Category 6™

Glacial Pace for Southern Hemisphere Cyclone Season; Tornado Threat in Midwest

By: Bob Henson and Jeff Masters , 5:06 PM GMT on February 28, 2017

From Antananarivo to Darwin to Suva, an odd tranquility has filled the heart of the Southern Hemisphere’s tropical cyclone season. In a turn of events that’s mystified even the experts, hurricane-strength cyclones have been virtually absent since July from the entire Indian Ocean and Pacific Ocean south of the equator. (Tropical cyclones are quite rare over the Atlantic Ocean south of the equator, though they do occur.)

In much the same way as the Northern Hemisphere hurricane and typhoon seasons normally hit a peak in late summer, the Southern Hemisphere’s cyclone season is usually reaching a crescendo by late February. This year, it’s been more like crickets than a crescendo. Total accumulated cyclone energy (ACE) across the Southern Hemisphere since July 1 was just 14% of average as of February 26, according to Dr. Phil Klotzbach (Colorado State University). “The S. Hemisphere still hasn't gotten the memo that their hurricane season is well underway,” tweeted Klotzbach on Sunday.

Figure 1. Tropical cyclone activity for the Southern Hemisphere during the period July 1, 2016, to February 27, 2017. Shown in parentheses is the climatological activity one would expect from July 1 to Feb. 27, based on statistics for the period 1981 through 2010. Image credit: Phil Klotzbach, Colorado State University.

A well-distributed quiet spell
One of the most striking aspects of this quiet southern season is how extensive it is. In the Northern Hemisphere, El Niño or La Niña will favor rising motion in one basin and sinking motion in another. This tends to make the North Atlantic active while the Northeast Pacific is less so, and vice versa. There hasn’t been any such trade-off across the Southern Hemisphere in recent months: it’s been calmer than usual across the board. The South Pacific east of longitude 135°E has been especially tranquil, with only 2.25 named storm days since last July as opposed to an average of 26.2 named storm days by this point. There may still be time for the Southwest Pacific to catch up: the latter half of the season tends to be especially active over this region, as noted in this extensive climatology of the region’s tropical cyclones, published in 2013 in the Journal of Climate.

Another factor in play: the large-scale rising motion needed for sustained tropical cyclone action has been in the wrong places. Over the last three months, the strongest areas of rising motion across the southern tropics and subtropics have been located over land--across southern Africa and western Australia. Meanwhile, downward motion at these latitudes has predominated across the South Indian and Southwest Pacific Oceans (see Figure 2), where most of the hemisphere’s tropical cyclones develop. “A good way to kill a tropical cyclone season is to have upward motion over land!” noted Klotzbach in an email.

Figure 2. Departures from average in long-wave radiation averaged over the three-month period from Nov. 29, 2016, through Feb. 26, 2017. OLR anomalies show where high, cold clouds associated with thunderstorms are most prevalent. Areas in blue correspond with frequent thunderstorms and rising motion; orange is correlated with calmer weather and sinking motion. Many of the areas where tropical cyclones tend to form in the Southern Hemisphere have been dominated by sinking air over the past three months. Image credit: NOAA/ESRL/PSD Map Room

Figure 3. In a typical Southern Hemisphere cyclone season (black trace), more than half of the total accumulated cyclone energy (ACE) for the July-through-June period has already been racked up by February 26. This season (blue trace) has mustered less than 10% of the final seasonal total, or only about 14% of the season-to-date average. Image credit: Phil Klotzbach, @philklotzbach.

Figure 4. Category 1 Tropical Cyclone Dineo making landfall in Mozambique at 11:15 UTC February 15, 2017. Image credit: NASA.

The only Southern Hemisphere storm to make landfall thus far in 2017 has been Tropical Cyclone Dineo, which hit southern Mozambique on February 15 as a Category 1 storm with 80 mph winds. At least seven people were killed and over 20,000 homes were destroyed. Dineo dumped approximately 4 - 8 inches of rain along its path, and caused widespread flooding in Zimbabwe. Hurricane-force tropical cyclones are not that common in Mozambique; since 1990, there have been nine cyclones of Category 1 or higher intensity (including Dineo) to hit, with February and March being the most common months for landfall. The strongest cyclone in Mozambique history was Category 4 Tropical Cyclone Eline, which hit the country on February 22, 2000. The most recent hurricane-force storm was on March 11, 2008--Category 3 Tropical Cyclone Jokwe.

Plenty of water in Australia, despite no landfalling cyclones
This is the first year in modern records that Australia has made it from July all the way to the beginning of March without at least one tropical cyclone making landfall. The previous record was held by Tropical Cyclone Charlie, Australia’s first landfall of the 1987-88 season. Charlie came ashore on Feb. 29, 1988, just southeast of Townsville. Official records date back to 1969-70, and it appears that Australia has seen at least one landfall in every year since 1945. Only last week, Tropical Cyclone Alfred developed in the Gulf of Carpentaria just off Australia’s northern coast on Feb. 19, but it quickly dissipated to a remnant low.

“There are several theories we are wanting to test as to why this season has been so benign,” said Andrew Watkins (Australia Bureau of Meteorology) in an email. “Especially given that we started with warm waters around Australia and weak cool conditions [La Niña] in the tropical Pacific, that should have pushed us toward an average to above-average tropical cyclone season. We are all intrigued by this one.”

In spite of tropical cyclones having gone missing, there’s been significant flooding across Australia over the last several months, consistent with the upward motion over the continent indicated in Figure 2. The monsoonal trough that normally sits offshore has moved onto land at times, and at least two large but weak “landphoon”-type systems have tracked into the continent, bringing light winds but extremely heavy rain. One of these systems tracked southward through interior Western Australia in late December. The resulting floods triggered the closure of the iconic, typically bone-dry Uluṟu-Kata Tjuṯa National Park on Christmas Day (see image at bottom) and contributed to record monthly rains of 14.7” at the town of Kintore, most of it falling in just two days (see this BOM report). Several outback locations notched all-time records for precipitable water (the amount of moisture in a column above the surface) and monthly records for daily rainfall.

Figure 5 WU depiction of the outlook for severe weather issued at 10:30 am CST Tuesday, February 28, 2017, by NOAA’s Storm Prediction Center. Parts of Missouri, Illinois, Indiana, and Kentucky have been upgraded to moderate risk, which is actually the second-highest of five risk categories.

Strong tornadoes possible across mid-Mississippi and Ohio Valleys on Tuesday
A broad area from northern Arkansas and southeast Missouri to western Indiana will be on the lookout for potentially tornadic supercell thunderstorms on Tuesday afternoon and evening. NOAA’s Storm Prediction Center placed the heart of this region under a moderate risk of severe weather at 10:30 am CST Tuesday, an upgrade from the enhanced risk in place earlier in the day. Hourly runs of the HRRR mesoscale model on Tuesday morning indicated that several rounds of severe storms could be rolling through Missouri and into Illinois from about 4 PM CST onward. Although the strongest cells may be widely dispersed, this could allow one or more of them to organize into sustained supercells, given the available instability and wind shear. “A few strong tornadoes are possible, especially if discrete structures evolve as it appears they may,” noted SPC in an outlook early Tuesday. Very large hail is also a good bet with any supercells that form. The highest tornado probabilities extend near and north of the Ohio River from southeast Missouri to southeast Indiana, but significant tornadoes (F2 or greater) are possible even after dark as far afield as northern Illinois and far western Ohio.

By late Tuesday night, the storms should eventually congeal into a wind-packing squall line (with a risk of embedded tornadoes) moving across parts of Illinois, Indiana, Kentucky, and Tennessee. More severe weather--especially high wind--is possible on Wednesday as a cold front pushes the squall line toward the Appalachians and mid-Atlantic/Northeast.

SPC has also outlined an "Extremely Critical Fire Weather Area" across eastern NM, western TX, the TX Panhandle, and far western OK for Tuesday afternoon, when a corridor of 30 - 45 mph sustained southwesterly winds with gusts to 55 - 65 mph is expected to materialize. Relative humidities in the 8 - 13 percent range in tandem with very dry vegetation will create extremely critical fire concerns, characterized by very rapid and erratic fire spread behavior.

Bob Henson and Jeff Masters

More Record Heat Invading the U.S. as Cleanup From Rare February Tornadoes Begins

By: Bob Henson and Jeff Masters , 6:04 PM GMT on February 27, 2017

Record warmth slathered the Northeast on Friday and Saturday, the latest chapter in a phenomenal sequence of unseasonal mildness during the last half of February. As of Monday morning, NOAA’s U.S. Records site had catalogued 5857 daily record highs for the month, with only 95 daily record lows. Most of the record lows have occurred across the western U.S., whereas the bulk of record warmth has been east of the Rockies. The warmth has been even more impressive when you look at the ratio of monthly records: 408 record monthly highs thus far, versus just one record monthly low.

Our pick for the most astounding single report of the weekend comes from Vermont’s largest city, Burlington, which soared to 72°F on Saturday afternoon. This broke multiple records by incredible margins:

Previous daily record high:  55°F  (broken by 8 AM EST Sat!)
Previous monthly record high:  63°F, set on Thursday, Feb. 23 (which had broken the longstanding record of 62°F from Feb. 19, 1981)
Previous high for any winter month:  68°F on Dec. 24, 2015

The reading also tied Vermont’s state record high for February, which had been set in Bennington just a day earlier. New Hampshire also set a state record on Friday with 73°F in Nashua, according to WU weather historian Christopher Burt. Other all-time state records for February set this month include Oklahoma (99°F at Magnum on Feb. 11) and Wisconsin (72°F at Janesville and Boscobel on Feb. 22, with multiple stations breaking the previous state record of 69°F).

Record February warmth extended last week into Canada, where Nova Scotia recorded their warmest February reading on record, 20.0°C (68°F) at Greenwood on February 25, 2017 (previous record: 19.5°C set at Windsor Martock on 20 Feb 1994 and at Margaree Forks on 28 Feb 2000.) Toronto’s Pearson Airport set its all-time record for February with a temperature of 17.2°C (63°F) on February 23, 2017 (previous record: 14.9°C (58.8°F) set on Feb. 23, 1984.) Thanks go to Maximiliano Herrera and Christopher C.. Burt for the Canada info.

Figure 1. Many locations across the eastern two-thirds of the U.S. are on track to achieve their warmest February on record (red “1”) for rankings compiled across the period Feb. 1-26. Image credit: Southeastern Regional Climate Center.

More record-warm mildness expected in eastern half of the U.S. on Tuesday and Wednesday
Last week’s warm weather ended with a bang across eastern New York and New England on Saturday, as a sharp cold front sent the temperature plummeting more than 30°F in just a few hours. However, record-warm temperatures of 30°F or more above average are expected to invade a large portion of the U.S. again on Tuesday and Wednesday, thanks to a resumption of the jet stream pattern that brought last week’s record warmth.

Figure 2. Departure of surface temperature from average as predicted by the 00Z Monday, February 27, 2017 run of the GFS model for 7 pm EST Tuesday, February 28, 2017. Record-warm temperatures of 30°F or more above average are expected over a large portion of the eastern half of the U.S. Note also that another remarkable surge of warm air is predicted to pass over Greenland and into the Arctic, which has seen record-low sea ice extent this winter due to repeated incursions of warm air. Image credit: Climate Reanalyzer™ (, Climate Change Institute, University of Maine, Orono, Maine.

Figure 3. Leaf data compiled by the National Phenology Network show that vegetation is running three weeks ahead of average as far north as Kansas City, MO; Columbus, OH; and Philadelphia, PA. Image credit: U.S. National Phenology Network.

Spring is already 3 weeks ahead of schedule
Spring is already three or more weeks ahead of schedule across much of the U.S., and in Washington, D.C., is 22 days ahead of schedule, according to the USA National Phenology Network. These estimates were made using nature’s calendar—for example, when flowers bloom, trees begin to leaf out, and birds build their nests. According to a 2015 study by Allstadt et al., this year’s early arrival of spring will be typical by the year 2100. By that time, assuming a business-as-usual approach to burning fossil fuels, spring will arrive, on average, about 23 days earlier it does in the present climate. Over the past thirty years, spring has come an average of 3 - 5 days earlier across most of the U.S., when comparing the period 1991-2010 vs. 1961-1980 (Figure 4.)

Figure 4. Over the past thirty years, spring has come an average of 3 - 5 days earlier across most of the U.S. (when comparing the period 1991-2010 vs. 1961-1980.) Image credit: Climate Central.

Springtime warmth a classic signal of U.S. climate change
With a few exceptions, warm temperatures are becoming more likely year round as a result of human-produced greenhouse gases, but the signal appears to be especially strong during the months of meteorological spring in the Northern Hemisphere (March through May). Snow cover across the hemisphere has shown little significant trend over the months from autumn through January, but there has been a distinct decline in snow cover over recent decades from February through June, as shown in monthly analyses from the Rutgers Snow Lab. “We’ve known for over a decade now that climate change is variably advancing the onset of spring across the United States,” reports the National Phenology Network.

Warmth that comes too soon in late winter and spring can be thoroughly enjoyable for us humans, but it can be devastating for crops and ecosystems that depend on reliable seasonal signals, as Bob Henson discussed on NPR’s “Weekend Edition” on Sunday. A case in point is the Great March Warm Wave of March 2012, which produced readings between 85°F and 90°F as far north as Michigan and southeastern Canada. Fruit crops burst into bloom across Michigan, only to be decimated by a more seasonable late-April freeze. Damages to apple, blueberry, grape, peach, and cherry crops totaled more than $200 million across Michigan alone, leading to the state’s worst crop failure on record.

Rare February tornadoes pummel the Northeast
Tornadoes aren’t super-common east of the Appalachians and north of the Mason-Dixon line at any time of year. During winter, they’re almost unheard of. Yet at least three tornadoes developed in Saturday’s burst of severe weather. Massachusetts experienced its first February tornado on record, as a damage survey on Sunday confirmed that an EF1 twister packing top winds of 110 mph swung along a 5-mile path across the towns of Goshen and Conway between 7:18 and 7:25 pm EST. The twister developed at the leading edge of an eastward-moving, fairly linear severe thunderstorm. Only one injury was reported, but downtown Conway experienced substantial damage, with many trees and power lines down. “Several people that we spoke to heard a tell-tale roaring sound and immediately sought shelter in their basements. It was very fortunate that nobody was killed in this event,” reported the National Weather Service office in Taunton, MA. Official tornado statistics extend back to 1950, but in a separate database assembled by Theodore Fujita and the University of Chicago that goes back to 1916 (published in the book “Significant Tornadoes 1680-1991”), there are no tornado reports from Massachusetts for February.

In Pennsylvania, only four tornadoes (two of them just last year) had been reported in any February prior to the EF2 powerhouse on Saturday that swept just east of the heavily populated Wilkes-Barre/Scranton corridor. After a damage survey conducted on Sunday, the NWS/Binghamton, NY, office placed a Facebook photo album online with a number of photos and analyses of the twister. It was clearly generated by a supercell thunderstorm--the type more common in the Midwest and Great Plains--with a prominent hook echo and very strong rotation evident on Doppler radar. Top winds of 120 mph were reported along a 12.8-mile-long, 500-yard-wide path. Two homes were extensively damaged and 28 others experienced at least some damage, but no injuries were reported. At least 1,000 trees were knocked down. Although the twister’s path ended very close to Lake Scranton, it was never classified as a waterspout, since it originated as a land-based tornado within a supercell thunderstorm.

One other twister struck on Saturday: an EF1 tornado confirmed about 2 miles north-northwest of La Plata, Maryland (the town devastated by an F4 tornado on April 28, 2002). This EF1 tornado generated top winds of 90 mph along its 8.4-mile-long, 125-yard-wide path. No injuries were reported, and damage was generally minor. This was the eighth February tornado in Maryland since reliable records began in 1950, reported the NWS office in Sterling, VA.

Figure 5. The large tree that crushed this truck was felled by an EF2 tornado that moved through Lackawanna and Luzerne Counties, Pennsylvania, on February 25, 2017. Image credit: Dennis Macheska and Jeffrey LaCoe, via NWS/Binghamton.

Figure 6. Path of the EF2 tornado in northeast Pennsylvania on February 25, 2017. The tornado roughly paralleled Interstate 476, moving just 2-3 miles southwest of the Wilkes-Barre/Scranton corridor. Image credit: Patrick Favola and NWS/Binghamton.

Non-tornadic storms also had a noteworthy impact in unusual places over the last few days. According to a wrap-up of the week’s wild weather, the damaging winds experienced in eastern New York on Saturday were the farthest-north severe reports in New York State on record for February. A severe storm produced wind damage in southeast Michigan on Friday--only the sixth day since 1950 with severe weather reported in the state of Michigan during February.

Multi-day round of severe weather expected early this week
More severe weather is likely over the next several days as warm, moist air again surges northeastward ahead of a potent upper-level trough swinging through the eastern U.S. As of Monday morning, the NWS Storm Prediction Center had placed a slight risk of severe weather for Monday across parts of northeast Texas. Any supercell that forms could spit out large hail, with high winds and a small risk of tornadoes in storms that push eastward through the region along a warm front into northern Louisiana. The severe threat will ramp up considerably on Tuesday and Wednesday, with a region of enhanced risk for Tuesday over and near northern Arkansas, and on Wednesday from northern Mississippi and Alabama into central eastern Tennessee and Kentucky.

Models are in some disagreement on storm development mode for Tuesday, but SPC notes that any tornado that develops across northeast Arkansas could be a strong one. By Wednesday night, severe storms packing high wind could make it all the way into the Washington-to-New York corridor, especially if warm, unstable air makes it back into the region soon enough. “I’m concerned about Wednesday evening,” meteorologist Steve Sosna (WNBC/New York) told me. “The trajectory of the surface low is very favorable for severe weather around here.”

Bob Henson and Jeff Masters

Figure 7. Severe weather outlook for Tuesday, February 28 (top) and Wednesday, March 1 (bottom), from NOAA’s Storm Prediction Center.

Heat Severe Weather Tornado

All-Time Warmth for February Stretches to New England

By: Bob Henson and Jeff Masters , 5:47 PM GMT on February 24, 2017

A February remarkable for its long stretches of mildness steamed onward Thursday, with more all-time records for the month continuing to tumble across wide stretches of the U.S. The apex of the record-setting warmth expanded on Thursday from the Midwest (which we covered in our last post) into New York and New England (see below). A staggering number of daily record highs have been set in recent days, especially when juxtaposed against the sparse number of record lows this month. As of Friday morning, NOAA’s U.S. Records site had compiled 4492 daily record highs for February 2017, against a mere 29 daily record lows, for a lopsided highs-to-lows ratio of 155-to-1. With record highs expected to far outpace record lows through the end of the month, February has a very good chance of smashing the highest ratio in modern records: 44-to-1, from November 2016, as reported by longtime records tracker Guy Walton (@climateguyw) in his new Guy on Climate blog. Brian Kahn (Climate Central) puts it this way: “The U.S. is poised to set a record-setting record.”

Another astounding tidbit: the NOAA site shows 248 monthly record highs for February, but no monthly record lows at all. This is the first time that Walton recalls seeing such a skewed ratio of monthly records. It almost goes without saying that this onslaught of February records is entirely consistent with the warming of national and global climate being generated by human-produced greenhouse gases, as noted by Andrew Freedman (Mashable).

Mild air flowing into U.S. from atop record-warm northwest Atlantic waters
The polar jet stream and associated surface front that typically swings through the United States in late winter has been hovering close to the U.S./Canada border, with intrusions of seasonally cold air into the central and eastern United States either absent or short-lived over the last few days. The air mass south of this boundary has been notably mild and humid, flowing northward after spending time atop sea-surface temperatures that are at record-warm levels for late February.

“Western Atlantic basin SSTs are on fire!” tweeted hurricane forecaster Eric Blake (@EricBlake12) on Thursday. “Easily warmest on record--especially the Gulf of Mexico.” This warmth is especially well reflected in a swarm of daily record highs and record-warm lows at Galveston, TX, where records began in 1874. Since September 1, Galveston has set an impressive 33 heat records of various types--more than any other Southeast city during that period in a compilation pulled together late Thursday by Houston meteorologist Matt Lanza (@MattLanza). Eric Berger (Space City Weather) has more on the extremely mild Houston/Galveston winter.

Figure 1. Sea-surface temperatures early on Thursday, February 23, 2017, were running 1-2°C (1.8-3.6°F) above average over large parts of the Gulf of Mexico, Caribbean, and northwest Atlantic. Image credit:, via Eric Blake.

Figure 2. An enhanced risk of severe weather is predicted by NOAA’s Storm Prediction Center for Friday, February 24, 2017 from Detroit, MI, to Cincinnati, OH, including parts of four states. Image credit: WU, via NOAA/SPC.

Severe storms possible in eastern Great Lakes on Friday
With a potent upper-level trough approaching the relentlessly warm, moist air mass over the eastern Great Lakes, an outbreak of severe weather may erupt on Friday. At 6:30 am CST, NOAA’s Storm Prediction Center placed an “enhanced risk” area from southern Michigan across eastern Indiana and western Ohio into north central Kentucky. Severe weather outbreaks in winter typically feature very strong wind shear (winds increasing and/or turning with height), along with just enough instability to get thunderstorms forming. There’s ample instability in this case, given the very mild, moist surface air in place, but the wind shear is fairly linear, with little directional change with height. As a result, the odds are tilted away from rotating supercell storms (the kind most likely to produce violent tornadoes) and instead toward lines or clusters of severe storms, eventually forming a longer squall line. The biggest threat of the day appears to be locally damaging winds, although tornadoes and marginally severe hail (0.75” or larger in diameter) can’t be ruled out. The odds of widespread severe weather will be lower on Saturday as the system moves across the Northeast and New England, but strong winds may still mix to the surface where thunderstorms do occur.

The best odds for a supercell on Friday is close to a surface low that will be traversing southern Michigan--a state where any severe weather in February is rare. Since 1986, the NWS office in Detroit has issued tornado or severe thunderstorm warnings for just two severe weather events, the most recent being in 1999. According to the Tornado History Project, since 1950, only one tornado has ever touched down in February in Michigan: an F2 twister that hit southeast Michigan on February 28, 1974. Ohio has recorded 17 February tornadoes since 1950, and Indiana has had 31.

Texas and the century mark: 100°F heat on Thursday
We expect to see temperatures over 100°F in Texas in July, but not in February! Temperatures soared past the 100 degree mark at several stations in southern Texas on Thursday, flirting with the all-time U.S. temperature record for February. According to wunderground weather historian Christopher C. Burt, the Texas (and national) February heat record is either a questionable 104° at Fort Ringgold (now known as Rio Grande City) on Feb. 20, 1902 or, more likely, 103° at La Joya on Feb. 28, 2009 and also at Laredo on Feb. 20, 1986 and Feb. 27, 2011. The 101°F reading in McAllen, Texas on Thursday was their hottest February temperature ever recorded. A number of COOP and Mesonet stations also exceeded 100°F on Thursday, with the hottest being a 107°F mark at Falcon Lake on the Mexican border. However, we asked south Texas weather expert Richard "Heatwave" Berler (@Heatwave KGNS) about this mark, and he responded:  "I think that the thermometer is miscalibrated or exposed. It consistently runs higher than nearby thermometers during the daytime." Another site at Falcon Lake recorded 103°F (originally reported as 105°) though, and this may be a reasonable measurement, since there were three Mexican stations near Falcon Lake that reported 103°F - 104°F at that time. Update: The NWS/Brownsville office reported in a tweet Friday afternoon that the Falcon Lake COOP station recorded 103°F on Thursday. This ties the most reliable candidates for the national February record noted above.

Here are the 100°F readings in Texas from February 23 as recorded in the NOAA Weather and Hazards Viewer (thanks go to Hal Needham for alerting us to this tool):

107°F at Falcon Lake RAWS
105°F at Falcon Lake COOP (APRSWXNET/CWOP)
102°F in Atlee
102°F in Dilley
101°F at Zapata
100°F at Faith Ranch Airport
100°F at Cotulla
100°F - 101°F at three stations in McAllen
101°F at Laredo

The hot temperatures in southern Texas have increased wildfire risk this week, and a Red Flag Warning for dangerous fire conditions was posted on Friday for most of the region.

Figure 3. As piles of snow melt in the foreground, Williams College students take advantage of the unseasonably warm weather by dressing in shorts and tank tops as they hang out and study outside Chapin Hall on the school's campus in Williamstown, Massachusetts, on Thursday, February 23, 2017. The campus lies just a few miles south of Bennington, Vermont, where a new state record high for February was set on Thursday. Image credit: Gillian Jones /The Berkshire Eagle via AP.

Monthly records melt in Hudson and Champlain valleys
At least two states have seen all-time statewide highs for February this week. Vermont had its warmest February temperature on record Thursday, February 23, with Bennington soaring to 69°F. According to WU weather historian Christopher Burt, the previous state record for February was 68°F, set in Bennington in February 1957. It’s possible other sites in Vermont also reached or topped 69°F on Thursday. In Wisconsin, Janesville and Boscobel both hit 72°F on Wednesday, February 22. According to Burt, it appears that the previous state record was 69°F at multiple locations. Amazingly, he adds, at least 12 other official reporting sites in Wisconsin tied or broke that previous state record on Wednesday!

All-time records for February set on Thursday, February 22, included:
Albany, NY: 69°F (previous record 68°F on Feb. 22, 1997; records began in 1874)
Glens Falls, NY: 68°F (previous record 65°F on Feb. 21, 1981; records began in 1944)
Burlington, VT: 63°F (previous record 61°F on Feb. 22, 1981; records began in 1883)
Montpelier, VT: 63°F (previous record 61°F on Feb. 19, 1981, and Feb. 22, 1997; records began in 1948)
St. Johnsbury, VT: 62°F (tied) (previous record 62°F on Feb. 21, 1981; records began in 1984)

Some of these brand-new all-time monthly records in northern New England may be in jeopardy on Friday and/or Saturday, as yet another surge of very mild air pushes into New England ahead of the severe-weather-producing storm now over the Great Lakes. We can also expect a continuing avalanche of daily record highs throughout much of the eastern U.S. (see images below). Update: Boston reached 71°F at around 12:30 pm EST Friday, breaking the city’s all-time February record of 70°F from Feb. 24, 1985. Records in Boston go back to 1872.

Flood threat from snowmelt ramping up across New York and New England
Flood watches are in effect this weekend from the Adirondacks of New York to parts of eastern Maine. Although an inch or more of rain could fall this weekend, the bigger reason for the flood watches is the persistent warmth that’s been kicking snowmelt season into early overdrive. The equivalent of 3” - 4” of rainfall could be produced by snowmelt alone over the Adirondacks and eastern Vermont, according to the National Weather Service in Burlington, with the potential for significant rain atop the snowmelt. “That’s a lot of liquid for our rivers to handle. And the ground is also frozen, so not much will soak in,” noted the office in a morning forecast discussion. In general, flooding is expected to be mild to occasionally moderate, but more significant floods could occur over the weekend if and where ice jams complicate the picture.

Have a great weekend, everyone!

Bob Henson and Jeff Masters

Figure 4. High temperatures across the northeastern U.S. on Thursday, February 23, 2017. Image credit: NWS Eastern Region.

Figure 5. Record daily highs set or tied across the northeastern U.S. on Thursday, February 23, 2017. Image credit: NWS Eastern Region.

The Milding of February: All-Time Winter Warmth in Midwest

By: Bob Henson , 4:41 PM GMT on February 23, 2017

Residents of Wisconsin have never experienced a winter day like the one that enveloped the state in a springlike balm on Wednesday. An uncommon lack of late-February snow cover across Illinois and southern Wisconsin allowed very mild air streaming northward to sweep across the state with very little surface cooling. All three of Wisconsin’s largest cities saw the highest temperatures observed on any December, January, or February day in more than a century of recordkeeping. Milwaukee’s 71°F smashed its winter record of 68°F (Dec. 5, 2001 and Feb. 11, 1999). Madison’s 68°F beat out 65°F from Dec. 3, 2012, as well as the monthly record of 64°F from Feb. 25, 2000. Meanwhile, Green Bay’s 65°F eclipsed the previous winter record of 64°F (Dec. 5, 2001) and the monthly record of 61°F (Feb. 26, 2000).

Wednesday’s warmth was a fitting coda to a remarkably warm stretch across most of the Midwest. In some ways, the ultra-mild period is reminiscent of the Great Warm Wave of March 2012, if not quite as spectacular as that summerlike spell was. Duration is one of the most impressive aspects of the past week’s Midwestern mildness. St. Cloud, Minnesota, saw its sixth consecutive day above 50°F on Wednesday, the longest such streak on record for any February, while Chicago, Illinois, set a similar record for its first six-day streak of 60°F readings in any February (or in any winter month, for that matter). Rockford, Illinois, set six daily record highs in a row on February 17-22. Each of these new records was between 66°F and 70°F, beating out previous records that ranged from 58°F to 64°F.

In Detroit, Michigan, the high on Wednesday hit 65°F, and was already at 66°F at 1 pm Thursday, marking the third and fourth time in the past week the Motor City has reached or exceeded 65°F. The forecast for Friday calls for a fifth February 2017 day of 65°F or greater, with a high of 67°F—a full thirty degrees above average.  Between 1874 and 2016, Detroit reached or exceeded 65°F only six times in February. Jeff Masters reports from southeast Michigan: “My lawn is starting to green up--an extraordinary occurrence for a time of year when the ground is usually frozen and covered with a hefty layer of snow!”

Figure 1. Spring in February? A crocus blooms in Dravosburg, Pennsylvania on February 20, 2017. Image credit: Wunderphotographer gingyb

Figure 2. Snow cover was lacking across the Northern Great Lakes on Wednesday, February 22, 2017. Image credit: NOAA/NWS/National Operational Hydrologic Remote Sensing Center.

Snow is a rare commodity in the Upper Midwest right now
Only 26.5% of the Upper Midwest was covered by snow on Wednesday, with an average coating of just 1.7 inches. Even the Northern Great Lakes were just 27.2% snow-covered. These are striking numbers to witness a full month before the spring equinox. The only states in the contiguous U.S. east of the Rockies where snow cover truly predominated on Wednesday were North Dakota, New York (the eastern half), and the New England states, still buried after a sequence of storms earlier this month.

Lake ice is also in relatively short supply across the Midwest. Only 8.7% of the Great Lakes were ice-covered as of Tuesday, compared to 12.7% on that date in 2016 and a far more impressive 82.8% in 2015. It appears that the maximum coverage this year will be the already-observed 15%. That would place 2015-16 in fourth place for lowest maximum ice extent among all winters tracked since 1973 by NOAA, as related by George Leshkevich (NOAA Great Lakes Environmental Research Laboratory) to the Detroit Free Press.

Back to a more late-winter-like pattern
A strong, blustery winter storm pushing across the Midwest late Wednesday into Thursday will send the region back into a more seasonable pattern for at least a few days, starting off with a swath of snow extending from Colorado and Wyoming across the central and northern Great Plains into the Midwest. After reaching the mid-60s on Wednesday (35°F above average), Green Bay was expecting 1” - 3” of snow late Thursday into Friday. A blizzard warning was in effect for Thursday night into Friday across northwest Iowa and neighboring areas. It looks like Chicago will get mostly rain until at least Friday, thus prolonging its record-long “snow drought.” As of Wednesday, it had been 67 days since Chicago got its last inch of snow, surpassing the record of 66 days (Dec. 25, 1921, to Feb. 28, 1922).

We’ll be back with a new post by Friday afternoon. Stay tuned for more in coming days on how this strikingly mild late winter is affecting other parts of the U.S.

Bob Henson

Extreme Weather Winter Weather

More Floods and Evacuations in California--Plus Wind Gusts Topping 190 MPH

By: Bob Henson and Jeff Masters , 6:50 PM GMT on February 21, 2017

The atmospheric river that slammed the central third of California on Monday left its mark in multiple ways, including what could end up as the highest reliably recorded wind gusts for the state (see below). Fortunately, the storm underperformed somewhat when it came to rainfall, much like its older sibling that hit southern California last Friday. Rainfall amounts in Bay Area cities on Monday came in well short of the potential suggested by multiple model runs, although both San Francisco (2.16”) and San Jose (1.87”) managed to set rainfall records for the date.

Even if the rains of the last week haven’t lived up to model-based expectations, they have caused plenty of havoc (see Figures 1 through 3). Power was knocked out to more than 100,000 people in the Los Angeles area on Friday, with several fatalities reported. More than two dozen debris flows had been recorded in nine counties as a result of the Sunday/Monday storm, according to a comprehensive roundup of the last week’s storms from One levee breach on Monday night in San Joaquin County was quickly repaired after some 500 people had been ordered to evacuate. Residents of the town of Wilton in southern Sacramento County were under a voluntary evacuation on Monday night, but the Cosumnes River ended up peaking at 12.06 feet, less than an inch above the 12-foot flood stage and more than 3 feet below predictions from earlier Monday.

The storms of the past week have added to multi-month precipitation totals that are getting steadily more impressive. Many points across central and northern California have already recorded more precipitation than they get on average in an entire October-to-September water year. As of 4:00 pm PST Monday, San Francisco International Airport had racked up 15.70” of rain since January 1. Phil Klotzbach (Colorado State University) noted that this is the fourth highest January-February total on record for the airport, where data collection began in 1945. By midnight Monday night, this year’s Jan-Feb total had climbed to 16.38”. Meanwhile, downtown San Francisco is already at its seventh wettest Jan-Feb in records going back to 1855, with 17.63” as of Wednesday morning. The station is likely to vault to at least fourth place by the time the month is done, but going any further will be a challenge, based on stats tweeted by Klotzbach. During the catastrophic Jan-Feb of 1862, downtown San Francisco recorded 31.89”.

Figure 1. For the first time since the floods of 1997, the Don Pedro Reservoir spillway gates were opened on Feb. 20, 2017, in Tuolumne County, California. The Stanislaus Consolidated Fire Protection District told that up to 20,000 cubic feet per second of water was being discharged as of 3 pm PST Monday. Water flowing from the reservoir will enter the Tuolumne River, where authorities are advising some residents to evacuate and seek higher ground. The spillway will be open for at least four days. Image credit: Twitter/@TuolumneSheriff

Figure 2. For the first time in over a decade, water flows into the iconic 72-foot diameter Glory Hole spillway at Monticello Dam on Monday, Feb. 20, 2017, in Lake Berryessa, California. The unique spillway operates similarly to a bathtub drain. Lake Berryessa is the largest lake in Napa County, California, and is formed by the Monticello Dam, which provides water and hydroelectricity to the North Bay region of the San Francisco Bay Area. Image credit: AP Photo/Eric Risberg. See also the video embedded at bottom.

Figure 3. Officials look over the scene where a San Bernardino County Fire Department fire engine fell on February 17, 2017, from southbound Interstate 15, where part of the freeway collapsed due to heavy rain at Cajon Pass, California, late last week. Image credit: David Pardo/The Daily Press via AP.

A truly wild night in the high Sierra
Two high-elevation weather stations at California’s Squaw Valley resort experienced incredible winds on Monday night as the core of the jet stream associated with the atmospheric river came through, together with localized wind acceleration from a low-level jet encountering the Sierra crest. (Thanks to WU member BayFog for pointing out the multiscale interactions.] Between 10:45 pm and 11:00 pm PST, the Siberia (Sierra Crest)-Squaw station, or SIBSV--located at an elevation of 8700 feet near the top of Squaw Peak--recorded a peak wind gust of 193 mph, with sustained winds reported at 123 mph. During the same interval, only about two miles to the southeast, the Summit (Ward Mt)-Alpine station, or SUMAM--perched atop Mt. Ward at 8643 feet--recorded a gust to 199 mph, with sustained winds of 148 mph.

Extreme gusts over 150 mph are no stranger to the high Sierra. In a 2011 blog post, WU weather historian Christopher Burt referred to an undated state record gust of 176 mph from the Mt. Ward station. Just last month, on January 8, the same station notched a 174-mph gust. (If it’s any comfort, the atmosphere at this height is about 25% thinner than at sea level, so the wind exerts less force.)

Figure 4. Preliminary data from the summit of Ward Mountain in California’s Squaw Valley ski resort show a gust to 199 mph (highest green dot). The gust occurred between 10:45 and 11:00 pm PST on Monday, February 20, 2017. Image credit: MesoWest/University of Utah via National Weather Service.

The closeness of Monday night’s amazing gusts in both time and space, as part of a multi-hour ramp-up in wind speeds, is a strong clue that the data are likely valid. Also lending credence is the location of these two stations: near ridgetops in a highly wind-prone area. “Everything would suggest that it’s pretty legit,” said John Horel (University of Utah), an expert in Western weather and climate and coordinator of the MesoWest observation network. I also got in touch with Sam Kieckhefer, the public relations coordinator for Squaw Valley/Alpine Meadows. “As far as what people have seen in recent history, it’s definitely the highest [wind gust] that has been noted,” Kieckhefer said of the 199-mph gust. The two Squaw Valley stations were installed in the 1980s, with the Siberia station at close to standard height (10 meters, or about 33 feet); information on the height of the other station wasn't immediately available. Gusts at these stations are reported every second (i.e., instantaneously), according to Western Weather Group, which works with Squaw Valley on data collection. The 1-second tempo is typical of Remote Automatic Weather Stations (RAWS). It would tend to yield slightly higher values than the 5-second gusts used by stations in the Automated Surface Observing System (ASOS). Still, it appears that the 199-mph gust could be a valid contender for the highest wind gust in California weather annals and one of the strongest gusts recorded near ground level in U.S. history.

Bob Henson and Jeff Masters

Video 1. Drone footage of the iconic 72-foot diameter Glory Hole spillway at Monticello Dam on Monday, Feb. 20, 2017, in Lake Berryessa, California.

Flood High Wind

Dangerous, Multipronged Storm Strafing Central/Northern California

By: Bob Henson , 5:57 PM GMT on February 20, 2017

What may become known as the President’s Day Storm of 2017 barreled into the San Francisco Bay area on Monday morning. The core of the storm was an atmospheric river roughly 75 to 100 miles wide, pointing a firehose of moisture toward vulnerable foothills and urban areas. With soils already sodden, the risk of flash flooding was high, and the tail end of the storm promised to bring ferocious winds into the area that could knock out power for many thousands of residents, in some cases for prolonged periods. Toward the Sierra, the storm will deliver yet another onslaught of torrential rain and several feet of mountain snow, as the region’s water infrastructure groans under its fiercest assault in a number of years.

Figure 1. An atmospheric river of moisture extended from Hawaii to the San Francisco Bay area in California at 3 am PST Monday, February 20, 2017, as seen in this satellite-derived measurement of total precipitable water (TPW)--the total amount of water that would fall on the ground if one were to condense out all of the water vapor in the atmosphere. Image credit: University of Wisconsin SSEC.

Heavy rain: Location is everything
Monday’s atmospheric river (AR) extends back in a fetch almost directly from Hawaii, as shown in Figure 1, making it a classic “Pineapple Express.” The AR was carrying at least 1.25” to 1.5” of precipitable water, or the amount of moisture in the column of air above a particular spot. That’s an amount seen on average once every 5 to 10 years in the area, noted the Sacramento office of the National Weather Service. Unlike many big storms, this one won’t arrive with a strong surface low; instead, a relatively weak low will be moving into Oregon on Tuesday, well north of the fairly linear AR.

Oriented from west-southwest to east-northeast, the AR will be translating north and south across the southern Bay Area on Monday. The exact timing and duration of those north-south shifts are difficult to predict, but they will largely control where the heaviest rains fall. Since Sunday, models have tamped down the peak storm totals somewhat, and pushed the most likely location of the heaviest rains southward into the South Bay region, roughly from San Mateo to Santa Cruz. Localized amounts could be enormous--potentially 10” or more on the west side of the Santa Cruz Mountains.

The cities of San Francisco, Oakland, and Sacramento will see moderate to heavy rain throughout Monday, most likely totaling 2” to 3”. These amounts could be lower or higher depending on how much time the AR spends on the northern edge of its north-south range. Pockets of urban flash flooding are a given, but the bigger impact in these cities could be the high winds expected to rip through the area later on Monday, toward the tail end of the storm (see Figure 3). With the soils so wet, these winds could easily knock large trees onto power lines. If these outages are especially widespread, it may take days for repairs to be completed.

Figure 2. Precipitation forecast from the 12Z Monday run of the 3-km NAM model for the 24-hour period from 4 am PST Monday to 4 am PST Tuesday, February 20-21, 2017. Image credit:

Figure 3. Potential top wind gusts predicted for Monday night, February 20, 2017. Widespread, extended power outages are possible. Image credit: NWS/Sacramento.

Oroville and other dams and levees
Precipitation totals of 5” or more are also possible across parts of the Feather River watershed feeding into Lake Oroville. This is bound to push lake levels toward a new spike even as water continues pouring from the lake’s damaged main spillway. Fortunately, the lake level is down some 50 feet from its overflow state last Sunday, February 12, when the emergency spillway at Oroville Dam showed signs of failure that prompted the evacuation of more than 180,000 people. By Sunday, the amount of water in the reservoir had dropped to 79% of capacity. This greatly reduces the odds that the impending storm will bring the lake back near capacity. Meanwhile, repair work has proceeded along the emergency spillway (see embedded video at bottom).

Other levees and dams across central and northern California will need to be watched over the next few days, as new trouble spots could easily emerge. Overall, the region’s saturated soils will be raising the flood risk to very concerning levels. “We may see flooding in locations which haven`t been impacted in many years. We are strongly advising all residents in interior Northern California to be prepared for flooding,” warned the National Weather Service’s Sacramento office in a flood warning for urban areas and small streams that covers 24 counties through 4 pm PST Thursday. More wet weather is possible toward the end of the week and into early next week, although these storms look much less potent than Monday’s.

Climate change and atmospheric rivers
California’s patterns of rain and drought are notoriously variable, and climate change promises no help in alleviating this whiplash. Recent work has shown that warming temperatures associated with human-produced climate change are worsening the impacts of drought when it occurs in California. Climate change may also intensify the atmospheric rivers (ARs) that bring the U.S. West Coast its most intense multiday rains.

In many parts of the world, the most extreme rainfall events are getting heavier, as greenhouse-warmed oceans pump more moisture into the atmosphere. Up to now, this effect has been difficult to detect in the Southwest, and especially in California, when juxtaposed against the high natural variability of the state’s hydrological regime (evident in Figure 4 below). The 2014 U.S. National Assessment showed that the amount of precipitation falling from 1958 to 2012 on the wettest 1% of days climbed by 71% in the Northeast and New England, and by 37% in the Midwest, but by only 5% in the assessment’s Southwest region, which includes California.

Figure 4. Averages of contributions to water-year total precipitation on Pineapple Express days, plus the following day of each event, at 202 cooperative weather stations in central and northern California, 1951–2008. The graph shows that Pineapple Express events contribute as little as 0 or as much as 54% (0.54) of water-year precipitation for any given year. Image credit: Michael D. Dettinger, Fred Martin Ralph, Tapash Das, Paul J. Neiman and Daniel R. Cayan, “Atmospheric Rivers, Floods and the Water Resources of California,” Water 2011, v. 3, pp. 445-478.

There remains a good deal of uncertainty over whether total precipitation will tend to increase or decrease over California and the Southwest as the century unfolds. It’s entirely possible that intense periods of multiyear drought--made more destructive by higher temperatures--will alternate with some very wet winters. Regardless of whether average precipitation goes up or down, there is evidence that the strongest ARs events will dump more rain and exert more of an impact over time. The 2014 USNA noted: “An increase in winter flood hazard risk in rivers is projected due to increases in flows of atmospheric moisture into California’s coastal ranges and the Sierra Nevada.” A 2015 study in the Journal of Hydrometeorology shows that West Coast rainfall on the most extreme AR days could increase by as much as 39% by the end of this century, mainly because of more water vapor within the ARs.

A plausible worst-case scenario: 1861-62
Even without any help from our changing climate, we know that California can already get intense multiday rain spells and mammoth multi-week totals unlike anything in living memory. As we noted in Sunday’s post, most of the top 1-, 2-, and 3-day rainfall totals in the cities of central California occurred in several landmark events before 1900. The great concern among water managers and hydrologic scientists is the recurrence of a winter like the one of 1861-62, which produced nearly 30” of rain in San Francisco over a month’s time and more than 100” in the town of Sonora in just two months.

A major study called ARkStorm evaluated the potentially catastrophic effects if a winter similar to 1861-62 were to occur today. The study found that direct damages and losses to economic activity would total a mind-boggling $725 billion. Paleoclimate data indicate that we could expect such an event about once every 300 years, even before taking climate change into account. An ultra-mega-flood is indeed the other “big one” that Californians must take seriously. For more on ARkStorm, see these posts from Jeff Masters and Christopher Burt.

We’ll be back on Tuesday afternoon with a post reviewing the impacts of the southern California storm on Friday as well as the currently unfolding storm over central and northern California.

Bob Henson

Figure 5. Downtown Sacramento at the height of the flood in January 1862. Sacramento recorded 23.68” of rain during the two-month period of December-January 1861-62, compared to its annual average of 19.87”. Massive runoff from the mountains during the warm storms filled the Sacramento and San Joaquin Valleys almost from the foothills of the Sierra on the east to the hills on the west side of the Great Valley, and a giant lake, estimated to be 250-300 miles long and 20 miles wide, covered the present-day locations of cities and farmland across much of the San Joaquin Valley. Image credit: Bancroft Library Collection, University of California, Berkeley.

No Rest: Another Round of Intense Rains Heading for Central and Northern California

By: Bob Henson , 4:08 PM GMT on February 19, 2017

While southern California tries to dry out from Friday’s watery onslaught, yet another atmospheric river will be pointed at central and northern California from late Sunday through Monday, exacerbating the woes of what’s already been a record-wet winter to date across the northern Sierra. Precipitation totals of 10” or more are possible early this week across parts of the Feather River watershed feeding into Lake Oroville. This is bound to push lake levels toward a new spike even as water continues pouring from the lake’s damaged main spillway. Fortunately, the lake level was down almost 50 feet on Saturday from its overflow state last Sunday, February 12, when the emergency spillway showed signs of failure that prompted the evacuation of more than 180,000 people. By Saturday, the amount of water in the reservoir had dropped to 81% of capacity. This greatly reduces the odds that the impending storm could bring the lake back near capacity.

While officials will be monitoring the Oroville situation and continuing their spillway repair work, many other dams and levees across the region will come under increasing stress as this week’s rains fall atop already-saturated ground. “Given record wetness to date, Monday #AtmosphericRiver will be stress test for CA water infrastructure,” noted Daniel Swain (California Weather Blog).

Figure 1. Precipitation forecast for the 3-day period from 4:00 am PST Sunday, February 19 to Wednesday, February 22, 2017. Amounts in California amay peak at more than 10” at higher elevations of the Bay Area and in the northern Sierra. Image credit: NOAA/NWS Weather Prediction Center.

Now it’s the Bay Area’s turn
The impending storm is likely to pack a big punch for city dwellers from San Francisco to Sacramento. Models have been varying on the location and movement of the atmospheric river, or AR, which is expected to push across the Monterey area late Sunday and gradually work its way northward into Monday. The AR’s orientation over time is the critical variable in how much rain falls across the heavily populated corridor from San Francisco to Sacramento. Although Friday's storm caused widespread local havoc in parts of Southern California, it brought a bit less rain than feared to the immediate Los Angeles area (2.01” in downtown Los Angeles), as the main moisture channel ended up focused just a bit further west. Santa Barbara’s airport experienced its wettest February day in 77 years of recordkeeping with 4.16” on Friday, beating out 3.97” from Feb. 8, 1985.

The AR heading into the Bay Area late Sunday is expected to be carrying at least 1.25” to 1.5” of precipitable water (the amount of moisture in the column of air above a particular spot). The higher end of this range is seen on average once every 5 to 10 years in the area, noted the Sacramento office of the National Weather Service. Overall, the southwest-northeast-oriented AR will lift northward with a warm front late Sunday into early Monday, then sag southward with the subsequent cold front later on Monday. Between the rich moisture feed and strong atmospheric dynamics, the potential exists for totals of 3” or more of rain at lower elevations--even in the Bay Area cities--should the AR stall for very long over a particular spot. The GFS model has been particularly bullish on the potential for very heavy amounts. In those places where the AR shifts north or south fairly quickly, totals may end up closer to 2” or less. Official forecasts are calling for 1.5” - 2.5” in the Sacramento area and 2” - 5” in and near San Francisco. As usual, much higher amounts can be expected at higher elevations, and flooding and mudslides will again be a distinct threat. High winds will topple vulnerable trees in increasingly wet soils.

Longtime Bay Area forecaster Jan Null (Golden Gate Weather Services, @ggweather) expects that Oakland could see 3”, with 6” - 8” in the Coast Range above 2000 feet. “I think this will be a memorable President’s Day Storm,” Null told me. “There will be major problems in the swath from the Bay Area to Lake Tahoe. Lots of slides, trees down, and localized flooding. I am actually recommending people stay home on Monday.”

What are the records to beat?
California precipitation is notoriously variable, and we’re fortunate to have records extending well back into the 19th century to remind us of this. Even though climate change is boosting the intensity of extreme rainfall in many parts of the world, most of the heaviest 1-, 2-, and 3-day rainfall events in central California occurred before the year 1900, as shown below. Records go all the way back to 1877 in Sacramento and 1849 in downtown San Francisco.

Maximum 1-day rainfall
Sacramento: 5.28” (Apr. 20, 1880)
San Francisco: 5.44” (Nov. 5, 1994)

Maximum 2-day rainfall
Sacramento: 8.37” (Apr. 20-21, 1880)
San Francisco downtown: 7.90” (Dec. 19-20, 1866)

Maximum 3-day rainfall
Sacramento: 8.81” (Apr. 19-21, 1880)
San Francisco downtown: 8.85” (Dec. 18-20, 1866)

Only a dozen two-day rainfalls have topped 5” in San Francisco, and just three of those have occurred in the last century: 6.78” (Jan. 5, 1982), 6.76” (Nov. 5-6, 1994), and 5.68” (Nov. 4-5, 1994). Only three calendar days have seen more than 4”.

Figure 2. A before-and-after shot of Cachuma Reservoir, located north of Santa Barbara. The amount of water in Cachuma Lake has more than tripled since the start of February. Located on the leeward side of the Santa Ynez Mountains, Cachuma Reservoir often misses out on big precipitation events, and drought relief had been limited in the area till the last couple of weeks. As recently as late January, the reservoir held only 9% of its capacity and 13% of its historical average for that date. As of Saturday, the lake held 32% of its capacity. Image credit: Santa Barbara County, @countyofsb

Figure 3. Water expert Peter Gleick (Pacific Institute) tweeted this astonishing image on Saturday: “In an average 12-mo California #water year, northern CA gets 50 inches of rain. The first half of the 2017 water year has produced 70 inches.” On average, northern California has received about 65% of its water-year total by this date--about half of what’s actually fallen this water year. Image credit: California Department of Water Resources, annotated by Peter Gleick, @PeterGleick.

Get set for one of the warmest winter weeks on record in the heart of the Midwest
St. Cloud, Minnesota, hit 59°F on Saturday--tying the warmest reading observed in St. Cloud during any February in 123 years of recordkeeping (that record occurred just last year, on Feb. 27, 2016). International Falls also tied its February record on Saturday with 58°F, previously set on Feb. 22, 2000. A number of Midwestern cities set or tied their second-warmest February reading on Saturday, including:

Detroit, MI: 69°F (monthly record 70°F on Feb. 11, 1999)
Flint, MI: 65°F (monthly record 68°F on Feb. 11, 1999)
Minneapolis, MN: 63°F (monthly record 64°F on Feb. 26, 1896)
Milwaukee, WI: 67°F (monthly record 68°F on Feb. 11, 1999)
Sault Ste. Marie, MI: 49°F (monthly record 50°F on Feb. 16, 1921)

Saturday’s warmth is a harbinger of a very mild week to come for the heart of the Midwest, especially across snow-starved northern Illinois. As reported by Chicago weathercaster Tom Skilling, the city’s longest winter period without a one-inch snowfall in records dating back to 1884 was a 64-day streak that occurred twice: Dec. 3, 1905, to Feb. 4, 1906, and Dec. 23, 1953, to Feb. 24, 1953. Chicago’s last inch of snow fell on Dec. 17. With no snow in the forecast, the city’s snow-drought record will fall on Monday when the current streak hits 65 days. Other cities experiencing an unusual lack of snow this winter thus far, as noted by Illinois state climatologist Dr. Jim Angel:

• Champaign: 4.6” (record is 6.7 inches in 1953-54)
• Springfield: 5.7” (record is 5.8 inches in 1953-54)
• Peoria: 9.5” (record is 7.8 inches in 1965-66, 1994-95)

The extreme lack of snow is helping an already-mild pattern maximize its potential for warmth at ground level. Rockford, IL, cracked 60°F on both Friday and Saturday, and the forecast is for Sunday through Wednesday to do the same, making for a six-day streak. No winter (Dec/Feb/Jan) has ever brought Rockford more than three 60-degree days in a row. Chicago may also manage a 6-day streak of 60-degree days, which would break its longest winter streak of 5 days set on Dec. 2-6, 1998. Records extend back to 1872 in Chicago and 1893 in Rockford. Even Detroit could rack up a solid week of temperatures breaking the 50°F mark, which would be just one day short of its record for any February.

We’ll be back on Monday with more on the California rains, including the dousing that caused several deaths and massive disruption across the Los Angeles-Santa Barbara area.

Bob Henson


Epic Storm Pounds Southern California With Heavy Rain, High Wind and Huge Waves

By: Jeff Masters , 5:20 PM GMT on February 17, 2017

The epic assault of the winter of 2016 - 2017 on California continued on Friday morning as torrential rains, damaging winds and huge waves from a massive and powerful Pacific storm system pounded the Golden State. Carrying with it an “atmospheric river” of moisture originating in the subtropics near Hawaii, Friday’s storm was most dangerous because of its heavy rains. According to the National Weather Service in Oxnard, California, Friday and Saturday could be the heaviest two-day rainfall event for the entire L.A. Basin since Dec. 19 - 20, 2010. Rainfall amounts of 2 - 6 inches are expected along the coast west of Los Angeles, from Santa Barbara to Ventura, with 5 - 10 inches likely in favored foothill and mountain locations. As of 7:10 am PST Friday, Santa Barbara had received 0.97” of rain, causing a sink hole to open up on Olive Street. The coast about 50 miles northwest of San Luis Obispo had received over 3” of rain as of 9 am PST, according to radar estimates. Soils are already wet in Southern California from previous storms, and the heavy rain is likely to runoff quickly and create dangerous mudslides, rockslides and flash floods. In wildfire burn-scarred areas, debris flows are likely. In anticipation of debris flows, an Evacuation Warning has been issued for the greater Sherpa Fire Burn area inland from El Capitan Beach State Park. In the high mountains, the precipitation will fall as snow, with 1 - 2 feet of snow expected above 8,000’ elevation.

Strong winds were sweeping the area Friday morning, with numerous wind gusts in excess of 50 mph in the foothills of Los Angeles County and Santa Barbara County. The top wind gust as of 7 am PST Friday was 60 mph, recorded at both Grass Mountain and Mill Creek in Los Angeles County. Wind gusts as high as 75 mph are predicted at higher elevations near San Diego. The strong winds were being driven by the extremely low central pressure of the storm. According to a tweet by NWS San Diego, the storm’s expected central pressure of 986 mb on Friday evening, when it will be over San Francisco, will rank as the lowest pressure of any Central California coastal storm during the past 30 years (for the period February 7 - February 28.)

Figure 1. An atmospheric river of moisture extended from Hawaii to Southern California at 6 am PST Friday February 17, 2017, as seen in this satellite-derived measurement of Total Precipitable Water (TPW)—the total amount of water that would fall on the ground if one were to condense out all of the water vapor in the atmosphere. Image credit: University of Wisconsin SSEC.

Figure 2. Predicted 66-hour rainfall amounts in southern California ending at 10 pm Saturday, February 18. Image credit: NWS Los Angeles.

California’s beaches receiving a pounding
Today’s storm is bringing south to southeasterly gale-force winds to the coastal waters of Southern California, which is churning up huge battering waves. At Santa Rosa Island in Channel Islands National Park, about 100 miles west of Los Angeles, sustained winds as high as 41 mph, gusting to 60 mph, were recorded between 5 - 8 am PST Friday. Significant wave heights of up to 11.2 feet were recorded Friday morning at buoy 46054, located 44 miles west of Santa Barbara. Breaking waves of 6 - 9 feet are expected along the coast of Santa Barbara on Friday, increasing to 10 - 14 feet on Saturday. These battering waves, which are riding up on top of a storm surge of more than one foot in some locations, will cause beach erosion and dangerous swimming conditions. Fortunately, due to the phase of the moon (third quarter), water levels along the Southern California coast are about two feet lower than would have been the case if this storm had hit during a full moon. Thus, coastal damage is not likely to be severe.

Figure 3. Big waves affecting beach access and ocean bluffs at the Isla Vista, California study site in March 2016. Image credit: David Hubbard, UCSB.

California beaches received a record pounding during the winter of 2015 - 2016
This week’s storm comes on the heels of unprecedented coastal damage wrought along portions of the California coast by the El Niño-fueled storms of the winter of 2015 - 2016. According to Patrick Barnard, a geologist with the U.S. Geological Survey and lead author of a February 2017 paper, Extreme oceanographic forcing and coastal response due to the 2015–2016 El Niño, published in the journal Nature Communications, winter beach erosion in California was 76 percent above normal, and most beaches were eroded beyond historical extremes. Added David Hubbard, a UCSB marine ecologist and paper co-author, “The winter wave energy equaled or exceeded measured historical maximums along the West Coast, corresponding to extreme beach erosion across the region. The waves that attacked our coast, generated from storms across the North Pacific, were exceptional and among the largest ever recorded. But the lack of rainfall means that coastal rivers produced very little sand to fill in what was lost from the beaches, so recovery has been slow." If strong El Niño events become more common in the future, as some studies suggest, the California coast will become increasingly vulnerable to storm damage. Sea level rise will make these damages even greater. The authors concluded that “Water level anomalies of 7–17 cm above normal were measured across the US West Coast during the El Niño winter of 2015–2016, similar to anticipated global mean sea-level increases expected within the next few decades. Therefore, the 2015–2016 El Niño also provides an indication of future background coastal water-level conditions and the associated beach hazards that will become more common during typical winters.”

Jeff Masters

January 2017: Earth's 3rd Warmest January on Record; Lake Oroville Water Levels Drop

By: Jeff Masters and Bob Henson , 5:38 PM GMT on February 16, 2017

January 2017 was the planet's third warmest January since record keeping began in 1880, said NOAA's National Centers for Environmental Information (NCEI) on Thursday. Along with NOAA, NASA also rated January 2017 as the third warmest January on record. The only warmer Januarys were 2016 (highest) and 2007 (second highest). Global ocean temperatures during January 2017 were the second warmest on record, and global land temperatures were the third warmest on record. Global satellite-measured temperatures in January 2017 for the lowest 8 km of the atmosphere were the sixth warmest in the 39-year record, according to the University of Alabama Huntsville (UAH).

It's remarkable that Earth saw its third warmest January on record without any help from El Niño, which works to raise global air temperatures by exporting heat from the oceans. Sea-surface temperatures in the Niño 3.4 region of the tropical Pacific rose into the cool side of the neutral range during January, although a La Niña Advisory was still in effect. In contrast, the warmest and second warmest Januarys (2007 and 2016) both occurred during an El Niño event.

Figure 1. Departure of temperature from average for January 2017, the 3rd warmest January for the globe since record keeping began in 1880. Three of the six continents had at least a top six warm January, with South America having its second warmest January since continental records began in 1910 (behind 2016.) Image credit: National Centers for Environmental Information (NCEI).

No billion-dollar weather disasters in January 2017
No billion-dollar weather-related disasters hit the Earth last month, according to the January 2017 Catastrophe Report from insurance broker Aon Benfield. The most destructive weather-related event during the month was Chile’s worst wildfires in modern history, which killed eleven people and cost at least $890 million. The deadliest weather-related disaster of January was the rainy season flooding in the southern African countries of Mozambique and Zimbabwe, which killed at least 179 people.

Figure 2. Smoke settles over Santiago, Chile on January 20, 2017. January fires in Chile cost the nation at least $890 million, and killed eleven people. Pudahuel Airport in western Santiago on January 20 hit 37.7°C (99.9°F), the hottest temperature ever recorded in the Santiago metropolitan area. Santiago Observatory (with records back to 1866) set its all-time heat record on January 25, 2017 with 37.4°C. Image credit: Martin Bernetti/AFP/Getty Images.

So Long, La Niña; Hello again, El Niño?
In its February monthly advisory, NOAA’s Climate Prediction Center (CPC) sounded the death knell for the 2016-17 La Niña. Sea surface temperatures (SSTs) in the benchmark Niño 3.4 region (in the equatorial Pacific) warmed to 0.3°C below average during early February; SSTs of 0.5°C or more below average in this region are required to be classified as weak La Niña conditions. Over the past week, SSTs have warmed rapidly in the Niño 3.4 region to more than 0.5°C above average but this surge may be temporary (Figure 3). We would need to see sustained warmth for many weeks at this level before crying, “El Niño is coming!” NOAA forecasters estimate an approximately 60% chance of neutral conditions lasting through the spring. For the September - November 2017 period, they predict a 12% chance of La Niña conditions, a 40% chance of neutral conditions, and a 48% chance of an El Niño. The latest Australian Bureau of Meteorology models are more aggressive about El Niño, showing development by this spring, and the latest May-June-July run of the UKMET model predicted a moderate El Niño by early summer. El Niño conditions tend to suppress Atlantic hurricane activity by bringing strong upper-level winds to the tropical Atlantic, creating high wind shear that tears storms apart.

Figure 3. Sea surface temperatures (SSTs) in the benchmark Niño 3.4 region (in the equatorial Pacific) have warmed above the 0.5°C above average threshold over the past week; SSTs of 0.5°C or more above average in this region are required to be classified as weak El Niño conditions. This recent surge in SSTs may be temporary; as Micheal Ventrice noted on Twitter today, there was a westerly wind burst over the past week that helped fuel this warming, but near-normal easterly trade winds have resumed. Image credit: Levi Cowan,

Arctic sea ice falls to lowest January extent on record
Arctic sea ice extent during January 2017 was the lowest in the 39-year satellite record, beating the record set in January 2016, according to the National Snow and Ice Data Center (NSIDC). Very warm air invaded the Arctic in mid-January, part of a trend we’ve seen all winter. A drifting buoy located near the Pole, at about 87°N latitude, has recorded temperatures at or above freezing three times since November: once in November 2016, once in December 2016, and once on February 10. In a February 10 interview in the Washington Post, atmospheric physics expert Kent Moore of the University of Toronto noted that these types of anomalous warming events have been recorded since the 1950s, but only occurred once or twice a decade. Record arctic sea ice loss in recent years is allowing these events to occur more frequently. Moore said: “As that sea ice moves northward, there’s a huge reservoir of heat over the north Atlantic. As we lose the sea ice, it allows essentially this reservoir of warmth to move closer to the pole.”

Notable global heat and cold marks set for January 2017
Hottest temperature in the Northern Hemisphere: 41.5°C (106.7°F) at N'Djamena, Chad, 24 January
Coldest temperature in the Northern Hemisphere: -58.7°C (-73.7°F) at Summit, Greenland, 12 January
Hottest temperature in the Southern Hemisphere: 47.0°C (116.6°F) at Bourke Airport, Australia, 13 January
Coldest temperature in the Southern Hemisphere: -45.3°C (-49.5°F) at Dome A, Antarctica, 31 January
(Courtesy of Maximiliano Herrera.)

Major weather stations that set (not tied) new all-time heat or cold records in January 2017
Durres (Albania) min. -9.0°C, 8 January
Vlore (Albania) min. -9.4°C, 8 January
Dudince (Slovakia) min. -30.5°C, 8 January
Apia (Samoa) max. 35.2°C, 9 January
Santiago Airport (Chile) max. 37.7°C, 20 January
Isla de Maipo (Chile) max. 37.9°C, 20 January
Santiago Observatory (Chile) max. 37.4°C, 25 January
Rapel (Chile) max. 36.8°C, 25 January
Linares (Chile) max. 41.8°C, 26 January
Chillan (Chile) max. 41.5°C, 26 January
Quinchamali (Chile) max. 43.0°C, 26 January
Los Angeles (Chile) max. 42.2°C, 26 January 
Parral (Chile) max. 40.8°C, 26 January
Concepcion Airport (Chile) max. 34.1°C, 26 January
Cauquenes (Chile) max. 45.0°C, 26 January;  (new national record high for Chile)
Robinson Crusoe Island-Juan Fernandez (Chile) max. 28.8°C, 26 January
Trelew (Argentina) max. 42.2°C, 27 January
Puerto Madryn (Argentina) max. 43.4°C, 27 January

(Courtesy of Maximiliano Herrera.)

One all-time national heat record set in January 2017
One nation set an all-time record for hottest temperature in recorded history in 2017: Chile (see above). Most nations do not maintain official databases of extreme temperature records, so the national temperature records reported here are in many cases not official. I use as my source for international weather records researcher Maximiliano Herrera, one of the world's top climatologists, who maintains a comprehensive list of extreme temperature records for every nation in the world on his website. If you reproduce this list of extremes, please cite Maximiliano Herrera as the primary source of the weather records.

Figure 4. Departures from average temperature (left) and precipitation (right) for the contiguous United States in January 2017. Image credit: NOAA/NCEI.

U.S. in January: Warmer and wetter than average
Last month the contiguous U.S. saw its 18th warmest and 9th wettest January in 123 years of record-keeping, as reported last week by NOAA/NCEI. Warmer-than-average temperatures covered nearly all of the nation east of the Rockies during January as a whole, although there was considerable variability, including a sharp cold spell in the second week of the month. Most states along a swath from Texas to Maine saw a top-ten-warmest January, although no state set a record. Only two states (Washington and Montana) experienced precipitation well below average, while ten states from California to Georgia saw the month place among their top ten wettest Januarys.

Figure 5. Predicted 7-day rainfall amounts in northern California beginning on Thursday, February 16. Image credit: NWS Sacramento.

Water levels in Lake Oroville continue to drop even as rains hit California
The water level at the troubled Lake Oroville reservoir in California continued to drop on Thursday morning, even as rainy weather moved into the region. The lake level fell by nearly 5 feet in the 12-hour period ending at 6 a.m. PST Thursday, to 869 feet, about 30 feet below its capacity. According to reports from the Sacramento Bee, state water officials continued to release 100,000 cubic feet per second (cfs) of water from the lake’s main spillway, and damage to that spillway has not worsened. Water was flowing into the lake at 34,000 cfs Thursday morning. About one half inch of rain is expected in the area on Thursday, with another half-inch on Friday (the rains will be much heavier in Southern California, see embedded tweet below.) Dam operators are expecting inflows of up to 50,000 cfs through Friday, so the lake level will continue to fall as long as the main spillway continues to release 100,000 cfs of water. During last week’s heavy rains that caused the reservoir to overflow, inflow peaked at 197,000 cfs. On Sunday, Monday and Tuesday, another very wet Pacific storm system is expected to dump at least three inches of rain on the area. This is about the same amount of rain that fell during the storm that caused inflow rates to reach 197,000 cfs last week. If the upstream rainfall amounts also end up being similar in magnitude to last week’s storm, we can expect Lake Oroville to begin rising by Monday. However, assuming that dam operators can continuously release 100,000 cfs of water from the reservoir during the coming week, it appears unlikely that the lake will reach 900 feet and force usage of the emergency spillway again. has an excellent summary of how climate change may have contributed to the Lake Oroville Dam emergency.

We'll have a new post on Friday.

Jeff Masters and Bob Henson

Climate Summaries Flood

This is February? 80°F in Denver, 99° in Oklahoma, 66° in Iceland, 116° in Australia

By: Bob Henson , 4:17 PM GMT on February 14, 2017

The strong, recurrent Pacific jet stream that’s been delivering massive amounts of rain to California has also been pushing mild Pacific air downslope off the Rockies and eastward, keeping the southern two-thirds of the U.S. absurdly warm for early February. From New Mexico to Virginia southward to the Gulf Coast, trees and shrubs are budding out en masse up to three weeks ahead of schedule (see Figure 1). In Texas, Dallas-Fort Worth recorded its last freezing temperature on January 8. With no freezes expected into at least the last week of the month, there’s a chance that the Jan. 8 reading of 20°F will be DFW’s last freeze of the winter. That would eclipse the earliest final freeze of the season (Feb. 5, 2000), in records extending back to 1899. The February warmth comes after a three-month span that was milder in Texas than any Nov/Dec/Jan period since the 1930s Dust Bowl, according to state climatologist John Nielsen-Gammon.

The warm, moist air prevailing along the South has been teaming up with occasional jet-stream intrusions to produce severe thunderstorms, including an unusually large number of tornadoes for the year thus far. This includes six confirmed tornadoes across southeast Louisiana on February 7, with an EF3 twister causing more than 30 injuries and damaging or destroying more than 600 homes in and near East New Orleans (see the detailed National Weather Service survey report on all six tornadoes). As of February 13, NOAA’s Storm Prediction Center had tallied 163 U.S. tornadoes for the year thus far, not quite a record but far above average. On Tuesday morning, NOAA/SPC placed parts of the western and central Gulf Coast under a slight risk of severe weather, with a small enhanced-risk area along the central Texas coast near a large thunderstorm complex that had already produced several tornado reports west of Houston.

Figure 1. An index of the seasonal progress of leafy plants shows conditions 20 days or more ahead of schedule over large parts of the South and Southwest as of Sunday, February 12. Image credit: USA National Phenology Network via @TheresaCrimmins.

Figure 2. Spectators watch as a tornado-damaged water tower comes down in Rowlett, TX, on Monday, Feb. 6, 2017. Workers toppled the Dallas-area water tower that was severely damaged during a 2015 tornado outbreak blamed for more than a dozen deaths. Image credit: Vernon Bryant/The Dallas Morning News via AP.

Close to the century mark in Oklahoma
While there’s been quite a few ups and downs to the national temperature picture in recent days, with frequent frontal passages, the low temperatures haven’t been all that low and the highs have been unusually high, as noted by WU blogger Steve Gregory. For the month to date through February 12, NOAA had compiled a preliminary total of 1207 daily record highs and 10 daily record lows, for a staggering ratio of more than 100 to 1. It’s a picture in line with recent months: November 2016 had the largest ratio of record highs to lows of any month in modern records. It’s also consistent with the inexorable effect of human-produced greenhouse gases in boosting temperatures to make record warmth more widespread and extreme than record cold.

One especially strong pulse of warm air jet pushed across the Southern Rockies and into the South from Friday into Sunday. As the already-mild air descended the Rockies, it warmed further due to downslope compression, leading to some eye-popping readings. Several stations in southwest Oklahoma soared into the upper 90s on Saturday. The town of Mangum hit an astounding-for-February 99°F, which tied the state record for any winter month (Dec/Jan/Feb) that was set at Arapaho on Feb. 24, 1918.

Here’s a sampling of the all-time February heat records set over the past several days. In many cases, you have to go to mid-March to find comparable warmth!

Friday 2/10:
Wichita Falls, TX: 94°F (next-earliest reading at least this warm was 98°F on 3/1/2006; records began in 1923)
Liberal, KS: 90°F (next-earliest 90° was 3/11/1989; records began in 1893)
Amarillo, TX: 89°F (next-earliest 89° was 3/10/1989; records began in 1892)
Goodland, KS: 87°F (next-earliest 87° was 3/10/1989; records began in 1895)
Denver, CO: 80°F (next-earliest reading at least this warm was 81°F on 3/16/2015; records began in 1872). A cooperative observing station at the site of Denver’s former Stapleton Airport, where official readings were taken until the mid-1990s, reported 83°F.

Saturday 2/11:
Lubbock, TX: 91°F (next-earliest reading at least this warm was 95°F on 3/11/1989; records began in 1911)

Sunday 2/12:
Norfolk, VA: 82°F (ties all-time monthly high set on 2/4/1890 and other dates; records began in 1874)

Figure 3. High temperatures across Oklahoma on Saturday, February 11, were similar to readings one might expect in early July. Image credit: Oklahoma Mesonet, @okmesonet.

Figure 4. Temperature departures from average for the period February 1-12, 2017. The warm anomalies will likely persist, as models are calling for continued milder-than-average weather over most of the nation through late February. Image credit: NOAA/CPC Climate Prediction Center.

Cold enough to ski; too mild to ice-climb
The abnormally mild February hasn’t put a dent in Colorado’s bang-up ski season. The highest slopes are still more than cold enough to support a healthy snowpack even with above-average temperatures. At, Joel Gratz noted that the statewide snowpack as of Sunday, February 12, had already matched the level reached during the early-April peak of an average year. “What an awesome season so far with more to come!” exclaimed Gratz. Meanwhile, at Colorado’s lower elevations, those hankering for winter recreation felt the pinch of unseasonal warmth. The state’s Ouray Ice Park climbing venue was forced to close for the season on Friday, February 10, a full month earlier than average. “While we still hold a glimmer of hope for this season at the Park, that is fading fast,” said the park in a plaintive online statement.

Surges of warmth continue to funnel into high Arctic
The strong jet streams crossing the U.S. of late have spun up several powerful Northeast snowstorms (see embedded video below) and gone on to push very mild, moist air deep into the Arctic. One such spike arrived late last week, with temperatures of 50°F or more above average approaching the North Pole as reported by Capital Weather Gang and The Weather Network (Canada).

Well downstream from the nor’easter that was slamming eastern New England on Monday, a swath of low-latitude air pushed the temperature at Eyjabakkar, Iceland, up to 19.1°C (66.4°F). If validated, this will rank a full 1°C (1.8°F) above the previous national record for February, set at Dalatangi on Feb. 17, 1998, according to international weather records researcher Maximiliano Herrera. He adds that temperatures in the free atmosphere over central Sweden were analyzed above the freezing mark on Monday at heights of up to 11,000 feet.

Unsurprisingly, the extent of Arctic sea ice remains at record-low levels for mid-February. Moreover, the extent of Antarctic sea ice is on the brink of setting a record-low value for any time of year.

Figure 5. This year is lagging all other years since records began in 1979 for sea ice extent in February. Image credit: National Snow and Ice Data Center.

Figure 6. Smoke billows from a wildfire near Mudgee, Australia, on Monday, Feb. 13, 2017. The fire has consumed more than 5000 hectares (12,350 acres) of bush and grasslands northwest of Sydney. Image credit: New South Wales Rural Fire Service via AP.

Eastern Australia blisters in all-time record heat
Another swarm of heat records invaded eastern Australia, where a brutal summer is unfolding. Port Macquairie, where records have been kept since 1910, broke its all-time record for any date on Sunday with a scorching high of 46.6°C (115.9°F). That’s an incredible 3.3°C (5.9°F) above the city’s previous all-time high. “You don’t break [100-plus-year] records by 3C,” noted Andrew Watkins (@windjunky). An even older all-time high fell at Toowoomba, Queensland, where a maximum of 40.3°C (104.5°F) was the first reading above 40°C (104°F) since records began at Toowoomba way back in 1869. Fire danger across parts of tinder-dry New South Wales has been at near-record levels, and bushfires have already swallowed up dozens of homes, with more hot weather returning late this week.

Bob Henson

Figure 7. James Cagney, 13, of Portland walks on Noyes Street on his way to shovel a neighbor's driveway on Monday, Feb. 13, 2017. A major nor’easter dumped 1 to 3 feet of snow across parts of Maine. South of the intensifying low, wind gusts howled at 50-60 mph or more from the mid-Atlantic to southern New England. Image credit: Derek Davis/Portland Press Herald via Getty Images.

Video 1. Annotated GOES-16 imagery of the winter storm that pummeled eastern New England and the Canadian Maritimes on Monday, February 13. Image credit: @NOAASatellites.

Tornado Heat

More than 180,000 Under Evacuation Orders as Oroville Dam Spillways Compromised

By: Bob Henson , 3:46 PM GMT on February 13, 2017

Tens of thousands of Californians fled their homes on short notice Sunday evening about 60 miles north of Sacramento when the emergency (auxiliary) spillway at Oroville Dam--the nation’s tallest dam--showed signs of failure, prompting mandatory evacuations along the Feather River downstream, including the entire city of Oroville (population 16,000.) It was a dramatic turn of events in a situation that has gotten progressively worse over the last few days. Record amounts of precipitation to date this winter across the northern Sierra (see Figure 4)—much of it falling as rain or melting prematurely—have filled Lake Oroville to capacity for the first time in years.

On Tuesday, February 7, as massive amounts of water poured through the main spillway (see figures below), a patch of erosion developed on the spillway’s concrete base. This erosion has since spread across a wide stretch of the spillway, spanning roughly 200 by 150 feet and extending 40 to 50 feet deep. To reduce further damage and to help keep debris from flowing downstream, water was shunted from the main spillway to the emergency spillway starting on Saturday morning, February 11. This was the first time the emergency spillway had been used since the dam was put into service in 1968.

A hole developed in the broad concrete lip at the top of the emergency spillway on Sunday afternoon, as several inches of water cascaded over the top of the spillway. By late afternoon, the California Department of Water Resources had issued this dire statement: “Officials are anticipating a failure of the Auxiliary Spillway at Oroville Dam within the next 60 minutes.” Residents of Oroville and neighboring areas were ordered to leave the area as soon as possible, sparking major traffic jams. By around 8:45 pm PST, water was no longer flowing over the lip of the emergency spillway, reducing the immediate threat that the spillway would fail. The lake’s water level had dropped an additional three-plus feet by 7:00 am PST Monday. However, mandatory evacuations remained in effect as officials examined the state of the dam’s infrastructure.

Along with these photos, see the embedded video at bottom for added perspective.

Figure 1. Undated photo of Oroville Dam and Lake Oroville, with the Feather River at bottom. The main spillway (left side of image) is used to relieve pressure on the dam. The emergency spillway, a broader earthen structure just to the left of the main spillway, had never been activated before this past weekend. Image credit: Wikipedia/California Department of Water Resources.

Figure 2. This aerial photo from Saturday, February 11, 2017, shows the main spillway, bottom, and a broader auxiliary spillway, upper, of the Oroville Dam at Lake Oroville. The dam is located on the other side of the main spillway, off the right side of the photo. Image credit: Albert Madrid/California Department of Water Resources via AP.

Figure 3. Another aerial photo from Saturday, February 11, 2017, shows the damaged main spillway. Water pouring through the damaged area had already caused significant erosion to the hillside (orange areas). Image credit: William Croyle/California Department of Water Resources via AP.

Figure 4. The cumulative precipitation across eight key stations in the northern Sierra was at 226% above the 1922-1998 average for the season to date as of Saturday, February 12, 2017. This is more than 50% more precipitation than had fallen by this point during the record-wet year of 1982-83 and the very wet year of 1997-98 (both of which were "super" El Niño events, along with 2015-16). The year-to-date total of 68.05" through February 12 is already well ahead of the record for any year up through the end of February of 65.86" (1955-56), according to Jan Null, @ggweather (these records extend back to 1921-22). Frequently mild conditions this winter have pushed a higher fraction than usual of this precipitation into the reservoir system, either as rainfall or as melted snowfall. Image credit: California Department of Water Resources.

What are the risks now?
Water expert Peter Gleick (Pacific Institute) provided this pithy summary of the situation in a tweet on Sunday night:

“1. Calm down.
2. Evacuate if ordered.
3. The dam won’t fail, but
4. Severe flooding still possible if emergency spillway fails.”

Point 3 is based on the fact that the spillways are independent structures from the dam itself. It’s extremely good news that the Oroville Dam itself is sound, because the amount of water behind it would produce a truly cataclysmic flood, inundating much of California’s Central Valley. However, residents downstream are by no means out of the woods. Now that the only two spillways from Oroville Dam are both damaged, officials face a very challenging task as they attempt to carry out repairs on the emergency spillway while keeping the main spillway functional. If either spillway were to fail at this point, catastrophe could still result.

When the crisis arose with the emergency spillway on Sunday evening, engineers roughly doubled the flow through the damaged main spillway--from around 50,000 to around 100,000 cubic feet per second (cfs)--in order to quickly relieve pressure on the emergency spillway. The Sacramento Bee reported late Sunday that officials will examine the main spillway on Monday to see how much additional damage was incurred by Sunday’s sudden release and to ensure that the main spillway can still be used without risking more serious damage or failure.

“It’s a dynamic situation,” said Bill Croyle, acting director of California’s Department of Water Resources, in a press briefing Sunday night. “The key here is we need some drier weather or some cooler weather to keep those inflows down….We want to maintain the system at a rate that doesn’t further degrade the infrastructure that we have.” Croyle said that the hope is to keep the main spillway flow at the newly accelerated rate of around 100,000 cfs, if the structure permits. Given the huge amount of runoff still flowing into the lake, water levels will remain quite high. The net goal is to cut the total amount of water in the lake by about 3% by midweek.

Figure 5. Rivers throughout the northern part of California’s Central Valley were swollen with runoff on Saturday, February 11, as seen in this NASA satellite image annotated by the National Weather Service office in Sacramento. Oroville is located along the Feather River north of Yuba City. Image credit: NWS/Sacramento.

The forecast
Northern California will get a much-needed break from rain and snow during the first part of the upcoming week. Then the forecast turns more ominous. Light rain and mountain snow will begin Wednesday and intensify by Thursday, and there will be additional pulses of rain and mountain snow throughout the following week. On Sunday night, the National Weather Service office in San Francisco identified five separate frontal passages in GFS model output for the week starting this Wednesday, February 15. At present, these do not look like record-smashing storms, but they could add up to 2” or more of valley rain falling on saturated soils, with 4” - 6” possible in the Sierra foothills and even more at higher elevations (much of the latter as snow). The rainfall will keep water flowing into Lake Oroville and keep the pressure on engineers and officials scrambling to protect downstream areas from a hydrologic threat whose end is not yet in sight.

There is sure to be controversy over the emergency spillway itself and why it nearly failed in its very first weekend of use. The flow on Sunday through the emergency spillway was only around 6,000-12,000 cfs, far less than the engineered maximum flow of 350,000 cfs, as reported by the San Jose Mercury News. In 2005, three environmental groups filed a motion with the Federal Energy Regulatory Commission to require that the earthen spillway be reinforced with concrete. State and local water agencies concluded that these upgrades were not necessary, and the federal government agreed.

In a harrowing interview with the Sacramento Bee, a member of the Central Valley Flood Protection Board describes how a breach of the emergency spillway could have devastating consequences. The Bee’s website also features a livestream from the Governor’s Office of Emergency Services.

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

Bob Henson

Figure 6. Total precipitation (rainfall and the amount of water in snowfall) projected by the 00Z Monday run of the GFS model for the ten-day period ending at 4:00 pm PST Wednesday, February 22, 2017. Image credit:

Figure 7. Reservoir conditions in California as of February 11, 2017. The state’s second largest reservoir, Lake Oroville, was at 101% of capacity, forcing use of its emergency spillway for the first time. California’s largest reservoir, Lake Shasta, was at 96% of capacity. Image credit: California Department of Water Resources.

Video 1. Multiple vantage points of Oroville Dam and its main and emergency (auxiliary) spillways, as captured by drone by the California Department of Water Resources. Image credit: California DWR.

One Snowy, Windy Nor’easter Gone; More on the Way?

By: Bob Henson , 5:04 PM GMT on February 10, 2017

A fast-moving, hard-hitting snowstorm walloped large swaths of the Northeast U.S. and New England on Thursday, a mere day after record highs above 60°F had enveloped much of the region. Widespread wind gusts of 50 to 70 mph--qualifying the storm as a blizzard for several hours in many areas, including Boston--added to the impact of this classic midwinter event, which dropped widespread snow totals of a foot or more from Long Island, New York, to southwest Maine. Only one fatality had been reported as of Friday morning, a doorman in New York City who slipped and fell through a plate-glass window while shoveling.

The high winds and heavy snow were fueled by a powerful upper-level low sweeping atop the strong low-level temperature contrasts. The result was a very intense surface low that underwent “bombogenesis” near 40°N and 70°W, the benchmark location most closely associated with heavy snow in New York and New England. A bomb-type low requires surface pressure to drop at least 24 mb in 24 hours. Thursday’s storm more than did the trick, with pressures falling from 1002 to 973 mb in 24 hours.

February is the peak month for big snows in the Northeast, and while this storm didn’t smash many records for total accumulation, it was still notably intense, as the fierce winds were accompanied by very heavy snowfall rates. New York’s LaGuardia International Airport received 6” of snow in just two hours, between 8 AM and 10 AM EST Thursday morning, en route to a storm total of 10”.

Figure 1. Pedestrians in western Brooklyn navigate the heavy snow and high winds on Thursday, February 9, 2017. Image credit: Spencer Platt/Getty Images.

The strong temperature and moisture contrasts led to an unusually unstable air mass that generated a truly impressive amount of thunder and lightning for a winter storm (see embedded video at bottom). Matthew Cappucci, an undergraduate at Harvard University, uses data from the National Lightning Detection Network to calculate the number of cloud-to-ground flashes in Northeast winter storms. Cappucci tallied a total of 120 cloud-to-ground lightning strikes with Thursday’s nor’easter. No other winter storm analyzed by Cappucci over the last decade has produced more than 6 strikes, except for the 19 strikes recorded on December 29, 2016. (Thursday was the first time Cappucci himself experienced thundersnow.) A house fire in Providence, RI, on Thursday may have been caused by a lightning strike.

Top snow totals by state, as compiled on Friday morning by the NOAA/NWS Weather Prediction Center, included:

Connecticut: 19” (East Hartford)
Massachusetts: 19” (East Longmeadow)
Maryland: 11.5” (Redhouse)
Maine: 15.4” (near Berwick)
New Hampshire: 17” (Nottingham)
New Jersey: 10” (Vernon)
New York: 16” (Guilderland)
Ohio: 3” (Ravenna)
Pennsylvania: 11.0” (near Champion)
Rhode Island: 14” (Greene)
Virginia: 6” (Hightown)
Vermont: 10” (Woodford)
West Virginia: 8.5” (near Cheat Lake)

See the roundup for more details on the impact of this storm, dubbed Niko by The Weather Channel.

Figure 2. Larry Habermehl shovels his driveway on King Street in Enfield, Connecticut, on Thursday, Feb. 9, 2017. Habermehl said, "I need the exercise and I don't like plows gouging up my lawn." See this Harvard Health Blog post for tips on how to protect your heart from the risk posed by shoveling snow. Image credit: Brad Horrigan/Hartford Courant via AP.

Figure 3. Seven-day snowfall predicted by the 06Z Friday run of the GFS model for the period from early Friday morning February 10 to February 17, 2017. Longer-range model projections like these can be expected to shift over time in the location and intensity of snowfall. Image credit:

More snow likely for parts of the Northeast/New England
After a highly variable but not-too-severe winter thus far, the Northeast and New England are in for a week or more of multiple snowfall threats. This idea is supported by the Madden-Julian Oscillation, which will be very active over the tropical Pacific over the next few days. Large clusters of showers and thunderstorms associated with the MJO can produce upper-level effects that propagate thousands of miles poleward into the midlatitudes. A 2016 paper led by Phil Klotzbach (Colorado State University), showed that when the MJO is active in the tropical regions from the western Pacific toward South America (phases 7 and 8), it tends to boost the amount of snow falling across southeast New England. During Boston’s record-snowy winter of 2014-15, more than 90% of the snow at Logan International Airport fell while the MJO was in phases 7 and 8, according to Klotzbach and colleagues. The MJO is predicted to be quite strong in regions 7 and 8 for the next week-plus (see Figure 4 below).

One potentially major Northeast storm is taking shape for late Sunday into Monday. Like the storm just ended, the Sunday/Monday event will be produced by upper-level energy translating quickly across eastern Canada and the Northeast U.S. rather than digging deeply into the Eastern U.S. This time, the warm sector of the storm should be far enough north to keep precipitation in liquid form along the Washington–New York megalopolis. However, the fast-moving surface low may have just enough time to bomb out east of Boston and help generate heavy snow in the 6” - 12” range (or even more) from upstate New York across northern New England, especially over southern and eastern Maine. Another compact upper-level low will scoot along a similar track later next week. As of Friday, it was unclear whether this impulse will dig enough to produce yet another significant snow for the Northeast and New England.

We’ll be back on Monday with a new post. Enjoy your weekend, everyone!

Bob Henson

Figure 4. Predicted state of the Madden-Julian Oscillation for the period from February 10 to 24, 2017, based on output from the ensemble GFS model. This phase-state map shows MJO energy progressing counterclockwise (eastward) through eight geographic phases, each shown by a map sector defined by dotted lines. The further the MJO is located from the map center, the stronger the activity. The green line indicates the GFS ensemble average, while yellow lines show the individual model runs. Image credit: NOAA/NWS Climate Prediction Center.

Winter Weather Blizzard

So Long, La Niña; Arctic Temperatures Soar 63°F in 24 Hours

By: Jeff Masters , 5:15 PM GMT on February 09, 2017

In its latest monthly advisory, issued Thursday, NOAA’s Climate Prediction Center (CPC) sounded the death knell for the 2016-17 La Niña. SSTs in the benchmark Niño 3.4 region (in the equatorial Pacific) warmed to 0.3°C below average during early February; SSTs of 0.5°C or more below average in this region are required to be classified as weak La Niña conditions. As further evidence of the demise of La Niña, subsurface cold waters across the equatorial Pacific have completely vanished, and much warmer-than-average waters built off the coast of Peru in late January and early February, bringing unusual El Niño-like flooding rains to that nation. The 2016 - 2017 La Niña event was one of the weakest and shorted-lived La Niñas on record, lasting just six months and peaking with sea surface temperatures (SSTs) in the Niño3.4 region of 0.8° below average. According to CPC, only one other La Niña since 1950 has been this short and weak: the 1967 - 1968 event, which lasted five months, and also peaked at SSTs of 0.8°C below average in the Niño 3.4 region.

Figure 1. Average sea surface temperatures during January 2017, shown as departure from the long-term (1981-2010) average. Weak La Niña conditions were present in the Niño 3.4 region, but the waters were growing unusually warm along the coast of Peru in the Niño 1+2 region. figure from CPC data.

The forecast: Neutral this summer, then El Niño this fall?
In a Thursday ENSO Blog entry, NOAA/CPC’s Emily Becker reviews the El Niño forecast for the rest of 2017. Most computer models agree that neutral conditions will continue into the summer, and forecasters estimate an approximately 60% chance of neutral conditions lasting through the spring. After that, it gets complicated. We have a very difficult time predicting the future beyond the March–May period: the so-called spring predictability barrier. “In fact, a forecast made in June for the sea surface temperature in December (six months away) can be more successful than a forecast made in February for May (three months away)!” Becker relates. Some of the computer models are calling for a return of El Niño conditions by the second half of 2017. CPC’s current consensus forecast for the September—November 2017 period estimates a 12% chance of La Niña conditions, 40% chance of neutral conditions, and a 48% chance of El Niño. The latest Australian Bureau of Meteorology models are more aggressive about El Niño, showing development by this spring. If El Niño materializes in 2017, it would give us an unusual three-year series of El Niño/La Niña/El Niño: something that has only happened once since 1950—in 1963/1964/1965.

Figure 2. Weather data from Kap Morris Jesup, Greenland—the northernmost land weather observing station in the world—shows the remarkable surge of warm air that invaded the Arctic this week. The temperature trace (red line in top graph) soared 63°F (34.8°C) in 24 hours, from -29°F at 15 UTC February 7 to 33°F at 15 UTC February 8. The temperature peaked at 35°F (1.5°C) at 21 UTC February 8.

Summer in February in the Arctic: temperatures surge 63°F in 24 hours in Northern Greenland
The temperature at the northernmost land station in the world, Kap Morris Jesup, located on the northern coast of Greenland at 83.65°N latitude, soared to a remarkable 35°F (1.5°C) on Wednesday—beating the previous day’s high of -22°F by a shocking 57°, and marking a temperature more typical of June at this frigid location. The mercury skyrocketed an astonishing 63°F (34.8°C) in just 24 hours, from -29°F at 15 UTC February 7 to 33°F at 15 UTC February 8. As summarized by Jason Samenow of the Capital Weather Gang on February 6, the incredible warmth in the Arctic is due to a massive hurricane-force North Atlantic storm that bottomed out on Monday with a central pressure of 932 mb—a common reading in Category 4 hurricanes, and one of lowest pressures ever measured in a storm in this region. (He noted that the strongest North Atlantic winter storms on record—in December 1986 and January 1993—had pressures of 900 and 916 millibars, respectively.) The warm air flowing into the Arctic this week was reinforced by a second massive extratropical storm that pounded Iceland on Wednesday, which brought sustained winds of 61 mph, gusting to 91 mph, to the Reykjavik Airport. Warm air near the freezing point—about 50 to 60°F above average in temperature—likely came close to the North Pole on Thursday morning, according to the latest temperature anomaly maps from the University of Maine’s Climate Reanalyzer website. A drifting buoy located near the Pole, at about 87°N latitude, recorded temperatures above freezing once in November 2016 and once in December 2016, and hit 32°F on Friday. The warm air in the Arctic this week continues a trend of record to near-record heat seen in the Arctic throughout the winter of 2016 - 2017. The warm air has helped bring about the lowest arctic sea ice extent ever recorded during January, according to the National Snow and Ice Data Center. in a February 20 interview in the Washington Post, atmospheric physics expert Kent Moore of the University of Toronto noted that these types of anomalous warming events have been recorded since the 1950s, but only occurred once or twice a decade. Record arctic sea ice loss in recent years is allowing these events to occur more frequently. Moore said: “As that sea ice moves northward, there’s a huge reservoir of heat over the north Atlantic. As we lose the sea ice, it allows essentially this reservoir of warmth to move closer to the pole.”

Jeff Masters

El Niño Heat

EF3 Tornado Rips Through New Orleans East, Injuring 25

By: Jeff Masters , 3:53 PM GMT on February 08, 2017

At least nine tornadoes touched down in south Louisiana and south Mississippi on Tuesday, causing widespread damage and dozens of injuries, but no deaths. The largest tornado was an EF3 with winds over 135 mph that tore through New Orleans East, injuring 25, with three of the injuries deemed serious (the tornado was preliminarily rated EF2 on Tuesday, but was upgraded to EF3 on Wednesday after an NWS damage survey.) The tornado cut a swath through a residential area and a stretch of motels and trailer parks, and damaged roofs at NASA's Michoud Assembly Facility. About 250 buildings were damaged along the tornado’s 2.5 mile-long path, prompting mayor Mitch Landrieu to declare a state of emergency for New Orleans. Many of the homes damaged were also damaged during Hurricane Katrina in 2005, when a levee break flooded the area. According to, some Katrina survivors had a miraculous escape when the tornado ripped through a mother and daughter’s neighboring houses, and the falling rubble hit almost everything except the people trapped inside (thanks go to wunderground member Patrap for this link.) Two more injuries were reported from a tornado near Watson, Louisiana, which damaged approximately ten homes; an additional two injuries were reported from a tornado in Killian, Louisiana, where five homes were damaged.

Figure 1. A man walks through the debris of what once was a motel on Chef Menture Ave. after a tornado touched down on February 7, 2017 in New Orleans East, Louisiana. According to the NWS, 25 people were injured in the aftermath of the tornado. (Sean Gardner/Getty Images) 

Figure 2. Forecasts from 1 am EST Tuesday morning (top) from NOAA’s Storm Prediction Center (SPC) showed only a “Slight” chance of severe weather over south Louisiana and south Mississippi, but by 8 am, SPC homed in on the potential for a more serious localized outbreak of severe weather, and upgraded their outlook to an “Enhanced” chance of severe weather (bottom.)

An unusually active start to tornado season
While it is not uncommon to get wintertime tornadoes along the Gulf Coast, the tornado activity so far in 2017 has been unusually high. The preliminary tally of U.S. tornadoes as of February 7 now stands at 151, which is more than double the 2005 - 2015 average of 67 we expect to see by this date. Most of this activity came in the January 21 - 23, 2017 tornado outbreak. This outbreak spawned 79 twisters, including three EF3s, over the Southeast U.S., killing 20 people and causing at least $600 million in damage. Since 2005, the only year that has had more tornadoes than 2017 by this date was 2008, when approximately 260 tornadoes had been reported by February 7.

Video 1. The EF3 tornado in New Orleans East on the morning of Tuesday, Feb. 7, 2017. Video by Aundra Woodfin, courtesy of

Jeff Masters


The Cure for Catastrophe: How We Can Stop Manufacturing Natural Disasters

By: Jeff Masters , 5:40 PM GMT on February 07, 2017

In his excellent new book, The Cure for Catastrophe: How We Can Stop Manufacturing Natural Disasters, Robert Muir-Wood presents a fascinating expert guided tour of the history of catastrophes and how humans have responded to them. Robert Muir-Wood is the chief research officer of the catastrophe risk modeling company Risk Management Solutions, and a visiting professor at University College London’s Institute for Risk and Disaster Reduction. He recounts disasters of the past two thousand years, touching on such stories as the destruction of Pompeii by Vesuvius in 79 A.D., the great earthquake in Lisbon in 1755, the Mississippi River flood of 1927, the 2011 Japanese earthquake and tsunami, and Hurricane Katrina in 2005. His treatment of the birth of the insurance industry in the 1800s in response to fires in London is particularly interesting.

Muir-Wood emphasizes that we need to develop better disaster policy and disaster culture, and make awareness of disaster risks more a part of our culture through story telling, like the analogy of The Three Little Pigs. He advocates that societies undergo regular “risk audits”, where the 1-in-10 year and 1-in-100 year odds of loss of life, livelihoods, and money are evaluated, and where “reliance brokers” identify the most cost-effective ways to reduce those risks. He also stresses the need to fund disaster reduction and preparedness, which can reduce disaster costs by a factor of fifteen compared to the money spent.

A few interesting highlights from the book:

- “The irony of a catastrophe is the funds to prevent it only become available after it has happened.” The U.S. government funded a $14.5 billion upgrade to New Orleans’ flood protection system in the wake of Hurricane Katrina in 2005, and the city is now protected against a 1-in-100 year Category 3 storm (one that has a 1% chance of occurring in a given year.) But New Orleans needs protection against a Category 5 storm, currently deemed to be a 1-in-500 year event (a 0.2% chance of occurring in any given year.) The Army Corps claimed this would cost at least $70 billion, and it was not funded. With climate change expected to make the strongest storms stronger and cause sea level rise to accelerate, the odds of a Category 5 storm surge 6 - 10 feet higher than Katrina’s may increase to a 1-in-130 year event by the year 2100.

- “Mobile homes have proved to be ‘houses of straw’ in tornadoes.” From 1985 - 1995, more than 60% of all tornado deaths in U.S. homes were people living in mobile homes, where only 6% of the U.S. population lived.

- “It’s not the earthquake that kills you, it’s the builders…It all comes down to bad design, bad execution, bad reinforcing, and bad concrete.” Muir-Wood lauds the construction in earthquake-prone Chile, where earthquake preparedness is a national passion and building codes against earthquakes are some of the world’s best. Developers hold a ten year liability for building damage, with the threat of a jail term. The 2010 magnitude 8.8 earthquake in Chile was 1,000 times bigger than the smaller 2009 L’Aquila earthquake in Italy, but killed fewer people in building collapses. He advocates that every public school in an earthquake zone should post the annual number of expected deaths in that building due to the details of school construction, time children spend in school, and earthquake frequency. That would motivate retrofitting of construction in earthquake zones!

- “The irony of a flood wall is that it can make us less resilient…The flood wall lures new buildings to shelter behind it.” The higher the wall, the deeper flood. A flood on Japan’s Shonai River after 24” of rainfall in September 2000 inundated 70,000 buildings and 100,000 cars after a single section of the river’s 16’ flood wall collapsed.

- The U.S. passed legislation in 2012 (the Biggert-Waters Act) to reform the National Flood Insurance Program and make people living near the coast pay more of the true costs of flood damage. However, after insurance rates rose by a factor of four or more for some coastal residents, the outcry led Congress to repeal the act in 2014. “National funds would continue to be used to subsidize people who wanted to live in the beach.”

- “U.S. disaster relief per citizen was twenty times more than spending on disaster reduction. Each dollar of extra preparedness spending reduced disaster impacts by an average of $7 over a single four-year election cycle and disaster costs overall by an average of $15. With multiples of this magnitude, a politician should clearly invest in disaster reduction. The problem is that money spent on preparedness wins no votes.”

My only complaint about the book is that Muir-Wood does not present an organized set of conclusions identifying the problems and potential solutions. One has to hunt around to piece together what he is advocating. The Cure for Catastrophe (published in September 2016) is $23.14 from I give the book four stars our of five.

Jeff Masters

Book and Movie Reviews

Avalanches Kill at Least 137 in Afghanistan

By: Jeff Masters , 4:36 PM GMT on February 06, 2017

Heavy snowfall in Afghanistan near the Pakistan border has triggered avalanches that have killed at least 137 people in recent days, reported The Guardian today. The death toll is expected to rise as rescuers reach remote areas where blocked roads and mountainous terrain were hampering rescue efforts. Some villages in the worst-hit province of Nuristan, which received nearly 3m (10ft) of snow, have been cut off from communication. The latest wunderground forecast for the region is calling for less than an inch of accumulating snow during the coming week, which should aid recovery efforts, fortunately.

Avalanches are common in Afghanistan’s mountainous areas in winter. In February 2015, heavy snows triggered 40 avalanches in Panjshir Province in Afghanistan, killing at least 124 people, according to EM-DAT, the international disaster database. Insurance broker Aon Benfield put the death toll at 230.

Jeff Masters

Winter Weather

Climate Science Denial Shifts to a New Tactic Among Trump Appointees

By: Jeff Masters , 5:29 PM GMT on February 03, 2017

Our planet has just experienced three consecutive warmest years on record—2014, 2015, and 2016—which has made it difficult to find politicians who continue to deny the reality of global warming and climate change. However, denial of climate science has shifted to a new tactic: to claim that the indisputable heating of the planet is primarily a natural phenomenon, and that there is major uncertainty among scientists on the issue. These assertions are false. Based on the evidence, more than 97% of climate scientists have concluded that human-caused climate change is happening; scientists’ “best estimate” is that ALL of the global warming since 1950 has been human-caused, primarily through an increase in carbon dioxide due to the burning of fossil fuels. Many prominent members of the Trump administration, who all have ties to the fossil fuel industry, have been making false claims about scientists’ understanding that global warming is human-caused. For example:

 - During his hearing in January 2017 to become the new EPA administrator, Scott Pruitt claimed: “There is a diverse range of views regarding the key drivers of our changing climate among scientists.”

- Former Exxon-Mobil CEO Rex Tillerson, who is now President Trump’s Secretary of State, claimed in his confirmation hearing: “I agree with the consensus view that combustion of fossil fuels is a leading cause for increased concentrations of greenhouse gases in the atmosphere. I understand these gases to be a factor in rising temperatures, but I do not believe the scientific consensus supports their characterization as the ‘key’ factor.”

- On the February 21, 2014, edition of MSNBC’s The Daily Rundown, host Chuck Todd asked future Vice President Mike Pence if he was “convinced that climate change is man-made.” Pence responded: “I don't know that that is a resolved issue in science today.” Pence similarly stated on the May 5, 2009, edition of MSNBC’s Hardball that “I think the science is very mixed on the subject of global warming.”

- Rick Perry, Trump’s nominee for Secretary of Energy, told the Senate Energy and Natural Resources committee in January: “I believe the climate is changing. I believe some of it's naturally occurring and some of it is caused by man-made activity.”

Figure 1. Global annual temperatures up to the year 2015 (thin light red, with an 11-year moving average shown as a thick dark red line) have increased steadily, even though the total amount of energy from the sun (the annual Total Solar Irradiance, thin light blue, with an 11-year moving average shown as a thick dark blue line) has decreased slightly. Climate in past eras has seen many instances of global warming, which have been caused by an increase in heat-trapping gases like carbon dioxide or an increase in the amount of solar energy being absorbed by the Earth. Since solar energy cannot be to blame for the increase in global temperatures since 1950, scientists are confident that the steadily rising levels of heat trapping gases like carbon dioxide due to human activities is causing the observed global warming. Image credit:

The best science says: ALL of the warming since 1950 is human-caused
Based on the evidence, more than 97% of climate scientists have concluded that human-caused climate change is happening. That’s about the same certainty with which scientists link smoking cigarettes to lung cancer. The latest 2013 Intergovernmental Panel on Climate Change (IPCC) report—the enormous consensus scientific summary of the science of climate change prepared once every six years--had this to say about the observed warming of Earth since 1950:

“The best estimate of the human-induced contribution to warming is similar to the observed warming over this period.” In other words, ALL of the observed warming after 1950 (0.6°C, 1.1°F) is due to humans. A total of 0.85°C (1.5°F) total global warming has been observed since 1880. The IPCC further quantified that human activity is extremely likely (at least 95% chance) to be responsible for more than half of Earth's temperature increase after 1950.

Figure 2. The changing view of the IPCC's assessment reports on the human contribution to climate change.

Related news and links
Climate change denial is not dead (January 31 op-ed by climate scientist Michael Mann.) (February 3 article by Justin Gillis of the New York Times.)

Here’s how we know Trump’s cabinet picks are wrong on human-caused global warming (January 30 article from Dana Nuccitelli of The Guardian.)

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

Climate Science Legal Defense Fund (CSLDF) files brief to protect NOAA climate scientists (CSLDF post on  February 1.)

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

If You Liked the Inquisition, You'll Love the House Science Committee (January 31 article from Mother Jones.)

The March for Science is set for April 22 (Earth Day) in Washington D.C.

The People's Climate Movement is happening in Washington D.C. on April 29.

Have a great weekend, everyone!

Jeff Masters

Winter Abandons South Florida: A Record-Warm Two-Month Stretch

By: Bob Henson , 11:05 PM GMT on February 01, 2017

Millions of people head to Florida to soak up the state’s famed winter mildness—but this year’s snowbirds may feel more like they flew into a summer sauna. The winter of 2015-16 featured periods of exceptional warmth in South Florida, yet even that high bar is being eclipsed by the persistent simmering that’s gone on for most of the last two months. In Miami, the average temperature of 74.65°F for the two-month period of Dec. 2016 - Jan. 2017 is a full degree above the 73.6°F record from 1971-72 in NOAA/NCEI data going back to 1948, and it also tops any two-month Dec-Jan interval in NWS/Miami data going back to 1895. Likewise, Key West averaged 75.25°F for the two-month Dec-Jan period, besting the record of 74.8°F (1990-91) in NCEI records going back to 1901.

The two cities also racked up an impressive pile of daily records along the way. Between Dec. 1, 2016, and Jan. 31, 2017, a total of 11 warmest highs for the date and 6 warmest lows for the date were tied or broken in Miami, where record-keeping began in 1895. In Key West, 5 daily record highs and 6 daily warmest-low records were set. Another sign of this winter’s persistent warmth: Miami has yet to dip below 50°F. It’s only the third time in Miami history that a winter has gone this late without reaching the 40s at least once. Hand in hand with the extremely warm air, sea-surface temperatures (SSTs) in the adjacent Gulf of Mexico and northwest Atlantic have also been unusually high. As reported by Brian McNoldy, on January 27, the water temperature in Miami's Biscayne Bay was 80.2°. The average for the date: 70.8°.

The potential role of the now-fading La Niña
La Niña may have played a part in South Florida’s summerlike winter. The last several months of 2016 featured weak La Niña conditions in the Pacific, and temperatures across the United States were very consistent with that: generally cooler than average toward the northwest and milder than average toward the southeast, including Florida. However, the current La Niña event appears to be on its last legs: the cooling of the tropical equatorial Pacific has weakened and retreated to the central Pacific, while unusually warm SSTs and sultry air invade the coast of Peru and Ecuador, producing conditions more akin to El Niño than La Niña. Daily low temperatures over the weekend of around 77°F were among the warmest on record in Lima, Peru. The latest roundup of international climate models posted on Monday by the Australian Bureau of Meteorology shows that full-fledged El Niño could be in place as soon as this summer, even by the more strict Australian definition (SSTs in the Niño3.4 region of at least 0.8°C above average, vs. the 0.5°C required by NOAA).

Cooler air finally moved into the state over the weekend, producing a chilly, rainy Sunday. Fort Lauderdale tied its record lowest high for the date (62°F), as did West Palm Beach (59°F). South Florida then saw the lowest temperatures of the winter thus far, including 51°F in Miami (Mon), 51°F at Fort Lauderdale (Mon & Tues) and 43°F in West Palm Beach (Tue). The cooldown will be short-lived, though, as upper-level ridging will help build the warmth back into the state over the next week.

Bob Henson


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