Storm Prediction Center has slight risk areas in effect for Thursday, Friday, and Saturday, with the highest localized odds of severe weather at just 15% on each day. (Day 1 tornado odds are even lower, peaking at 2% along the dry line).

The next sequence of severe weather should kick off Sunday in deja-vu fashion across northern Texas and Oklahoma as a second upper-level low moves across, a bit weaker and further south than Thursday’s upper low. It’s not yet clear how much moisture will have returned by then, but a compact severe weather threat late Sunday is certainly possible—as suggested in SPC’s Day 4 outlook—perhaps expanding on Monday into the Mississippi Valley.

Two more upper-level lows are projected to move across the Southern Plains later next week. Models remain in disagreement on how these will evolve, but they may be even further south than their predecessors, so the most focused area for severe weather by that point could end up being Texas. Several bouts of heavy rain appear likely from parts of KS to TX and points east, which might not be a bad thing at all. This week’s U.S. Drought Monitor shows that drought conditions now cover 64% of the south-central U.S., up from 55% last week.

We’ll be back with a new post on Friday.

Bob Henson

Figure X. Total precipitation projected by the GFS model run from 06Z Thursday, March 23, 2017, for the 8-day period ending at 06Z (1:00 am EDT) Friday, March 31, 2017. The exact locations of heavy precipitation over the Southern Plains are likely to vary in subsequent model runs. Image credit:

Severe Weather

It’s Time to Give Air Quality the Attention It Deserves

By: Bob Henson , 3:20 PM GMT on March 22, 2017

Each day of every year, a quiet disaster unfolds in households and hospitals across the world. More than 10,000 lives are lost worldwide every 24 hours as a direct or indirect consequence of poor air quality. Bad air takes its toll quietly, with no need for the oversized drama of a hurricane or tornado. Sometimes air quality becomes so dangerous that it can’t be ignored. Much of the time, though, dangerous air goes about its dirty work with little attention from policymakers and the public.

The World Health Organization (WHO) has dubbed air pollution “the world’s largest single environmental health risk.” It is high time we treated the life-threatening aspects of dirty air, and the life-sustaining properties of a clean atmosphere, with the full appreciation they ought to have.

Figure 1. Los Angeles, CA, shrouded in late-afternoon smog as viewed from the Hollywood Hills. Griffith Observatory is at far left. Image credit: Diliff/Wikimedia Commons

Here at Weather Underground, we are taking steps in this direction by bringing air quality sensors into our 250,000-strong network of personal weather stations. We believe there is great power in being able to measure the quality of the air in one’s own neighborhood and to share that information with the world at large.  

We are also ramping up our coverage of air pollution issues here at Category 6. Along with occasional guest authors, Jeff Masters and I will be exploring the many facets of air quality, including its effects on people and ecosystems and how it intersects with both weather and climate. For example, Jeff will soon be posting an overview of the health hazards posed by poor air quality. This topic was highlighted on March 6 by a distressing report from the World Health Organization: Each year, respiratory infections linked to indoor and outdoor air pollution and second-hand smoke take the lives of some 570,000 children under the age of 5. That’s roughly 10% of all deaths in that age group each year.

Figure 2. Schoolchildren in Delhi, India, wore masks as schools re-opened on November 10, 2016, after three days of closure due to severe smog. Image credit: Sajjad Hussain/AFP/Getty Images.

For both children and adults, the air indoors can be just as dangerous as the air outdoors. Each year more than 4 million people die prematurely as a consequence of household air pollution—largely the result of inefficient, smoke-belching cookstoves that are used routinely in developing nations. This toll is even higher than the WHO’s estimate of 3 million premature deaths a year from outdoor air pollution.

Even the most pristine places can be touched by the global spread of air pollution. In Antarctica, scientists have found traces of lead trapped within ice cores. Using isotopes (variations in the number of neutrons within an element), researchers were able to track the heavy-metal pollution to industrial activity in Australia as far back as the late 1800s.

Today, as much as 25% of the sulfate and mercury pollution along the U.S. West Coast comes from emissions from coal-fired power plants in China. These pollutants take just five to eight days to cross the Pacific on the prevailing upper-level westerly winds.

Figure 3. Motorcyclists ride through thick smog on January 9, 2017, in Zhengzhou, China. The nation’s Central Meteorological Observatory issued a yellow alert for smog in Zhengzhou on Sunday night, January 8. Visibility dropped below 50 meters (160 feet) in parts of the city on Monday morning. Image credit: VCG/VCG via Getty Images.

What do we mean by clean air and dirty air?
Some pollutants are invisible and odorless, but you don’t always need highly precise instruments to tell you when the air is at its most polluted. Often you’ll see it, smell it, and even feel it in your lungs.

Observations do tell us a great deal about how air quality varies over time and across regions. The U.S. Environmental Protection Agency tracks six substances known as criteria air pollutants, meaning that the EPA has established criteria (National Ambient Air Quality Standards) for the safe and unsafe levels of these airborne substances. The six criteria air pollutants are:

•  Ground-level ozone
•  Carbon monoxide
•  Sulfur dioxide
•  Particulate matter
•  Lead
•  Nitrogen dioxide

All of these are proven health hazards. In many cases, the U.S. has made real progress in reducing their impact. For example, the amount of airborne lead in the United States and other nations has dropped drastically since the 1970s with the advent of unleaded gasoline. This may even be a key factor in reduced crime rates since the 1990s.

The two biggest airborne health concerns these days are ground-level ozone and particulate matter—especially the tiny particles known as PM2.5 (those that are less than 2.5 microns or 0.0001 inch in diameter).

Ozone is a boon to health when it’s in the stratosphere, because it shields us from harmful ultraviolet solar radiation. The problem is when certain fossil-fuel emissions react in the presence of sunlight to form ozone where we live. High levels of atmospheric ozone can cause our respiratory muscles to contract, irritating our body’s airways and aggravating conditions such as asthma and chronic bronchitis.
Particulates are even more insidious. Along with compromising the respiratory system, the tiniest particles (PM2.5) can also work their way into the bloodstream. This can elevate one’s risk for heart attacks and lead to a higher mortality risk among people with preexisting heart or lung problems.

Figure 4. Diagram showing the relative sizes of particulates compared with beach sand and human hair. Particles less than 2.5 microns (0.0001 inch) in diameter are the most dangerous. Image credit: U.S. Environmental Protection Agency.

New ways to track air quality through WU
Tracking the ups and downs of weather in your own neighborhood—through your own personal weather station or your neighbor’s PWS—has been a core part of WU since our earliest years. We’ve now embarked on a concerted effort to examine the growing options for consumer-level AQ measurement. One of our first goals is to find out which platforms offer the best mix of affordability and quality. As this process evolves, we’ll be sharing what we find so that our community can help build a new network of personal air quality stations.

We are also adding key air quality indexes to many of our “dashboard” pages, which summarize the data gathered at each personal weather station in our network. For example, we’ve recently added AQ data for around 1500 stations across North America that are part of the U.S. Environmental Protection Agency’s AirNow network. For each of these sites, the weather history graph now includes hourly levels of various criteria pollutants, depending on location (see example below).

AirNow stations are located in both large cities and more rural areas, including Minneapolis, MN; Provo, UT; and Washington, DC. AirNow stations vary in the types of meteorological and AQ data monitored.

Figure 5. Hourly measurements of PM10 (top, in micrograms per cubic meter) and ozone (bottom, in parts per billion) at station KCASACRA81 in downtown Sacramento, CA, on Friday, March 17, 2017.

When it comes to AQ forecasts, you can find an array of local health-related data and forecasts at the “Health” tab when you specify a city or town on WU’s desktop or mobile platforms (see example at bottom).

Watch this space
Between major cuts proposed to the U.S. Environmental Protection Agency and limited public access to air pollution data in other countries, it is more clear than ever that we cannot take air quality information for granted. WU intends to do its part by expanding our international network of personal weather stations into the realm of air quality.

We'd greatly appreciate knowing what features you'd like as we develop tools for accessing, mapping, and displaying AQ data for both desktop and mobile platforms. Please leave any suggestions as a comment on this post and our developers will collect your input. Watch for more news on this initiative later in the spring.

Bob Henson

Figure 6. A variety of health-related features can be accessed when you select “Health” beneath a city name on WU’s city pages. This health dashboard for Atlanta, GA, on Tuesday afternoon, March 21, 2017, showed that air quality was rated “moderate” for PM2.5 and was predicted to remain moderate on Wednesday. Pollen counts were running high for pine, oak, and birch trees.

Air and Water Pollution Wunderground News

The Extreme Temperature Index: Identifying Which Records are Most Significant

By: Guy Walton , 4:16 PM GMT on March 21, 2017

Our guest author today on Category 6 is Guy Walton, an independent meteorologist in Atlanta who spent more than 30 years as a forecaster at The Weather Channel. For more than a decade, Guy has kept detailed records on U.S. daily, monthly, and all-time record high and low temperatures across the United States. His efforts helped lead to NOAA’s establishment of its U.S. Records site. In 2009, Guy coauthored a high-profile paper in Geophysical Research Letters with lead author Gerald Meehl (National Center for Atmospheric Research), showing that U.S. daily record highs have increasingly outpaced daily record lows since the 1980s. Guy’s work can be found on Twitter (@climateguyw) and on his new website, Guy on Climate (not to be confused with an unrelated site called “Climate Guy”).

In 2007, when Bob Henson and I were first discussing the potential for a new climate study based on U.S. ratios of record surface highs to lows, we thought that it would be fantastic to engineer an index that would allow for ranking, rating, and comparing individual tallies.

Up to now, I’ve carried out my research without such an index. My most recent analysis uses record ratios to show that U.S. nights are actually warming faster than days, most likely due to carbon pollution interacting with moisture.

Studies like this one pit one tally of a set record against another. One problem that Bob and I recognized early on is that a report, or tally, of a surface record could be a tied record coming from a station with only a period of record (time that a station has been reporting reliable temperature measurements) of 30 years, or a report from a station with a period of record well over 100 years breaking an old record by several degrees. So we have been proverbially comparing apples to oranges.

Bob and I thought there ought to be some simple mathematical index taking into account variables hidden in those individual record tallies. The first two variables were obvious: (1) the period of record, or the length of time that regular observations have been collected at a given location, and (2) the difference (e.g., degrees Fahrenheit) between the old record and new. Bob also thought that the difference between the average maximum and minimum at each location on each given date is a factor and should be built into an algorithm or index. The name we came up with is the Extreme Temperature Index (ETI).

Figure 1. In the United States, record highs have outpaced record lows by an increasing margin since the 1980s. Shown here are the annual ratios of daily record highs to daily record lows for each year since the 1920s, when enough reliable data had accumulated to begin calculating such ratios. The only two years this century with more record lows than highs were 2013 and 2014. Image credit: Climate Central.

How the ETI works
Think about this: During the middle of the summer at Miami, FL, the average low is near 80°F while the average high is near 90°F, so the average diurnal temperature spread there is 10°F. Miami has a marine climate while Des Moines, IA, has a continental climate. The average low at Des Moines during that same midsummer day may be 60°F with a max near 85°F, or a spread of 25°F. Because of these differing spreads, it should be easier to exceed a record high or low by a margin as large as, say, 2°F in Des Moines versus Miami. Therefore, a useful ETI will generally weigh a statistical tally higher for a record set in a more marine environment than in a continental one, or at a lower-elevation site versus a higher-elevation one. These factors do not have to be explicitly added, though; they are incorporated automatically because of their influence on the average diurnal temperature spread.

Dr. Bruce Rose, a good colleague of mine at The Weather Channel for more than a decade, came up with an initial algorithm for the ETI:

γ = sign of record (-1 = record low, +1 = record high)
n = number of years of record keeping (period of record, or POR)
| ΔTγ | = magnitude of record, in degrees
TD = average diurnal temperature range on day of record, in degrees

The ETA would work in either degrees Celsius or Fahrenheit. The beta exponent, which could be used to calibrate the ETI for monthly and all-time records, can be neglected here.

Using some simple mathematics, one can see how the ETI might work. All else being equal, the ETI will increase as n, the period of record, increases. The ETI will also increase in line with the magnitude of the difference between an old record and a new one. And if the average diurnal range of temperature gets larger, then the ETI number gets smaller.
The following are a couple of examples from the hot summer of 2007 calculated from the ETI algorithm. The periods of record shown here are for specific reporting sites as of 2007, rather than for the two cities as a whole.

Tupelo, MS (TUP):
n = 44 (as of 2007)
record high = 103
previous record high = 101
normal diurnal range for date = 89/72
ETI = + [(1 - .023)(2 + 1)/17] x 10 = 1.72

Louisville, KY (SDF):
n = 59
record high = 105
previous record high = 100 (monthly record)
normal diurnal range for date = 86/68
ETI = + [(1 - .017)(5 + 1)/20] x 10 = 2.95

As shown, we get an ETI value that is greater for Louisville than in Tupelo. The daily record at Louisville (which also happens to be a monthly record) is clearly more significant than the daily record set in Tupelo.

An idea ready for research
By 2009, we had the framework for the ETI in hand, and off we went to do a scientific paper, right? Eh…wrong. All of us had competing priorities, and to be honest, I lack the mathematical and statistical skills to produce such a paper. I have brought the ETI concept to many individuals who love the idea of ranking records but who have also been too busy with other priorities to take on this project. So, if any graduate student or other individual wants to take a serious look at the viability of the Extreme Temperature Index, just contact me or Bob and you have our blessing.

The more direct way of judging a record hot or cold event is its standard deviation from average (also known as its sigma value). These can be evaluated locally or across a region. For example, the Russian heat wave event of 2010 was deemed a “three sigma” event, or a very rare hot event far outside of norms or averages. An interesting alternative way for ranking a heat wave, if enough long-term observations are present, would be to take all the deemed tallies of records of said event and put them through the ETI algorithm. The local results could be added and then divided by the number of tallies to produce a regionally averaged Extreme Temperature Index (ETI) for that heat wave. Such a method could allow climatologists to better compare events from different eras.

WU weather historian Christopher Burt and I have envisioned a great repository of surface records from the entire planet. Based on this dataset, each new record would have its own calculated ETI to help meteorologists and climatologists better compare cold or hot events. The U.S. Records site (NOAA/National Center for Environmental Information), where I get my tallies, is a good start. By using some sort of ETI, I believe it could be vastly enhanced.

Any serious work on the ETI could prove to be both a personal opportunity and beneficial to science. For those who are interested, have at it!

Guy Walton (The Climate Guy)

Figure 2. A young girl plays in the waterfall at The Yard Park in Washington, DC, on July 25, 2016 as a heat wave rolled across the area. Washington’s Reagan National Airport hit 100°F, with a low of 81°F. Both were records for July 25 in data for Washington going back to 1872. Image credit: Jim Watson/AFP/Getty Images.

Heat Extreme Weather

Tornado Risk Amping Up This Week and Beyond

By: Bob Henson , 4:31 PM GMT on March 20, 2017

Spring began in the Northern Hemisphere at 6:28 am EDT Monday, and the U.S. atmosphere seems to have gotten the memo. A multi-day stretch of severe weather should kick off by late Thursday or Friday. There are hints that the pattern will remain stormy off and on through next week, with upper-level energy expected to remain fairly progressive and the Gulf of Mexico supplying ample moisture.

Widespread damage from Southeast freeze
At least 90 percent of the peach crop in South Carolina (the nation’s top peach producer behind California, with a typical crop value of $90 million) was wiped out by freezing temperatures late last week, according to the state’s agriculture commissioner. The state’s wheat and corn fields also suffered heavy damage, reported WISTV. A less severe freeze in Georgia may have ruined anywhere from 25 to 75 percent of that state’s peach crop. Blueberries across the Southeast also experienced major damage, as summarized by Louisville, KY, broadcast meteorologist John Belski. It dropped to 25°F in Gainesville, FL, on Thursday morning, the coldest reading for so late in the year in more than a century of Gainesville records. Jacksonville’s 28°F was also a record for so late in the year. Update: Total crop losses in South Carolina and Georgia could approach $1 billion, according to an AP report filed Monday afternoon.

Fruit trees that budded and blossomed weeks ahead of schedule took a major hit across the mid-South during last week’s freeze. Temperatures that dipped to 21°F on Wednesday and 22°F on Thursday in Louisville spelled a hasty end to the city’s pear blossoms. “I have never seen the blooms go from white to brown while still on the trees,” Belski said.

In Washington, D.C., a large portion of the renowned Tidal Basin cherry blossoms were toasted by the deep freeze, but some of the less-developed buds (about half of the total, according to the National Park Service) apparently made it through. The survivors are now expected to transition quickly into peak bloom later this week, well ahead of the March 25 opening ceremony of the National Cherry Blossom Festival.

Figure 1. Visitors make their way through a deflating lineup of flash-frozen cherry blossoms in Washington, D.C.’s Tidal Basin on Saturday, March 18, 2017. Cold weather killed half of the blossoms on Washington's famous cherry trees just as they were approaching peak bloom. Image credit: AP Photo/Alex Brandon.

Major pattern shift will usher in severe weather
Marginally severe storms are possible across parts of Indiana and Illinois on Monday and the Tennessee Valley on Tuesday, as a spoke of energy rotates around a upper-level low sweeping through eastern Canada. The bigger event will come later this week as the upper-level pattern shifts back toward a Pacific-dominated regime. Several inches of rain and major mountain snows are headed for parts of California, Oregon, and Washington as one storm swings through on Tuesday/Wednesday and a stronger one around Friday/Saturday.

The first upper-level wave in this sequence will reach the Great Plains by late Thursday. Low-level moisture will be rapidly returning from the Gulf, but it’s not yet clear whether enough instability will be on hand to support severe weather. If there is, the focal point would be along a strong dryline expected to be over the High Plains of western KS/OK/TX by late Thursday. A more robust severe threat appears likely for Friday over eastern TX/OK into AR/LA, and on Saturday across parts of MS/AL/GA/FL, as the system marches east into more-unstable air. The NOAA/NWS Storm Prediction Center has outlined both regions with a 15% likelihood of severe weather for Friday and Saturday. I’d expect those odds to rise as the timing and locations become clearer through the week.

Figure 2. The 7-day precipitation forecast issued on Monday morning, March 20, 2017, reflects increased Pacific energy that is expected to generate heavy rain and mountain snow on the U.S. West Coast and fire off one or more rounds of severe weather across the Southern Plains and Southeast. Image credit: NOAA/NWS Weather Prediction Center.

The next multi-day round of severe weather will likely erupt with the second wave in the series, in tandem with the gradual establishment of a upper-level trough in the western U.S. Models are struggling with the evolution of these features, although recent runs of both the GFS and ECMWF models tend to agree on a pattern that would favor severe thunderstorms over the Southern Plains of TX/OK for at least a day or two early next week.

Wildfire also a threat this week; Boulder dodges a bullet
Fire danger may hit critical levels on Thursday and Friday as high winds and warm, dry air sweep across parts of NM/CO/TX as part of the first central U.S. storm. The landscape is drying quickly in this region following a very warm, dry February and early March. Moderate to severe drought now covers most of eastern CO, western KS, and northern OK, according to last week’s U.S. Drought Monitor.

After setting a record high of 80°F on Saturday, Boulder, CO, had a major scare on Sunday: a fire that erupted just west of town on Saturday night swelled to just over 100 acres before it was largely contained by late Sunday. More than 1000 people were under mandatory evacuation orders, and a pre-evacuation zone extended nearly to downtown. Nationwide, the 2.06 million acres burned in wildfires from January 1 to March 17 is by far the largest amount burned by mid-March in data going back to 2007.

Figure 3. Smoke rises from a wildfire on Sunday morning, March 19, 2017, near the west edge of Boulder, CO. Image credit: Seth Frankel via AP.

Extending severe weather outlooks to three weeks: Year 3
Meteorologists in a multi-institution effort based at the College of DuPage have embarked on their third year of providing generalized guidance on the likelihood of U.S. severe weather up to three weeks in advance. The Extended Range Tornado Activity Forecasts (ERTAF) are released each Monday, featuring outlooks for week 2 (the week beginning the following Monday) and week 3. For each forecast week, ERTAF indicates whether the likelihood of U.S. tornadoes is above, near, or below the climatological average, together with a confidence rating (high, medium, or low).

The technique is based on atmospheric angular momentum (AAM), which relates to the pace at which momentum imparted by Earth’s spin is being transferred to higher latitudes (see Figure 4 below). Gensini and colleagues employ an AAM-related index called the global wind oscillation (GWO), which is broken into eight phases similar to the daily Madden-Julian oscillation index. When AAM is relatively low, we’re more likely to see upper-level troughs in the U.S. West and ridging in the Southeast, a favorable setup for springtime severe weather.

Figure 4. Angular momentum is transferred from the tropics to midlatitudes as air rotating more quickly at the tropics (because of Earth’s larger diameter) ascends and then descends at midlatitudes, transferring momentum to the surface. Image credit: UCAR/COMET Program.

Gensini and colleague Alan Marinaro (Northern Illinois University) demonstrated the utility of their approach in a 2015 Monthly Weather Review paper. That same year, they introduced the ERTAF, which performed very well: 10 of 16 two-week outlooks, and 10 of 15 three-week outlooks, correctly specified whether activity would be above, below, or near the climatological norm for that week (with “normal” defined as between 75% and 125% of the weekly average number of tornadoes). The forecasts were a bit more challenging in 2016, but 6 of the 13 two-week outlooks and 5 of 12 three-week outlooks were on target, and only 4 of the 25 outlooks erred by more than 50% (e.g., by calling for above-average activity when below-average activity occurred, or vice versa). The ERTAF website includes all of the verification statistics for 2015, 2016, and 2017 thus far, based on SPC preliminary tornado totals.

For the week beginning March 26, ERTAF’s six forecasters are calling for an above-average likelihood of tornadoes with high confidence. “We all agreed week 2 is going to be above average. It was a slam dunk,” Gensini told me. The current week-3 outlook, valid April 2-8, is also for above-average activity but with low confidence. “At that range, we’re using primarily statistical analogs, but you only have the realm of what’s been historically observed. Week 2 is where we can couple the statistical and dynamical approach. In terms of subseasonal forecasting, this is really low-hanging fruit.”

Remembering Matt Parker
The U.S. meteorological enterprise suffered a major blow on Friday with the untimely loss of Matthew Parker (Savannah River National Laboratory), who died in his sleep on Wednesday night. Matt had just begun a one-year term in January as president of the American Meteorological Society. However, he had been heavily involved as president-elect in 2016 and was a key player in many other AMS activities before then. A native of Ohio, Matt spent more than 27 years at DOE’s Savannah River National Laboratory after completing his bachelor’s and master’s degrees at North Carolina State University.

I always enjoyed running into Matt at AMS annual meetings, though we never had a chance to work closely together. "He was not just a colleague but a close friend that has stayed in my family's home," said Dr. Marshall Shepherd, past-president of the AMS and host of The Weather Channel's WxGeeks, in a article by Jon Erdman. "He was as committed as anyone I know to the weather enterprise and bringing academia, government, and private sector together,” Shepard added.

“This is an enormous loss not just for the AMS family but for the entire scientific community,” said Keith Seitter, AMS Executive Director. “Matt was deeply admired for his commitment to the AMS community. He was a leader and a friend, and we will all miss him tremendously.” 

Succeeding Parker at the helm of AMS for the remainder of this year will be Dr. Roger Wakimoto (National Science Foundation), who was this year’s president-elect for 2018.

We’ll be back with a new post on Tuesday.

Bob Henson

Severe Weather Tornado Fire Winter Weather

February 2017: Earth's 2nd Warmest February and 4th Warmest Month in Recorded History

By: Jeff Masters , 4:07 PM GMT on March 17, 2017

February 2017 was the planet's second warmest February since record keeping began in 1880, said NOAA's National Centers for Environmental Information (NCEI) on Friday; NASA also rated February 2017 as the second warmest February on record. The only warmer February was just last year, in 2016. Remarkably, February 2017 ranked as the fourth warmest month (expressed as the departure of temperature from average) of any month in the global historical record in the NASA database, and was the seventh warmest month in NOAA’s database—despite coming just one month after the end of a 5-month long La Niña event, which acted to cool the globe slightly. The extreme warmth of January 2017 (tenth warmest month of any month in NASA’s database) and February 2017 (fourth warmest) gives 2017 a shot at becoming Earth’s fourth consecutive warmest year on record, if a moderate or stronger El Niño event were to develop by summer, as some models are predicting.

With the exception of last month, the top five warmest months on record since 1880 (expressed as departure from the 1951 - 1980 average) in the NASA database all occurred during the strong El Niño event of 2015 - 2016, which worked to raise global air temperatures by exporting heat from the oceans:

February 2016, 1.32°C above average
March 2016, 1.28°C above average
January 2016, 1.13°C above average
February 2017, 1.10°C above average
December 2015, 1.10°C above average

Global ocean temperatures last month were the second warmest on record for any February, as were global land temperatures. Global satellite-measured temperatures for the lowest 8 km of the atmosphere were the fourth warmest for any February in the 39-year record, according to the University of Alabama Huntsville (UAH).

Figure 1. Departure of temperature from average for February 2017, the 2nd warmest February for the globe since record keeping began in 1880. Warmer- to much-warmer-than-average conditions were present across much of the world's land surfaces, with the most notable warm temperature departures from average (3°C–5°C above the 1981–2010 average) across much of the contiguous U.S., southeastern Canada, and across much of central and eastern Russia. Record warmth was observed over parts of the eastern contiguous United States and northern and southern Mexico. Image credit: National Centers for Environmental Information (NCEI).

No billion-dollar weather disasters in February 2017; one so far in 2017
No billion-dollar weather-related disasters hit the Earth last month, according to the February 2017 Catastrophe Report from insurance broker Aon Benfield. However, a destructive tornado outbreak in the southern U.S. on January 21 - 23 accumulated enough damage claims to be rated a billion dollar weather-related disaster ($1.3 billion in damage) by the end of February, the only billion-dollar weather disaster on Earth during January - February 2017. The deadliest weather-related disaster of February was the rainy season flooding in the southern African country of Zimbabwe, which killed at least 246 people and cost over $100 million.

Figure 2. The only billion dollar weather-related disaster on Earth during January - February of 2017 was a destructive tornado outbreak in the southern U.S. on January 21 - 23 that killed 21 people and did $1.3 billion in damage. At least 79 tornadoes touched down between January 21 - 23, with three of them being rated EF3. These three EF3s were responsible for 20 of the 21 deaths in the outbreak. The deadliest tornado hit Adel, Georgia, killing 11 people. In this image, we see the William Carey University's School of Business on Saturday, Jan. 21, 2017, after it was damaged by a pre-dawn EF3 tornado that moved through Hattiesburg, MS, killing 4 people. Image credit: AP Photo/Rogelio V. Solis.

El Niño on its way?
In its early March monthly advisory, NOAA’s Climate Prediction Center (CPC) stated that neither El Niño nor La Niña conditions were present in the Eastern Pacific, and sea surface temperatures (SSTs) in the benchmark Niño 3.4 region (in the equatorial Pacific) were near average. SSTs of 0.5°C or more above average in this region are required to be classified as weak El Niño conditions. NOAA forecasters estimate an approximately 75% chance of neutral conditions lasting through the spring, with increasing chances of an El Niño after June (50 - 55% chance.) The latest Australian Bureau of Meteorology models are more aggressive about predicting El Niño, showing El Niño conditions by April (using NOAA's SST benchmark), and the latest June-July-August run of the UKMET model predicted a moderate El Niño this summer. However, predictions made in March of El Niño are of low skill, due to the so-called “spring predictability barrier”, and we should have lower-than-usual confidence in these forecasts. The GFS model is currently not predicting any “westerly wind bursts” of surface winds in the Western Pacific that would help along the development of El Niño during the next two weeks. El Niño conditions tend to suppress Atlantic hurricane activity by bringing strong upper-level winds to the tropical Atlantic, creating high wind shear that tears storms apart.

Figure 3. Sea surface temperatures (SSTs) in the benchmark Niño 3.4 region (in the equatorial Pacific) have been a few tenths of a degree above average since mid-February; SSTs of 0.5°C or more above average in this region are required to be classified as weak El Niño conditions. Image credit: Levi Cowan,

Arctic and Antarctic sea ice falls to lowest February extent on record
Arctic sea ice extent during February 2017 was the lowest in the 39-year satellite record, beating the record set in February 2016, according to the National Snow and Ice Data Center (NSIDC). The record low ice extent was due, in large part, to very warm air temperatures in the Arctic—temperatures at the 925 mb level (approximately 2,500 feet above sea level) were 2 - 5 degrees Celsius (4 - 9 degrees Fahrenheit) above average over the Arctic Ocean during February.

Sea ice has been exceptionally scant on the other end of the globe. Antarctic sea ice extent dropped below the lowest values recorded in any month in the satellite record by mid-February. They continued to sag until reaching a new record-low extent in early March.

Aging satellites for monitoring Arctic sea ice bring concern
In their March 6 monthly update, NSIDC sounded the alarm about a looming satellite gap that threatens the continuity of the 39-year satellite record of sea ice extent. After the 2016 failure of the F19 polar-orbiting satellite, there are just three satellites remaining that perform sea ice extent monitoring. These are the American F18 and F16 satellites, which are operating 2 and 8 years beyond their designed 5-year lifetimes, respectively, and the Japan Aerospace Exploration Agency (JAXA) Advanced Microwave Scanning Radiometer 2 (AMSR2), which will reach its 5-year design lifetime in May 2017. It is unlikely that a new sea ice extent monitoring satellite will be launched before 2022.

Notable global heat and cold marks set for February 2017
Hottest temperature in the Northern Hemisphere: 42.5°C (108.5°F) at Matam, Senegal, 27 February
Coldest temperature in the Northern Hemisphere: -58.0°C (-72.4°F) at Delyankir, Russia, 2 February
Hottest temperature in the Southern Hemisphere: 48.2°C (118.8°F) at Tarcoola, Australia, 9 February
Coldest temperature in the Southern Hemisphere: -58.8°C (-73.8°F) at Dome A, Antarctica, 28 February
(Courtesy of Maximiliano Herrera.)

Major weather stations that set (not tied) new all-time heat or cold records in February 2017
Kish Island (Iran) min. 7.6°C, 3 February
Jabel Jais (United Arab Emirates) min. -5.4°C,  3 February: New national record low for the United Arab Emirates (for uninhabited places)
Abu Samra (Qatar) min. 1.5°C,  5 February: New national record low for Qatar
Tromelin Island (French Southern Territories, France) max. 34.9°C,  8 and 10 February
Cilaos (Reunion Island, France) max. 30.5°C,  10 February
Oberon (Australia) max. 36.2°C,  10 February
Hillston (Australia) max. 46.1°C,  10 February increased to 47.2°C on 11 February
Applethorpe (Australia) max. 39.7°C,  11 February
Warwick (Australia) max. 42.2°C,  11 February
Wyalong (Australia) max. 46.3°C,  11 February
Peak Hill (NSW) (Australia) max. 46.0°C,  11 February
Condobolin (Australia) max. 46.9°C,  11 February
Nyngan (Australia) max. 47.4°C,  11 February
Guyra (Australia) max. 35.1°C,  11 February
Williamtown (Australia) max. 45.5°C,  11 February
Paterson (Australia) max. 47.0°C,  11 February
Cessnock (Australia) max. 46.8°C,  11 February
Singleton (Australia) max. 47.2°C,  11 February
Gulgong (Australia) max. 43.5°C,  11 February
Mudgee (Australia) max. 43.9°C,  11 February
Bathurst (Australia) max. 41.5°C,  11 February
Bathurst Airport (Australia) max. 42.1°C,  11 February
Katoomba (Australia) max. 37.7°C,  11 February
Orange (Australia) max. 40.1°C,  11 February
Dunedoo (Australia) max. 45.4°C,  11 February
Wellington (Australia) max. 45.0°C,  11 February
Parkes (Australia) max. 45.9°C,  11 February
Forbes (Australia) max. 46.7°C,  11 February
Dubbo (Australia) max. 46.1°C,  11 February
Goulburn (Australia) max. 41.2°C,  11 February
Young (Australia) max. 43.0°C,  11 February
Oakey (Australia) max. 42.1°C,  11 February, increased to 42.8°C on 12 February
Toowoomba (Australia) max. 39.5°C,  11 February, increased to 40.8°C on 12 February
Tenterfield (Australia) max. 38.9°C,  11 February, increased to 39.9°C on 12 February
Murrurundi (Australia) max. 42.0°C,  11 February, increased to 42.2°C on 12 February
Scone (Australia) max. 45.7°C,  11 February, increased to 46.5°C on 12 February
Gatton (Australia) max. 45.7°C,  12 February
Kingaroy (Australia) max. 41.6°C,  12 February
Injune (Australia) max. 44.2°C,  12 February
Tamworth (Australia) max. 45.9°C,  12 February
Armidale (Australia) max. 37.6°C,  12 February
Grafton (Australia) max. 46.3°C,  12 February
Casino (Australia) max. 45.7°C,  12 February
Kempsey (Australia) max. 46.7°C,  12 February
Yarras (Australia) max. 43.2°C,  12 February
Port Macquarie (Australia) max. 46.6°C,  12 February
Taree (Australia) max. 45.7°C,  12 February
Mangalore (India) max. 38.7°C,  15 February
Cocos Island Airport (Cocos Islands, Australia) max. 32.9°C,  23 February: New Territorial record high for Cocos Islands
Tacna Airport (Peru) max. 33.2°C,  26 February

(Courtesy of Maximiliano Herrera.)

One all-time national heat record and two all-time national cold records set in February 2017
One territory set an all-time record for hottest temperature in recorded history in February 2017: Australia’s Cocos Islands. Two nations set all-time national cold records last month: United Arab Emirates (for an uninhabited place), and Qatar. Most nations do not maintain official databases of extreme temperature records, so the national temperature records reported here are in many cases not official. I use as my source for international weather records researcher Maximiliano Herrera, one of the world's top climatologists, who maintains a comprehensive list of extreme temperature records for every nation in the world on his website. If you reproduce this list of extremes, please cite Maximiliano Herrera as the primary source of the weather records. So far in 2017, we have two all-time national heat records and two all-time national cold records.

All-time national heat records set in 2017:
Chile: 113°F (45.0°C), 26 January
Cocos Islands: (Australia): 91.2°F (32.9°C),  23 February

All-time national cold records set in 2017:
United Arab Emirates: Jabel Jais, 22.3°F (-5.4°C),  3 February
Qatar: Abu Samra, 34.7°F (1.5°C),  5 February

Have a great weekend, everyone!

Jeff Masters

Climate Summaries

March Madness: Trump Proposes 31% Cut to EPA and Big Cuts to Climate Change Programs

By: Jeff Masters , 4:01 PM GMT on March 16, 2017

President Trump’s first proposed budget was released on Thursday, and recommends maddening cuts to programs and agencies responsible for ensuring the health of Americans and for understanding and combating climate change. Among larger U.S. agencies, the biggest cuts come to the EPA, which would see its $8.1 billion budget slashed by over 31%, and layoffs hitting about 3,200 of the agency’s 15,000 workers. This would be the biggest cut in EPA since the 35% reduction that the agency endured in 1981, the first year of the Reagan presidency. The EPA’s budget peaked in 2010, at $10.3 billion. The proposed EPA budget eliminates funding for the Clean Power Plan—America’s chief effort to reduce greenhouse gas emissions under the 2015 Paris Climate Agreement—and cuts international climate change programs, climate change research, and partnership programs, at a savings of over $100 million. Other cuts include:

$330 million to the Superfund toxic clean-up program (30% cut)
$129 million cut to enforcement efforts (24% cut)
$233 million cut to research and development (47% cut)
$300 million cut to Great Lakes Restoration Initiative (100% cut)
$73 million cut to Chesapeake Bay restoration (100% cut)
Energy Star energy efficiency program (100% cut)

Figure 1. The proposed cuts to the EPA do not reflect public sentiment; Americans support the EPA’s efforts to protect clean air, clean water, and the environment. A January 2017 poll by Reuters found that 39 percent of Americans would like to see the EPA "strengthened or expanded," 22 percent wanted it to "remain the same," and just 19 percent said they would like to see the agency "weakened or eliminated.” The rest said they "don't know." Image credit: John Mashey,

NASA climate science and education receive a major hit
NASA climate change and education programs have significant proposed cuts. Total elimination of the $115 million Office of Eduction was proposed, which includes camps and enrichment programs, internships and scholarships for young scientists, and support for women and underrepresented minorities in science, technology, engineering and math (STEM) fields. NASA’s Earth-science budget received a $102 million cut—5 percent of the program’s annual budget, including money for four satellites intended to study climate change:

PACE, intended to better understand how aerosol particles and clouds influence climate change
Orbiting Carbon ­Observatory (OCO-3)
Deep Space Climate Observatory, which will no longer use its Earth-facing cameras to monitor ozone, deforestation, and weather
CLARREO Pathfinder, which measures heat in Earth’s atmosphere

State Department cuts target Paris Climate Agreement promises
A significant commitment was made by the U.S. as part of the 2015 Paris Climate Accord: a $3 billion contribution to the Green Climate Fund, which assists developing countries in adaptation and mitigation practices to counter climate change. Obama already sent $1 billion of this promised amount, but Trump’s budget cuts the other $2 billion. Other nations may significantly scale back their commitments to cut greenhouse gas emission after seeing the U.S. renege on its Paris Climate Agreement promises.

Department of Energy sees clean energy cuts
Trump is proposing a 5.6 percent cut to the Department of Energy, including a sharp 17.9 percent cut to core energy and science programs intended to accelerate the transition to new clean energy technologies.

NOAA weather programs escape the ax
The proposed budget for NOAA does not have major cuts to weather programs, although grants and programs supporting coastal and marine management, research, and education—including Sea Grant, which helps coastal communities adapt to a climate change—are entirely eliminated. Here is what the proposed budget had to say about NOAA:

• Zeroes out over $250 million in targeted National Oceanic and Atmospheric Administration (NOAA) grants and programs supporting coastal and marine management, research, and education including Sea Grant, which primarily benefit industry and state and local stakeholders. These programs are a lower priority than core functions maintained in the budget such as surveys, charting, and fisheries management.

• Maintains the development of NOAA’s current generation of polar orbiting and geostationary weather satellites, allowing the Joint Polar Satellite System and Geostationary Operational Environmental Satellite programs to remain on schedule in order to provide forecasters with critical weather data to help protect life and property.

• Achieves annual savings from NOAA’s Polar Follow On satellite program from the current program of record by better rejecting [sic.] the actual risk of a gap in polar satellite coverage, and provides additional opportunities to improve robustness of the low earth orbit satellite architecture by expanding the utilization of commercially provided data to improve weather models.

• Maintains National Weather Service forecasting capabilities by investing more than $1 billion while continuing to promote efficient and effective operations.

Trump to drop climate change from environmental reviews, source says, March 14 Bloomberg article

The EPA Used to Tweet About the Environment. Now It Just Tweets About Scott Pruitt, March 14 article from Mother Jones, that says “The EPA hasn't mentioned climate change once since Trump became president.”

Group of 17 Republicans sign US House resolution to fight climate change, March 14 Reuters article

Trump’s war on EPA regulations will kill jobs and a lot of people: Clean air and water standards create jobs, spur innovation, and save lives (January 25 post by Joe Romm of ThinkProgress.)

A Lesson Trump and the E.P.A. Should Heed, March 7, 2017 editorial by Reagan’s head of the EPA, William D. Ruckelshaus.

Take action!
At at time when we should be dramatically increasing our funding and commitment to combating and researching climate change, President Trump’s proposed budget moves us sharply in the opposite direction. In May, the White House will provide more specific line-by-line detail on the proposed cuts, and then it will be up to Congress to decide the final numbers. If you’re not in the 19% of Americans who believe EPA should have their budget cut, I encourage you to contact your House Representative and Senators to let them know that you want to see EPA’s budget held the same or increased.

Contact your House Representative
Contact your Senator

Jeff Masters

Climate Change Politics

Inland Northeast Gets Record-Burying Snow

By: Bob Henson , 4:40 PM GMT on March 15, 2017

If the millions of people living along the I-95 corridor were situated just 100 miles northwest, they’d be digging out on Wednesday from one of their biggest March storms in decades. Instead, the big coastal cities came out of Tuesday’s storm with relatively little impact, while many points inland are still buried.

There was no second-guessing the intensity of the fast-hitting storm, dubbed Stella by The Weather Channel. Surface pressures dropped at incredible rates downstream of the surface low (see Figure 2 below), on par with pressure drops observed with some hurricanes. The quick intensification led to very strong winds, especially along the New England coast. On Cape Cod, Wellfleet, MA, gusted to 79 mph, and widespread gusts to 50-70 mph knocked out power to more than 50,000 customers in northeast Massachusetts. At the storm crescendoed around 6:00 pm EST Tuesday, Boston’s Logan International Airport was enduring northeast winds of 46 mph gusting to 56 mph, with mixed rain and snow and a temperature of 37°F.

Figure 1. People watch as waves crash over the seawall along Lynn Shore Drive as Stella bears down on Lynn, MA, on Tuesday, March 14, 2017. Image credit: Photo by Scott Eisen/Getty Images.

Figure 2. The NY State Mesonet station at Southold, on the north fork of Long Island, experienced a pressure drop of more than 50 millibars (maroon line on right side of image) in less than 36 hours, with pressures dropping at a rate of roughly 15 mb per 3 hours as Stella approached on Tuesday afternoon, March 14, 2017. Image credit: New York State Mesonet.

Figure 3. The intense surface low associated with Winter Storm Stella (979 mb) was located at the eastern tip of Long Island at 2100Z (4:00 pm EST) Tuesday, March 14. Two-hour pressure falls (blue dashed lines) were analyzed at greater than 9 mb near the coast of Maine ahead of Stella. Image credit: NOAA/NWS Storm Prediction Center.

Putting the semi-bust into context
Meteorologists were frequent interviewees on Tuesday, explaining why a small shift inland of the rain/snow transition zone had such big consequences on the outcome from Washington to Boston. Probabilistic graphics issued by several National Weather Service offices had amply highlighted the large uncertainties. In some cases, when it became more apparent a given spot would be located very near the transition zone, the probabilistic uncertainties actually grew. One such graphic on Monday night showed that there was a 10% chance that New York’s John F. Kennedy International Airport would receive 1” or less, and a 10% chance that it would get 21” or more! Overall, the snowfall amounts in the major East Coast cities came in on the low side of the probabilistic ranges, though in some cases they were below the “expect at least this much” (the lowest 10% range).

The main complication was a slice of warm air several thousand feet thick that was pulled onshore northeast of the fast-strengthening low a bit more strongly than expected. This meant a changeover from snow to a messy mix of sleet, freezing rain, and snow in some of the most heavily populated areas—very unpleasant, but not truly crippling.

Cliff Mass, a professor at the University of Washington, labeled the event “Slushmaggeddon.” He noted that with this storm, heavy precipitation occurred just as expected, even in the big cities, but the form of that precipitation was different than many had expected. In other storms, the big uncertainty isn’t with the type of precipitation but the amounts: the edge of heavy snow can shift just outside of an urban area, leaving the city with much less than expected, as occurred in New York City in January 2015. “Both were difficult forecasts with a large gradient of snow,” said Mass in an email.

Snow and sleet totals along the I-95 corridor included:

2.0” Washington (Reagan National)
5.6” Washington (Dulles)
2.5” Baltimore, MD
6.0” Philadelphia, PA
7.3” Newark, NJ
7.4” New York (LaGuardia)
5.1” New York (JFK)
3.3” Providence, RI
6.6” Boston, MA

You don’t have to go far inland to find much bigger amounts. For example:

14.4” Worcester, MA (50 miles west of Boston)
15.8” Hartford, CT (75 miles west of Providence)

Figure 4. The strong gradient in snowfall amounts near the East Coast is evident in this map of preliminary snowfall totals across southern New England as of 9:00 pm EDT Tuesday, March 14, 2017. Image credit: NWS/Taunton, MA.

Figure 5. A horse and buggy drive through the snow on Tuesday, March 14, 2017, in Gap, PA. Image credit: AP Photo/Matt Slocum.

Snow-prone Binghamton gets its heaviest 1-day snowstorm on record
Stella’s heaviest snows extended from the Poconos of Pennsylvania across eastern New York and into western Vermont. The large domed portion of the Hutton Sports and Recreation Center at Utica College collapsed on Tuesday night around 7:30 pm EDT (see photos at bottom). Fortunately, the campus was on spring break, and the sports complex had been closed around 2:00 pm, according to a statement from the college. A trained spotter at West Winfield, NY, just south of Utica, reported 42”, and 36” was reported from nearby Ilion, NY.

Some other noteworthy totals:

Binghamton, NY, notched its heaviest-ever 24-hour snowfall with a phenomenal 31.3”, far eclipsing the previous 23” record from Feb. 3-4, 1961. Moreover, all but 0.1” of the snow fell between midnight Monday night and midnight Tuesday night, making for a calendar-day total of 31.2” that smashes the previous calendar-day record of 21.0” from Feb. 19, 1972. Records in Binghamton don’t go back terribly far: only to 1951.

Albany, NY, racked up a storm total of 17”, all falling on Tuesday, which ties for the city’s eighth biggest calendar-day snowfall on record. Five of the other eight top calendar-day snows in Albany history occurred in March. Records began way back in 1884.

Burlington, VT, received 29.6” in the 27-hour period from 9:00 am EDT Tuesday to noon Wednesday, with light snow still falling. This makes it at least Burlington’s third heaviest snow on record, behind 33.1” (Jan. 2-3, 2010) and 29.8” (Dec. 25-28, 1969). Records go back to 1893.

Figure 6. The Binghamton office of the National Weather Service is draped in the city's heaviest snowfall on record early Wednesday, March 15, 2017. Image credit: NWS/Binghamton.

Multiday freeze could be a costly event for Southern growers
Freezing temperatures covered much of the southeastern U.S. on Wednesday, and an even more widespread freeze is likely on Thursday morning. Lows on Wednesday AM included 28°F at the NWS/Atlanta office in Peachtree City and 31°F in Augusta, GA.

A hard freeze warning is in effect for inland northeast Florida and southeast Georgia, where lows are expected to reach the 25°F to 30°F range for several hours, well below record lows for the date. Temperatures may briefly dip below freezing as far southeast as Ocala and St. Augustine, FL. Anything below 29°F in Jacksonville would be the city’s latest-ever temperature so low in records going back to 1871. As we discussed in Tuesday’s post, a widespread hard freeze could have especially large impacts this year because of extremely mild late-winter weather that’s put spring vegetation (including fruit crops) several weeks ahead of schedule.

We’ll be back with our next post by Thursday at the latest.

Bob Henson

Winter Weather

Big Cities Largely Spared by Northeast Storm; Huge Totals Piling Up Inland

By: Bob Henson and Jeff Masters , 5:30 PM GMT on March 14, 2017

Even though Tuesday’s much-anticipated storm (dubbed Stella by The Weather Channel) was producing more of an icy mess than a winter wonderland along the corridor from Washington, D.C., to New York, it wouldn’t be entirely fair to call it a bust. Power outages were piling up quickly at midday Tuesday throughout the region as fierce winds battered the area, gusting well above 40 mph along the coast from New Jersey to Massachusetts. Precipitation has been very intense, just as expected, and you don’t have to go far inland from the Interstate 95 corridor to encounter extreme snowfall.

Mount Pocono, PA, had received 23.0” of snow as of 11 am EDT Tuesday, and Endwell, NY, just west of Binghamton, had racked up 18.3” as of 10 am. Highland Lakes, NJ—only about 30 miles northwest of Manhattan—reported 14.5” as of 10:25 am, with an astounding 4.5” of snow reportedly falling in just one hour.

Figure 1. The Weather Channel's Jen Carfagno reports on Winter Storm Stella from the Tidal Basin in Washington, D.C. on Tuesday, March 14, 2017. (Kevin Wolf/AP Images for The Weather Channel)

Conditions were already improving in the Washington area at noon Tuesday, according to Capital Weather Gang. Snow totals in the District have been fairly underwhelming, around 2” - 3”, although the White House CoCoRaHS station reported a healthy 2.34” of liquid equivalent.

Near I-95 in Pennsylvania, the snow turned to freezing rain and sleet early Tuesday morning. The National Weather Service office in Philadelphia relayed several reports of 1/4” ice accumulations (“…what could have been snow,” the office pointed out). Snowfall in the Philadelphia metro area was generally in the 3” - 4” range as of late Tuesday AM.

While more than a foot had fallen by midday across New York City’s northern suburbs, Central Park had received only 4” as of 8:00 am EDT, with lighter snowfall reported after that point. Further upstate, far eastern New York and western New England were on track to get very heavy snow toward Tuesday afternoon and evening. As of 10:40 am EDT, the most likely totals predicted by the NWS/Albany office include 18” - 24” in the Albany area and 24” - 30” in far southern Vermont.

Figure 2 People struggle to walk in heavy windblown snow on Tuesday, March 14, 2017, in Boston. Image credit: AP Photo/Michael Dwyer.

After a quick burst of snow Tuesday morning, southeast New England will be experiencing mostly rain as a wedge of warmer air surges into the region. Boston will be on the knife edge of the snow/rain transition zone, which makes the ultimate snow totals there very hard to call. “Snow accumulations are quite difficult [to predict] across eastern New England because of the extreme snowfall rates likely at the time of the changeover,” explained the Boston-area NWS office. “Being off by an hour or two on the changeover will have huge implications.”

Most of Maine should stay on the snowy side of the developing coastal front, although a changeover could occur along the mid-Maine coast as the intense surface low moves nearby. Portland, ME, may end up in the running with Albany, NY, for the heaviest accumulations in a sizable Northeastern city, with as much as 18” possible.

Figure 3. Observed water levels above MLLW (mean low low water) at Atlantic City, New Jersey, on March 13-14, 2017. The MLLW level (red trace) peaked at 7.8 feet above MLLW at 9:18 am EDT Tuesday morning, March 14. This corresponded to a peak storm tide (the height of water above the high-tide mark, or the difference between the red and blue traces) of 3.40 feet. Image credit: NOAA TIdes and Currents.

A modest coastal flooding threat by nor’easter standards
The exceptionally strong winds of Stella drove a storm surge of 1 - 3.5 feet on Tuesday morning along the coasts of Virginia, Maryland, Delaware, New Jersey, and New York. The most notable storm surge occurred at Atlantic City, New Jersey, where the storm tide (the height of the water above the high tide mark) reached 3.40 feet—placing it #9 in the top ten list of highest water levels on record for the city. (The previous tenth-highest water level in Atlantic City's recorded history was 3.24’, set during last year’s nor’easter on January 23, 2016; the highest was 4.38’ during the December 11, 1992 nor’easter.) Tuesday morning’s storm surge caused moderate flooding, shutting down Route 322 and smaller streets in West Atlantic City, and was just 0.2’ short of the major flooding threshold, according to

As of this writing, the peak storm surge and storm tides had yet to occur along the coasts of Connecticut, eastern New York, Rhode Island, Maine, New Hampshire and Massachusetts; mostly minor coastal flooding is expected, with a few pockets of moderate flooding, due to the relatively rapid motion of the storm across the area. Slow-moving nor’easters are a much bigger coastal flooding threat, since the wind has more time to pile large amounts of water up against the coast. The main concern for coastal flooding will come during the early Tuesday afternoon high tide cycle, when the strong winds of the storm will coincide with high waters from a higher-than-usual high tide, due to the full moon that occurred on Sunday. Wave heights on the ocean waters off the coast of Rhode Island are forecast to range from 11 to 16 feet, causing considerable beach erosion.

According to the NOAA Quicklook Tides and Currents page for Stella, the following approximate peak storm surges (height of the water above normal) and storm tides (height of the water above the high tide mark) were observed on Tuesday morning:

Chesapeake Bay Bridge Tunnel, VA: 2.0’ storm surge, 0.2’ storm tide (peak storm surge occurred near low tide, so a relatively low peak storm tide occurred)
Ocean City Inlet, MD: 1.3’ storm surge, 0.8’ storm tide
Lewes, DE: 2.7’ storm surge, 2.1’ storm tide
Cape May, NJ: 2.5’ storm surge, 2.0’ storm tide
Atlantic City, NJ: 3.4’ storm surge, 3.19’ storm tide (Peak surge occurred near the time of high tide)
Sandy Hook, NJ: 3.5’ storm surge, 2.65’ storm tide
The Battery, New York City, NY: 3.0’ storm surge, 2.57’ storm tide

Figure 4. Freeze warnings (dark purple) occupied a huge swath of the east-central U.S., from southern Missouri to South Carolina, as of Tuesday morning, March 14, 2017. Image credit: NOAA/NWS.

Freeze damage a significant threat this week
A moderately cold air mass for mid-March could have outsized impacts on vegetation in the eastern U.S. this week, given that the cold blast is arriving on the heels of a remarkably warm late winter. Crops and landscapes have been budding, greening, and blossoming several weeks ahead of their usual pace across most of the eastern U.S., so the impact of this week’s expected freeze will be more akin to getting such a cold shot in early April. Temperatures may dip below 25°F as far south as Atlanta on Wednesday morning.

“The greatest risk of the late-season deep freeze in the Southeast will clearly be to the agricultural and farming sector,” said Steve Bowen (Aon Benfield) in an email on Tuesday. “Following such a warm winter, many farms have been reporting earlier-than-normal blooms for some crops (fruit crops in particular). If temperatures fall as much as currently forecast, and stay cold for consecutive days, there could be many millions of dollars of damage from lost crops. The dollar amount will ultimately depend on how cold it actually gets, of course. Even a few degrees in either direction could make a huge difference in financial cost.”

The beloved cherry blossoms of Washington, D.C., were on a record-early pace before this week’s cold and snow. The peak bloom in D.C.’s Tidal Basin is now expected between March 19 and 22, according to the National Park Service—still quite early by historical standards—although the quality of the display we can expect is now in question.

Bob Henson

Figure 5. Temperatures predicted by the 12Z Tuesday run of the GFS model for 8:00 am EDT Wednesday, March 15, 2017. Overnight lows could be several degrees lower than these values. Image credit:

Winter Weather

All Eyes on East Coast as Big Snowmaker Looms for Tuesday

By: Bob Henson and Jeff Masters , 5:30 PM GMT on March 13, 2017

A classic late-season nor’easter has all the ingredients to produce what could be near-record-heavy March snow and dangerously strong winds in coastal cities from Washington, D.C., to Boston, and onward into southeast Canada. But if the devil were ever in the details, it’s right now. The dividing line between rain and snow in this storm, dubbed Stella by The Weather Channel, will be close enough to the Interstate 95 corridor to keep forecasters sweating. Right now it appears that the meteorological bounty will be mainly in the form of snow for the big East Coast cities. However, just a minor shift in track could bring rain or sleet into the metropolitan areas, at least for a brief period.

There’s no doubt that a big storm is in the cards. Upper-level energy from two sources—a large trough swinging across the Midwest and an upper-level wave at the base of this trough over the Southern Plains—will be joining forces along the East Coast by Tuesday. The interplay between these two factors is just one of the elements of uncertainty on the table.

What’s clear is that a surface low off the central Gulf Coast on Monday morning will begin to strengthen near the Outer Banks Monday night, then rapidly intensify as it moves northeast along and/or just off the East Coast through the day on Tuesday. As shown in Figure 1 below, the 12Z Monday run of the GFS model deepens the low 23 millibars in 24 hours, from 2:00 am EDT Tuesday to 2:00 am Wednesday, as it moves from near Cape Hatteras, NC (1000 mb), to the central coast of Maine (977 mb). This would bring the low very close to the official definition of a meteorological “bomb”—a midlatitude low that deepens at least 24 millibars in 24 hours.

Figure 1. The surface low associated with Winter Storm Stella will deepen very rapidly as it progresses from offshore Delaware to Maine from 2:00 am EDT Tuesday, March 14, to 2:00 am EDT Wednesday. Colors depict the altitude, in tens of meters, of the 500-millibar surface, corresponding to the upper-level low digging sharply into the East Coast and supporting the strengthening of the surface low. Image credit:

Snow lovers will be delighted to hear that Monday morning’s models are leaning toward a storm track just far enough offshore to keep the big cities mainly in the snow camp, especially north of Washington. This had been thrown into some doubt on Sunday night, when the major models began inching the system just far enough toward the coast to raise the odds of rain or sleet nudging into the urban corridor, especially Washington and Boston. There is still room for the models to swing a bit eastward or westward before the storm arrives, though.

Regardless of precipitation type, this storm’s intensity and rapid development will make it a formidable wind producer. Where it snows heavily, downed trees and power lines could jeopardize electricity and transportation for an extended period. Tuesday morning will be an especially tough point: we can expect at least some major airports to be closed, and highway travel will be extremely unpleasant where it’s not impossible. Blizzard warnings are in effects from northern New Jersey across the New York metro area and western/central Long Island into southern Connecticut. Winds gusts of up to 55 mph are expected on Tuesday, especially near the coast.

Figure 2. Snowfall totals projected by The Weather Company/IBM's Deep Thunder model (formerly known as RPM) for the period from 8:00 am EDT Monday, March 13, through 7:00 pm EDT Tuesday, March 14. "It does look like eastern PA through northern NJ and into central upstate NY will be the 'jackpot' zone," said Michael Ventrice (TWC). Image credit: The Weather Company, An IBM Business.

Outlooks for some major cities

Washington: The forecast remains especially tricky for D.C., not only because the rain/snow transition line will angle from southeast to northeast very close to the metro area, but also because the storm’s heaviest precipitation rates will kick in from D.C. northeastward. This leaves Washington on the edge of two transition zones sitting at right angles. It’s quite possible that a slice of warmer air will wrap toward the D.C. area ahead of the fast-strengthening surface low, bringing a period of rain and/or sleet near or into the city. On the other hand, the storm’s heaviest precipitation will hit the District in the early morning hours Tuesday, a time frame that will maximize the odds of accumulating snow (which would be tougher to accomplish at midday this late in the season).

The probabilistic NWS guidance posted at 8 am EDT Monday morning gave the District as little as 3” or as much as 13” of snow, with best odds of around 5”. Capital Weather Gang was slightly more pessimistic in its outlook issued just before noon EDT Monday, giving the northwest part of the District best odds of 3” - 7” but deeming 1” - 4” most likely in the southeast District. “We have bumped down snowfall totals in the immediate metro area for the second time in the last 12 hours as the likely storm track has shifted closer to the coast, which will draw in more mild air,” wrote CWG’s Jason Samenow.

New York: The New York City area is just far enough northwest of the expected storm track to give it the best odds among the I-95 cities of avoiding a changeover to rain during the storm. Some of the very heaviest snow could be within 100 miles of the city, especially across northern New Jersey into central Connecticut and perhaps extending into the metro area as well. The probabilistic snow outlook for New York, issued by the city’s National Weather Service office at 6:00 am EDT Monday morning, pegged the most likely snowfall amount for New York City at a very impressive 20”, with a reasonable chance of as little as 11” or as much as 23”.

Boston: Snow totals are more likely to be higher in Boston than in D.C., but again there’s the chance here that warm air wrapping around the nearby surface low will work its way near or into the city. “This will cut into snowfall totals,” tweeted meteorologist Michael Ventrice at The Weather Company (@MJVentrice), pointing to output from TWC’s Deep Thunder model. “If this changeover happens, it would be just for 1-2 hours, then flip back to snow as the low pulls away,” he added. The 11:30 am EDT briefing from NWS/Boston did not include the type of probabilistic guidance noted above for Washington and New York, but it showed an expected range of 12” - 18” for Boston.

Figure 3. The rapidly strengthening surface low associated with Winter Storm Stella will be located just east of the Delmarva Peninsula at 8:00 am EDT Tuesday, March 14, 2017, according to the 12Z Monday run of the GFS model. Precipitation amounts shown are for the six-hour period ending at 8:00 am EDT Tuesday. The rain-snow dividing line evident near Washington, D.C., could end up further northwest or southeast, and the transition zone will move northeastward over time. Image credit:

What might be Stella’s place in history?
“Nail biter!” said NOAA’s Paul Kocin when I asked him for his take on the storm just after noon on Monday. Kocin is coauthor with NWS director Louis Uccellini of the definitive reference book “Northeast Snowstorms.” “As you can tell, this is a nightmare to forecast, with the rain/sleet/snow transition region right near the big cities,” he added. Northwest of the urban corridor, it’s not so tough, Kocin said: “Easy for Allentown, Poughkeepsie, Hartford, etc.”

There is certainly the potential for Stella to go down in the record books among the bigger March storms in Northeast history. The two greatest March storms on record for the region as a whole are the Great Blizzard of 1888 and the 1993 Storm of the Century, both of which we discussed in our Friday post. Below are the top three March snowstorms for the three cities discussed above.

12.0”: March 27-28, 1891
11.5”: March 28-29, 1942
10.7”: March 7-8, 1941

New York
21”: March 12-14, 1888
18.1”: March 7-8, 1941
14.5”: March 3-4, 1960, and March 1-2, 1914

25.4”: March 31–April 1, 1997
19.8”: March 3-5, 1960
15.5”: March 3-5, 1981

A modest coastal flooding threat by nor’easter standards
The exceptionally strong winds of Stella will drive a peak storm surge of 1 - 3 feet on Tuesday along much of the coast of Delaware, New Jersey, New York, Connecticut, and Massachusetts, including Cape Cod and the islands. The main concern for coastal flooding will come Tuesday during the late morning/early afternoon high tide cycle, when the strong winds of the storm will coincide with high waters from a higher-than-usual high tide, due to the full moon that occurred on Sunday. The highest storm tides are expected in western Long Island Sound, where the peak storm surge is expected about two hours after high tide early Tuesday afternoon. Wave heights on the ocean waters off the coast are forecast to range from 12 to 18 feet, with breaking waves of 6 to 10 feet at the shore, especially along the Atlantic-facing Delaware and Jersey beaches.

The waves and storm surge will cause significant coastal erosion. However, only minor to moderate coastal flooding is expected, due to the relatively rapid motion of the storm across the area. Slow-moving nor’easters are a much bigger coastal flooding threat, since the wind has more time to pile large amounts of water up against the coast. According to Monday morning run of the experimental NOAA Extratropical Storm Surge Model, these are the peak storm surge (height of the water above normal) and storm tide (height of the water above the high tide mark) expected on Tuesday along the coast:

Boston, MA: 2.6’ storm surge, 0.7’ storm tide (peak storm surge occurs at low tide, so a relatively low peak storm tide occurs)
Bridgeport, CT: 3.0’ storm surge, 1.5’ storm tide
King’s Point, NY (east side of NYC): 3.5’ storm surge, 2.5’ storm tide
The Battery, NY: 2.3’ storm surge, 1.4’ storm tide
Sandy Hook, NJ: 2.6’ storm surge, 1.6’ storm tide
Atlantic City, NJ: 2.1’ storm surge, 1.6’ storm tide
Lewes, DE: 2.1’ storm surge, 1.3’ storm tide

In advance of Stella, a dramatic Great Lakes low
A compact area of low pressure called a mesovortex developed over southern Lake Michigan on Sunday, March 12, associated with the strong upper-level trough that will help intensify Winter Storm Stella on Tuesday. Below is a remarkable loop of preliminary, non-operational imagery from the new GOES-16 satellite (animation courtesy NWS/Marquette). See the CIMSS Satellite Blog for more on this feature.

We'll be back with a new post on Tuesday.

Bob Henson and Jeff Masters

Winter Weather

EPA Chief Denies Basic Climate Science

By: Jeff Masters , 9:27 PM GMT on March 10, 2017

Scott Pruitt, the head of the Environmental Protection Agency (EPA), said on Thursday that carbon dioxide was not a primary contributor to global warming. On CNBC’s “Squawk Box”, Mr. Pruitt was asked, “Do you believe that it’s been proven that CO2 is the primary control knob for climate?” His response was: “I think that measuring with precision human activity on the climate is something very challenging to do and there’s tremendous disagreement about the degree of impact, so, no, I would not agree that it’s a primary contributor to the global warming that we see.” This view denies fundamental climate science as expressed on the EPA website and summarized by the 2013 report by Intergovernmental Panel on Climate Change (IPCC), which found that it is “extremely likely” that more than half the global warming that occurred from 1951 to 2010 was a consequence of human emissions of carbon dioxide and other greenhouse gases, and that their best estimate was that all of the warming after 1950 was due to human causes. A January report by NASA and the National Oceanic and Atmospheric Administration, which documented that 2016 was the warmest year on record, agreed, stating: “The planet’s average surface temperature has risen about 2.0 degrees Fahrenheit (1.1 degrees Celsius) since the late 19th century, a change driven largely by increased carbon dioxide and other human-made emissions into the atmosphere.”

Figure 1. EPA administrator Scott Pruitt at his January 18, 2017 Senate confirmation hearing (Aaron P. Bernstein/Getty Images.)

Commentary: Scott Pruitt a destructive choice for head of EPA
It’s difficult to imagine a more destructive choice for the health of Americans, the avoidance of dangerous climate change, and the health of the American economy than Scott Pruitt as head of EPA. Mr. Pruitt’s denial of the basic science behind climate change makes him as unfit for the office of EPA administrator as an astrologer would be for head of NASA. Decisions based on the best science are critical for the success of any endeavor, as summed up well by Mindy Lubber, president of Ceres, in a March 10 editorial at CNBC: “Businesses thrive when they make smart decisions based on the best available information. The reality is that climate change is happening now and is having wide-ranging ripple effects on businesses. Ignoring risks and long-term trends for short-term benefits is how to drive a company—and the economy—into the ground.”

The EPA’s mission is to ”protect human health and the environment -- air, water and land,” and the regulations the EPA issues should be guided by the best science we have. But in his first speech as EPA administrator, Mr. Pruitt envisioned an EPA that can be "pro-energy, pro-jobs and pro-environment." EPA’s mission statement has no requirement that the agency protect the profits of industry, though, nor should it, since there are plenty of pro-business and pro-job interests out there. Apparently, though, science and protection of people’s health at the EPA are increasingly going to take a back seat to protecting the profits of industry. An early example of this came on January 30, in a shift of the mission statement by the EPA’s Office of Science and Technology to stop issuing “science-based” standards for water pollution, and instead develop “economically and technologically achievable standards” (Figure 2.)

Figure 2. The EPA’s Office of Science and Technology develops clean water standards for states. Before January 30, 2017, their website said those standards were “science-based”, meaning they were based on the best peer-reviewed science available. As reported by, the reference to “science-based” standards has since disappeared, and the web site now says the EPA develops “economically and technologically achievable standards” for water pollution.

Mr. Pruitt, the Attorney General of Oklahoma from 2010 - 2016, is a self-described “leading advocate against the EPA’s activist agenda”, and is apparently contemptuous of the law in pursuit of that goal. Three examples of this have surfaced:

1) Mr. Pruitt illegally withheld emails from an open records request in 2015, and was finally forced to turn them over last week. Those emails revealed that he worked closely with the fossil fuel industry to promote their interests, including such groups as the Koch Industries-funded Americans for Prosperity. Additional emails are still being withheld, and are scheduled to be released pending review by a judge.

2) As reported by Fox News in Oklahoma City, Mr. Pruitt used a private email account to perform government business, in direct contradiction to his sworn testimony at his January 2017 Senate confirmation hearing before Congress.

3) As reported by, Mr. Pruitt may have made another false statement under oath to the Senate: he said he filed briefs in support of a case where 12 poultry companies had allegedly dumped waste into the Illinois River. Investigators found no evidence that he or his office had filed any such briefs.

Mr. Pruitt is packing EPA management with fellow fossil fuel industry-friendly staffers. Two former staff members of Sen. James Inhofe (R-Okla.), the most outspoken climate science denier in Congress, have already been added. A third, Andrew Wheeler, who now works as a lobbyist for the fossil fuel industry, awaits Senate confirmation to be Pruitt’s deputy EPA chief.

Mr. Pruitt sued the EPA fourteen times while he was Attorney General of Oklahoma; none of those cases have succeeded thus far, and at least eight have yet to be settled. This sets up the absurd situation where Pruitt is now the originator and defender of these lawsuits against the agency. According to the New York Times, “In all but one of these 14 cases, regulated industry players also were parties. And these companies or trade associations in 13 of these cases were also financial contributors to Mr. Pruitt's political causes.” details that Pruitt has received at least $345,246 in campaign contributions from the oil and gas industry since 2002.

A January 2017 poll by Reuters found that 39 percent of Americans would like to see the EPA "strengthened or expanded," 22 percent wanted it to "remain the same," and just 19 percent said they would like to see the agency "weakened or eliminated.” The rest said they "don't know." Well, the wishes of the 19% who want to see the EPA weakened are going to be well-served by the gang of pirates Mr. Pruitt is assembling to run the EPA, as the common treasure we all share—clean air, clean water and a future livable climate—are plundered and sold off.

Substantially weakening air pollution regulations is going to end up killing a lot of people. A peer-reviewed 1997 EPA Report to Congress reviewed the benefits of the Act from 1970 to 1990, and concluded that in 1990 alone, pollution reductions under the Act prevented 205,000 premature deaths—deaths that occurred, on average, about twelve years earlier than they would have. A 2013 study estimated that air pollution was still responsible for about 200,000 premature deaths per year in the U.S.—about three times the number of U.S. combat deaths (58,000) during the entire Vietnam War. Any significant weakening of U.S. air pollution regulations goes against widespread public support for clean air, and is going to kill a lot of people and cost tens of billions of dollars in health-related costs.

Preliminary plans have been leaked on Trump’s intention to cut EPA’s $8.1 billion budget by 26%, laying off about 3,000 of the agency’s 15,000 workers. This would be the biggest cut in EPA since the 35% reduction that the agency endured in 1981, the first year of the Reagan presidency. The EPA’s budget peaked in 2010, at $10.3 billion. As with all of the Trump administration's proposed budget, these major EPA cuts must get through Congress before becoming law, and it is quite possible that the scale of the cuts would be reduced in the appropriations process.

Climate science in NOAA is also at risk, according to this March 3, 2017 Washington Post article:
White House proposes steep budget cut to leading climate science agency.

If you want to find out the amount of money politicians who deny or downplay climate science have received from the fossil fuel industry, is the place to go. Donald Trump’s two largest campaign contributors in the 2016 election were coal companies, Murray Energy and Alliance Coal.

The Trump Administration Is Filling Up With Koch Allies (December 2016 post from Ben Jervey at DeSmogBlog.)

Trump’s war on EPA regulations will kill jobs and a lot of people: Clean air and water standards create jobs, spur innovation, and save lives (January 25 post by Joe Romm of ThinkProgress.)

A Lesson Trump and the E.P.A. Should Heed, March 7, 2017 New York Times editorial by Reagan’s head of the EPA, William D. Ruckelshaus.

Climate Science Denial Shifts to a New Tactic Among Trump Appointees, my February 3, 2017 post.

How to Save $23 Trillion Per Year: 100% Renewable Energy for the World, my January 2, 2017 post.

Take Action!
These escalating assaults on our health and on the air we all breathe must be protested, and I urge you to write your Senators and Representatives on this issue:

Contact your House Representative
Contact your Senator

Jeff Masters

Climate Change Politics

Will the East Coast Be Snowed In or Washed Out Next Week?

By: Bob Henson , 5:45 PM GMT on March 10, 2017

A big nor’easter is heading for the Eastern Seaboard early next week, but it’s still too soon to tell whether the urban corridor from Washington to Boston will be doing more digging versus more wading. The timing and location of rain/snow transition is a perennial forecast challenge with Northeast snowstorms, especially in late-winter and early-spring storms like this one. What we do know is that this storm at least has the potential to be a prodigious snow-maker.

The thermal foundation for next week’s big storm is a sharply frigid air mass for early March that’s now descending on the eastern two-thirds of the U.S. This air mass can be traced back to Canada’s Northwest Territories, and it feels that way. Readings were a few degrees below zero Fahrenheit on Friday morning across North Dakota and northern Minnesota. This is far from record cold for the region—Grand Forks, ND, has dipped below –30°F in mid-Marches past—but it’s a distinct change from the record warmth that’s enveloped much of the eastern U.S. in recent weeks. Temperatures will be 20°F to 30°F below average in many places east of the Mississippi by Sunday, with a light freeze possible as far south as Columbia, SC. Some daily record lows are possible across the Northeast as temperatures drop into the single digits in Boston, teens in New York City, and low 20s in Washington.

Another lobe of the polar jet stream will push down a second dose of chilly air across the East early next week. That lobe will also dig more sharply, pulling in subtropical energy and moisture and cutting off as a strong upper low around New York and New England by Wednesday. Energy will be transferred from a surface low in the Ohio Valley to another surface low predicted to strengthen rapidly near the mid-Atlantic coast on Tuesday. Meteorology buffs will recognize this as a classic Miller Type B set-up. Because Type B lows are usually located closer to shore than their more straightforward Type A counterparts, they typically bring more warm, moist air inland and produce a messy, hard-to-predict array of precipitation types. Whether the low tracks well offshore, near the coast, or just inland will largely determine who gets snow or sleet as opposed to rain. Model trends have leaned in the direction of snow for the urban corridor, and I’m leaning that way as well, given the intense dynamics associated with this storm and the cold air masses that will both precede and follow it.

Figure 1. Locations of the nor’easter surface low predicted by the 06Z Friday run of the 20-member GFS model ensemble (GEFS) for 7:00 am EST Tuesday, March 14, 2017. Numbers show the last two digits of the surface pressure in millibars (e.g., “91” = 991 millibars). The map shows how much uncertainty remains in the forecast. The ensemble members agree that a surface low will be intensifying along or off the mid-Atlantic coast, but the locations differ by hundreds of miles—enough to produce vastly different outcomes along the East Coast. The European model ensemble is trending a bit further offshore, which would result in higher odds for a major snowfall from Washington to New York. Image credit:

Whatever form it takes, the precipitation from this storm could be quite heavy across the Northeast’s urban core. The 12Z Friday run of the GFS model, consistent with runs from late Thursday, is dumping more than 2” of liquid equivalent from just east of Washington, D.C., across the New York metro area, with another two-inch-plus stripe over eastern Massachusetts. The heaviest snows are projected to be just northwest of these corridors. The 12Z GFS run shows snow amounts of more than a foot possible close to the D.C.–New York corridor, with potential totals approaching two feet over eastern Pennsylvania and the Hudson Valley of New York. Again, everything will hinge on the exact placement of warmer vs. colder air and the precise configuration of the upper and surface lows, and it’s far too soon to know these with confidence.

Late Friday morning, Capital Weather Gang’s Jason Samenow gave 55% odds that central D.C. would get at least an inch of snow, with a 30% chance of at least eight inches. The latter would be among the heaviest March snows on record for the city, he noted.

“While we want folks to be aware of this possibility, for it to materialize in the immediate area would require all of the storm ingredients coming together just right — which has a low likelihood — maybe one-in-three,” wrote Samenow.

Mid-March can produce memorable Northeast snowstorms
Some of the most epic nor’easters on record have occurred at the tail end of the winter snow season, even as far south as Washington, D.C. On March 12-15, 1993, the “Storm of the Century” dropped incredible snows all the way from the Florida Panhandle (4”) and Birmingham, AL (13”) to Pittsburgh, PA (25.2”) and Syracuse, NY (43”). Along the urban corridor, where sleet mixed with the snow in some areas, Dulles International Airport notched 14.1” and LaGuardia International Airport racked up 12.3”, with winds gusting to 71 mph. This was the first weather event to trigger the closure of every major East Coast airport. Some 270 deaths were attributed to the storm.

Figure 2. Meteosat-3 infrared image of the 1993 Storm of the Century at 1200Z (7:00 am EST) Saturday, March 13, 1993. Along with huge amounts of snow, the storm pushed a major storm surge into Florida’s west coast and a destructive squall line across the peninsula. Image credit: CIMMS Satellite Blog.

Another famed mid-March storm is the Great Blizzard of 1888 (March 11-14), which focused its snowy wrath on eastern New York and New England. The Smithsonian Institution called it “a weather event so fierce that it's still a storm by which other East Coast storms are measured.” Mildness gave way to brutal cold as this ferocious system moved in, dumping snow so heavy and wind-drifted that we still don’t know exactly how much fell in some places. Measured totals included 22” in New York City; 45” in New Haven, CT; 48” in Albany, NY; and 58” in Saratoga Springs, NY. New York’s Central Park recorded a low of 6°F and a high of 9°F on March 13; these remain the coldest values ever recorded at Central Park so late in the season.

More than 400 people are believed to have perished in the Blizzard of 1888, including some 200 in New York City. The storm’s impact on elevated train lines prompted the city to begin planning its now-iconic subway system.

We’ll be back with a new post by Monday. Have a great weekend, everyone!

Bob Henson

Figure 3. A scene from Northampton, MA, on March 13, 1888. Image credit: Forbes Library, Northampton, via Smithsonian Institution.

Winter Weather

Hellacious Great Lakes Windstorm Fells Trees, Knocks Out Power to More than 1 Million

By: Bob Henson , 3:57 PM GMT on March 09, 2017

Under brilliant blue skies, an onslaught of high wind swept across the Great Lakes region on Wednesday, causing damage and disruption on par with a major winter storm or a severe thunderstorm complex. About 1 million customers lost power in Michigan alone, and more than 800,000 of those remained without electricity on Thursday morning. More than 100,000 others were affected in parts of Indiana, Ohio, Pennsylvania, and New York. It’s been the largest weather-related outage in the history of DTE Energy, which serves southeast Michigan. Countless huge trees were topped across the region.

Widespread high winds are not uncommon across the Great Lakes in late winter and early spring, as the typical midlatitude storm track edges north toward the region. In this case, the unusually mild winter appears to have stoked the destruction. Most of the affected areas just had their warmest or second-warmest February on record. DTE Energy noted that the ground was softer than usual for this time of year. In addition, the soil was saturated after recent rains in southeast Michigan, said DTE. Trees were thus easier to topple than they otherwise would have been, and these falling trees played a big role in bringing down power lines.

Figure 1. Jackson Fire Department personnel respond to a gas leak after a tree fell on a house in Jackson, Mich., on Wednesday, March 8, 2017. Image credit: J. Scott Park/Jackson Citizen Patriot via AP.

Figure 2. A Volkswagon owned by Lincoln Russell sits crushed under a tree in the Woodbridge neighborhood of Detroit, Wednesday, March 8, 2017, as strong winds moved through. Image credit: David Guralnick/Detroit News via AP.

Peak wind gusts across the Great Lakes region on Wednesday included:

Chicago, IL (O’Hare): 58 mph
Gary, IN: 63 mph
Saginaw, MI: 68 mph
Detroit Metro Airport: 68 mph
Grand Rapids, MI: 64 mph
Toledo, OH: 62 mph
Cleveland, OH: 61 mph
Youngstown, OH: 70 mph
Batavia, NY (5 miles east): 76 mph
Rochester, NY: 81 mph

The 81-mph gust in Rochester was the city’s second strongest on record, beaten only by the 89-mph gust recorded during a major thunderstorm/derecho event on Labor Day (Sept. 6), 1998.

Jeff Masters, who lives just northwest of Detroit, relayed this first-hand report through a marginal cell-phone connection: “Wednesday's wind storm was the most extreme I've ever observed in my 50 years living in Michigan, with multiple hours of tropical storm-force sustained winds, and gusts approaching hurricane force. Most extraordinary were the sustained winds of 51 mph recorded in Grand Rapids, which brought down power lines that completely blocked I-96. I had to clear away multiple downed trees on my street to get out of my neighborhood, and it was an unnerving experience to saw at the downed trees while looking up at the swaying trees above, wondering which ones were ready to come down as violent 60+ mph gusts tore through.”

Weather-related power outages are becoming more frequent
A 2014 study by Climate Central found that major U.S. power outages (those affecting more than 50,000 customers) increased tenfold between 1984 and 2012. Even after adjusting for improvements in outage reporting, weather-related outages increased dramatically across the period. At the same time, there was no trend in the number of outages unrelated to weather (see Figure 3 below). The study found that Michigan experienced 71 major weather-related outages from 2003 to 2012—the most recorded in any state—with Ohio placing third and Pennsylvania fourth.

“Climate change is a threat multiplier,” the report noted. Even if there is no direct link between climate change and the type of midlatitude storm that drove Wednesday’s high winds, the warm soils noted above appear to have facilitated the damage to trees and power lines. And as we discussed in our post on Wednesday, there is strong evidence that late-winter U.S. warmth over recent decades is an outgrowth of human-induced climate change.

Figure 3. Annual number of reported weather-related and non-weather related power outages in the U.S., 1984-2012. Image credit: Fig. 2, “Blackout: Extreme Weather, Climate Change and Power Outages,” Alyson Kenward, PhD, and Urooj Raja, Climate Central, 2014.

Fires, tornadoes, and blowdowns: A multi-day siege of wind-driven mayhem
The massive Great Lakes windstorm of Wednesday capped off several days of wind-related threats that took on a variety of forms. The culprit behind the whole event was a massive upper-level trough and associated surface low that barreled northeast from the northern Great Plains into central Canada, with multiple fronts pinwheeling around its south side. The surface pressure fell to 980.4 millibars in Fargo, North Dakota, on Monday, just a whisker above Fargo’s all-time March record low of 979.3 mb.

Along the south side of this system, a ribbon of very strong west to southwest winds extended through the lowest several miles of the atmosphere. These winds were able to reach the surface easily because of strong downward forcing and warm low-level temperatures that facilitated mixing through the depth of the atmosphere.

Figure 4. Winds at 850 mb, about a mile above the surface, were howling at more than 64 knots (74 mph) on Wednesday morning, March 8, 2017, along a ribbon from eastern Iowa to southwest Michigan. These winds mixed down to the surface in frequent strong gusts as a midlatitude storm centered in Canada moved eastward. Image credit:

Figure 5. Firefighters from across Kansas and Oklahoma battle a wildfire near Protection, Kan., Monday, March 6, 2017. Image credit: Bo Rader/The Wichita Eagle via AP.

At least six people were killed on Monday as wind-driven wildfires raged across the plains of eastern Colorado, western Kansas, northwest Oklahoma, and the Texas Panhandle. In just a few hours, an estimated 1.5 million acres of prairie—almost twice the area of Rhode Island—were scorched. Four deaths were reported in Texas, including three young ranchers who perished trying to save cattle. Another rancher in Colorado lost nearly 200 cattle to a blaze near Haxtun. In Kansas, a motorist died from smoke inhalation, and an Oklahoma woman fighting a blaze with her husband died of a heart attack.

Fires across the Great Plains can represent a notably high fraction of all U.S. land affected by fire in a given year. In 2006, the East Amarillo Complex fire in the Texas Panhandle killed 12 people and burned more than 900,000 acres, more than 40% of that entire year’s U.S. wildland fire acreage.

Figure 6. Ashley Strother, left, hugs her aunt Brenda Johnson among the wreckage of Johnson's house in Oak Grove, Missouri, on Tuesday, March 7, 2017, after an EF3 tornado moved through the area. Image credit; Allison Long /The Kansas City Star via AP.

Just northeast of the fire-stricken zone, a significant outbreak of severe weather unfolded late Monday. NOAA’s Storm Prediction Center received 47 preliminary tornado reports extending from Oklahoma to Minnesota. Fortunately, most of these tornadoes were weak and short-lived. No deaths were reported, but significant damage and 12 injuries occurred in an EF3 tornado that struck Oak Grove, Missouri, just east of Kansas City. 

Further north, two EF1 tornadoes were confirmed in Minnesota, one near Clarks Grove and the other near Zimmerman. These are the earliest tornadoes ever confirmed in Minnesota for any year, beating the previous record of March 18, 1968, by nearly two weeks. Few if any tornadoes have been recorded this early in the year as far north in the U.S. as the Zimmerman tornado, which struck just north of Minneapolis.

We’ll be back with a new post by Friday.

Bob Henson

High Wind Tornado Fire

Second Warmest U.S. February on Record: Chalk It Up to Greenhouse Gases

By: Bob Henson , 6:35 PM GMT on March 08, 2017

As suggested by plants budding and blooming several weeks ahead of schedule, last month placed second among all U.S. Februaries in records going back 123 years, according to NOAA’s National Centers for Environmental Information. In its quarterly climate summary, NCEI announced that the 48 contiguous United States saw its second warmest February and sixth warmest winter (December - February) on record.

The month’s warmth was remarkably widespread. Every contiguous state but Washington came in above average, and 16 states from Texas to New York had their warmest February on record (see Figure 2). The warmth and a fast-drying landscape helped pave the way for enormous wildfires that raged across the Southern Plains on Monday, killing at least seven people.

The most spectacular index of February’s warmth is the 28-to-1 ratio of daily record highs (11,743) to daily record lows (418) noted in Wednesday’s report. When it comes to all-time monthly records, the ratio was even more wildly skewed: 1151 to 2.

Figure 1. Tulip magnolia trees bloom in Washington, on Feb. 28, 2017. Crocuses, cherry trees, and magnolia trees were blooming several weeks early because of an unusually warm February. The National Park Service predicted on March 8 that the peak bloom of the famed cherry trees at D.C.’s Tidal Basin would occur on March 14-17. This would put it on par with the earliest bloom on record: March 15, 1990. Image credit: AP Photo/Cliff Owen.

Figure 2. Statewide rankings for average temperature during February 2017 as compared to each February since 1895. Darker shades of orange indicate higher rankings for warmth, with 1 denoting the coldest month on record and 123 the warmest. Image credit: NOAA/NCEI.

Figure 3. Average temperatures for the contiguous U.S. for each February from 1895 to 2017. Image credit: NOAA/NCEI.

A new norm evolving for late-winter temperature
As shown in Figure 3, NOAA data show that only February 1954 (average temperature of 41.41°F) topped February 2017 (average 41.16°F). The only other February to rack up an average above 40°F was in 1930. It’s noteworthy that February 2017 was much less of a leap from the “new normal” than its rivals. Against the long-term linear trend of the last century (the blue line in Figure 3), last month came in about 5°F above the trend line, whereas February 1954 was nearly 7.5°F above the trend line.

The message here is that it’s not as difficult to get this kind of February warmth as it used to be. Increased greenhouse gases are the main reason, according to a study released Wednesday by the World Weather Attribution project. The WWA, led by Climate Central with several partners worldwide, uses observations and in-depth climate modeling to provide prompt assessments of how recent weather and climate events fit into the context of a changing planet.

The new WWA report, led by Geert Jan van Oldenborgh (KNMI, the Netherlands center for climate research), analyzed NOAA data from 1900 to show that a month as warm as February 2017 could now be expected about every 8 years on average, whereas the odds of getting such a month in 1900 were about 160 to 1.

The second part of the study pinned this trend on greenhouse gases by examining output generated for the most recent IPCC report from 42 comprehensive climate models, as well as two higher-resolution weather-only models. A series of historical model runs spanning 1960 - 2015 found that solar variations and volcanic eruptions had no effect on the warming trend. Because natural climate variations cancel each other out across this 55-year ensemble of 15 model runs, human-produced greenhouse emissions are the only solid explanation for the long-term warming. Another striking finding: “Around 2050 temperatures like this are projected to be completely normal, occurring approximately every three years on average.”

Warm-weather lovers may rejoice at this news (while cross-country skiers may cringe), but a shift toward Februaries on par with 2017 would have major consequences for U.S. forests and agriculture, especially with the possibility of damaging late-winter freezes still in the mix.

Figure 4. Statewide rankings for average temperature during winter 2016-17 (December through February), as compared to each Dec-to-Feb since 1895. Darker shades of orange indicate higher rankings for warmth, with 1 denoting the coldest month on record and 122 the warmest. Image credit: NOAA/NCEI.

Sixth warmest U.S. winter on record
The average contiguous U.S. temperature for December through February of 35.90°F tied with 1997-98 for sixth place among the 122 years of recordkeeping, according to Wednesday’s NOAA report. All but one of the seven warmest U.S. winters on record have occurred since 1997, with three of those recorded in the 2010s. The only cooler-than-average pocket this past winter (see Figure 4 above) was the northwestern corner of the country, including Washington, Oregon, Idaho, and Montana. Mildness was overwhelming from the southern Rockies northward and eastward, with both Texas and Louisiana notching their warmest winters on record and every state east of the Mississippi having a top-ten warmest winter.

Figure 5. Relentless storms this winter have left a trail of damage on California roadways, including this section of westbound Highway 50 near Pollock Pines photographed on Feb. 21. By late February, the bill to repair California's roadways hammered by floods and rockslides in an onslaught of storms this winter is already at least $550 million, more than double what the state budgeted for such emergencies. Image credit: AP Photo/Rich Pedroncelli.

An unexpected deluge in California
The biggest precipitation news of the winter was the return of ample moisture to California after five years of withering drought. The state scored its second-wettest winter on record in 2016-17 after a near-average winter in 2015-16 (focused mainly on the state’s northern half) and four below-average years before that. The statewide average precipitation of 21.67” in 2016-17 compares to a total of just 4.81” in 2011-12! Sierra snowpack in Phillips Station south of Lake Tahoe was at 185% of the average for the date on March 1, putting it among the four biggest accumulations on record at this point in the year.

Figure 6 below makes it clear that wild swings in precipitation are the norm for California. What’s new in recent years is that dry periods are now much more likely to be paired with extreme warmth, as was the case in the early to mid-2010s. Higher temperatures tend to exacerbate the impact of drought by pulling moisture from already-parched soils and reservoirs.

Figure 6. Winter precipitation for California showed a phenomenal jump in 2016-17 compared to the previous few years, while the average precipitation has shown little trend over the last century. Image credit: NOAA/NCEI.

El Niño, La Niña, and West Coast precipitation
This was the second winter in a row to vex seasonal forecasters who leaned on signals from the El Niño-Southern Oscillation (ENSO) to predict precipitation across the West Coast. The very strong El Niño of 2015-16 failed to produce the expected downpours across southern California (which trends wet during El Niño) while giving Seattle (which tends dry during El Niño) its wettest winter on record. This year’s weak La Niña also ran against the grain of expectations, leaving the state of Washington slightly below average in precipitation while giving California a bumper crop of moisture all the way to San Diego.

Although strong El Niño events are very likely to produce wet winters in California, the relationship is not an ironclad guarantee. “The bottom line is that California can get wet during El Niño, but not always,” noted Jan Null (Golden Gate Weather Services). Likewise, a weak or borderline La Niña event tends slightly toward dryness across Southern California, but annual precipitation during these events has varied widely, from as little as 54% to as much as 127% of average, not counting this year’s deluge. There is sure to be fascinating research ahead on the winters of 2015-16 and 2016-17 and their wildly divergent West Coast precipitation outcomes.

This winter’s ample moisture extended from California across the Rockies and into the Midwest (see Figure 7 below). Both Nevada and Wyoming had their wettest winters on record, while the only significant pockets of seasonal dryness were across the mid-Mississippi Valley and the mid-Atlantic. Dry conditions intensified and expanded across both of these areas last month: Missouri, Illinois, South and North Carolina, Virginia, Maryland, and Delaware all saw a top-ten driest February.

We’ll be back with a new post on Friday at the latest.

Bob Henson

Figure 7. Statewide rankings for average precipitation during winter 2016-17 (December through February), as compared to each Dec-to-Feb period since 1895. Darker shades of green indicate higher rankings for moisture, with 1 denoting the driest month on record and 122 the wettest. Image credit: NOAA/NCEI.

Climate Summaries

Category 4 Tropical Cyclone Enawo Hits Madagascar

By: Jeff Masters , 2:44 PM GMT on March 07, 2017

Extremely dangerous Tropical Cyclone Enawo hit northeastern Madagascar near 3 am EST Tuesday as a Category 4 storm with 145 mph winds. Enawo is the third strongest tropical cyclone on record to strike the island, and severe impacts are likely from the storm’s torrential rains, high winds, and large storm surge (though in their 1 am EST (6 UTC) Tuesday advisory, Meteo France in La Reunion reduced their peak storm surge forecast for the storm to 1 - 2 meters.) Of most concern are the rains from Enawo, as it is an unusually large and wet storm. The amount of water vapor detected by satellite is near the very high end of what is observed in tropical cyclones—precipitable water values up to 3.0 inches. Recent runs of the HWRF model (Figure 2) predict extreme rainfall amounts falling on heavily populated regions of Madagascar, and Enawo has the potential to be a top-three most damaging storm in the island’s history. Enawo will decay rapidly as it takes a track directly down the length of Madagascar, exposing the entire island to flooding rains. However, the disaster could have been worse—more than half of the rivers in Madagascar have dried up or are flowing at less than 5 percent of their average streamflow, thanks to a two-year El Niño-linked drought. Enawo’s rains will help break the drought, which has caused large-scale crop failures and put over half a million people into acute food insecurity, according to the Famine Early Warning Systems Network.

Figure 1. Visible MODIS image of Enawo taken at 10:24 UTC (5:24 am EST) Tuesday March 7, 2017. At the time, Enawo had just made landfall over northeast Madagascar as a Category 4 storm with 145 mph winds. Image credit: NASA.

Figure 2. Predicted storm-total rainfall amounts for Tropical Cyclone Enawo from the 06 UTC Tuesday (1 am EST) March 7, 2017 run of the HWRF model. Rainfall amounts in excess of 16 inches (orange colors) are expected in many areas of Madagascar, with 4 - 8” expected near the capital of Antananarivo (population 1.6 million).

Figure 3. Streamflow as a percent of average in Madagascar on March 4, 2017. Most rivers on the island were flowing at less than 5 percent of average due to a two-year El Niño-linked drought. Image credit: Princeton African Flood and Drought Monitor.

Enawo is the strongest tropical cyclone in the Southern Hemisphere so far in the 2016 - 2017 season, and the first one to exceed Category 1 strength. It has been an unusually quiet tropical cyclone season in the Southern Hemisphere this year, as we discussed in detail in a February 28 post.

Madagascar’s cyclone history
According to NOAA’s Historical Hurricane Tracks website, Madagascar has been struck by twelve major (Category 3 or stronger) tropical cyclones since 1983. The deadliest of these was Tropical Cyclone Gafilo, which hit the island on March 7, 2004, as a Category 4 storm with 150 mph winds. Gafilo killed 363 people; damage was estimated at $250 million, the fifth costliest natural disaster on record in Madagascar. The island’s costliest storm was Tropical Storm Emilie, which caused devastating flooding on February 1, 1977 of $1.4 billion (2017 dollars.) The strongest cyclone to hit Madagascar was Cyclone Hary, which brushed the northeastern coast of the island on March 10. 2002, as a Category 5 storm with 160 mph winds. Hary was a small storm, and caused four deaths and relatively little damage in Madagascar.

Figure 4. Tracks of all major (Category 3 and stronger) tropical cyclones to make landfall in Madagascar, 1983 - 2016. Image credit: NOAA’s Historical Hurricane Tracks website.

Jeff Masters


Severe Weather Threat, Extreme Fire Danger over Southern Plains

By: Bob Henson , 6:34 PM GMT on March 06, 2017

A windy, fast-moving storm system will bring the risk of severe weather, including tornadoes, as it barrels across the Great Plains on Monday afternoon and evening. The severe storms will be generated by a very large upper-level trough swinging east across a broad area of fairly warm, moist air feeding into a surface low in the Dakotas. The NOAA/NWS Storm Prediction Center highlighted an enhanced risk of severe weather covering most of Missouri in its 10:30 am CST outlook on Monday. A slight risk extends from eastern Oklahoma and Arkansas northward to central Minnesota.

Today’s setup is a fairly typical one for March, with a very strong late-winter-style polar jet stream encountering an early-spring air mass. While a large swath of the Plains could experience a fast-moving severe storm, the most potent juxtaposition of unstable air and upper-level forcing will evolve near and just northwest of the Ozarks. Surface dew points in this area were already approaching 60°F at midday Monday, with temperatures near 70°F. A dry line now over western Kansas and Oklahoma will sharpen this afternoon, serving as a focal point for thunderstorm development. Supercell thunderstorms over far eastern Kansas and southwest Missouri ahead of the dry line have the potential to generate very large hail and significant tornadoes, according to SPC. As a cold front overtakes the dry line and sweeps through, this evening’s storms should eventually morph into a squall line, possibly extending from the upper Midwest all the way to Texas.

Figure 1. Convective outlook issued by the NOAA/NWS Storm Prediction Center at 10:30 am CST Monday, March 6, 2017.

Figure 2. Visible GOES satellite image from 1645Z (10:45 am CST) Monday, March 6, 2017. A large field of low-level moisture is evident in the cumulus streaming north across Texas into the Central Plains, while a ribbon of higher clouds angling from southwest Texas to Illinois corresponds with strong upper-level winds overtopping the moisture across parts of Oklahoma, Missouri, and far southeast Kansas. Image credit: NASA MSFC Earth Science Office.

Figure 3. Model depiction of surface and upper-level features produced by the 12Z Monday run of the GFS model, valid at 00Z Tuesday, March 7, 2017 (6:00 pm CST Monday). A cold front across the Plains, evident in the kinked black lines (isobars, or lines of constant surface pressure) from Minnesota to Texas, will be shoved eastward by the strong upper level low evident in the blue colors (these show the height of the 500-millibar surface, shown in tens of meters). Image credit:

Extremely critical fire danger over parts of Southern Plains
Powerful upper-level winds and the surface low wrapping up over the Dakotas are teaming up to generate a swath of strong, warm, and very dry southwest winds behind the dry line across the Southern Plains—bad news for fire risk. SPC has issued an “extremely critical” fire risk area, its most dire, along a band from east-central New Mexico to eastern Nebraska. While drought conditions are not nearly as widespread or intense across this region as they were last fall, moderate drought has persisted across large parts of Oklahoma, western Kansas, and eastern Colorado through the winter.

Figure 4. Fire weather outlook issued by the NOAA/NWS Storm Prediction Center at 9:00 am CST Monday, March 6, 2017.

The 2017 tornado season is running far ahead of average
The highly progressive pattern that’s kept midlatitude storms shuttling across the United States all winter has given an early boost to the U.S. tornado season of 2017. Such a progressive pattern is important but not sufficient for producing early-season severe weather. Even if upper-level conditions favor severe weather, there may not be enough time between midlatitude storm systems for unstable air to flow back into place from the Gulf of Mexico. This year, however, the Gulf and Caribbean have been consistently warm, which has helped generate plenty of warm, moist air for midlatitude storms to access. In records back to 1981, this is the first year in which sea surface temperatures averaged across the entire Gulf never dropped below 73°F, as discussed by Eric Berger at ArsTechnica and shown in Figure 5 below (thanks to WU member Mark Cole for this tip). As of Monday, SSTs over the western Gulf were running 1°C - 2°C (1.8-3.6°F) above the seasonal norm.

Thus far in 2017, NOAA/SPC has logged 268 preliminary tornado reports. This is roughly double the average of 133 reports racked up by March 5 over the preceding 11 years (2005-2015). This year also stands out in a longer-term perspective, even after you “inflation-adjust” the data back to 1954 to account for the increased tendency since then for a given tornado to be spotted, chased, photographed, videotaped, etc. After the inflation adjustment, this year’s preliminary total of 228 tornado reports (see Figure 6 below) compares to a long-term average of just 69 reports by this point in the year.

Figure 5. In data extending back to 1981, sea surface temperatures averaged across the Gulf of Mexico were the warmest on record this winter. Image credit: Michael Lowry, @MichaelRLowry.

Figure 6. “Inflation-adjusted” cumulative tornado totals for the period 1954 - 2016 (various colors) and 2017 to date (black). The red trace shows the highest adjusted value observed on each date through the year, with the lowest value on each date in magenta. Image credit: NOAA/SPC.

Enawo churns toward Madagascar
Tropical Cyclone Enawo continued to chug toward the east coast of Madagascar late Monday local time. Satellite imagery suggests that Ewano is now at least a Category 3 storm—the first to be reported anywhere in the Southern Hemisphere since its 2016-17 season began last July. Enawo is also only the third hurricane-strength tropical cyclone to develop this season, which marks the latest appearance on record of the Southern Hemisphere’s third hurricane, according to Phil Klotzbach (Colorado State University). See Jeff Masters’ post earlier today for more on Enawo.

Bob Henson

Severe Weather Fire

Madagascar Braces for Extreme Rains From Category 2 Tropical Cyclone Enawo

By: Jeff Masters , 2:33 PM GMT on March 06, 2017

Dangerous Category 2 Tropical Cyclone Enawo was plowing westwards at 6 mph on Monday morning towards Madagascar, and is expected to make landfall on the island on Tuesday morning. The storm is passing over waters of 29°C—approximately 0.5°C above average in temperature—and is an unusually wet storm, with amounts of water vapor near the very high end of what is observed in tropical cyclones (precipitable water values up to 3.0 inches.) Recent runs of the HWRF model (Figure 2) have shown some very worrisome amounts of rain falling on heavily populated regions of Madagascar, and Enawo has the potential to be a top-five most damaging storm in the island’s history. With warm waters, moderate wind shear of 15 - 20 knots, and plenty of moisture available, intensification into a Category 3 storm appears likely on Monday afternoon and evening, before interaction with land knocks the intensity of the storm back to Category 2 at landfall on Tuesday.

Figure 1. Visible MODIS image of Enawo taken at 10:10 UTC (5:10 am EST) Monday March 6, 2017. At the time, Enawo was a Category 2 storm with 105 mph winds. Image credit: NASA.

According to the 7 am EDT (12 UTC) Monday bulletin from the official cyclone forecasting agency for the Southwest Indian Ocean, Metro France on La Reunion, Antongil Bay in northeast Madagascar is likely to undergo a significant storm surge of 3-4 meters (10-13 feet) near Maroantsetra, but only 1 meter south of Antalaha.

Figure 2. Predicted storm-total rainfall amounts for Tropical Cyclone Enawo from the 06 UTC Monday (1 am EST) March 6, 2017 run of the HWRF model. Rainfall amounts in excess of 16 inches (orange colors) are expected in many areas of Madagascar, with 4 - 8” expected near the capital of Antananarivo (population 1.6 million).

Enawo is the strongest tropical cyclone in the Southern Hemisphere so far in 2017. It has been an unusually quiet tropical cyclone season in the Southern Hemisphere this year, as we discussed in detail in a February 28 post.

Madagascar’s cyclone history
According to NOAA’s Historical Hurricane Tracks website, Madagascar has been struck by twelve major (Category 3 or stronger) tropical cyclones since 1983. The deadliest of these was Tropical Cyclone Gafilo, which hit the island on March 7, 2004, as a Category 4 storm with 150 mph winds. Gafilo killed 363 people; damage was estimated at $250 million, the fifth costliest natural disaster on record in Madagascar. The island’s costliest storm was Tropical Storm Emilie, which caused devastating flooding on February 1, 1977 of $1.4 billion (2017 dollars.) The strongest cyclone to hit Madagascar was Cyclone Hary, which brushed the northeastern coast of the island on March 10. 2002, as a Category 5 storm with 160 mph winds. Hary was a small storm, and caused four deaths and relatively little damage in Madagascar.

Figure 3. Tracks of all major (Category 3 and stronger) tropical cyclones to make landfall in Madagascar, 1983 - 2016. Image credit: NOAA’s Historical Hurricane Tracks website.

There is an enhanced risk of severe weather over Missouri and portions of neighboring states on Monday afternoon, and Bob Henson plans to have an update on this potential in a post later today.

Jeff Masters


Sea Ice Extent in Antarctica Bottoming Out at Lowest on Record

By: Bob Henson , 5:50 PM GMT on March 03, 2017

As summer draws to a close across the Southern Hemisphere, the extent of sea ice ringing Antarctica has fallen to the lowest values ever observed in satellite records dating back to 1979. On Wednesday, March 1, the daily extent data from the National Snow and Ice Data Center (NSIDC) showed 2,109,000 square kilometers of Antarctic sea ice, its lowest value on record. That value nudged up slightly on Thursday, but a more useful measure, the five-day rolling average, hit its lowest value yet on Thursday (see Figure 1 below). Update: The five-day average fell even lower on Friday, March 3, dropping from 2,113,000 to 2,106,000 sq. km.

We can expect the regular autumn rebound in southern ice to kick in very soon now. However, this has been a notably persistent melt season--one that wouldn’t take too much longer to break a record for tardiness. If Thursday’s five-day average turns out to be the lowest for the summer, it will be tied with March 2, 1991 for third-latest minimum behind March 6, 1986 and March 3, 2003.

“It could start trending upward any day,” sea ice expert Walt Meier (NASA Goddard Space Flight Center) told me on Thursday. “Of course, this year has been rather unusual, so it would not surprise me to see it going into unprecedented territory.”

Figure 1. Sea ice extent for the five-day period ending March 2 (right-hand end of pale blue line) is lower than at any point since satellite measurements began in 1979. Averaged over the preceding five days, the extent on Thursday, March 2, was 2.113 million square kilometers. The next-lowest value for this date, in 1997, had about 236,000 more sq km than 2017. Image credit: NSIDC.

A head-turning switch
For now, at least, Antarctic sea ice has relinquished its role as a poster child for counterintuitive events on a warming planet. Unlike the Arctic, where sea ice extent, area and thickness have all undergone dramatic dips consistent with human-produced climate change, the Antarctic has not only held its own but expanded to record-high extents at times. The southern summers of 2013, 2014, and 2015 each retained enough sea ice to rank among the five highest minimums in yearly extent since 1979.

If you find it odd that Antarctic ice has proven so resilient, you’re not alone. A majority of simulations carried out in support of the most recent IPCC report predicted that Antarctic sea ice coverage should have declined between 1979 and 2013. In a 2015 review paper published in Nature Climate Change, a group of Antarctic experts identified some factors that may be enhancing regional sea ice production in spite of global warming. These include:

--stronger westerly winds ringing the continent
--increased meltwater flowing into the Southern Ocean
--a stronger prevailing low in the Amundsen Sea. This tends to favor cold offshore flow and enhanced ice production in the Ross Sea, with mild onshore flow and reduced sea ice in the Amundsen-Bellinghausen region.

Figure 2. Sea ice extent on Thursday, March 2, 2017 (white area) compared to the average extent for this date in the period 1981-2010. Most of the deficit this year is in the Bellingshausen, Amundsen, and Ross Seas, which are typically the areas hardest hit during summers with low sea ice extent. Image credit: NSIDC.

What will autumn bring?
While this year’s minimum is a clear record-setter, it shouldn’t pack the same regional punch as we’ve seen from similar events in the Arctic. There’s an increasing body of work showing connections between newly opened water in the Arctic, especially in autumn, and the weather and climate of the subsequent winter over both poles and midlatitudes. But several factors work to blunt the impact of low sea ice extent in the Antarctic, according to Meier. For one, “the ocean is much more dynamic than in the Arctic, so any extra heat that gets absorbed gets mixed fairly quickly,” he said. “Plus, there is a very white, very cold continent right next to the ice, so that helps cool things down quickly.” Big swings from maximum to minimum extent are also the norm in Antarctica, where such swings are about 60% bigger on average than in the Arctic.

La Niña events tend to strengthen the Amundsen Sea Low mentioned above, and the frequent La Niña conditions from about 1999 to 2014 may have helped bolster Antarctic sea ice. Since then, El Niño conditions have predominated, and there’s another El Niño event potentially taking shape for 2017-18. If so, then we might see another big bite out of Antarctica’s late-summer sea ice next year. But the region’s climate is so complex and variable in both time and space that it’s risky to offer predictions.

“It’s possible that we’ll look back in a decade and see this year as a turning point when the Antarctic sea ice finally started to feel the long-term global warming influence above the natural variability,” Meier told me. “But we may also look back and see this year as an unusual blip in the time series--an anomalous spike that is quickly gone.”

Figure 3. The rift in the Larsen C ice shelf photographed from NASA’s DC-8 research aircraft on November 10, 2016. The rift is about 0.2 miles wide and 0.3 miles deep. Image credit: John Sonntag, NASA.

The big fracture in the Larsen C shelf: It’s still there
A chunk of ice as large as Delaware continues to cling to the Antarctic Peninsula, but an ever-lengthening crack is likely to sever it in the not-too-distant future. Now extending more than 100 miles, the crack in the Larsen C shelf is roughly 1000 feet wide and about 1500 feet deep. More than half of the crack’s length has developed since 2010. If it proceeds for another 20 miles, which may happen in the next few months, then it will release an enormous iceberg (or collection of smaller icebergs), perhaps one of the largest on record. The New York Times has an excellent multimedia feature on the physics and geography of the crack.

The largest iceberg measured by satellite in Earth’s history, Iceberg B-15, broke off of Antarctica’s Ross Ice Shelf in March 2000. Iceberg B-15 was about 1.7 times larger in area compared to the chunk about to break off from the Larsen C ice shelf. According to the Guinness Book of World Records, the largest tabular iceberg ever observed was approximately three times the size of B-15, at over 12,000 square miles. It was 208 miles long by 60 miles wide, and was sighted 150 miles west of Scott Island in the Southern Ocean by the USS Glacier on November 12, 1956 (thanks go to WU member lifeblack for this info.)

The apparently doomed slice of Larsen C wouldn’t affect sea level rise directly, since it is already floating. The real concern is that its loss might destabilize the balance of forces that keeps a much larger area of glacial ice behind Larsen C from flowing off the Antarctic Peninsula and into the sea. According to a Washington Post article filed by Chris Mooney, researchers believe enough ice could flow seaward in the wake of a Larsen C collapse to raise sea level by as much as 10 cm (3.9 in).

The Larsen shelves lining the east coast of the peninsula are disintegrating in alphabetic order, it seems. The relatively small, furthest-north Larsen A collapsed in 1995, and the gradual disintegration of Larsen B should be complete this decade after a large chunk—about half the breadth and depth of the vulnerable Larsen C chunk—detached into the sea in early 2002.

“Iceberg calving is a normal part of the glacier life cycle, and there is every chance that Larsen C will remain stable and this ice will regrow,” said Paul Holland (British Antarctic Survey) in a BAS news feature on February 21. “However, it is also possible that this iceberg calving will leave Larsen C in an unstable configuration. If that happens, further iceberg calving could cause a retreat of Larsen C. We won’t be able to tell whether Larsen C is unstable until the iceberg has calved and we are able to understand the behaviour of the remaining ice.”

A 2016 study led by scientists from Swansea University and BAS concluded that the main cause of glacial retreat along the west side of the Antarctic Peninsula since the 1990s has been ocean warming. There is no direct evidence on whether the Larsen C rift is a product of climate change, but the peninsula as a whole has been warming rapidly since the 1950s.

Figure 4. Established in 1953 and now one of 76 Antarctic research stations maintained by 30 countries, the Argentine-managed Esperanza Base sits near the northern tip of the Antarctic Peninsula. This photo was taken on January 15, 2016. Image credit: Godot13, Wikimedia Commons.

And speaking of warming on the Antarctic Peninsula…
The official record high for the continent of Antarctica is now 17.5°C (63.5°F), according to the World Meteorological Organization. In a news release issued Wednesday, the WMO announced that a committee of experts (including WU weather historian Christopher Burt) had investigated and confirmed the new record. It was set on March 24, 2015, near the tip of the Antarctica Peninsula at the the Argentine research station Esperanza Base.

A post written by Chris Burt on March 26, 2015, explains in detail the complexity of determining exactly what qualifies as Antarctica when it comes to weather records. For the “Antarctica Region,” defined by the WMO and UN as all land and ice south of 60°S, the all-time high remains 19.8°C (67.6°F), recorded at Signy Research Station, Signy Island, on January 30, 1982.

An important caveat from the WMO: “It is possible, indeed likely, that greater extremes can and have occurred in the Antarctic Region. However, the extremes presented here are the highest observed temperatures placed before the WMO for adjudication. When higher extreme events are effectively recorded and brought to the attention of the WMO, subsequent evaluations of those extremes can occur.”

Next week: Potential threat for Madagascar next week from Tropical Cyclone Enawo
A tropical cyclone long predicted by models to develop in the southwest Indian Ocean is finally taking shape. As of Friday morning, the Joint Typhoon Warning Center was projecting that Tropical Cyclone Enawo would vault to Category 4 strength, with top winds of 125 knots (145 mph), as it nears the east coast of Madagascar by next Wednesday. Earlier this week, Jeff Masters and I covered the Southern Hemisphere’s oddly quiet tropical cyclone season to date. We're keeping an eye on Enawo.

Have a great weekend, everyone!

Bob Henson

Figure 5. This visible image of newly developed tropical cyclone Enawo was taken from the VIIRS instrument aboard NASA-NOAA's Suomi NPP satellite on March 3 at 0954 UTC (4:45 a.m. EST). The tropical storm formed northeast of the African island country of Madagascar. Image credit: NOAA/NASA Goddard MODIS Rapid Response Team.

Antarctic Sea Ice

Echoes of a 1920s Calamity in Deadly Midwest Tornado Outbreak

By: Bob Henson and Jeff Masters , 6:48 PM GMT on March 01, 2017

Several long-lived supercell thunderstorms cranked out destructive tornado families across the Midwest from late Tuesday into Wednesday morning. At least 3 deaths had been reported, according to a summary. Power was knocked out for tens of thousands of people as the wind-packing storms barreled east toward the Appalachians.

The NOAA/NWS Storm Prediction Center received 24 preliminary tornado reports for the period from 6:00 am CST Tuesday to 6:00 am Wednesday, with 2 additional reports as of late Wednesday morning. It’s possible that the final tally of tornadoes will come down from these numbers. Most of the reports were generated by just two sequences of supercell thunderstorms that spun out twisters for hours on end. One of these storm complexes tracked from far eastern Iowa into northern Illinois, while the other followed a track from far southeast Missouri through southern Illinois into southwest Indiana--a path eerily reminiscent of the nation’s deadliest tornado on record: the Tri-State Tornado of March 18, 1925 (see below).

Figure 1. Pat Harber of Perryville, Missouri, looks through the wreckage of her home after it was destroyed by a tornado on February 28, 2017. At least one person was killed when the tornado crossed interstate 55. (Jon Durr/Getty Images) 

Figure 2. This large tornado was photographed at 5:36 pm CST Tuesday, Feb. 28, 2017, by associate meteorology professor Walker Ashley (Northern Illinois University) as it passed just northwest of Washburn, IL. Image credit: (c) Walker Ashley.

The first and more northerly of the day’s two major tornado sequences unfolded with a short line of fast-moving supercell storms from around 4:00 to 6:00 pm CST Tuesday. A large, wedge-shaped tornado struck near Naplate and Ottawa, IL, around 4:45 pm, causing one death and producing extensive damage. As this circulation weakened, it was succeeded by one in a storm just to the south that generated frequent tornado reports from around Washburn toward Long Point (see Figure 1 above and embedded tweet at bottom). Continuing east as a non-tornadic complex, the storms produced hail as large as golf balls across the south part of the Chicago area. Tuesday’s storms across northern Illinois were being surveyed on Wednesday by NWS staff from Chicago and Lincoln, IL; results will be posted on this NWS/Chicago website.

Figure 3. A debris signature (often called a “debris ball”) is evident on this radar reflectivity image from the NWS Doppler radar located near Owensville, IN. The image was taken at 10:04 pm CST Tuesday, Feb. 28, 2017. Image credit: NWS/Paducah, KY.

The other major tornado producer was a more classic, isolated supercell storm that maintained its identity for more than 100 miles across parts of Missouri, Illinois, and Indiana, spitting out tornadoes along much of its path. The radar signature of the storm was especially strong over far southeastern Illinois, with a clear debris ball evident (see Figure 3 above). CNN reported that one man was killed and his wife seriously injured near Crossville, IL. The intense circulation passed extremely close to the NEXRAD radar stationed at Owensville, IN, near the NWS office serving the Evansville, IN, area (see Figure 4).

Figure 4. Stu Ostro (The Weather Channel) tweeted this uniquely amazing radar image late Thursday night: “Effect of beam height on 3-D radar presentation as the #tornado-producing thunderstorm passed right over the Evansville radar site.” The tornadic circulation lies very close to the radar, with the core of the storm passing just to the northwest (into the page). Image credit: Stu Ostro, @StuOstro.

Figure 5. Most of Tuesday’s tornadoes (red dots) occurred within the areas highlighted by the NOAA/NWS Storm Prediction Center at 10:30 am CST Tuesday with the top tornado probabilities. The hatched lines indicate an especially high risk of significant tornadoes (EF2 or stronger). Image credit: NOAA/NWS/SPC.

Another Tri-State event, but this time without the horrific death toll
NOAA’s Storm Prediction Center did a superb job with its Tuesday outlook. On Tuesday morning, it successfully identified the small corridor where the southern tornado supercell tracked as being the area with the highest probabilities of significant tornadoes. Throughout the Midwest, tornado watches were issued well ahead of the day’s worst activity, and the fact that tornadoes were concentrated within long-lived storms allowed for plenty of lead time on many NWS tornado warnings.

The impressively small death and injury toll from Tuesday stands in stark contrast to what occurred with what may be the most analogous storm to the southern supercell: the Tri-State tornado of March 18, 1925. This event was identified as a tornado family in more recent research led by former SPC forecaster Bob Johns, with the longest continuous path length at 174 miles and frequent damage recorded over a stretch of 219 miles. “Witnesses saw a wedge tornado along most of the damage path and a large multivortex tornado in some areas,” noted Johns and colleagues in a 2013 open-access paper in the E-Journal of Severe Storms Meteorology. The human tragedies left by this single-thunderstorm event remain unparalleled in U.S. history, with an official death toll of 695 people.

As shown below, the path of Tuesday’s supercell was remarkably similar to that of the Tri-State supercell as implied by damage records from 1925. (One can only imagine how that storm might have looked on NEXRAD radar!) Moreover, the broad, strong upper-level trough in place on Tuesday also closely resembled the one believed to have been in place during the Tri-State Tornado, as noted by Embry-Riddle associate professor Shawn Milrad, @shawnmilrad. (Because upper-air observations were not made in the 1920s, such reanalysis maps are generated by inferring the upper-level conditions that would correspond to surface observations available from the period.) Of course, there are big differences between the 1925 and 2017 events: the Tri-State tornado was rated F5, whereas it appears very unlikely that any of the 2017 tornadoes will be placed in the F5 range.

Figure 6. Comparison of damage locations along the Tri-State tornado track from March 18, 1925, and selected preliminary tornado reports from Feb. 28, 2017. The first set of tornado reports, from far southeast MO into southwest IL, are a few miles north of the Tri-State track. After this supercell merged with another storm, the next batch of tornado reports occurred very close to the Tri-State track, from far southeast IL into far southeast IN. Original image from Johns et al., "The 1925 Tri-State Tornado Damage Path and Associated Storm System," E-Journal of Severe Storm Meteorology (2013).

Another exceptionally rare February tornado outbreak
February tornadoes are rare in Illinois, and unheard of as far north in Illinois as where the Ottawa tornado touched down. According to the Tornado History Project, Illinois experienced February tornadoes an average of once every six years between 1950 - 2007. However, their incidence of February tornadoes has increased dramatically over the past decade, with February tornadoes hitting once every other year, on average. Prior to Tuesday’s Ottawa tornado, there were only two other deadly February tornadoes in Illinois since records began in 1950, both of them well south of the Ottawa event: an F4 twister that hit Saline and Gallatin Counties on February 10, 1959, killing eight, and an F4 twister that hit just southeast of St. Louis on February 24, 1956, killing six. As of 10 am EST Wednesday, NOAA’s Storm Prediction Center put Tuesday’s tornado tally in Illinois at seventeen, which would make it the state’s largest February tornado outbreak on record. Their previous largest February tornado outbreak came on February 20, 2014, when eleven twisters touched down, including two EF2s.

According to the Tornado History Project, Missouri experienced February tornadoes an average of once every four years between 1950 - 2007, and once every two years between 2008 - 2017. The deadliest February tornado in Missouri hit St. Louis on February 10, 1959, killing 21 people. Including Tuesday’s Perryville tornado, there have now been six deadly February tornadoes in Missouri since 1950.

Tuesday’s outbreak was the second exceptionally rare February tornado outbreak in the U.S. this year. On February 25, a total of four tornadoes hit Pennsylvania, Maryland, and Massachusetts. The EF1 that touched down in Massachusetts, damaging two houses, was their first February tornado on record--and at latitude 42.51°N, the most northerly February tornado recorded in the Northeastern U.S. since reliable records began in 1950.

Figure 7. Debris is seen from above Wednesday, March 1, 2017, where Tuesday's tornado destroyed homes in Perryville, Missouri. (Robert Cohen/St. Louis Post-Dispatch via AP) 

How did Tuesday’s tornadoes happen so far north?
One reason February tornadoes are practically nonexistent as far north as northern Illinois is that it’s very difficult to get a warm, moist air mass into the region during late winter without a very potent low-level storm system pulling the air northward from the Gulf of Mexico and a very strong upper-level trough passing through. Such a setup, though, can also lead to thunderstorms that are so widespread that they weaken the ability of more scattered rotating supercells to maintain themselves. In Tuesday’s case, however, the February “warm wave” of the last few days had already brought unstable air close to the region, so it only took a moderately strong surface feature (a 998-millibar low in northern Illinois) to get the unstable air into position beneath a powerful upper-level trough and jet stream. There was also just enough of a “cap” above the unstable air to keep a lid on thunderstorm development until daytime heating peaked and the tornado potential was maximized. “To me, today confirms that, as long as the ingredients come together, the calendar is not important--further evidence that big CAPE [a measure of instability] is not necessary on big days.” said NIU’s Walker Ashley. “It really is about that marriage of sufficient instability with solid [wind] shear, and just a peppering of convective initiation, to make for a big day.”

The severe weather threat continued into Wednesday ahead of the eastward-moving upper storm and associated cold front, with an enhanced risk of severe weather from northeast Mississippi all the way to southern New Jersey. Odds are especially high for damaging thunderstorm-related winds from the central Appalachians into the mid-Atlantic, perhaps including the Washington, D.C. area. Tornadoes should be less widespread and intense than on Tuesday, but a few are still possible, especially with any supercells that develop across northern Alabama and Georgia near the tail end of the cold front.

Bob Henson and Jeff Masters

Severe Weather Tornado

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Category 6™


Cat 6 lead authors: WU cofounder Dr. Jeff Masters (right), who flew w/NOAA Hurricane Hunters 1986-1990, & WU meteorologist Bob Henson, @bhensonweather