Category 6™

Brazil, California Face Specter of Worsening Drought

By: Bob Henson , 9:35 PM GMT on January 30, 2015

January has not been kind to two parched corners of the Americas. A large chunk of California’s San Francisco Bay area is wrapping up the month with no measurable rainfall, a first for January since records began--all the way back to 1850 in the case of downtown San Francisco. This week’s U.S. Drought Monitor dataset shows 77.5% of California in the worst two categories of drought (extreme and exceptional), compared to 67.1% at this point last year. There is still hope that February, March, or even April could bring a few wet storms to salvage the rainy season across central and southern California, but for now the atmosphere appears locked in this year’s version of the Ridiculously Resilient Ridge that delivered severe drought and record heat to California in 2014. With virtually no chance of rain through Saturday, the January records below look certain to be broken (or tied, in the case of Redding).

Downtown San Francisco: no rain reported through 1/29 (record 0.06”, 2014)
Downtown Sacramento: 0.01” (record 0.07”, 2007)
Oakland Airport: trace (record 0.04”, 2014)
Monterey: 0.01” (record 0.04”, 2014)
San José: 0.02” (record 0.10”, 1920)
Napa: trace (record 0.11”, 2014)
Redding: 0.26” (record 0.26”, 1984)
Stockton: 0.02 (record 0.14”, 1976)

Figure 1. Frank Gehrke, chief of the California Cooperative Snow Surveys Program for the Department of Water Resources, conducts the second snow survey of the season at Echo Summit, California, on Thursday, January 29. The survey showed the snowpack to to be 7.1 inches deep with a water content of 2.3 inches, which is just 12 percent of normal for the site at this time of year. Image credit: AP Photo/Rich Pedroncelli.

California’s water year--defined as October 1 to September 30--got off to a reasonably promising start. According to NOAA, statewide precipitation was almost two inches above the average of 7.34” for the period October through December, thanks largely to a cluster of very wet storms in December. But those were also very warm storms that added to reservoirs and aquifers in the Central Valley but left the normally snow-clad slopes of the Sierra Nevada shockingly bare. The Sierra snowpack provides about a third of California’s water supply; it’s vital for keeping rivers and streams flowing into the summer, as well as for attracting tourists, skiers, and boarders in winter. On Thursday, the second California snow survey of the winter found 7.1” of snow and 2.3” of liquid in the snowpack at Echo Summit (see Figure 1). The liquid value was only 12 percent of the average for this time of year. As a whole, the northern Sierra snowpack is the lowest on record for January. One of the most stark symbols of the drought is the landscape around Lake Tahoe, where lower-elevation snow has been almost nonexistent. The average snowfall at South Lake Tahoe from October to January is 68.1”. As of January 29, the resort had received just 7.1”, with nothing measurable on the ground since January 2.

Water crisis looms in São Paulo

The state of water supply is far more dire in the region around São Paulo, Brazil, which is the most populous city in the Western Hemisphere and the third largest metropolitan area. The city’s 11 million residents, and the 20 million across the urbanized region, depend on a system of reservoirs that are perilously close to running completely dry in the midst of the region’s worst drought since at least 1930. Almost half of the São Paulo metro area relies on the main reservoir system, Cantareira (see Figure 2), which has slumped to just 5.1% of capacity as of January 29, according to data available online from Sabesp, the local water utility. The crisis is affecting not only water access but power, since the region is highly dependent on hydroelectricity. Sporadic power cuts have been reported, and close to 100 cities have implemented some type of water rationing, affecting some 4 million people. There have also been reports of unofficial rationing in the São Paulo area itself.

Figure 2. View of the bed of Jacarei River Dam, in Piracaia, during a drought affecting São Paulo state, Brazil on November 19, 2014. The dam is part of the São Paulo's Cantareira system of dams, which supplies water to 45% of the metropolitan region of São Paulo and is now at a historic low. Image credit: Nelson Almeida/AFP/Getty Images.

Climatologically, rainfall is ample across this subtropical area, and unlike San Francisco, the São Paulo region hasn’t been completely bone-dry this month. Weather Underground’s monthly summary page for São Paulo's Conghonas International Airport Inter shows that showers and thunderstorms have dropped modest amounts of rain on the city on about half of all days this month, totaling 4.21.” However, this is far short of the average monthly total for January of 13.76" indicated at Conghonas for a period of record extending back at least to 1996. The latest rainfall forecasts for the region are not especially encouraging--the Friday Weather Underground forecast for Sao Paulo predicted near-average rains of about 2" for the coming week, and the Friday morning 12 UTC run of the GFS model predicted near-average rains of about 5" in the Sao Paulo region through mid-February.

Even assuming water can be found elsewhere in the region to help get the city through the immediate crisis, the impacts on power supply may continue to loom large. São Paulo sits more than 40 miles inland and 2600 feet above sea level, making desalination an impractical option. The Center for Climate Change and Security notes the major risks presented by the current drought as well as other droughts that could develop across Brazil in the coming decade and beyond. Although the nation has made great strides in reducing deforestation over the last few years, the losses already incurred cut back on the ability of forests--especially those in the Amazon--to catch moisture and return it to the atmosphere through evapotranspiration. Many studies have shown potential links between the loss of Amazon rainforest and regional droughts, findings that were recently summarized by Antonio Donato Nobre (a senior researcher at the National Institute of Space Research and National Institute of Amazonian Research) in a widely discussed report, “The Future Climate of Amazonia.” No direct links have yet been made between the São Paulo drought and deforestation. However, Nobre cautions: “Because most of the water that irrigates the bread-basket quadrangle of southern South America originates from the Amazon, the future climate of the continent may be considerably dryer. In a worst-case scenario, it would resemble present-day Australia: a vast desert interior fringed on one side by strips of wetter areas near the sea.”

We'll have another post on Monday and will keep an eye on the storm making its way across the Midwest this weekend, which could bring significant snow to New England early next week.

Bob Henson

Figure 3. When water becomes political: Members of the Homeless Workers Movement (MTST) take part in a protest in São Paulo on September 25, 2014, against the rationing of water in neighborhoods on the city’s outskirts. The supply of water to many cities in the state of São Paulo has been hampered by the worst drought since 1930. Image credit: Nelson Almeida/AFP/Getty Images.

Video 1. Dry conditions in drought-stricken Central Brazil helped spawn a huge dust devil which hit Araguapaz in late January. Local news showed the video on January 30. Thanks to wunderground member barbarmz for posting this.


What Do the Latest Climate Assessments Tell Us about Nor’easters?

By: Bob Henson , 4:00 PM GMT on January 29, 2015

An ever-lengthening procession of winter storms has marched across the mid-Atlantic and Northeast over the last few years. Even their names have grown more prolific and colorful, from Snowmaggedon of January 2010 to this week’s Blizzard of 2015, also known as Winter Storm Juno. Do these monikers imply the storms themselves are getting more fierce? The naming trend can be explained largely by the demands of social media. However, recent overviews of national and global climate indicate that, as a whole, the most intense rainstorms and snowstorms in the Northeast U.S. are growing even more intense. Our understanding of a warmer climate with wetter extremes arises from both observations of past trends and model-based projections of future climate. It’s also supported by basic physics: in a warmer global environment, more water vapor evaporates from oceans and lakes, where it can be steered into rain- and snow-producing storms.

The most recent findings from the Intergovernmental Panel on Climate Change appear in its fifth major assessment, released in 2013-14. According to Chapter 2 of the Working Group 1 report, many parts of the world are reporting more frequent and intense bouts of extreme precipitation over the last few decades, though a few areas (such as western Asia and southern Australia) are bucking the trend. Notably, the IPCC found that “evidence is most compelling for increases in heavy precipitation in North America, Central America and Europe.” (FAQ 2.2, p. 218). The report also confirms earlier findings that the Northern Hemisphere jet stream continues a long-term poleward migration. That trend is widely expected to continue in the next several decades, though not all studies agree.

Within the United States, the region where nor’easters prowl is also where we find the most pronounced turn toward extreme rainfall and snowfall. The most comprehensive report to date on our nation’s climate is the latest U.S. National Climate Assessment, released early in 2014. It found that the trend toward intensified precipitation is stronger in the Northeast than in any other part of the country (Fig. 2.18 in the report, and Figure 1 above). For the period 1958 – 2012, this region saw a 71% increase in the amount of precipitation that fell on the wettest 1% of all days. “In the mid-latitudes, where most of the continental U.S. is located, there is an upward trend in extreme precipitation in the vicinity of fronts associated with mid-latitude storms,” noted the report. “Projections of future climate over the U.S. suggest that the recent trend towards increased heavy precipitation events will continue. This is projected to occur even in regions where total precipitation is projected to decrease, such as the Southwest.” (full report, Chapter 2, p. 37).

Figure 1. The map shows percent increases in the amount of precipitation falling in very heavy events (defined as the heaviest 1% of all daily events) from 1958 to 2012 for each region of the continental United States. These trends are larger than natural variations for the Northeast, Midwest, Puerto Rico, Southeast, Great Plains, and Alaska. The trends are not larger than natural variations for the Southwest, Hawai‘i, and the Northwest. The changes shown in this figure are calculated from the beginning and end points of the trends for 1958 to 2012. Image credit: U.S. National Climate Assessment, Fig. 2.18.

For a more specific take on U.S. trends in heavy snow, we can call on a 2013 paper led by Ken Kunkel (NOAA/North Carolina State University) that appeared in the Bulletin of American Meteorological Society (BAMS). It uses the recently developed Regional Snow Index, a spinoff of the Northeast Snowfall Impact Scale that ranks snowfalls by depth and coverage and by the population of affected areas. Kunkel and a large set of collaborators analyzed the 50 strongest snowstorms observed from 1900-01 to 2009-10 in each of six climate regions east of the Rockies. Among the six regions, the Northeast (see Figure 2) saw the second-greatest increase (13%) in the number of extreme snowstorms per decade across the century-plus period. Overall, said the report, “the greater number of extreme storms in recent decades is consistent with other findings of recent increases in heavier and more widespread snowstorms.”

Figure 2. Number of extreme snowstorms (top 10% of all snowstorms, 1900 - 2010) occurring each decade within the six U.S. climate regions in the central and eastern U.S., based on an analysis of the 50 strongest storms for each of the six climate regions from Oct 1900 to Apr 2010. Shown in the map for each region are (left) temperature and (right) precipitation trends, calculated as departures from the 20th-century average for all snow seasons in which each storm occurred. Snow seasons are defined as Dec–Mar for the South and Southeast regions and Nov–Apr for the other four regions. Image credit: Kunkel et al., 2013, BAMS/American Meteorological Society.

Given the potential for disaster inherent in the worst winter storms, even a 13% increase in their frequency could pack a notable punch. As evident in Figure 2, however, there is sharp variability from decade to decade in the frequency of such extreme snowstorms, something that should come as no surprise to any longtime weather observer. Which brings us back to the last decade and its bumper crop of Northeastern storms. At New York City’s Central Park, five of the 10 biggest storm-total snowfalls on record have occurred since 2000; in Boston, it’s four of the top 10, and in Washington, three of the top 10. This 21st-century onslaught could be related to the longer-term boost provided to extreme rains and snows by a warming planet, as well as a shorter-term jump in the frequency of Northeast storms related to cycles in global and regional climate. In addition, a growing amount of research suggests that Arctic amplification and sea-ice loss could be influencing jet-stream behavior and fostering outbreaks of cold and snow in North America and Eurasia (see the subsection "Is the jet stream getting weird?" in this Jeff Masters post from last November). Variations in snow-measuring practice over time may also play a role in local trends and records, although these can generally be factored out of broader-scale studies. For example, the study above led by Kunkel drew on a subset of U.S. reporting stations where confidence in the long-term quality of snow reports was highest.

And finally, the latest version of a query that can never be answered with razor-sharp precision: to what extent was the Blizzard of 2015 a product of climate change? All storms are now unfolding in a warmer, moister global climate. To get the closest thing to a quantitative answer on this particular storm, you would need to carry out an “attribution” study, using computer models to simulate the storm with and without such factors as the warmer-than-normal North Atlantic ocean temperatures that helped fuel the blizzard. Such studies have shown that events such as the deadly European heat wave of 2003 and Russian heat wave of 2010 became considerably more likely in a greenhouse-warmed climate. For the last three years, BAMS has released special reports, each featuring a set of attribution studies on extreme events from the previous year. The BAMS report on 2013 analyzed a violent midlatitude storm in Germany and Denmark, with inconclusive results. To my knowledge, no attribution work has yet been done specifically on nor’easters. Friederike Otto (University of Oxford) has put together an informal writeup explaining how attribution studies are carried out, using England’s destructive flooding of 2000–01 as an example.

Bob Henson

Nor'Easter winter weather Climate Change

Blizzard of 2015 Brings 2 - 3' of Snow and Questions About Forecast Accuracy

By: Bob Henson and Jeff Masters , 4:02 PM GMT on January 28, 2015

The snows from the Blizzard of 2015 have finally ended over most of New England, leaving some truly historic snowfall totals. The biggest snows hit Central Massachusetts, with three feet measured at Auburn, Hudson, and Lunenburg. More than two feet of snow fell across five other states, with 33.2" at Nashua, NH; 30" at Orient, NY; 28.5" at Burrillville, RI; 31.5" at Sanford, ME; and 34.1" at Winthrop, CT. Some superlatives for stations with a long period of snow records:

Worcester, Massachusetts: All-time record snowfall (34.5")
Boston, Massachusetts: 6th heaviest snowstorm (24.4")
Providence, Rhode Island: 4th heaviest (19.1")
Portland, Maine: 4th heaviest (19.1")
Blue Hill Observatory, SE Massachusetts: 2nd heaviest (30.8")

Figure 1. A combination of the day-night band and high resolution infrared imagery from the Suomi NPP satellite shows the blizzard near peak intensity as it moves over the New York through Boston Metropolitan areas at 06:45Z (1:45 am EST) on January 27, 2015. The nighttime lights of the region are blurred by the high cloud tops associated with the most intense parts of the storm. Visit NOAA's Environmental Visualization Lab for a spectacular hi-res version of the image.

The top six snowstorms on record in Boston, Massachusetts since 1890:

1. 27.6" Feb 17-18, 2003
2. 27.1" Feb 6-7, 1978
3. 25.8" Feb 24-26, 1969
4. 25.4" Mar 31-Apr 1, 1997
5. 24.9" Feb 8-9, 2013
6. 24.6" Jan 26-28, 2015

The top seven snowstorms on record in Providence, Rhode Island, since 1905:

1. 28.6" Feb 6-7, 1978
2. 23.4" Jan 22-23, 2005
3. 22.8" Jan 7-8, 1996
4. 19.1" Jan 26-28, 2015
5. 18.9" Feb 14-16, 1962
6. 18.3" Feb 3-4, 1961
7. 18.0" Feb 8-9, 2013

The top 4 snowstorms on record in Portland, ME:

1) 31.9" Feb. 8-9, 2013
2) 27.1" Jan. 17-18, 1979
3) 25.3" Feb. 17-18, 1952
4) 23.8" Jan 26-28, 2015

The Blue Hill Observatory in Southeast Massachusetts, with snowfall records going back to 1885, recorded 30.8"--its second greatest snowstorm on record. Their top 5 snowstorms on record:

1. 38.7" Feb 24-28, 1969
2. 30.8" Jan 26-28, 2015
3. 30.3" Mar 3-5, 1960
4. 30.1" Feb 6-7, 1978
5. 30.0" Mar 31 - Apr 1, 1997

The storm's powerful winds, gusting as high as 78 mph at Nantucket Island, brought a significant storm surge to the coast. As storm surge that peaked at 4.51' at 15:18 UTC January 27 hit Nantucket Island, flooding downtown Nantucket to a depth of 3.5'. The storm surge at Boston Harbor peaked at 4.78' at 16:12 UTC January 27, and caused damage to buildings and roads all along the Southeast Massachusetts coast.

There will be no rest for snow-weary New Englanders in the near future. A clipper-type system will drop light to occasionally moderate snow across the Northeast on Friday - Saturday, followed by an intense shot of bitter cold. The extended-range models suggest a much stronger system early next week, a potential nor'easter that could deliver heavy precipitation from the mid-Atlantic to Maine. There are still major uncertainties about timing, location, and precipitation type, as this storm will carry a good bit of warm, moist air--and our experience with this week's storm (see discussion below) should give us pause before jumping too quickly on any particular model solution.

An extreme jet stream pattern brought blizzard to the Northeast, record January warmth to the West
This week's Northeast U.S. blizzard was triggered by an unusually extreme jet stream pattern, featuring a sharp ridge of high pressure along the U.S. West Coast and a deep trough of low pressure diving to the south over the Northeast United States. This configuration allowed cold air to spill out of the Arctic behind the trough to feed into the blizzard, while at the same time allowing anomalously warm air to flow northwards across the Western U.S., a contrast that’s been playing out repeatedly across the nation for more than a year. More than 40 daily record highs and 7 monthly highs were tied or broken last weekend in California, Oregon, and Washington, according to NOAA’s U.S. records website; most notably, Death Valley, California hit a remarkable 87° on Sunday, tying its record for warmest January day on record. Many more records were smashed across a broader swath of western and central states early this week. East Rapid City, SD, had its warmest January low on record Monday, dipping only to 50°F, and Denver, CO, saw its warmest temperature for any January day in 127 years, with a balmy 75°F on Tuesday (exceeded only by a 76°F reading on the same date in 1888.) Numerous stations set or tied records for all-time warmest January day on record Monday and Tuesday:

North Platte. NE (74°)
Imperial, NE (77°)
Valentine, NE (72°)
Goodland, KS (79°)
Hill City, KS (83°)
Colby, KS (82°)
Great Falls, MT (67°)

…and a number of daily records were broken by impressive margins on Tuesday, including:

Dickinson, ND: 61°F (old record 51°F)
Oklahoma City, OK: 78°F (old record 71°F)
Russell, KS: 83°F (old record 65°F)

Figure 2. An extreme jet stream patten observed at 7 am EST (12 UTC) on January 27, 2015. Color-coded wind speeds at a pressure of 300 mb (roughly 9,000 meters or 30,000 feet) show the axis of the jet stream over North America, with a large upside-down "U"-shaped ridge of high pressure over the West Coast. All-time record high temperatures for the month of January were observed over several locations in the Western U.S. underneath this ridge. The strongest winds of the jet stream (orange colors, 160 knots) were observed over the Southeast Canada, downstream from where a strong "U"-shaped trough of low pressure was anchored. The surface low pressure system associated with this trough brought the Blizzard of 2015 to the Northeast U.S. As I've discussed many times (most recently in my April 2014 post, California Drought/Polar Vortex Jet Stream Pattern Linked to Global Warming), extreme jet steam patterns like this one have increased in recent years. I wrote a story for the December 2014 issue of Scientific American called, "Is the Jet Stream Getting Weird?" which discusses how climate change could potentially be responsible for this increase in extreme jet stream patterns. Recent runs of the GFS and European models point to a highly amplified jet stream pattern continuing over North America and spreading to Europe next week, which will produce a variety of extreme weather over both continents. This image was generated from the 12 UTC January 27, 2015 run of the GFS model, and plotted using our wundermap.

The NYC forecast: Moving from diagnosis to treatment
The underwhelming snow totals in New York City are on track to become one of the most famous U.S. forecast “busts” of the 21st century. Many journalists, bloggers, and meteorologists donned their rear-view goggles on Tuesday to analyze what went wrong. Most of them, including the New York Times, correctly observed that in the big picture, this wasn’t a bust at all. NWS computer models and public outlooks captured the nor’easter as a whole--including its extreme intensity--remarkably well. The record snowfalls in eastern Massachusetts bore out the pre-storm designation of “historic.” The devil lay in the details of predicting where the storm’s west edge would be, as a dramatic gradient in snowfall totals (which forecasters did anticipate) ended up being overlaid atop the nation’s largest metro area. As discussed in our post yesterday, forecast models diverged markedly on where to place that crucial western edge. In turn, there were sharp differences among various forecast sources on what would happen in New York City, even as late as Monday evening. In a press conference with reporters on Tuesday, NWS director Louis Uccellini strongly defended his agency’s science and staff while acknowledging, “We all know in this business you’re only as good as your last forecast.”

Clearly, the outcome for New York was more uncertain than for Boston, where there was much greater model agreement on the risk of two to three feet of snow. Probabilistic tools, such as the SREF plume featured in our post yesterday, are one way that the NWS captures such distinctions. Another is the nationwide probabilistic winter weather outlooks issued by the NWS’s Weather Prediction Center twice each day. Some NWS local offices also provide experimental online graphics showing the potential best- and worst-case outcomes. “This is an important step forward,” noted Jason Samenow (Capital Weather Gang), “but these pages are difficult to find on their Web sites, and this information is not included in public forecasts.” The University of Washington’s Cliff Mass summarized the New York forecast and its implications in his blog: " . . .the NWS has to move to a much more probabilistic form of forecasting preparation and dissemination, one in which forecast uncertainties are made clear to users. The computer workstations used by NWS forecasters and NWS websites are not designed to facilitate probabilistic prediction. This needs to change."

Regardless of how well probabilities are assessed and conveyed, it’s still up to the recipients of forecasts to make critical yes/no decisions. University of Georgia’s Marshall Shepherd put it this way in a Weather Underground blog post: “There is more risk and nuance in weather forecasts than the public is interested in consuming, so it is a challenge to craft a message that gets attention, is not 'hype', yet has actionable information. We must continue to have the discussion about how to communicate uncertainty and risk effectively.” Social scientists are increasingly collaborating with NOAA on research-based strategies for improving how forecasts are communicated. NCAR’s Julie Demuth has been involved in such work on hurricanes and tornadoes. According to Demuth, though, “very, very little social science work has been done on winter weather events.” There’s also the growing problem of information overload. Weather forecasters have to sift through an enormous amount of data under intense stress and time pressure. Consumers have to reconcile what they hear about an impending storm from public and private outlets, family and friends, colleagues, and other sources, and then decide how and when to act. Analyzing this complex chain of events isn’t an overnight project, but the recent experience in New York suggests that taking the time to learn how best to convey winter storm threats could be well worth the effort.

Figure 3. 8:20 am Brooklyn, Tuesday January 27. Three days of emergency food stockpiled for this? A Brooklyn streetscape early on Tuesday morning in the wake of less-than-expected snowfall. Image credit: wunderphotographer hartKitt.

Bob Henson and Jeff Masters

Winter Weather

Historic Blizzard Rips across New England; New York City Largely Spared

By: Jeff Masters and Bob Henson , 4:46 PM GMT on January 27, 2015

Although the New York City metropolitan area was largely spared, the Blizzard of 2015 is pulling no punches this morning across much of eastern New England. Some locations in Massachusetts have already topped two feet of snow, with heavy snowbands still pounding the Boston metropolitan area and Cape Cod, extending northeast into coastal Maine. Although the heaviest snow will exit New England later this afternoon, lighter snow could persist into tonight in some areas.

According to the 10 EST Tuesday NWS Storm Summary and reports from the Boston NWS and New York City NWS, total snowfall amounts as of 9 am EST Tuesday at some Northeast U.S. locations included:

26.0" Worcester, MA
20.9" Islip, NY
18.0" New Bedford, MA
14.8" Portland, ME
11.0" Providence, RI
11.0" NYC La Guardia Airport
8.6" NYC JFK Airport
7.8" NYC Central Park
4.5" East Hartford, CT
3.5" Bridgeport, CT
7.0" New Haven, CT
6.0" Newark, NJ
1.1" Washington DC

At 10:10 am EST, an observer in Framingham, MA, reported 30.0”.
Top wind gusts:

78 mph, Nantucket Island, MA
78 mph, Mount Washington, NH
74 mph, Humarock, MA
70 mph, Sagamore on Cape Cod, MA

The highest sustained winds thus far have occurred at Nantucket Island: 59 mph at 6:09 am Tuesday.

Figure 1. Photo credit: A vehicle buried under a night’s worth of heavy snow in East Lyme, Connecticut. Photo credit: Wunderphotographer Xchange.

The Massachusetts coastline experienced high waves, moderate coastal flooding, and a few areas of major coastal flooding this morning. According to the Boston Globe, Scituate, located southeast of Boston, reported “rapidly deteriorating conditions’’ after the predawn high tide, with residents along Central Avenue and Surfside Road calling for help to evacuate their flooded homes. Preliminary data from the NOAA Tides and Currents website shows that the storm surge in Boston Harbor (the amount delivered by the storm above normal high and low tides) was exceeding 4.5 feet as of 11:00 am EST--considerably higher than expected. This surge is higher than the maximum storm surge observed in the blizzard of February 1978, but slightly less than the 5 feet observed in the “Perfect Storm” of Halloween 1991. Fortunately, the maximum surge occurred as the tide was going out; during the 4:30 am Tuesday high tide, the surge was lower, about 3.2 feet.

Figure 2. Infrared satellite images of the “Storm of the Century” (March 13, 1993) and the Blizzard of 2015 (January 27, 2015). Image credit: CIMMS Satellite Blog (left), WunderMap (right).

Why was the snowfall forecast for New York City too high?
On Monday morning, the National Weather Service predicted storm-total snowfall amounts of 20 - 30" for New York City. As of 9 am EST Tuesday, snowfall amounts in the city ranged from 7.8" in Central Park to 11" at La Guardia Airport, with just 1 - 2" more snow likely. So what went wrong with the forecast? Heavy snow forecasts are notoriously difficult, since our computer models struggle to accurately predict where the very narrow bands of heavy snow with snowfall rates of 2 - 4" per hour will set up. Furthermore, an error of 50 miles in predicting the track of the storm can make a huge difference in snowfall amounts, and a 50-mile error in track in a 24-hour forecast is fairly common for a storm system 1000 miles across. The 7 am EST (12 UTC) Monday run of what is usually our top forecast model, the European model, predicted that the storm would track about 100 miles farther west than it actually did. The American GFS model, which just underwent a significant upgrade over the past month to give it increased horizontal resolution, performed better, putting the storm farther to the east. Forecasts that relied too heavily on the European model put too much snow over New York City. The heaviest snows were about 50 miles east of the city, over central Long Island (Islip Airport, located 50 miles east of New York City, got 20.9" of snow as of 9 am EST Tuesday.) Moral of the story: the European model, which famously out-predicted the GFS model during Hurricane Sandy, is not always right. The GFS model is also a top-notch model, and will sometimes outperform the European model. The Weather Channel forecasts relied less heavily on the European model, and predicted 15" of snow for NYC early on Sunday. The forecast snow amounts were cut to less than 10" by Sunday evening, and stayed that way for the duration of the storm.

Figure 3. Surface pressure (blue contours) and precipitation (color-fill) forecast for 7 am Tuesday January 27, 2015, as predicted by the 7 am EST (12 UTC) Monday January 26 run of the European model. The model's predicted center location of the blizzard (marked with an "L") was about 100 miles farther west than the what actually occurred. Image taken from our wundermap with the model maps layer turned on.

As recently as Monday morning, the Short-Range Ensemble Forecast system suggested a wide range of possibilities for total snowfall in the New York area (considerably wider than for Boston, where models were in closer agreement on a big storm). Forecasters are increasingly looking to probabilistic tools as a way to convey the uncertainty inherent in multiple model solutions. As we noted yesterday, the NWS Boston office released maps showing the lowest and highest 10% of accumulations that might be expected based on a range of model guidance. Such maps remain experimental, and it is not yet clear what formats will be most useful to the wide range of public and specialized users of NWS forecasts. The recent growth in collaboration among social scientists and meteorologists could shed light on the best routes forward as probabilistic guidance grows in complexity (and potential usefulness). For more on the probabilistic aspects of the Blizzard of 2015, see Lee Grenci’s Wunderground post “Misleading Snowfall Forecasts.” We will continue to update our live blog on the storm through the day.

Figure 4. Cumulative snowfall predictions for New York (LaGuardia Airport) from the Short-Range Ensemble Forecast system issued at 5 pm EST (21 UTC) Monday, January 26. The SREF ensemble is drawn from several independent runs using the NAM, WRF-NMM, and WRF-ARW models. A split between model clusters is evident in the large spread of projected accumulations, with predicted snowfall amounts ranging from 4" to 40". Image credit: NOAA Storm Prediction Center.

Bob Henson and Jeff Masters

Winter Weather Juno Blizzard

Historic Nor’Easter to Wallop New York, New England

By: Jeff Masters and Bob Henson , 4:22 PM GMT on January 26, 2015

Observations and model output over the last few hours continue to point toward a snowstorm/blizzard tonight and Tuesday that will affect tens of millions of Northeasterners with potential record snowfall, extremely high winds, and significant coastal flooding. Snow was quickly developing on Monday morning across the New York metro area and southern New England. Below is a summary of the potential impacts from this major weather event. We will provide frequent updates as the storm unfolds through a live blog created by Weather Underground’s Shaun Tanner.

Snow amounts: holding firm
Computer models continue to vary somewhat in the placement and intensity of this storm’s heaviest snowfall. However, the big picture has not changed appreciably. A strong upper-level wave of low pressure in the atmosphere moving toward the mid-Atlantic coast is the main driver of the impending blizzard. On Sunday, a fast-moving, intense line of thunderstorms developed over Mississippi and Alabama, bringing severe wind gusts (58-59 mph) at the Tuscaloosa and Birmingham airports. The fact that such strong thunderstorms could develop in relatively cool, dry air suggests how powerful this upper-level wave is.

As the wave pivots around a much larger upper-level low stationed in eastern Canada, it will generate a surface low off the mid-Atlantic coast that will rapidly intensify tonight and Tuesday. Together, these features will generate very strong dynamics and rapid snowfall rates, with the heaviest amounts expected along a broad swath from northern New Jersey to southern Maine. Throughout this region, a foot or more of snow is likely, and some areas could receive 24” or more. The placement of the overall swath of snow will be determined largely by where the upper-level and surface features evolve, and especially by how far east or west they are. While there is still some model uncertainty here, the surface low is expected to move very slowly while at peak intensity just southeast of Long Island and Cape Cod. The New York area is toward the southwest end of the snow swath, so the overall east-west placement of the overall storm will be vital to how much snow falls there.

Within the overall snow swath, the heaviest amounts will hinge on where persistent bands of snow (mesoscale bands) develop. It is still too soon to know exactly where these will take shape. In a Monday morning discussion, National Weather Service forecasters in Boston noted the possibility of parallel bands of very heavy snow, with an outer arc located inland (perhaps from central Massachusetts to interior Maine) and another band closer to Rhode Island and eastern Massachusetts, where a coastal front will separate milder marine air from the frigid inland air. Later today, the new High-Resolution Rapid Refresh model will provide increasingly detailed guidance on where the mesoscale bands may develop. The HRRR model is updated every hour using radar data and other current observations.

Here are some current ranges of snowfall being predicted in NWS local forecasts:

New York: 18 – 24”
Providence: 20 - 30”
Boston: 20 – 30”

These numbers suggest that the storm has a good shot of placing in the top-ten list for heaviest snow accumulations at all three of these cities. For a summary of top snowfall events at New York, Boston, and Providence, see our live blog post.

As indicated by the ranges above, no single number can capture the range of possibilities in a rapidly evolving, highly dynamic storm like this one. Another way to view the potential is through probabilistic maps, such as the experimental ones posted by NWS/Boston on its winter weather page. Drawing on model guidance, these maps indicate the likelihood of a given amount of snow in two ways:

--What are the least, most, and most probable accumulations one could expect?
--What is the likelihood of exceeding a certain accumulation?

In these experimental maps, virtually all of eastern Massachusetts and Rhode Island show a 100% chance of at least a foot of snow, and the odds are 80-90% that most of these areas will receive at least 18”.

Figure 1. Experimental guidance on potential accumulations from the unfolding nor'easter, posted on Monday morning, January 26, by the National Weather Service forecast office in Boston. The maps show the lowest 10% (top) and highest 10% (bottom) of potential accumulations that one might expect from this storm based on computer model guidance. Image credit: NWS/Boston.

A storm surge of 2 - 4 feet and waves up to 31 feet high
The blizzard will feature a powerful low-level jet stream of strong winds that will dip close to the surface over the offshore waters of New England on Tuesday, bringing sustained winds of 40 - 50 mph with gusts as high as 75 mph to the waters of Southeast Massachusetts, including Cape Cod, Martha’s Vineyard, and Nantucket. These winds will create huge waves 26 - 31 feet high along the east coast of Cape Cod, and 7 - 13 feet high along more sheltered parts of the coast. Ocean-facing barrier beaches of Long Island, New York will see waves of 7 to 12 feet. A storm surge of 2 - 4 feet is expected along the coast from Maryland to Maine. The combined action of the storm surge and waves will cause coastal flooding and severe beach erosion, and could cut new inlets through exposed east and northeast facing barrier beaches in Southeast Massachusetts. Moderate coastal flooding will occur at many coastal locations during the Tuesday morning and Tuesday afternoon high tide cycles in Southeast Massachusetts, with a few areas of major flooding possible during the Tuesday morning high tide. The difference in water levels at Boston between low and high tide is twelve feet, so a storm surge arriving at low tide will do little damage, while a storm surge arriving at high tide has the potential to cause significant damage. According to the Monday morning runs of the National Weather Service's experimental storm surge model for extratropical storms, the peak storm surge in Boston is predicted to occur about 2 - 3 hours after the 4:30 am EST Tuesday high tide. A storm surge of 3.0 - 3.5 feet is expected, which should cause mostly moderate flooding. However, if the timing of the storms’s strongest winds shifts just 2 - 3 hours earlier, the storm surge could arrive at high tide, causing widespread major flooding along the coast and considerable damage. Even in this worst case scenario, the coastal flooding in Southeast Massachusetts should not be as great as that of the great Blizzard of 1978.

Significant storm surges of 3 - 4 feet are also predicted to occur along the coasts of New York and Connecticut in Long Island Sound, causing mostly moderate coastal flooding. Monday morning storm surge model runs show a storm surge of about four feet hitting Bridgeport, Connecticut and Port Jefferson, New York near high tide on Tuesday morning.

Figure 2. Forecast wave heights for 10 am EST (15 UTC) Tuesday, January 27, 2015 from the 2 pm EST (18 UTC) Sunday January 25, 2015 run of NOAA's Wavewatch III model. Significant wave heights of 7 - 8 meters (23 - 26 feet, yellow green colors) are predicted for the waters just offshore from Boston, Massachusetts.

Bob Henson and Jeff Masters

Winter Weather Blizzard Juno

Potentially Historic Blizzard Taking Aim on New England

By: Bob Henson , 6:30 PM GMT on January 25, 2015

The densely populated area from New York City to Boston could experience one of its ten biggest snowstorms on record early this week, as a textbook nor’easter takes shape over the next 48 hours. While local details are bound to evolve somewhat as the storm develops, the models are now in strong, consistent agreement on a potentially crippling snowstorm. Blizzard watches were hoisted on Sunday morning from eastern New Jersey to northeast Massachusetts, including the New York, Providence, and Boston metropolitan areas.

Despite the increasing skill of computer forecast models in recent years, this week’s threat emerged remarkably quickly. As recently as Friday, the model consensus was for a weaker storm that would sweep through the region from west to east, then strengthen well offshore. One of the first models to switch gears was the ECMWF, whose operational run issued at 00Z Friday night highlighted the risk of a potential blockbuster storm for the Northeast U.S. By Saturday morning, most other models had quickly joined the bandwagon. “All operational models now have the forecast of a major snowstorm/blizzard,” said NOAA’s Weather Prediction Center on Sunday morning.

The driver for this record-threatening event is a strong upper-level wave now diving across the Midwest. In line with the pattern of several other storms this year, this wave will produce a stripe of snow from northern Indiana and Ohio into Pennsylvania, dropping several inches on the Washington and Philadelphia metro areas by Monday afternoon. On its heels, a powerful branch of the jet stream will continue diving southeastward, intensified by a unusually strong ridge over the western U.S. that produced record highs across Washington, Oregon, and California on Saturday. As it moves off the mid-Atlantic coast, the upper-level energy will consolidate into a powerful upper-level low and generate a rapidly intensifying surface low. Surface pressures may drop by more than 24 millibars in 24 hours, qualifying the storm as a true coastal “bomb". Sea surface temperatures are well above average off the northeast U.S. coast, which could help fuel the storm’s strengthening. As it reaches peak intensity on Tuesday, the surface low is expected to slow down just southeast of Cape Cod, which would keep the snow machine going at full strength and lash the New England coast with winds gusting to 60 mph or more in places.

Figure 1. Surface winds (knots) projected by the GFS model at 06Z Sunday, January 25, valid at 09Z Tuesday, January 27. As the surface cyclone winds up south of Long Island, winds exceeding 50 knots are projected to batter Cape Cod. For winds in mph, multiply by 1.15. Photo credit: WunderMap.

It appears that all of the classic ingredients are lining up to produce a historic nor’easter snowstorm. Temperatures on Sunday morning across southern New England were near or slightly above freezing, but a weak cold front is pushing through the area, steered by a separate branch of the jet stream over eastern Canada. This cold, dry low-level air, plus the storm’s track being far enough offshore, will ensure that nearly all precipitation falls as snow for the duration of this storm across the entire region. The main exception is the outer reaches of Cape Cod and Nantucket, where a periodic changeover to rain is possible.

How much snow?
The heaviest snow totals are likely to occur along a SW-to-NE belt oriented from somewhere near or just east of New York City to eastern Massachusetts in or near Boston. In situations like these, narrow strips of intense snow (mesoscale bands) are typically oriented along an upper-level “bent-back” warm front that arcs west from the consolidating storm. Wherever these bands set up, snowfall rates can easily exceed 3”/hour. It’s impossible to predict the exact location of the bands this far in advance. However, mesoscale forecast tools such as NOAA’s new High-Resolution Rapid Refresh model (which became operational just last fall) should provide more detailed guidance by late Monday.

Given the projected intensity of this storm, as well as the strong model agreement and the textbook nature of the overall pattern, it seems very plausible to expect widespread snowfalls from Monday night through Tuesday night of 12” to 24” between northern New Jersey and southwest Maine, with some areas in mesoscale bands getting 24” to 36”. Lesser amounts can be expected further to the southwest, with Philadelphia possibly getting a few inches on top of its Monday total. If the system moves more slowly than expected, it could add to the accumulations on the southern and western flank of the vast snow shield. Massive transportation impacts can be expected over the next several days, with reverberations to the air-traffic system nationwide. The high winds and snow could lead to large-scale power outages across New England.

Figure 2. Snowfall from this week's storm at some New England sites could rival the amounts produced by Winter Storm Nemo, shown here in its full glory at Auburn, Massachusetts, on the evening of February 8, 2013. Photo credit: wunderphotographer stoneygirl.

The most recent analog event for this week's storm is the Blizzard of 2013, aka Winter Storm Nemo, which dropped 24.9” in Boston (the city’s fifth highest snowfall on record) and a storm maximum of 40” at Hamden, Connecticut. The strongest banding and heaviest snowfalls in Nemo extended from central Long Island across eastern Massachusetts to southwest Maine, where Portland had its highest-ever storm total (31.9”). This storm is somewhat less likely to produce massive totals in Maine, but the amounts in southern New England could be comparable to Nemo in places. Only a slight difference in the orientation of the mesoscale banding can make a big difference in whether a particular spot gets a major snowstorm or a record-smashing one. If either Boston or New York gets 20” or more, this week’s storm will make it into either city’s top-ten list. This outcome appears somewhat more likely in Boston than New York, based on the latest models. Current NWS forecasts are calling for 12-24” in New York and 18-24” in Boston, with higher local amounts possible. Since cold temperatures are assured with this system, the snow-to-liquid ratios could be on the high side for nor’easters, which would enhance the expected snow totals further.

Jeff Masters and I are keeping a close eye on this unfolding situation. We’ll post an update by Monday morning.

Bob Henson

Figure 3. “Plumes” of projected total snowfall for Boston, based on an ensemble of more than 20 model solutions compiled at 09Z on Sunday, January 25 by NOAA’s Short Range Ensemble Forecast. The dark black line indicates the model mean, which suggests that 25-26” of snow is a strong possibility for Boston. Photo credit: NOAA Storm Prediction Center.

Winter Weather Nor'Easter

California Drought Worsening During Height of Rainy Season

By: JeffMasters, 9:10 PM GMT on January 23, 2015

The Western U.S. winter rainy season has reached its halfway point, and there is only bad news to report for drought-beleaguered California. November through March marks the period when California receives its heaviest rains and snows, thanks to the wintertime path of the jet stream, which dips to the south and brings wet Pacific low pressure systems to the state. The rainy season started out promisingly, with several December storms bringing precipitation amounts close to average for the month over much of the state. Troublingly, though, record-warm ocean temperatures off of the coast meant that the December storms were unusually warm. This resulted in snow falling only at very high elevations, keeping the critical Sierra snow pack much lower than usual. The jet stream pattern shifted during January 2015, bringing disastrously dry conditions to the state. January usually brings 4.19" of rain to San Francisco, but no rain at all has fallen in January 2015 in the city--or over much of Central California. The dryness has been accompanied by near-record warmth at higher elevations in the Sierras, with temperatures at Blue Canyon and South Lake Tahoe averaging nearly 8°F above average for the month of January. As a result, the snowpack in the Sierras--a critical reservoir of water that is used throughout the rest of the year--is abysmally low, running about 30% of normal for this time of year. California's eight largest reservoirs are 33% - 86% below their historical average, and the portion of the state covered by the highest level of drought expanded in mid-January--a very ominous occurrence for the height of the rainy season.

Figure 1. The Enterprise Bridge passes over a section of Lake Oroville that was nearly dry on September 30, 2014, in Oroville, California. Lake Oroville, California's 2nd largest reservoir, was at 49% of average (30% of capacity), the second lowest level on record (behind 1977.) Heavy rains in December 2014 allowed lake levels to recover slightly--as of January 23, 2015 Lake Oroville was at its 7th lowest level of the past 35 years. Image credit: California Department of Water Resources.

Figure 2. The same view of Lake Oroville in happier times: July 20, 2011. (Paul Hames/California Department of Water Resources/Getty Images) 

The forecast: hot and dry
An intense ridge of high pressure will build in over California this weekend, bringing near-record high temperatures in the low to mid-70s to San Francisco. The all-time hottest January temperature in San Francisco of 73°F, set just last year, could fall on Sunday. The ridge of high pressure will stay entrenched over California during the remainder of January, bringing continued dry conditions. A weak upper-level low pressure system will bring a few rain showers to the state beginning this Tuesday, but rainfall amounts will be generally less than 1/2"--an insignificant drop in a very large, dry bucket. With long-range models showing no shift in the jet stream pattern through the first week of February, California may be on its way to a fourth consecutive bone-dry rainy season--pushing the state into an increasingly dire drought situation.

Figure 3. Time series of the change in drought conditions in California from January 28, 2014 through January 22, 2015. The area covered by the worst category of drought--"Exceptional"--peaked at 58% during the summer of 2014. In December 2014, "Exceptional" drought coverage fell to 32%, thanks to heavy rains, but this area increased again to 39% in mid-January 2015 due to unusual dryness. Image credit:

Related blog post: The State of the California Drought: Still Very Bad, January 13, 2015, by water resources expert Dr. Peter Gleick of the Pacific Institute.

Jeff Masters


A Striking Change in Lightning Deaths

By: Bob Henson , 5:21 PM GMT on January 22, 2015

Already, the 21st century has brought us the deadliest U.S. hurricane since 1928 (Katrina, 2005) and the deadliest tornado since 1947 (Joplin, 2011). Here's much better news: the death toll from lightning has plummeted across the nation in recent decades, and the progress is holding up nicely. Veteran lightning analyst Ron Holle presented an update on national and global casualty trends at the American Meteorological Society's annual meeting in Phoenix earlier this month.

Figure 1. Cloud-to-ground lightning emanates from a summer storm in Albuquerque, New Mexico, on July 15, 2014. Image credit: wunderphotographer Don Armstrong.

A century ago, lightning killed more than 400 people in the United States each year, at a time when the nation's population was much lower. Back then, most Americans lived on acreages or in small towns, and lightning tended to strike people while they were working on the farm or ranch. Today, the U.S. death toll averages less than 30 per year. Unlike most other severe weather threats, lightning tends to kill people one by one, so there haven't been any mega-disasters to interrupt the long-term improvement. The progress is even more dramatic when looking at the death toll per million (see Figure 2, below).

Figure 2. U.S. lightning deaths per million people (red line) and the percentage of the population classified as rural (blue line). Image credit: Ron Holle, updated from López and Holle 1998.

What's behind the improvement? Holle cites a variety of factors, including the availability of lightning-safe buildings and metal-topped, fully-enclosed vehicles (i.e., cars and trucks) as ready sources of shelter. He also stresses the importance of NOAA's lightning safety initiatives, which have ramped up greatly over the last 15 years. The mantra "when thunder roars, go indoors" is widely known, and people are now urged to stay inside until at least 30 minutes have passed since the last clap of thunder.

When Americans do die from lightning, it's more likely they're boating on the lake instead of plowing the south forty. According to a statistical breakdown featured on the National Weather Service’s Lightning Safety website, leisure activities accounted for 64% of the 261 U.S. lightning deaths reported from 2006 to 2013. Routine daily or weekly chores, such as taking care of yard work or tending to farm animals, account for only 16% of deaths. Among leisure activities, the largest single category is "water-related," with nearly half of those deaths associated with fishing. The University of Florida has an extensive website on lightning’s hazard to sailboats. Being a sports fan also has its hazards: last month, seven people were taken to the hospital with minor injuries after a strike hit a car parked at Tampa Bay’s Raymond James Stadium following a Tampa Bay-Green Bay football game.

Lightning kills far more people in other countries
Data on lightning deaths around the world are hard to come by, said Holle, but the most recent analysis suggests that as many as 24,000 people around the world are killed by lightning in a typical year. The highest per-capita fatality rates are in southern Africa, whereas the largest national toll by far is in India, still a highly agricultural society with more than 1.2 billion residents. A typical year sees about 1,700 Indians killed by lightning.

U.S. society is affected more by lightning than our improving death toll might suggest. It's been estimated that for every person killed, roughly ten people are injured, often with life-changing consequences. And the proliferation of home electronics and gizmos means that a typical home lightning strike wreaks more havoc than it used to. According to Holle, the average U.S. insurance claim from a home strike was around $900 in the late 1990s, but more than $5000 in 2013. Structural fires caused by lightning inflict about half a billion in U.S. damage each year, according to the National Fire Protection Association. Throw in the additional expense from lightning-damaged utility systems, plus the average $1.8 billion in costs related to fighting wildfires triggered by lightning, and the broad economic toll of lightning becomes evident. (I’ve seen this on a personal scale, having lost a home computer to a lightning strike several years ago—thanks in part to an inadequate surge protector.)

Along with the increased damage that a single lightning strike can inflict on our highly wired society, lightning itself could become more frequent in coming decades. New research covered by Jeff Masters last autumn suggests the potential for 50% more lightning by the end of this century in a business-as-usual emissions scenario.

A manuscript expanding on Holle’s talk can be downloaded from the abstract web page. Video presentations will be linked to abstracts in February.

Bob Henson

Figure 3. Lightning prowls the cityscape of Tucson, Arizona, near sunset on August 13, 2012. Photo credit: wunderphotographer ChandlerMike.

Severe Weather

Icy Roads Cause Havoc in Oregon, Texas, Northeast

By: Bob Henson , 4:28 PM GMT on January 20, 2015

Motorists in widely dispersed parts of the country found themselves slipping and sliding over the last week in treacherous black-ice conditions. Hundreds of accidents and more than a dozen deaths were reported. Repeated shots of cold, shallow surface air pouring across much of the United States this winter are paving the way for multiple icing events. In a typical year, icy and snowy roads cause roughly 900 U.S. deaths, more than hurricanes, lightning, tornadoes, and floods combined. Ice on highways is an underappreciated, hard-to-predict threat, often lumped in with snowstorms yet distinctly different in its appearance and impact. The events of the last week were striking in their far-flung nature, and a spate of dramatic photos and videos showed millions of people what can happen when vehicles moving at highway speeds encounter ice.

Perhaps the most spectacular multi-vehicle pileup this month was the catastrophic wreck on January 11 along Interstate 94 near Battle Creek, Michigan, which involved nearly 200 vehicles, killed at least one person, and injured many others. The extended chain-reaction accident occurred in poor visibility and road conditions during heavy lake-effect snow squalls. In contrast to that wreck, several other deadly collisions over the last few days occurred in conjunction with freezing rain, drizzle, and fog. These conditions can be far more dangerous than packed snow, in part because the resulting ice buildup on roads can occur in unpredictable patches and can be difficult or impossible for motorists to see.

Figure 1. Temperature at various heights as measured in the National Weather Service radiosonde launched near New York City at 7:00 a.m. EDT on Sunday morning, January 18. Image courtesy Tom Niziol, The Weather Channel.

Sunday’s string of accidents from Philadelphia to New York–dubbed #Icezilla on Twitter—caused major havoc, with at least three deaths and more than 400 collisions across the area. The meteorological set-up on Sunday morning epitomizes how difficult it can be to predict ice. As a strong upper-level trough approached a coastal warm front, rain developed over parts of the Northeast, and warmer air flowed over a surface air mass that had kept readings in the teens and 20s for more than a day. The Weather Channel’s Tom Niziol created the table in Figure 1 using radiosonde data collected from the launch at 12Z (7:00 a.m. EDT) on Sunday morning, January 18. Only in the lowest 200 feet or so of the atmosphere were temperatures below freezing, too shallow a layer for raindrops to freeze into ice pellets before hitting the ground. The icing risk was greatly exacerbated by the preexisting cold, which chilled roadways enough so that some surfaces remained below freezing for a time even after the surface air warmed above 32°F. Later in the day, as a surface low intensified, temperatures at ground level finally warmed up while the rains increased and spread northeastward. Philadelphia saw its seventh-wettest January day on record (1.84”), and a narrow band of thunderstorms gave parts of the New York metroplex a rare midwinter encounter with thunder, lightning, heavy rain, and stout winds.

Figure 2. Black ice is believed to be the cause of a freeway pileup involving more than a dozen tractor-trailers on January 17 along Interstate 84 in eastern Oregon, police said. Photo credit: AP Photo/Oregon Department of Transportation.

Another multi-vehicle pileup, this one in black ice and fog, occurred on Interstate 84 southeast of Baker City, Oregon, on Saturday morning, January 17. The 26-car accident injured 12 people, and a truly phenomenal image of one survivor quickly became iconic. As one semi-truck ran into another, Kaleb Whitbey and his SUV were sandwiched in between. Amazingly, Whitbey escaped with only minor injuries. “I’ve got two Band-Aids on my right ring finger,” he told the Oregonian, “and a little bit of ice on my left eye.”

The nation’s deadliest accident so far this year occurred on Wednesday, January 14, as a truck carrying prisoners and guards from a Texas correctional facility slipped off Interstate 10 just west of Odessa and careened into a train. Eight prisoners and two guards died, with five other prisoners and guards injured. Odessa-Schlemeyer Field reported freezing fog but only a trace of precipitation on the day of the accident, with the NWS’s Midland-Odessa office noting light freezing drizzle across the area in its early-morning forecast discussion. The Texas Department of Highway Safety concluded that icy roads likely led to the accident, while the National Transportation Safety Board is investigating the wreck.

Icing events can be subtle and exceedingly hard to predict, yet they lead to many hundreds of injuries and deaths on our nation’s highways each winter. Even the most prudent motorist can happen upon black ice without warning and find himself or herself virtually helpless to change course. A good deal of useful background, including photos and videos specific to recognizing and dealing with icy roads (as opposed to snow-packed conditions) can be found in the short online course offered at the website As always, the best strategy is avoidance: waiting till the roads are clearly safe, especially if rain or drizzle is falling onto highways that have been well below freezing for hours or days.

Bob Henson

Figure 3. Salting a roadway near Breckenridge, Michigan, to combat icy conditions on November 22, 2014. (WunderPhoto credit: sterlingbreck)

Winter Weather

Floods Kill at Least 260 in Malawi, Mozambique, and Madagascar

By: Jeff Masters , 4:35 PM GMT on January 19, 2015

In what is likely to be one of 2015's deadliest natural disasters, two weeks of heavy rains have hit the southeastern African nations of Malawi, Mozambique, and Madagascar, triggering rampaging floods that have killed at least 260 people and left 260,000 homeless, said Bloomberg News today. Hardest hit was Malawi, where 176 people are dead or missing and 200,000 homeless. According to EM-DAT, the international disaster database, only one other flood disaster has killed more people in Malawi: the floods of March 10, 1991, with a death toll of 472. That flood was also the most expensive weather-related natural disaster in their history, with damages estimated at $24 million (1991 dollars.) The floods of 2015 may be ten times more expensive: last week, Malawi requested humanitarian assistance of $430 million for recovery efforts. Many areas remain cut off, with aid workers struggling to provide food to the hardest-hit southern portion of the country. The heaviest rains in Malawi came on January 13, when Chileka, Malawi measured 6.57" (167 mm) of rain in 24 hours. The tropical disturbance that spawned these heavy rains moved over Mozambique on January 14, triggering flooding that killed at least 71 people there. The next day, the disturbance moved over the Mozambique Channel between Mozambique and Madagascar, becoming Tropical Storm Chedza, which hit Madagascar on January 16, killing 13 people on the island. Ocean temperatures were up to 0.6°C (1.0°F) above average in the Mozambique Channel, which contributed to the high rainfall rates observed with Chedza and its precursor disturbance.

Figure 1. A bridge destroyed by flooding at Nchalo in Chikwawa, Malawi, the week of January 13, 2015. Image credit: Source: Department of Disaster Management Affairs, Malawi.

Figure 2. VIIRS image from January 13, 2015 showing a tropical disturbance over Malawi that would later become Tropical Storm Chedza (left side of image.) Category 4 Tropical Cyclone Bansi is seen to the east of Madagascar (right side of image.) Image credit: NOAA Visualization Lab.

Jeff Masters


Incredible Lightning Photos of the Eye of Bansi From the International Space Station

By: Jeff Masters , 2:10 AM GMT on January 18, 2015

One of the most incredible photographs ever of a tropical cyclone was taken this week of Tropical Cyclone Bansi in the South Indian Ocean, which peaked as a Category 5 storm with 160 mph winds on January 13 at 00 UTC. Lightning within an intense thunderstorm in the eyewall of the storm lit up the eye at night, which was captured on the International Space Station by Astronaut Sam Cristoforetti in the photos below. Bansi grazed the French island of La Reunion, off the coast of Madagascar, on January 13. The storm dumped up to 22 inches of rain, according to RSMC-Tropical Cyclone Centre La Reunion, the official agency for monitoring tropical cyclones in the southwest Indian Ocean. More populated areas of the island picked up 6 -10 inches of rain. La Reunion is notorious for its incredible rains from tropical cyclones, due to its steep volcanic terrain and location in the Southwest Indian Ocean's "hurricane alley." According to the World Meteorological Organization, world rainfall records that have been set there include:

12 hours: 45.00" (1.144 m), Jan. 7 - 8, 1966 during Tropical Cyclone Denise
24 hours:  71.85" (1.825 m), Jan. 7 - 8, 1966 during Tropical Cyclone Denise
72 hours: 154.72" (3.930 m), Feb. 24 - 26, 2007 during Tropical Cyclone Gamede
96 hours: 194.33" (4.936 m), Feb. 24 - 27, 2007 during Tropical Cyclone Gamede
10 days: 223.50" (5.678 m), Jan. 18 - 27, 1980 as Tropical Cyclone Hyacinthe moved slowly over the island

The 12-hour rainfall record of 45" on La Reunion is more rain than Death Valley, California gets in twenty years!

Figures 1 and 2. Lighting in the eyewall lights up the eye of Tropical Cyclone Bansi, as seen from the International Space Station. The date of the photos was not given, but presumably was January 13, 2015, when Bansi was near peak intensity as a Category 5 storm with 160 mph winds. Image credit: Astronaut Sam Cristoforetti.

Bansi one of the strongest tropical cyclones on record in the Southwest Indian Ocean
According to TWC's Michael Lowry, very few stronger tropical cyclones have been recorded in the Southwest Indian Ocean. The strongest storm on record to form there was Tropical Cyclone Agnielle of November 1995, which peaked as a Category 5 storm with 175 mph winds. The only other Cat 5s to form in the basin were Geralda (January 1994) and Gafilo (March 2004), which had top sustained winds of 165 mph and 160 mph, respectively. Bansi was a Category 1 storm on Saturday evening, and was headed east-southeastwards towards colder waters and an expected dissipation on Monday.

Jeff Masters


2014: Hottest Year in Recorded Human History

By: Jeff Masters , 5:05 PM GMT on January 16, 2015

Earth had its warmest year on record in 2014, said NOAA and NASA at a joint press conference today. According to NOAA's National Climatic Data Center, global surface temperatures in 2014 were 1.24°F (0.69°C) above the 20th century average, highest among all years in the 1880-2014 record, easily breaking the previous records of 2005 and 2010 by 0.07°F (0.04°C). Using independent measurement techniques but mostly the same set of surface stations, NASA also rated 2014 as the warmest year on record, as did the Japan Meteorological Agency (JMA). The other widely-cited global temperature measurement, from the UK Met Office, has not yet been released for 2014. Because there are variations in how each group handles the Arctic and other data-sparse areas, there are slight differences in the "top ten" lists of warmest years produced by each group. However, 2014 is the first year since 2005 that has topped the temperature charts for both NASA and NOAA.

Figure 1. Earth's departure in temperature from the 20th century average during the period 1880 - 2014, according to NOAA.

Including 2014, nine out of ten of the warmest years in the 135-year period of record have occurred during the 21st century (2001–2014), with 1998 (4th warmest year on record) rounding out the top ten. Global land temperatures were the 4th warmest on record during 2014, and ocean temperatures were the warmest on record. Global satellite-measured temperatures in the lower atmosphere were the 3rd or 6th warmest in the 36-year record, according to UAH and RSS, respectively. The year 2014 joined 2012 and 2013 as having near-average precipitation on balance across the globe.

Figure 2. Departure of global temperature from average for 2014. Record warmth was spread around the world, including Far East Russia into western Alaska, the western United States, parts of interior South America, most of Europe stretching into northern Africa, parts of eastern and western coastal Australia, much of the northeastern Pacific around the Gulf of Alaska, the central to western equatorial Pacific, large swaths of northwestern and southeastern Atlantic, most of the Norwegian Sea, and parts of the central to southern Indian Ocean. The only land areas cooler than average were the Central U.S. and the southern tip of South America; no land areas were record cold. Image credit: NOAA's National Climatic Data Center.

New record set without an El Niño event
The new temperature record in 2014 was not a “cheap” record—it was set without an official El Niño event. The previous three hottest years on record—2010, 2005, and 1998—were all characterized by an El Niño event at the beginning of the year, according to NOAA’s Climate Prediction Center. During an El Niño event, warm water in the equatorial Pacific can warm the global surface temperature by 0.1°C or more, making global temperature records more likely. Admittedly, El Niño-like conditions began developing in June 2014, and the threshold for a weak El Niño event was reached in October and maintained through December. However, since there is lag of about 2 - 4 months between the emergence of El Nino conditions and the impact of this warm water on global surface temperatures (Foster and Rahmstorf, 2011), the emergence of El Niño-like conditions late in 2014 did not have a big impact on global surface temperatures. Moreover, January - March of 2014 featured weak La Niña-like conditions in the Eastern Pacific, with cooler-than-average ocean waters that helped depress global temperatures well into the summer.

Figure 3. The global departure of temperature from average from 1965 - 2014, binned by whether or not the year was classified as an El Niño, La Niña, or neutral. 2014 was by far the hottest "neutral" year on record, and the first year since 1990 to set a record without influence from El Niño. Image credit:

UK Met Office forecasts another global temperature record in 2015
What about the new year? The UK Met Office predicts that 2015 is likely to top 2014. Assuming that the Met Office's final numbers for 2014 agree with NASA and NOAA on a global record, this forecast would make 2015 the second record-setting year in a row. The last time we saw consecutive global highs was in 1997 and 1998, when the strongest El Niño event on record gave a major boost to both years (see NOAA’s ENSO dataset). The previous pair of back-to-back record-setters was 1987 and 1988, again bolstered by El Niño conditions. A useful analog for our current situation may be 1980 and 1981. In those two years, new global highs were set without the benefit of any El Niño event. What’s more, the early 1980s marked the beginning of a dramatic rise in global atmospheric temperature that spanned nearly two decades. The rate of global warming since 2000 has been slower than in the 1980s and 1990s, but could back-to-back warmest years on record in 2014 and potentially in 2015 signal the end of this slow-down? Next week, Bob Henson will discuss new research presented at last week's American Meteorological Society meeting pertaining to this subject.

The fact that separate analyses by three major research groups rated 2014 as the warmest year on record should put to rest the bogus idea often espoused by climate change deniers that "global warming stopped in 1998." Based on the evidence, more than 97% of climate scientists have concluded that humans are primarily responsible for the warming of the planet to the record levels observed in 2014. Climate change is already causing significant impacts to people and ecosystems, and these impacts will grow much more severe in the coming years. New research is painting a clearer picture of the tough decisions that lie ahead if we hope to reduce the serious risks that we and our planet face. As we approach the critical negotiations in Paris in December to hammer out a new binding climate change treaty, we should keep in mind that we can choose to take economically sensible steps to lessen the damage of climate change, and the cost of inaction is much higher than the cost of action.

Jeff Masters and Bob Henson

Climate Summaries

The 25 Billion-Dollar Weather Disasters of 2014

By: Jeff Masters , 7:58 PM GMT on January 13, 2015

Earth had a relatively quiet year for natural disasters in 2014, with the combined economic losses adding up to $132 billion US dollars--37% below the $211 billion per year average damages from the previous ten years, said insurance broker Aon Benfield in their Annual Global Climate and Catastrophe Report issued today. There were 25 billion-dollar weather disasters in 2014, and 27 billion-dollar natural disasters (including earthquakes.) This is slightly below the ten-year average of 27 billion-dollar weather disasters and contrasts sharply with 2013, which set a new record for billion-dollar weather disasters with 41. The most expensive natural disaster of 2014 was September flooding in India and Pakistan caused by torrential monsoon rains. The $16 billion in damage done in India's Jammu and Kashmir region made the flood that nation's most expensive natural disaster in history, surpassing the $11.6 billion price tag (2014 dollars) of the July 1993 monsoon floods, according to EM-DAT, the International Disaster Database. India was the only nation to suffer its most expensive natural disaster in history in 2014. For comparison, six nations had their most expensive natural disaster in history in 2013. The deadliest disaster of 2014 was a multi-month period of flash flooding and landslides that killed an estimated 2,600 people in Afghanistan.

U.S. sees 8 - 9 billion-dollar weather disasters
In the U.S., there were nine billion-dollar weather disasters in 2014, according to Aon Benfield. NOAA's National Climatic Data Center gave a lower number of U.S. billion-dollar weather disasters in 2013: eight, which is also the ten-year average of these disasters. The eight billion-dollar weather disasters of 2014 marked the 6th highest yearly total since 1980. Five of the top six years for these disasters have occurred in the past seven years. Billion-dollar events account for roughly 80% of the total U.S. losses for all weather-related disasters.

Figure 1. The yearly number of billion-dollar U.S. weather disasters, adjusted for inflation, as compiled by NOAA's National Climatic Data Center.

Figure 2. The yearly number of billion-dollar global weather disasters, adjusted for inflation, as compiled by insurance broker Aon Benfield in their Annual Global Climate and Catastrophe Reports. The increasing trend in weather disaster losses is thought to be primarily due to increases in wealth and population, and to people moving to more vulnerable areas--though the studies attempting to correct damage losses for these factors are highly uncertain. Climate change may be partly to blame for the rise in disaster losses, but we are better off looking at how the atmosphere, oceans, and glaciers are changing to find evidence that climate change is occurring--and there is plenty of evidence there. I discuss this topic in more detail in a 2012 post, Damage Losses and Climate Change.

The 25 billion-dollar weather disasters of 2014

Multi-Month Drought Disaster 1. China's 2nd most expensive drought in its history hit during the summer of 2014, costing $5.2 billion and bringing nine Chinese provinces some of their lowest rain totals since 1961. Among the worst-hit areas were Shandong, Shaanxi, Henan, and Inner Mongolia, where the lack of rainfall caused severe damage to crops and limited the availability of drinking water. In this photo, we see a farmer standing in dried and cracked earth that used to be the bottom of Zhifang Reservoir on July 29, 2014 in Dengfeng, China. Photo credit: ChinaFotoPress/ChinaFotoPress via Getty Images.

Multi-Month Drought Disaster 2. Southeastern Brazil's worst drought in 50 years brought São Paulo, South America's largest city with a population near 20 million, to the brink of running out of water late in 2014. The drought cost at least $4.3 billion, making it the third most expensive natural disaster in Brazil's history. This is the second consecutive year of disastrous drought in Brazil--drought in Northeast Brazil during the first five months of 2013 caused an estimated $8 billion in damage, making it Brazil's second most expensive natural disaster in history. According to the international disaster database EM-DAT, Brazil's costliest natural disaster was the drought of 1978 ($2.3 billion in 1978 dollars, or $8.3 billion 2014 dollars.) In this photo, we see cattle in a drought-parched field in Quixada, Ceara state, Brazil on January 2, 2014. Small farmers in Ceara state have not able to harvest corn to feed cattle, and have been selling them at a loss. Aurelien Francisco Barros/AFP/Getty Images.

Multi-Month Drought Disaster 3. The Western U.S. drought of 2014 brought damages estimated at $4 billion. Severe, extreme or exceptional drought covered 95% of California by September 2014, thanks to a drought that one research team said was the state's worst 1-year and 3-year drought for at least 1,200 years. The California Farm Water Coalition estimated agricultural losses at $3.6 billion in California. In this photo, we see one of the key water supply reservoirs for Central California, Lake Oroville, on January 20, 2014. California endured its hottest year on record in 2014, which exacerbated the drought. Image credit: California Department of Water Resources.


Disaster 1. The cold wave and winter weather associated with the Midwest and Eastern U.S. "Polar Vortex" episode of January 5 - 8, 2014, cost an estimated $3 billion and resulted in 21 deaths. In this picture, we see snow shovelers take a break in South Haven, Michigan after an epic lake effect snowstorm buried the city on January 8, 2014. Image credit: Wunderphotographer nanamac.


Disaster 1. Volunteers use a pontoon to move a car that has been cut off by flood waters at Burrowbridge on the Somerset Levels on February 27, 2014 in Somerset, England. Portions of England and Wales experienced their wettest winter since records began in 1766, causing $1.5 billion in damage during December 23, 2013 - March 1, 2014. (Photo by Matt Cardy/Getty Images)

Disaster 2. Pedestrians cross a street in the snow in Tokyo on February 15, 2014. The heaviest snow in decades fell across portions of Japan February 8 - 16, 2014, killing 95 and injuring 2,750, mostly in traffic accidents. Tokyo's 27 centimeters (10.6 inches) of snow was the most snow in 45 years. The heavy snow caused widespread residential and commercial damage while also severely disrupting transportation and causing production delays. Total economic losses were estimated at $5 billion. Photo credit: KAZUHIRO NOGI/AFP/Getty Images.


Disaster 1. The U.S. tornado outbreak of April 27 - May 1 killed 39 and caused $1.6 billion in damage. Eleven tornadoes rated EF-3 or higher touched down, including two EF-4 tornadoes. In this photo we see tornado damage at an RV dealership in Mayflower, Arkansas, from an EF-4 tornado that hit on April 28, 2014, killing one person. Image credit: Wunderphotographer ChanChan72.

Disaster 2. An outbreak of severe thunderstorms and tornadoes April 2 - 4 did $1.5 billion in damage across the U.S. Midwest, Plains, and Southeast. In this image, we see the outcome when an April 3, 2014 severe thunderstorm in Belleville, IL snapped large pine tree about 20 feet up from its base and blew it across the street into a house and car. Image credit: wunderphotographer mwhiker.

Disaster 3. Visible satellite image of Tropical Cyclone Ita taken at 04 UTC April 11, 2014. At the time, Ita was a Category 4 storm with 145 mph sustained winds. Ita ravaged agriculture in Queensland, Australia, resulting in $1 billion in damage. Image credit: NASA.

Disaster 4. An outbreak of severe thunderstorms and tornadoes April 12 - 14 did $1 billion in damage across the U.S. Midwest, Plains, and Southeast. In this image, we a squall line blowing into Tulsa, Oklahoma on April 13, 2014. Image credit: Wunderphotographer mrwing13.


Disaster 1. Torrential rains on May 14 - 15 in Serbia and Bosnia-Herzegovina caused extreme flooding that killed 86 people and caused $4.5 billion in damage. The heavy rains were caused by Extratropical Storm Yvette, a strong and slow-moving upper-level low pressure that cut off from the jet stream and lingered over the region for two days, pulling up copious amounts of moisture from the Mediterranean Sea. This photo shows a landslide and floodwaters around houses in the village of Topcic Polje, near the central Bosnian town of Zenica, on May 15, 2014. Photo credit: ELVIS BARUKCIC/AFP/Getty Images.

Disaster 2. Flooding rains in China May 24 - 28 killed 37 people and caused $1.2 billion in damage. In this image we see dark clouds gathering in Guangzhou, Guangdong Province of China on May 22, 2014. Image credit: ChinaFotoPress/ChinaFotoPress via Getty Images.

Disaster 3. An outbreak of severe weather hit the Midwest, Rockies, and Northeast U.S. from May 18 - 23, causing $4 billion in damage. In this image taken by wunderphotographer Darhawk, we see a supercell thunderstorm near Denver, Colorado on May 22, 2014 that prompted issuance of a tornado warning.


Disaster 1. An outbreak of severe thunderstorms across Germany, France and Belgium on June 8 - 10, 2014 killed six people in Germany and did $4 billion in damage. Hail up to 7.0 centimeters (2.75 inches) in diameter and winds beyond 145 kph (90 mph) were recorded. Extensive crop damage was also noted in southwestern France around Bordeaux, Cognac, and Languedoc where swaths of vineyards were destroyed. In this image, a boy walks next to a tree that fell on a building on June 9, 2014 in Cognac, France a few hours after a violent storm. Image credit: NICOLAS TUCAT/AFP/Getty Images.

Disaster 2. An outbreak of severe thunderstorms and tornadoes June 3 - 9 killed three people and did $1.7 billion in damage across the U.S. Midwest, Plains, and Rockies. In this photo, we see lightning damage to a tree in Galesburg, IL on June 6, 2014. Image credit: wunderphotographer Netwalkr.


Disaster 1. With a name meaning “thunder of God,” Rammasun was the strongest typhoon to hit China’s Hainan Province in 41 years. Rammasun peaked as a Category 4 super typhoon with 155 mph, and hit China with top sustained winds of 140 mph. Rammasun killed 206 and did $7.2 billion in damage. This image was taken by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite at 1:35 p.m. local time (0535 UTC) on July 18, 2014, when Rammasun was just off the coast of northern Hainan Island. Image credit: NASA Natural Hazards.

Disaster 2. Torrential monsoon rains over southern China July 13 - 18, 2014, killed 66 people and did $1.25 billion in damage. In this photo, a bridge in Fenghuang Ancient Town is submerged by flood waters on July 15, 2014 in Jishou, China. Image credit: ChinaFotoPress via Getty Images.


Disaster 1. Torrential rains swamped Detroit, Baltimore, and Long Island August 11 - 13, killing one person and causing $2 billion in damage. About $1 billion of the damage occurred in the Detroit area, where two months’ worth of precipitation fell in just 24 hours. In this photo, we see flooding near Islip, New York, on August 13, 2014. Islip set an all-time New York state record for 24-hour precipitation with 13.57". Image credit: wunderphotographer Hurricane765.


Disaster 1. Torrential monsoon rains of over 12" (305 mm) lashed the India-Pakistan border region of Kashmir and Jammu Provinces on September 3 - 7, triggering devastating floods that swept through the mountainous region, killing at least 648 people and doing $18 billion in damage. Hardest-hit were India's Jammu and Kashmir region, where damages were estimated at $16+ billion. According to EM-DAT, the International Disaster Database, this is the most expensive natural disaster in India's history, surpassing the $11.6 billion price tag (2014 dollars) of the July 1993 monsoon floods. In Pakistan, at least 207 people died and damage was estimated at $2 billion. Crippling and catastrophic floods have become the new normal in Pakistan, where the six most expensive floods in their history have come in the past eight years--2010, 2011, 2012, 2014, 2007, and 2013. In this image, we see Indian residents look on from a roof as raging waters from the overflowing Tawi river inundate a Hindu Temple in Jammu on September 6, 2014. Image credit: STRDEL/AFP/Getty Images.

Disaster 2. Typhoon Kalmaegi hit the Philippines, China, and Vietnam between September 10 - 16, killing at least 31 and doing $3 billion in damage. The typhoon's first landfall, as a Category 1 storm, came in the Philippines’ Luzon Island, where 12 people were killed and at least 1,500 homes damaged, with damages estimated at $14 million. Kalmaegi killed nine people in China and did $2.9 billion in damage. In Vietnam, ten people were killed across northern sections of the country, and damages were estimated at $4.5 million. In this image, we see Kalmaegi as it swirled to the south of the island of Taiwan at night, as seen from the International Space Station by astronaut Reid Wiseman ‏(@astro_reid) at 3 pm EDT September 14, 2014. At the time, Kalmaegi had just crossed the Philippines' Luzon Island as a Category 1 typhoon, and had weakened to a tropical storm with 70 mph winds. Hong Kong is the other bright patch of lights. Image credit: Reid Wiswman.

Disaster 3. Hurricane Odile made landfall near Cabo San Lucas, Mexico on September 15, 2014, as a Category 3 storm with 125 mph winds. Odile was the strongest storm on record to hit Mexico’s Baja California Peninsula, and killed five people and injured 135. Tens of thousands of homes, structures and vehicles were damaged or destroyed by Odile’s high winds and flooding rains, and total damage was estimated at $2.5 billion. This is a MODIS satellite image of Hurricane Odile off the coast of Mexico's Baja Peninsula, taken at approximately 2 pm EDT Sunday September 14, 2014. At the time, Odile was a Category 3 storm with 125 mph winds. Image credit: NASA.

Disaster 4. Torrential rains in southwestern China on September 10 - 17 killed 50 and did $1.4 billion in damage. In this VIIRS satellite image from September 16, 2014, we see Typhoon Kalmaegi hitting southeast China at the same time as torrential rains from unrelated thunderstorms are causing this $1.4 billion flooding disaster in southwest China. Image credit: NOAA Visualization Lab.

Disaster 5. An outbreak of severe thunderstorms September 27 - 30 did $1 billion in damage across the U.S. Southwest and Rockies. In this image, we see a squall line blowing into Phoenix, Arizona on September 27, 2014, shortly before it knocked out power to 70,000 customers. Image credit: Wunderphotographer coolwiththecool2.


Disaster 1. Tropical Cyclone Hudhud powered ashore near Visakhapatnam in the Andhra Pradesh state of India on October 12 as a Category 4 storm with sustained winds of 135 mph. With damage estimated at $11 billion, Hudhud was by far the most expensive tropical cyclone in India's history, and their third most expensive weather-related natural disaster, according to EM-DAT, the International Disaster Database. However, Hudhud also represents a success story. Due to aggressive efforts to evacuate vulnerable areas, the death toll from Hudhud was held to 68, far below the 9,843 people killed during the similar-strength October 28, 1999 Orissa Cyclone which hit India's coast very close to where Hudhud hit. This MODIS satellite image of Tropical Cyclone Hudhud was taken at approximately 1 am EDT October 12, 2014, as the storm was making landfall near Visakhapatnam, India. At the time, Hudhud was a Category 4 storm with 135 mph winds. Image credit: NASA.


Disaster 1. One of the worst hailstorms ever in Australia’s greater Brisbane metropolitan region hit in late November, injuring at least 12 people and causing $1.25 billion in damage. In this photo, a man surveys the damage to his home in Brisbane on November 28, 2014 following a storm which struck the area on November 27. Photo credit: PATRICK HAMILTON/AFP/Getty Images.

I'll be back with a new post after 11 am Friday, discussing the joint NOAA/NASA press release on whether or not 2014 was the warmest year on record.

Jeff Masters

Climate Summaries Extreme Weather

The U.S. Climate of 2014: Remarkable Hot, Cold, Wet and Dry Extremes

By: Bob Henson , 4:17 PM GMT on January 12, 2015

How you experienced the climate of 2014 depended a great deal--by some measures, more than any year in U.S. history--on where in the nation you happened to be. This was made abundantly clear in the full 2014 report on U.S. temperatures and precipitation, released this morning by NOAA's National Climatic Data Center (NCDC). When looking at the entire contiguous 48 states, the annual rankings aren't especially striking: the year placed 34th warmest and 40th wettest out of 120 years of data. The overall warmth comes as no surprise, given that every year since 1996 has placed above the nation's long-term temperature average.

These unremarkable statistics obscure the real story of 2014: the titanic contrast between a parched, scorched West (especially California, where the heat left all-time records in the dust), a very warm New England and Florida, and a much cooler area in between, with some months at or near all-time record lows in states stretching from the Great Lakes to the Gulf Coast.

NCDC's state-by-state map of 2014 temperature rankings (see Figure 1) tells the tale vividly. California, Nevada, and Arizona all saw their hottest year on record, going back to 1895. The year placed among the top-twenty warmest in most of the other western states, as well as in Maine. At the same time, a corridor of seven central states--Louisiana, Arkansas, Missouri, Illinois, Indiana, Wisconsin, and Michigan--saw 2014 place among their top-ten coolest years.

Figure 1. State-by-state rankings for annual average temperature in 2014. A ranking of 1 denotes the coolest year in the 120-year record, while 120 denotes the warmest. Image credit: NOAA National Climatic Data Center.

Another way to look at these contrasts is through the statistical lens of NCDC's Climate Extremes Index. The CEI is made up of five different indicators that show how much of the nation experienced a particular type of weather extreme. Two of the indicators relate to the percentage of the nation experiencing either unusually warm or cold daily highs or unusually warm or cold daily lows (averaged from month to month in both cases). Some 23.2% of the contiguous U.S. qualified as having unusually warm highs for the year, which is the 18th-largest percentage out of the past 120 years. The percentage of the nation experiencing unusually cold highs (18.6%) ranks 21st. What's especially intriguing is that this is the first year on record that both the warm-high and cold-high percentages have exceeded 15%, a sign of how difficult it is to sustain such wildly divergent temperature regimes between the Pacific and Atlantic for an entire year. Overall, using all the elements of the CEI, 2014 ranked as the 9th most extreme year since 1910 (excluding the impact of tropical cyclones), or the 19th most extreme when including the impact of tropical cyclones. Interestingly, for the second year in a row, daily record low minimums occurred more often than daily record high maximums (20,937 vs. 14,122). This trend is unlikely to continue; the opposite occurred for a number of years prior to 2013.

The Midwest and Southern chill established itself early, with a series of cold-air outbreaks that came to be associated with the term "polar vortex". (That phrase's meaning became so mangled in press coverage and popular understanding that it led the American Meteorological Society to update its official definition). Colder-than-average weather persisted across much of the central and east until May and June, which came in above average in most states. Midsummer saw a return to strikingly cool weather across the nation's heartland. The pattern was even more unusual--and pleasant for millions of residents--in that it was accompanied by relatively dry weather. It was the coolest July on record for Arkansas and Indiana, and the second coolest in Illinois, Mississippi, and Missouri.

After the west-to-east contrast eased somewhat in late summer and early autumn, a record-setting Arctic outbreak in November reestablished the cold-east/warm-West pattern once more, leading to the second-coldest November on record for Alabama and Mississippi. Finally, just in time for the holidays, the 48 states got on the same temperature track, with unusual mildness nationwide producing the second-warmest December on record. Alaska joined in as well: the state's 19 first-order weather stations were a collective 7.5°F above average for the month, and Fairbanks saw its second warmest December in its 111-year record, according to the Alaska Climate Research Center. Overall, 2014 was Alaska's warmest year in a 97-year period of record, with an average statewide temperature 4°F above the average for 1971-2000.

Figure 2. State-by-state rankings for annual average precipitation in 2014. A ranking of 1 denotes the driest year in the 120-year record, while 120 denotes the wettest. Image credit: NOAA National Climatic Data Center.

Days of deluge
The national precipitation ranking and the state-by-state maps (see Figure 2) hide some dramatic contrasts as well. Most of the year was extremely dry in California, even though the state ended up near average for total annual precipitation. Elsewhere, intense bouts of precipitation made the headlines in a number of spots. Day after day of extreme rain pushed the June precipitation totals across parts of the Midwest into record-obliterating territory. Sioux Falls, South Dakota, received 13.70" for the month, with more than half of that falling in just three calendar days. The town of Canton broke South Dakota's monthly precipitation record with 19.65".

Several major one-day rainfall events emerged from an extremely moist summer air mass that slathered much of the eastern United States in early August. Detroit experienced its second-heaviest calendar-day rainfall (4.57") on August 11, as did Baltimore on August 12 (6.30"). Even more impressive was the 13.57" that fell at Islip, New York, on August 11-12. The downpour set a new state record for 24-hour rainfall, which is especially noteworthy given that a tropical cyclone was not directly involved. A few weeks later, not to be outdone, Phoenix set an all-time calendar-day rainfall record on September 8 with 3.29", fed by deep moisture from ex-Hurricane Norbert.

Figure 3. A highway in Brentwood, New York, resembles an infinity pool after more than a foot of rain fell across parts of central Long Island on August 11-12, 2014. WunderPhoto credit: Hurricane765.

The NCDC's Climate Extremes Index lends some statistical backing to this anecdotal portrait of deluges. The "extremes in 1-day precipitation" indicator measures how much precipitation for the year fell in calendar days with extreme amounts (equal to the wettest tenth percentile of all days). Some 15.3% of the nation saw a much-above-average number of days fall into this category for 2014. That's a bit less than the 2013 value of 16.3%, but still enough to put it at 11th highest of the past 120 years. Notably, all of the top seven years for this index, and 13 of the top 15 years, have occurred since 1990.

Wet days getting wetter, and droughts getting hotter
The recent uptick in extreme one-day precipitation totals across the nation is consistent with more than a decade of research showing that many parts of the world, including the United States, are seeing their heaviest bouts of rain and snow getting even heavier over time. This conclusion was reinforced on a national and regional scale in the 2014 U.S. National Climate Assessment and on a city-by-city scale in a study by Brian Brettschneider (Boreas Scientific LLC) highlighted by Weather Underground blogger Chris Burt last August. The result is also consistent with the basic concept that a warming planet will see an increase in hydrologic contrasts, as warmer temperatures allow for more water to evaporate from lakes, oceans, and plants--helping boost the output of rainstorms and snowstorms--while sucking more water from already-parched land, intensifying the effects of drought.

This process is vital to keep in mind when taking stock of the California drought, arguably the nation's most catastrophic weather event of the year. Although calendar year 2013 was the state's driest on record, the water year of 2013–14 (July to June) placed third driest. (Water years are the most commonly used index for assessing California precipitation, which occurs mainly in the fall through spring). A NOAA-led study released in December found that the severity of drought conditions over the last three water years--looking only at rainfall--is within the realm of natural variability, with 1974–75 to 1976–77 even drier than the period from 2011–12 to 2013–14. However, the temperatures associated with the more recent drought went well beyond what one would expect from historical analogs (see Figure 4), which has made the impact on ecosystems, agriculture, and people even more severe. The NOAA study acknowledged, "record-setting high temperature that accompanied this recent drought was likely made more extreme due to human-induced global warming." In a similar fashion, the intense Texas drought of 2011 was associated with all-time temperature records established during the brutal, more prolonged droughts of the 1930s and 1950s. As states and regions consider how best to adapt to drought conditions in the future, they would be well advised to consider the possibility that temperatures during drought periods could soar beyond anything observed in more than a century of experience.

Figure 4. The annual average temperature for California in 2014 came in far above the previous record for the last 120 years, and it was roughly 4°F above the 20th-century average. Image credit: NOAA National Climatic Data Center.

Figure 5. A lone weed grows on an unplanted field on August 21, 2014 in Firebaugh, California. As the severe California drought continued for a third straight year, Central California farming communities struggled to survive, with an unemployment rate nearing 40 percent in the towns of Mendota and Firebaugh. Photo credit: Justin Sullivan/Getty Images.

Bob Henson

Climate Summaries

Long Arm of Winter Brings Lake Effect Snow to Midwest, Ice Risk to South

By: Bob Henson , 5:19 PM GMT on January 09, 2015

Strong winds and recurrent blasts of bitter cold continue to plague much of the central and eastern United States, with little change in sight into early next week. Like spokes on a wheel, upper-level waves are circulating around a large, powerful center of low pressure anchored near Hudson Bay. At the surface, each wave has been driving a huge zone of frigid high pressure into the U.S. heartland. On Wednesday, sea-level pressure readings broke all-time records at four state capitols and a number of other locations, including:

Bismarck, North Dakota: 1055.4 mb

Concordia, Kansas: 1055.1 mb

Grand Island, Nebraska: 1056.9 mb

Huron, South Dakota: 1056.0 mb

Lincoln, Nebraska: 1055.9 mb

Pierre, South Dakota: 1055.9 mb

Sioux Falls, South Dakota: 1054.5 mb

Sioux City, Iowa: 1055.2 mb

Topeka, Kansas: 1054.3 mb

[Preliminary data courtesy David Roth, NOAA]

The sea-level pressure in Mitchell, South Dakota, soared to a preliminary reading of 1056.8 mb. If confirmed, this will be a statewide record, according to state climatologist Dennis Todey.

Temperatures this week fell below 0°F across much of the upper Midwest, with dangerous wind chills well below zero. Tallahassee, Florida, dipped to 24°F on Thursday morning. However, considering the strength of the surface highs, daily record lows have been surprisingly scarce. In Vermont, Barre-Montpelier managed to plummet to a new daily record low of -20°F.

Figure 1. The GFS model's surface forecast for 00Z Saturday, issued at 00Z Friday, shows high pressure firmly in control across most of North America. Image credit: Levi Cowan,

The dominance of surface high pressure across the nation has left little opportunity for major winter storms to develop. Even weaker systems have made the most of their limited moisture, though, with the help of jet-stream dynamics, biting winds, and bitter cold. Parts of the western Washington, D.C., metro area got socked with more snow than many forecasters expected on Tuesday--more than 4 inches in places. (Capital Weather Gang dubbed it "a 'clipper' that delivered.") The next spoke on our winter wheel rotated across the Midwest last night. Blizzard warnings were hoisted across southern Minnesota and northern Iowa, with winter storm warnings extending eastward into parts of Ohio. This morning's map is dominated by wind-chill advisories that stretch from Montana to Pennsylvania. On the southern fringes of the persistent high pressure, a winter weather advisory is in effect today across southern Mississippi for a potential mix of rain, snow, and freezing rain. A similar setup will play out across parts of southern Texas on Saturday, with freezing rain and sleet possible. In both cases, temperatures will be marginal and any accumulations should be on the light side. A somewhat greater risk of freezing rain could extend northeast through Arkansas later in the weekend.

Figure 2. Jeff Armstrong walks to work on Tuesday, January 6, in Rock Island, Illinois. The Quad Cities area woke up to 5 to 6 inches of fresh snow on Tuesday, with temperatures on Wednesday dipping to -12¯F and wind chills as low as -26¯F. Photo credit: AP Photo/The Dispatch, Todd Mizener.

Gearing up for the lake-effect machine
By far the most impressive precipitation this weekend can be expected downwind of the Great Lakes. Strong west-southwest winds and cold surface air will provide near-ideal conditions for an extended period of lake-effect snow downwind of Lake Erie and Lake Ontario. The region around Buffalo, New York--still reeling from as much as 88 inches in mid-November, is getting plastered once again. A CoCoRaHS cooperative observer in the Buffalo suburb of Kenmore reported 12.2 inches through 7 AM EST today. Up to five feet of snow could fall by Saturday in favored locations east of Lake Ontario, with up to three feet possible in far southwest New York, south of Buffalo and east of Lake Erie. The exact trajectory of the strong winds will determine where the heaviest snowbands set up. As the November storm demonstrated, snowfall totals in a lake-effect storm can vary hugely over just a few miles.

While it's the mega-lake-effect snowstorms that grab the headlines, residents of the lake-effect region of New York also experience many lighter snows that can gradually build up through a series of gray, cold midwinter days. Sometimes the snowpack gets partially or completely eroded by a round of rain, or simply by moist, mild air that facilitates melting. In his book "Lake Effect: Tales of Large Lakes, Arctic Winds, and Recurrent Snows" (Syracuse University Press, 2012), Mark Monmonier, a geography professor at Syracuse, waxes philosophical about his local winters: "For most of us, living with the 'lake-effect snow machine' is a small price for our pleasant summers, delightful autumns, and comparative freedom from devastating winds and floods."

I'll be back with a new post on Monday. Have a great weekend!

Bob Henson

Winter Weather

NOAA Reduces Odds of El Niño Conditions This Winter

By: Bob Henson , 2:29 PM GMT on January 08, 2015

The chance of a noteworthy El Niño event this winter is becoming more slender, diminishing along with California’s chances for more drought relief. In its latest monthly outlook on the state of the El Niño/Southern Oscillation (ENSO), issued this morning, NOAA's Climate Prediction Center continued its El Niño Watch but reduced the odds of El Niño conditions from the previous 65% to approximately 50–60%. Moreover, the agency now calls for ENSO-neutral conditions (neither El Niño nor La Niña) to be the most likely state of affairs from March onward. This is a significant change from NOAA’s previous monthly outlook, which had projected that El Niño conditions would likely extend into spring 2015.

NOAA considers El Niño conditions to be in place when monthly sea-surface temperatures (SSTs) are at least 0.5°C above average in the Niño3.4 region of the tropical Pacific. To qualify as an El Niño episode, the SSTs in this region must remain at or above the 0.5°C threshold for five consecutive overlapping periods of three months (i.e., a total of seven months).

Using this yardstick, weak El Niño conditions have now prevailed for more than two months. After rising above 0.5°C in mid-October, the Niño3.4 SST anomalies peaked near 1.0°C in late November, then began dropping (see Figure 1). The anomalies are now at 0.5°C, barely qualifying as El Niño-worthy. Should the 0.5°C anomaly hold for a few more months (not at all a sure thing), the 2014–15 El Niño would manage to go down in history as a bona fide episode, though a rather unimpressive one.

Figure 1. Departures from average sea-surface temperature in degrees Celsius (left-hand axis) across the Niño3.4 region of the tropical Pacific Ocean. After briefly surging above the El Niño threshold (0.5°C above average) in late May 2014, sea-surface temperatures sagged back into neutral territory until autumn. Image credit: NOAA Climate Prediction Center.

Because El Niño’s impacts on California and the southwest United States are closely tied to the intensity of the Niño3.4 anomalies, there is now less confidence that El Niño will help bring beneficial rain and snow this winter to these drought-stricken parts of the nation. NOAA’s Mike Halpert includes helpful background and graphics on typical U.S. impacts from El Niño in a feature story on the website.

Why has El Niño been so hard to predict lately?
Forecasters have been scratching their heads over the state of ENSO for almost a year. Early in 2014, several large, shallow pulses of warm water called Kelvin waves made their way across the tropical Pacific. One of these was comparable in size and strength to the Kelvin wave that helped kick off the record-setting, high-impact El Niño of 1997–98. The behavior of the Pacific in early 2014, together with impressive projections from some coupled atmosphere-ocean models, led NOAA and other forecast groups to call for a significant chance of El Niño conditions by mid- to late 2014. These observations and outlooks gained widespread attention in the press and blogosphere, leading to some eye-catching headlines trumpeting the chance of a "super El Niño." Official forecasts were more cautious, stopping short of calling for a strong event, as Weather Underground climate blogger Ricky Rood outlined in an illuminating comparision last August. (It's also important to keep in mind that even a 70% chance of an event like El Niño—quite high by seasonal prediction standards—means that there is a 30% chance the event won’t occur.)

Figure 2. Departures from average sea-surface height as detected by NASA's Jason satellite on December 10, 1997 (top), when a major El Niño event was in full swing, and by the Jason-2 satellite on December 20, 2014 (bottom). Since water expands as it warms, higher sea-surface heights (whites and oranges) indicate warmer waters. The bright white in the 1997 image conveys the power of that year’s record-breaking El Niño, especially when compared to the underperforming 2014. Image credit: NASA.

Although the tropical Pacific waters behaved as if a major El Niño was on tap, it seems the atmosphere didn't get the message. Throughout 2014, the atmospheric component of El Niño failed to emerge consistently even as oceanic conditions appeared favorable. For example, a developing El Niño typically sees trade winds weakening across the eastern Pacific, which facilitates the eastward spread of warm surface water. Although several bursts of westerly wind did appear in 2014, these have not translated into widespread, long-lived weakening of the easterly trade winds. Without the linkage that emerges from this kind of ocean-atmosphere interaction, it is difficult for El Niño conditions to take hold in a big way.

One researcher’s take on the mystery
ENSO was on the agenda at this week's annual meeting of the American Meteorological Society, where sessions on Tuesday morning and afternoon focused on the challenges of predicting El Niño and La Niña and what’s been learned over the last 20-plus years.

Eminent ENSO researcher Michael McPhaden (NOAA Pacific Marine Environmental Laboratory) presented a surprise talk on Tuesday called "Who Killed the 2014 El Niño?" The answer remains unclear, as McPhaden emphasized by presenting a rogue’s gallery of possible culprits in the form of a police lineup. These included:

--Negative feedbacks, or interactions that work against El Niño development rather than nourishing it.
--The negative state of the Indian Ocean Dipole, which supports rainfall in the far western tropical Pacific, as opposed to its typical eastward shift of rainfall during El Niño.
--The negative phase of the Pacific Decadal Oscillation, which has been in place since the late 1990s. A negative PDO tends to be associated with reduced El Niño activity.
--A lack of westerly wind bursts strong enough to kick off El Niño.
--Persistently warm SSTs in the "warm pool" of the western tropical Pacific, where water temperatures normally drop below average during El Niño.

It will take time and research to figure out to what extent the demise of the anticipated 2014 El Niño was a group effort versus a solo job. However, it seems clear that the lack of the usual atmospheric involvement sealed the deal. As McPhaden put it, "The atmosphere is not engaged."

Bob Henson

Atmospheric Phenomena

Global Extreme Temperatures in 2014: 3 All-Time National Cold Records, 2 Heat Records

By: Jeff Masters , 2:26 PM GMT on January 07, 2015

Despite the fact that 2014 will likely be classified as Earth's warmest year in history in an announcement due from NOAA on January 16, the year was not a notable one for all-time national heat records. Two nations tied or set all-time records for their hottest temperature in recorded history in 2014, and three territories set all-time cold records. For comparison, five countries and three territories set all-time hottest temperature records in 2013; the most all-time national heat records in a year was twenty nations and one territory in 2010. Since 2010, 45 nations or territories (out of a total of 235) have set or tied all-time heat records, and four have set all-time cold temperature records. Since each of those years ranked as one of the top twelve warmest years in Earth's recorded history (with 2010 being the warmest year on record), this sort of disparity in national heat and cold records is to be expected. 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 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. Wunderground's weather historian Christopher C. Burt maintains a database of these national heat and cold records for 235 nations and territories on's extremes page.

New all-time national and territorial heat records set in 2014
Iran set a new all-time heat record of 53.0°C (127.4°F) at Gotvand on 17 July, which tied the record set at Dehloran on 28 July 2011.

Latvia set a new all-time heat record of 37.8°C (100°F) at Ventspils on 4 August. Previous record: 36.4°C at Daugavpils on 4 August 1943.

New all-time territorial cold records set in 2014
Heard and McDonald Islands (uninhabited territory of Australia) set a new all-time cold record of -11.5°C (11.3°F) at The Split. Previous record: -10.6°C at Atlas Cove on 2 August 1949.

French Southern and Antarctic Lands (French territory) set a new all-time cold record of -9.5°C (14.9°F) at Port Aux Francais on 11 August. Previous record: -9.4°C at the same location on 27 June 1953.

Wallis and Futuna (French territory) set an all-time cold record of 18.0°C (64.4°F) at Hihifo on 13 July. Previous record: 18.4°C at the same location on 9 July 1978 and 26 August 2003.

Notable global heat and cold records set in 2014
Hottest temperature in the world in 2014: 53.0°C (127.4°F) at Gotvand, Iran on 17 July
Coldest temperature in the world in 2014: -80.8°C (-113.4°F) at Vostok, Antarctica, 20 August
Hottest temperature in the Southern Hemisphere: 49.3°C (120.7°F) at Moomba Aero, Australia, 2 January
Coldest temperature in the Northern Hemisphere: -63.3°C (-81.9°F) at Summit GEO, Greenland, 23 March

Number of major world stations which set their all time highest temperature in 2014: 198 (for comparison, this was 389 in 2013.)

Number of major world stations which set their all time lowest temperature in 2014: 15 (for comparison, this was 12 in 2013.)

New high temperature records in world capitals in 2014
Minsk, Belarus reached 35.6°C (96.1°F) on 3 August, beating the old record of 35.0°C set on 29 July 1936.

Jakarta, Indonesia reached 37.0°C (98.6°F) on 24 September, beating the old record of 36.8°C set on 2 October 2006.

A big thanks goes to Maximiliano Herrera for providing the information in this post.

Jeff Masters

Climate Summaries

High Pressure Records in Jeopardy Across Great Plains

By: Bob Henson , 2:00 PM GMT on January 06, 2015

A sprawling dome of high pressure is on track to spill from Canada across most of the eastern United States over the next several days, bringing sharp winds and some of the coldest air of the season to many locations. While the cold will certainly make its presence known, the truly remarkable aspect of this blast will be the strength of the high pressure itself. In some locations, barometric high pressure readings may reach levels never before observed in January, and one or more all-time records can't be ruled out.

Most high-pressure records east of the Rockies occur during the winter months, as darkness and snow cover allow frigid, dense cold air masses to develop and surge southward. Many all-time pressure records across the plains were established during the memorable cold wave of late December 1983, which sent temperatures down to 9°F as far south as San Antonio and kept Omaha lodged below 0°F for more than a solid week. On December 24 of that year, sea level pressure [SLP] soared to 1064 mb [31.42"] at Miles City, Montana. That value remains the highest sea-level-adjusted pressure on record for the contiguous United States.

Figure 1. Sea level pressures near the peak of the December 1983 cold wave, as mapped by the North American Regional Reanalysis. Image credit: Greg Carbin, NOAA.

A few monthly SLP records appear to be within reach this week, especially as the core of high pressure moves across the Northern and Central Plains on Wednesday. Models are projecting SLP to peak above 1050 mb [about 31.01"] across a relatively large area. Weather Underground historian Chris Burt has a comprehensive site listing all-time high-pressure records for many U.S. cities, and NOAA's David Roth has produced maps (in millibars, or mb) depicting the highest January and highest all-time values at many U.S. locations, typically going back to the 1890s (see this map showing the period of record at each site). Among the spots to watch:

Rapid City, South Dakota
Jan. record: 1054.9 mb [31.15"]
All-time record: 1056.2 mb [31.19"]

Des Moines, Iowa
Jan. record: 1051.1 [31.04"]
All-time record: 1051.8 mb [31.06"]

Springfield, Missouri
Jan. and all-time record: 1050.8 mb [31.03"]

If the nation does notch any all-time SLP records this week, it won't be the first time this winter. On December 30, Washington's Seattle-Tacoma Airport reached the highest SLP in its 67-year weather history: 30.87" [1045.5 mb]. Several nearby stations also set impressive marks, as noted by the University of Washington's Cliff Mass in his weather blog.

Ahead of the latest cold surge, an Alberta clipper storm will deliver light to moderate snow across a broad swath of the Midwest into the mid-Atlantic. Toward the weekend, yet another strong zone of high pressure appears set to invade the central and eastern U.S., keeping the bulk of the country free of major winter storms for the time being.

A head-spinning temperature range
Even for an area accustomed to large daily swings in temperature, the Front Range of northeast Colorado experienced a startling surge of warmth on Monday, courtesy of downslope winds feeding into the Midwest clipper storm. After an overnight low of –5°F, Denver International Airport surged to a high of 55°F, making for a diurnal range of 60°F! January is renowned for rapid temperature variations along the east slopes of the Rockies, where downslope winds often scour out Arctic air. The largest 24-hour diurnal spread in U.S. history (103°F, from –54°F to 49°F) was recorded by an NWS cooperative observer in Loma, Montana, on January 14–15, 1972.

AMS Annual Meeting:  Looking ahead to 2040
I'm in Phoenix this week, attending the 95th annual meeting of the American Meteorological Society. For anyone who loves weather and climate, the AMS meeting is a smorgasbord of excellent talks and special events. Each year the meeting opens with a weekend conference and career fair, aimed at college and university students, that's grown by leaps and bounds. There's also a free WeatherFest on Sunday afternoon that draws thousands of weather aficionados of all ages.

The main conference opened on Monday morning with a forward-looking Presidential Forum designed to get attendees pondering what the field of meteorology might look like in the year 2040 and what roles they can play. "In some ways, you might consider this meeting a gateway from the past into the future," said outgoing AMS president Bill Gail. Moderated by UCAR/NOAA postdoctoral research scientist and policy advisor Kim Klockow, the panel discussion included a keynote talk from NOAA administrator Kathryn Sullivan, followed by remarks from University of Nebraska graduate student Curtis Walker, Climate Central meteorologist Bernadette Woods Placky, and Mac Devine, who directs CloudFirst Innovation at IBM.

Figure 2. AMS Presidential Forum panelists (left to right) Kathryn Sullivan, NOAA; Kim Klockow, UCAR/NOAA; Curtis Walker, University of Nebraska–Lincoln; Bernadette Woods Placky, Climate Central; and Mac Devine, IBM. Photo credit: Bob Henson.

There's no telling exactly what technologies will be coming down the pike 25 years from now. Mobile phones were clunky, high-ticket items in 1990, as Sullivan observed, and Facebook and Twitter were years away from being born. However, the panelists agreed that weather and climate services can and must become more accessible and user-oriented than ever. I was especially struck by Curtis Walker's passion for improving road-weather prediction, given that thousands of Americans still die in weather-related highway accidents each year. It's a heartbreaking toll that we seldom truly ponder, and one that research and technology can go a great way toward reducing.

Figure 3. AMS attendees await the conference kickoff on Monday morning, January 5. Photo credit: Bob Henson.

Bob Henson

Winter Weather

Bob Henson Joins Weather Underground as a Full-Time Blogger

By: JeffMasters, 3:23 PM GMT on January 05, 2015

A major shake-up is at hand in the Weather Underground blog world: Bob Henson, who is probably the world's premier science writer in meteorology and climate change, has joined us as a full-time blogger, and will be making regular posts in my blog on weather and climate change topics. Bob has been a writer/editor/media relations specialist since 1990 for the University Corporation for Atmospheric Research/National Center for Atmospheric Research (NCAR) in Boulder, Colorado, where he updated their their excellent AtmosNews website. Bob literally "wrote the book on climate change"--he is author of ”The Thinking Person’s Guide to Climate Change” ($20.90 from The book is an updated version of his "Rough Guide to Climate Change", which I reviewed back in 2008. I've thought so highly of this book that I've purchased over 200 copies over the years, giving them to students, TV meteorologists, politicians running for U.S. Congress, and the leadership of The Weather Channel. If I were teaching a course on climate change at the high school or introductory college level, this would be the text.

Bob earned his Bachelor's degree in meteorology from Rice University in 1983, and went on to get a Master's degree in Journalism from the University of Oklahoma in 1988, where he engaged in a fair bit of storm chasing on the side. He has written five books on weather and climate change, including the number one textbook for 101-level college meteorology courses, Meteorology Today (11th edition), whose 11th edition (to be published in 2015) he co-authored with C. Donald Ahrens. Bob is a contributing editor of Weatherwise magazine and has also written more than 50 articles for Nature, Scientific American, Discover, Sierra, The Guardian, AIR & SPACE/Smithsonian, and other media outlets.

With Bob's arrival at Weather Underground, I plan on reducing the number of posts I do during the winter and spring, but will be blogging full-force once hurricane season begins in June. Bob has written his own introduction to the wunderground community, presented below. Bob is at the annual meeting of the American Meteorological Society in Phoenix this week, and plans on making several posts later this week on some of the more interesting research presented at the meeting.

Video 1. If we cared about the environment like we cared about sports, news of signing a major free agent like Bob Henson would be treated like LeBron James' signing with the Cleveland Cavaliers. Language warning: two F-bombs in video.

- Jeff Masters

Confessions of a Natural-Born Weather Geek
It was a dark and stormy night (really, it was) when meteorology grabbed hold of me. I was a seven-year-old at the time, watching a sitcom on a bedroom TV set in Oklahoma City. Suddenly, the laugh track was interrupted with the beep-beep-beep of a weather advisory. I saw a calm young weather anchor named Lola Hall standing in front of a hand-drawn weather map, announcing that we were in a tornado warning. I ran past my parents, darted out the front door, looked up at the sky—packed with swirling, low-hanging, city-lit clouds—and realized that I had to know more.

Within three years, I had a backyard weather station and was making forecasts by clipping daily maps from the newspaper and tracking the progress of highs, lows, and fronts. Each morning, I posted an outlook on the wall of my elementary school under the heading “The Far-Out Forecaster” (not realizing at the time that it was a pun!).

As you can tell, weather has been a keen interest of mine since childhood. I know that’s the case for many of you of as well. Whatever the extent of your own passion for the sky, I’m tremendously excited to be part of the Weather Underground team, so that together we can explore and discuss the spectacular atmosphere that we all share.

My number-one job here at Weather Underground is to continue the high-quality coverage of major weather events that you’ve come to expect from Jeff and our entire team. For the next several months, this includes the full array of wintertime weather, as well as the evolution of El Niño and its implications for national and global conditions. Later this year, as hurricane season arrives, Jeff will be ramping up his own posts once more, and I’ll be pitching in regularly.

Severe weather is what got me into meteorology, so you can expect a generous amount of storm coverage this spring as the convective season rolls around. Severe storm research and technology have made tremendous strides over the last several decades, and the innovations continue today. I’ve witnessed much of that evolution first hand, including meeting Ted Fujita, documenting the VORTEX1 and VORTEX2 research projects, and spending a summer chasing storms for NOAA to validate data from the first NEXRAD radar, which was deployed in northeast Colorado. (We found plenty of big hailstones, and more than a few “landspouts”—relatively weak tornadoes that form much like waterspouts.) Despite all the research progress, the toll from events like the Super Outbreak of April 2011 remains far too high, and the full process behind tornado formation remains elusive. What are some of the most promising developments for knowing where and when tornadoes will strike, and for keeping people safer? I’ll be covering these and many more topics.

For a number of years, I had the privilege of serving as a writer and editor at the University Corporation for Atmospheric Research, which operates the National Center for Atmospheric Research. This job gave me a front-row seat at a jaw-dropping array of research pertaining to the atmosphere—“from the Sun’s core to the ocean floor,” as we liked to put it. I encourage you to follow UCAR/NCAR’s diverse array of work through AtmosNews products on the web, Facebook, Twitter, and YouTube.

Here at Weather Underground, I’ll work to put ongoing weather events into the broader context of what we’re learning about our ever-evolving planet. This includes global warming, a topic that vaulted into public awareness and importance during my UCAR and NCAR days. I’ve devoted much of the the last decade to covering climate change and its effects, both in my UCAR/NCAR writing and in my after-hours book writing. Having given many public talks on the topic, I know how polarizing and distressing it can be. I am dedicated to presenting climate research in an accessible way, one that doesn’t preach to any choir and doesn’t sugarcoat the reality of the complex changes that researchers around the world are working to understand.

Sometimes it’s easy to turn our attention away from the risks of a warming atmosphere. It’s also easy to overlook the beauty of everyday weather events. Consider how many people on an aircraft keep their window shades shut during the entire flight, from takeoff to landing. I'd much rather keep my eyes and my mind open, taking in the full mystery of the atmosphere around us. It's a thrill to be part of Weather Underground, and I'm honored to be working alongside Jeff, the rest of the WU blogging team, and the community that all of you have built. Thanks for letting me join in!

Figure 1. Under a wall cloud in Oklahoma during the 2010 VORTEX2 tornado research campaign.

Bob Henson

Wunderground News

Arctic Air Heads For Central United States

By: JeffMasters, 9:01 PM GMT on January 02, 2015

02-JAN-15 (Next Update SUNDAY – JAN 4)

By Steve Gregory for vacationing Jeff Masters


A storm system will be forming over Northeast Texas/Arkansas tonight and will head towards the southeastern Great Lakes on Saturday and then up the St. Lawrence River Valley Sunday. Locally heavy rains, snow and potential ice storm conditions will accompany this major storm, but it appears quite likely a mostly rain events is in store for the major coastal cities of the Northeast – while ice storm conditions could occur over interior New England and the higher elevation or the northeast. The track on this storm has been 'rock solid' for well over a week now.

Arctic air will be surging southward behind the storm, with a secondary arctic front / Alberta Clipper moving through the Midwest early next week. Extremely cold air will follow behind this second disturbance – especially in the Midwest – with Temperatures to fall below zero across the upper Midwest.

A large scale upper level TROF covers much of North America, with high level ridging along the west coast of North America. This upper level flow pattern will continue to dominate the US weather for the next 10 days, but most models continue to show a gradual breakdown of the EPAC /Western US Ridge during Week 2, with a more zonal-like flow working its way across the nation in 12-15 days. This progressive and somewhat more zonal flow is supported by the intensifying MJO in the western Pacific (see below Figures), and the overall SST anomalies across the Pacific Basin. Model trends still suggest near or above normal average Temperatures across much of the nation (with the exception of the Northeast) during the middle of the month – with a potential for it to continue well into the second half of JAN. Regardless, the progressive nature to the hemispheric flow suggests any surges of very cold arctic air will be relatively brief (as in 3-6 days) versus ‘month long’ type cold as was experienced last year.

CLICK IMAGE to open full size image in new window

Fig 1: The various global model forecasts valid on the evening of JAN 11 ... There is now fairly decent agreement among the various global models at 10 Days out with the operational GFS still showing a colder bias in the central and eastern US compared to the European model (and is accepted). But in general – a progressive and somewhat zonal-like flow is shown by all models across much of North America during Week 2 – a pattern that supports near or above normal Temps developing during the week. The 15 Day GFS from last evening shows a general continuation of this more zonal-like pattern going into the 3rd week of JAN.

Fig 2: The MJO (top panel above) has continued to become better organized and somewhat stronger – with most models now forecasting a much stronger MJO signal propagating across the West Pacific during Week 2. A Phase 5 location statistically supports a milder pattern over the US. The bottom forecast graphic shows the expected area of enhanced convection (green shading) and suppressed convection (yellow shading) associated with the eastward moving MJO signal. The relatively strong signal shown in the eastern Pacific 15 Days out (bottom most panel) is the strongest I can recall in that region in over 2 years. IF IT VERIFIES – very strong forcing on the atmospheric pattern from the equatorial Pacific will develop over North America during the second half of JAN.

Fig 3: The above 2 images show the SST anomaly during late DEC (top panel) and Sea Surface Heights (SSH) as measured by satellite imagery (bottom panels) during early and mid DEC. A large heat sink covers the eastern half of the equatorial Pacific, which has helped maintain the weak El Niño condition. Though SST anomalies actually fell slightly in late DEC in the Niño 3.4 region as easterly trades increased – the warm sub-surface Temps as shown by the above normal SSH’s will continue supporting a weak El Niño. The anomalous SST pattern across the rest of the Pacific (Top graphic) has been a major player in this winters’ atmospheric pattern, forcing the jet stream to take on a more zonal pattern across much of the North Pacific (NORPAC). Since a broad zonal pattern is NOT typical for the cold season, weather systems have been highly progressive for this time of year and has led to the relatively moderate winter Temperature pattern overall.

Fig 4: The GFS Ensemble forecasts for 8-10 days out shows a highly zonal flow across the Pacific with an upper level High to the NW of the Aleutians – where the semi-permanent ‘Aleutian Low’ is normally located. (This pattern has led to the periodic weakening/breakdown of the EPAC Ridge and a moderate Temp pattern downstream across North America.) With the exception off the Northeast – the above normal heights and westerly flow into North America suggests moderate Temps during mid and possibly the last part of JAN.

Fig 5: The Temperature anomaly forecast is based STRICTLY on the GFS MOS model data output which calls for below normal Temperatures on average – with very cold conditions in the Midwest next week. The near normal readings in the Northeast will fall below normal after the storm passage by early Monday.

Fig 6: The Week 2 Temperature ANOMALY forecast is based on the 12Z run of the HI-RES operational GFS (75%) integrated with the 00Z EURO model (5%), the 12Z EURO ensemble mean (10%) and the 12Z GFS Ensemble (10%) - using the projected pattern, along with the GFS surface and 850mb Temperature forecasts. Some Temp forecasts are adjusted for known or expected anomalous thermal patterns and/or projected storm systems. Though below normal Temps will still hold on in the Great Lakes and Northeast – it appears a moderating trend will be overspreading much of the nation again during the second half of Week 2. Confidence in the general Temp anomaly pattern and its absolute values, is near average, with a rating of ‘3’ on a Scale of ‘1-5’ for both metrics.

✭ My next update will be on SUNDAY – JAN 04 on my own WU Blog✭



1. A GENERAL Glossary of Weather Terms can be found HERE

2. Another Glossary of weather terms is available HERE

2 Week Temperature Forecast Winter Weather

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