Dr. Jeff Masters' WunderBlog

Potentially historic winter storm poised to impact 100 million Americans

By: JeffMasters, 3:16 PM GMT on January 31, 2011

A huge and potentially historic winter storm is taking shape over the Southern Plains today. By the time the storm exits New England on Wednesday night, as many as 50 million Americans may see heavy snows of at least 6 inches or dangerous ice accumulations of 1/4" or more from the massive storm, and 100 million will be affected by the storm. A potent jet stream with strong winds will dive southwards over the central U.S. today, allowing a cold Arctic airmass to spill southwards out of Canada. In front of this cold air, a flow of very warm, moist air from the Gulf of Mexico will surge northwards, providing copious moisture to fuel snowfall amounts that will likely approach two feet across portions of Iowa and Illinois on Tuesday. The storm could be Chicago's biggest blizzard since January 1999, when a storm dumped 21.6" of snow. Accompanying the heavy snow on Tuesday will be strong winds gusting to 40 mph in Northern Illinois and Northwest Indiana, and a blizzard watch is posted for Chicago. Strong winds in Chicago are expected to generate 14 - 18 feet waves on Lake Michigan, with occasional waves up to 25 feet. A significant coastal flooding event is possible for Chicago, with beach erosion and flooding along Lake Shore Drive. Many major cities will likely receive over 8 inches of snow from the storm, including Kansas City, St. Louis, and Detroit. Perhaps of greater concern is the potential for a major ice storm along a swath from Northwest Oklahoma to Massachusetts. Widespread freezing rain is expected to bring over 1/4" of ice to many major cities, including St. Louis, Indianapolis, Columbus, Cleveland, and Pittsburgh. Some regions could see up to an inch of ice, and widespread power outages due to toppled power lines are likely for millions of people. Damages exceeding $1 billions are possible from this ice storm. In addition, the storm's powerful cold front will bring the potential for severe thunderstorms to the deep South. The NOAA Storm Prediction Center is giving Louisiana and surrounding states a "slight risk" of severe weather on Tuesday, and severe thunderstorms with damaging winds are likely Tuesday afternoon in this region.


Figure 1. Probability of receiving at least 1/4" of ice for the 24 hours ending at 7am EST on Wed Feb 2, 2011. Image credit: NOAA.

Very dangerous Tropical Cyclone Yasi headed for Australia's flooded Queensland
With February nearly upon us, the traditional peak of the Southern Hemisphere tropical cyclone season is here, and the waters surrounding Australia have been exceptionally active over the past week. We had the year's first two Category 4 tropical cyclones last week, Tropical Cyclone Wilma and Tropical Cyclone Bianca. Wilma passed over American Samoa as a strong tropical storm, and hit Tonga as a Category 3 storm, causing substantial damage to the islands, but no deaths or injuries. Wilma brushed New Zealand, bringing flooding and landslides to the North Island, and was the strongest tropical cyclone to affect that country in fourteen years, according to weatherwatch.co.nz. Tropical Cyclone Bianca skirted the west coast of Australia and dissipated before making landfall. Tropical Cyclone Anthony hit flood-ravaged Queensland, Australia, over the weekend, as a weak tropical storm with 40 - 50 mph winds. Fortunately, Anthony dropped only modest amounts of rain, and no new flooding disaster occurred in Queensland, which is struggling to recover from record floods. As reported in the latest Australian Bureau of Meteorology climate statement and flood summary, the past four months (September - December) have been the rainiest such period in Queensland's history, and the resulting flooding disaster has been Australia's most expensive natural disaster in history.

Queensland is in serious danger of renewed extreme flooding this week from Tropical Cyclone Yasi. Yasi has intensified to a Category 2 storm with 105 mph winds, and is undergoing a period of rapid intensification that is expected to take it to Category 4 strength. Yasi is expected to hit Queensland on Wednesday, probably as a major Category 3 or stronger storm. In addition the storm's damaging winds and storm surge, Yasi will bring torrential rains. The GFS model is predicting that Yasi will dump 5 - 10 inches of rain over a large swath of Queensland, which would likely cause destructive flooding.

One positive note: the European Center model was remarkably accurate predicting the formation of Yasi over a week in advance, so Queensland has had plenty of time to prepare for the arrival of the storm.


Figure 3. Tropical Cyclone Yasi at 23:20 GMT on January 30, 2011. At the time, Yasi was a Category 1 storm with 75 mph winds. Image credit: NASA.

Jeff Masters

Winter Weather

Updated: 4:09 PM GMT on January 31, 2011

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The ARkStorm: California's coming great deluge

By: JeffMasters, 4:04 PM GMT on January 28, 2011

For thirty days and thirty nights the rain fell in unending torrents. By the end of the biblical deluge, rivers of water ten feet deep flowed through the streets of Sacramento, and an astounding 29.28 inches of rain had fallen on San Francisco. According to wunderground's weather historian, Christopher C. Burt, in the Sierras, the moist flow of air from Hawaii--often called an "atmospheric river" or the "Pineapple Express"--hit the steeply sloping mountainsides and rose upwards. The air expanded and cooled, causing truly prodigious rains, with the mining town of Sonora receiving 8.5 feet of rain over a 2-month period. The resulting floods inundated California's Central Valley with a lake 300 miles long and 20 miles wide.

The above event occurred in January 1862, and similar extreme rain events have deluged in California seven times in the past 2,000 years--about once every 300 years. Great storms like the flood of 1862 will happen again. If the planet continues to warm, as expected, the odds of such an event will at least double by 2100, due to the extra moisture increased evaporation from the oceans will add to the air. A group of scientists, emergency managers, and policy makers gathered in Sacramento, California earlier this month to discuss how the state might respond to a repeat of the 1862 rain event--the ARkStorm Scenario. The "AR" stands for "Atmospheric River", the "k" for 1,000 (like a 1-in-1000 year event), and of course "ARkStorm" is meant to summon visions of biblical-scale deluge, similar to the great flood of 1862. The team's final report envisions the most expensive disaster in world history, with direct damages and loss of economic activity amounting to $725 billion.

"Atmospheric Rivers" was a term coined in the 1990s to describe plumes of moisture that ride up out of the subtropics into the mid-latitudes along the axis of a cold front. Traditional water vapor satellite imagery does not show these plumes very well, and it was only when microwave satellite imagery from polar orbiting satellites became available in the late 1990s that the full importance of these Atmospheric Rivers came to be revealed. Atmospheric Rivers account for a significant portion of California's cold season rainfall and snowfall, and an entire session was devoted to them at the December 2010 American Geophysical Union (AGU) meeting in San Francisco, the world's largest Earth Science meeting.


Figure 1. The total amount of rainfall one could get if all the moisture in the air were condensed and fell out as rain is called the Total Precipitable Water (TPW). Here, TPW values from microwave satellite measurements are plotted, and show a plume of very moist air connecting the subtropics near Hawaii with Southern California. TPW vales in excess of 20 mm (about 0.8 inches, blue and warmer colors) are "Atmospheric Rivers", and are often associated with heavy rainfall events capable of causing flooding. This Atmospheric River occurred on December 21, 2010, and brought very heavy flooding rains to Southern California. Image credit: University of Wisconsin CIMSS.

California's Delta Region levees at high risk of failure
Much of Central California's water supply and agricultural areas are protected by an antiquated and poorly maintained set of levees along the Sacramento and San Joaquin Rivers that are in serious danger of failure during an extreme flood or major earthquake. The 1,600 miles of levees protect 500,000 people, 2 million acres of farmland, and structures worth $47 billion. Of particular concern is the delta at the confluence of California's Sacramento and San Joaquin rivers, about 80 miles inland from San Francisco Bay. The Delta Region receives runoff from more than 40% of California, and is the hub of California's water supply system, supplying water to 25 million people and 3 million acres of farmland. Key transportation and communication lines cross the region. The Delta Region is home to dozens of islands with highly productive farms that have subsided to elevations as much as 25 feet below sea level. Jeffrey Mount, director of the Center for Integrated Watershed Science and Management at the University of California at Davis, said in a recent interview with MSNBC, "The chances of a catastrophic flood occurring in the Sacramento-San Joaquin Delta sometime in the next 50 years are about two out of three." He called Sacramento, which is only protected to a 1-in-80 year flood by its levees, "the most at-risk large metropolitan area in the country, with less than half the protection that New Orleans had. It is at extreme risk due to levee failure and subsidence."" The most serious catastrophe for the levees in the Delta Region would be a major earthquake occurring during the dry season. Such a quake would allow salt water to intrude from San Francisco Bay, shutting off the fresh water supply for millions of Californians for months. Collapse of the levees during the wet season would be less devastating, as water pressure from the relatively high flow rates of the Sacramento and San Joaquin Rivers would keep salt water from intruding into the Delta Region. There are no good solutions to California's Delta Region water vulnerabilities, but a new $10 billion dollar canal that would route fresh water around the region is being proposed as a possible way Califoria could avoid losing its fresh water supply if a catatrophic failure of the Delta Region levees allowed salt water intrusion to occur.

A 2009 study by the California Department of Water Resources concluded:

The Delta Region as it exists today is unsustainable. Seismic risk, high water conditions, sea level rise and land subsidence threaten levee integrity. A seismic event is the single greatest risk to levee integrity in the Delta Region. If a major earthquake occurs, levees would fail and as many as 20 islands could be flooded simultaneously. This would result in economic costs and impacts of $15 billion or more. While earthquakes pose the greatest risk to Delta Region levees, winter storms and related high water conditions are the most common cause of levee failures in the region. Under business-as-usual practices, high water conditions could cause about 140 levee failures in the Delta over the next 100 years. Multiple island failures caused by high water would but could still be extensive and could cause approximately $8 billion or more in economic costs and impacts. Dry-weather levee failures [also called sunny-day events] unrelated to earthquakes, such as from slumping or seepage, will continue to occur in the Delta about once every seven years. Costs to repair a single island flooded as the result of a dry-weather levee failure are expected to exceed $50 million. The risk of flooding in the Delta Region will only increase with time if current management practices are not changed. By the year 2100, Delta levee failure risks due to high water conditions will increase by 800 percent. The risk of levee failure from a major earthquake is projected to increase by 93 percent during the same period.


The ARkStorm scenario and Great Flood of 1862 are discussed in much more detail by weather historian Christopher C. Burt in his latest post.


Figure 2. Levee failure on the Upper Jones Tract in the Delta Region on June 4, 2004. Image credit: California Department of Water Resources. A 1997 flood in the Delta Region did $510 million damage, damaged or destroyed 32,000 homes and businesses, and left 120,000 homeless.

Wilma pounding New Zealand; Australia eyes two potential new tropical cyclones
With February nearly upon us, the traditional peak of the Southern Hemisphere tropical cyclone season is here. Activity has picked up markedly this week, with the formation of the year's first two Category 4 tropical cyclones, Tropical Cyclone Wilma and Tropical Cyclone Bianca. Wilma passed over American Samoa as a strong tropical storm, and hit Tonga as a Category 3 storm, causing substantial damage to the islands, but no deaths or injuries. Wilma is currently pounding New Zealand's North Island with heavy rains and strong winds, and is the strongest tropical cyclone to affect that country in fourteen years, according to weatherwatch.co.nz. Tropical Cyclone Bianca is expected to skirt the west coast of Australia over the next few days and rapidly weaken, but could bring heavy rains to the coast near Perth when it makes landfall on Sunday as a tropical storm. Of much greater concern for Australia are two potential tropical cyclones that could hit the flood-ravaged state of Queensland next week. Both the European Center and GFS models predict that the remains of Tropical Cyclone Anthony will regenerate into a tropical storm and hit Queensland early next week. A second and potentially more powerful storm is forecast by the European model to form next week in the islands to the east of Australia, and threaten Queensland at the end of the week. The GFS model has backed off on its prediction of such a storm forming. If the cyclone were to form, it would be a serious blow for Queensland, which is struggling to recover from record floods. As reported in the latest Bureau of Meteorology climate statement and flood summary, the past four months (September - December) have been the rainiest such period in Queensland's history, and the resulting flooding disaster has been Australia's most expensive natural disaster in history.


Figure 3. Tropical Cyclone Bianca, the globe's second major tropical cyclone of 2011, as seen at 06:30 GMT on January 28, 2011 by NASA's Aqua satellite. Biana is expected to rapidly weaken and hit the Australian coast near Perth as a tropical storm on Sunday. Image credit: NASA.

Have a great weekend, and I'll be back Monday with a new post.

Jeff Masters

Winter Weather Flood

Updated: 4:58 PM GMT on October 01, 2012

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Yet another record snowstorm wallops New England

By: JeffMasters, 3:08 PM GMT on January 27, 2011

The epic winter of 2010 - 2011 delivered yet another major pounding to New England yesterday and today, and residents are digging out today from the winter's third record snowstorm. The heaviest snows from this newest onslaught hit coastal New Jersey and New York City, where snowfall rates up to 4 inches per hour were accompanied by hundreds of lightning strikes. The 19.0" inches that fell in New York City's Central Park made it the 8th largest snowstorm for the city in recorded history. When combined with the heavy snows of 1 - 2 feet that fell during the Nor'easter just two weeks ago, January 2011 now ranks as the snowiest January on record in New York City, Newark, Bridgeport, and Hartford.


Figure 1. Scene from Times Square, New York during the peak of the January 26 - 27, 2011 Nor'easter. Near midnight, snowfall rates reached 4 inches per hour in thunderstorms. Image credit: Earthcam.com web cam, and captured by Christopher C. Burt.

Remarkably, five of New York City's top-ten snowfalls of the past 142 years have occurred in the past decade (highlighted in the list below.) According to the National Weather Service, the top ten snowstorms on record for New York City's Central Park since 1869 should now read:

1) 26.9" Feb 11-12, 2006
2) 26.4" Dec 26-27, 1947
3) 21.0" Mar 12-14, 1888
4) 20.8" Feb 25-26, 2010
5) 20.2" Jan 7-8, 1996
6) 20.0" Dec 26-27, 2010
7) 19.8" Feb 16-17, 2003
8) 19.0" Jan 26-27, 2011
9) 18.1" Mar 7-8, 1941
10) 17.7" Feb 5-7, 1978

Philadelphia, PA picked up 15.1", from today's storm, making it the tenth largest snowstorm in city history. Philadelphia has now had four of its top ten snowfalls in just over a year--a remarkable string of storms, considering record keeping began 127 years ago, in 1884. So far this winter, Philadelphia has picked up 37.8" of snow. An average winter should have had just 7.5" by now.

The top ten snowstorms on record for Philadelphia:

1. 30.7", Jan 7-8, 1996
2. 28.5", Feb 5-6, 2010 (Snowmageddon)
3. 23.2", Dec 19-20, 2009 (Snowpocalypse)
4. 21.3", Feb 11-12, 1983
5. 21.0", Dec 25-26, 1909
6. 19.4", Apr 3-4, 1915
7. 18.9", Feb 12-14, 1899
8. 16.7", Jan 22-24, 1935
9. 15.8", Feb 10-11, 2010
10. 15.1", Jan 26-27, 2011
10. 15.1", Feb 28-Mar 1, 1941


Figure 2. Change in snow depth for the 24 hours ending at 1am today shows that an area of 12 - 20" of snow fell from just southwest of Philadelphia, PA to near Bridgeport, CT. The heaviest snows had not quite ended by this time in Connecticut, Rhode Island, and Massachusetts. Up to two inches of snow melted in upstate New York (orange colors) during this period. Image credit: NOAA.

Just an ordinary-strength Nor'easter
The Nor'easter was of very ordinary strength, with a central pressure of just 987 mb this morning as it passed Cape Cod. Typically, a Nor'easter needs to have a central pressure in the 960 - 980 mb range to dump the kind of heavy snows that this storm generated. The storm did not have a widespread area of strong winds, though Provincetown on Massachusetts' Cape Cod recorded sustained winds of 40 mph, gusting to 60 mph, at 2am EST this morning. Only minor coastal flooding was reported in New England from the storm. However, like the January 12 - 13 Nor'easter of just two weeks ago, this week's rather ordinary-strength Nor'easter managed to assemble the perfect mix of conditions needed to transport moisture to a region of the storm highly favorable for heavy snow formation. Many heavy snow bands with snowfall rates up to 4 inches per hour formed over New England, with some of these bands intense enough to generate lightning and thunder.

Some selected city snowfall amounts for the January 26 - 27, 2011 storm:

NYC Central Park, NY 19.0"
Newark, NJ 18.9"
Philadelphia, PA 15.1"
Wilmington, DE 10.4"
Providence, RI 10.5"
Boston, MA 9.9"

An unusual Nor'easter for a La Niña year
This winter, we are experiencing La Niña conditions in the Equatorial Eastern Pacific, meaning that cold waters have upwelled from the depths off the coast of South America, cooling a huge region of Pacific waters to below-average levels. In most winters, the presence of La Niña acts to deflect the jet stream in such a way the the predominant storm track takes winter storms into the Pacific Northwest, then down through the Upper Midwest and Ohio Valley, particularly so in mid- late-winter. According to Dr. David A. Robinson, the New Jersey State Climatologist and Chairman of the Department of Geography at Rutgers University, this sort of flow pattern keeps New England safe from Nor'easters, as storms tend to move from the Ohio Valley northeastwards into Canada, keeping New England in a warm southwesterly flow of air. However, both the December 26 and today's storm defied climatology, and gave the mid-Atlantic and New England one of their worst poundings on record for a La Niña Nor'easter. These two storms were the first Nor'easters in at least ten La Niña winters, dating back to 1970, to bring 10" of more of snow to New Jersey, according to Dr. Robinson. Philadelphia got 12.4" from the December 26 Nor'easter and 15.1" from today's storm. The National Weather Service stated in December that prior to this winter, only one La Niña winter in the past century has had a storm that dumped more than 10" of snow on the city--a December 1909 Nor'easter.


Figure 3. The annual average number of snowstorms with a 6 inch (15.2 cm) or greater accumulation, from the years 1901 - 2001. A value of 0.1 means an average of one 6+ inch snowstorm every ten years. Image credit: Changnon, S.A., D. Changnon, and T.R. Karl, 2006, Temporal and Spatial Characteristics of Snowstorms in the Contiguous United States, J. Applied Meteorology and Climatology, 45, 8, pp. 1141-1155, DOI: 10.1175/JAM2395.1.

Why such an unusual number of top-ten snowstorms for the Northeast in recent years?
The Northeast has seen an inordinate number of top-ten snowstorms in the past ten years, raising the question of whether this is due to random chance or a change in the climate. This year's record snow storms were all the more unusual, as they came during La Niña conditions in the Eastern Pacific. Is it random chance, or did climate change play role? Well, it could be either, and we simply don't know the answer. A study by Houston and Changnon (2009) on the top ten heaviest snows on record for each of 121 major U.S. cities showed no upward or downward trend in these very heaviest snowstorms during the period 1948 - 2001. It would be interesting to see if they repeated their study using data from the past decade if the answer would change. As I stated in my blog post, The United States of Snow in February, bigger snowstorms are not an indication that global warming is not occurring. The old adage, "it's too cold to snow", has some truth to it, and there is research supporting the idea that the average climate in the U.S. is colder than optimal to support the heaviest snowstorms. For example, Changnon et al. (2006) found that for the contiguous U.S. between 1900 - 2001, 61% - 80% of all heavy snowstorms of 6+ inches occurred during winters with above normal temperatures. The authors also found that 61% - 85% of all heavy snowstorms of 6+ inches occurred during winters that were wetter than average. The authors conclude, "a future with wetter and warmer winters, which is one outcome expected (National Assessment Synthesis Team 2001), will bring more heavy snowstorms of 6+ inches than in 1901 - 2000." The authors found that over the U.S. as a whole, there had been a slight but significant increase in heavy snowstorms of 6+ inches than in 1901 - 2000. If the climate continues to warm, we should expect an increase in heavy snow events for a few decades, until the climate grows so warm that we pass the point where winter temperatures are at the optimum for heavy snow events.

I've done some other posts of interest I've done on snow and climate change over the past year:

Hot Arctic-Cold Continents Pattern is back (December 2010)
The future of intense winter storms (March 2010)
Heavy snowfall in a warming world (February 2010)

Jeff Masters

Winter Weather

Updated: 6:57 PM GMT on January 05, 2012

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Nor'easter poised to dump heavy snows; Australian tropical cyclone season heats up

By: JeffMasters, 2:31 PM GMT on January 26, 2011

A developing low pressure system along the North Carolina coast will intensify today and move northeast towards Cape Cod, Massachusetts, bringing heavy rain and snow to the mid-Atlantic and New England. A swath of 6 - 10" of snow is expected over inland regions of New England, from Philadelphia to Boston. A storm surge of up to 2.5' is expected along the Massachusetts coast, which will cause mostly minor coastal flooding, but considerable erosion damage.

The 1.9" of snow that fell in Hartford, Connecticut yesterday brought that city's January snowfall total to 44.9", a new record for the month. With an additional 6 - 10 inches expected today, Hartford will surpass its record for snowiest month of all-time, the 45.3" that fell in December 1945.

The storm brought heavy rains of 1 - 3 inches to much of the Southeast yesterday, easing that region's La Niña-related drought. The low swept a cold front across Florida last night, bringing severe thunderstorms with damaging winds gusts of up to 75 mph to twenty locations in the state. One tornado was reported, but no significant damage was reported.


Figure 1. The cold front from today's Nor'easter swept across Florida last night, bringing a line of severe thunderstorms that spawned one tornado and numerous reports of damaging winds.

Tropical Cyclone activity heats up near Australia
The year's first Category 4 tropical cyclone is Tropical Cyclone Wilma, which is churning the waters near Tonga in the Southern Hemisphere with sustained winds of 135 mph (minimum Category 4 strength.) Wilma passed over American Samoa as a strong tropical storm, and hit Tonga as a Category 3 storm. Substantial damage has been reported on Tonga, but no deaths or injuries. Wilma is recurving out to sea, and will not affect Australia.

Australia is keeping an eye on Tropical Cylone Bianca, which is expected to skirt the northwest coast of the country over the next few days. Of much greater concern for Australia are two potential tropical cyclones that could hit the flood-ravaged state of Queensland next week. Both the European Center and GFS models predict that the remains of Tropical Cyclone Anthony will regenerate into a tropical storm late this week and hit Queensland early next week. A second and potentially more powerful storm is forecast to form next week in the islands to the east of Australia, and threaten Queensland at the end of the week. This is potentially terrible news for Australia, which is attempting to recover from record floods. As reported in the latest Bureau of Meteorology climate statement and flood summary, the past four months (September - December) have been the rainiest such period in Queensland's history, and the resulting flooding disaster has been Australia's most expensive natural disaster in history.


Figure 2. Tropical Cyclone Wilma, the globe's first major tropical cyclone of 2011, as seen at 01:45 GMT on January 26. 2011 by NASA's Aqua satellite. Image credit: NASA.

Jeff Masters

Winter Weather

Updated: 3:16 PM GMT on January 26, 2011

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U.S. heavy precipitation events are increasing, but drought is not

By: JeffMasters, 3:12 PM GMT on January 25, 2011

Yesterday, I introduced the National Climatic Data Center's Climate Extremes Index, which uses temperature and precipitation records to see if the U.S. climate is getting more extreme. Today, I'll focus on how the drought and precipitation extremes that go into the Climate Extremes Index have changed over the past century. The three precipitation-related factors to go into the Climate Extremes Index are:

1) The sum of: (a) the monthly percentage of the United States in severe drought (equivalent to the lowest tenth percentile) based on the Palmer Drought Severity Index (PDSI) and (b) the percentage of the United States with severe moisture surplus (equivalent to the highest tenth percentile) based on the PDSI.

2) Twice the value of the percentage of the United States with a much greater than normal proportion of precipitation derived from extreme (equivalent to the highest tenth percentile) 1-day precipitation events.

3) The sum of (a) percentage of the United States with a much greater than normal number of days with precipitation and (b) percentage of the United States with a much greater than normal number of days without precipitation.

Items 1 and 3 have shown no change in annual average value over the past century, but there has been a marked increase in the number of heavy 1-day precipitation events in recent decades. Thus, the record and near-record values of the Climate Extremes Index in recent years have been due to a combination of the increase in heavy 1-day precipitation events and an increase in maximum and minimum temperatures.


Figure 1. The Annual Climate Extremes Index (CEI) for heavy 1-day precipitation events shows that these events, on average, have affected 10% of the U.S. over the past century (black line). However, heavy precipitation events have increased in recent decades. The seven most extreme years since 1910 have all occurred since 1995, with 2010 ranking as the 5th most extreme year in the past 100 years. Image credit: National Climatic Data Center.

Heavy precipitation events
Global warming theory predicts that global precipitation will increase, and that heavy precipitation events--the ones most likely to cause flash flooding--will also increase. This occurs because as the climate warms, evaporation of moisture from the oceans increases, resulting in more water vapor in the air. According to the 2007 Intergovernmental Panel on Climate Change (IPCC) report, water vapor in the global atmosphere has increased by about 5% over the 20th century, and 4% since 1970. The Climate Extremes Index plot for extreme 1-day precipitation events (Figure 1) does indeed show a sharp increase in heavy precipitation events in recent decades, with seven of the top ten years for these events occurring since 1995, and 2010 coming in 5th place in the past 100 years. The increases in heavy precipitation events have primarily come in the spring and summer, when the most damaging floods typically occur. This mirrors the results of Groisman et al. (2004), who found an increase in annual average U.S. precipitation of 7% over the past century, which has led to a 14% increase in heavy (top 5%) and 20% increase in very heavy (top 1%) precipitation events. Kunkel et al. (2003) also found an increase in heavy precipitation events over the U.S. in recent decades, but noted that heavy precipitation events were nearly as frequent at the end of the 19th century and beginning of the 20th century, though the data is not as reliable back then.

Drought and extreme wetness
Global warming theory predicts that although global precipitation should increase in a warmer climate, droughts will also increase in intensity, areal coverage, and frequency (Dai et al., 2004). This occurs because when the normal variability of weather patterns brings a period of dry weather to a region, the increased temperatures due to global warming will intensify drought conditions by causing more evaporation and drying up of vegetation. Increases in drought and flooding are my top two concerns regarding climate change for both the U.S. and the world in the coming century. Two of the three costliest U.S. weather disasters since 1980 have been droughts--the droughts of 1988 and 1980, which cost $71 billion and $55 billion, respectively. The heat waves associated with these droughts claimed over 17,000 lives, according to the National Climatic Data Center publication, Billion-Dollar Weather Disasters. Furthermore, the drought of the 1930s Dust Bowl, which left over 500,000 people homeless and devastated large areas of the Midwest, is regarded to be the third costliest U.S. weather disaster on record, behind Katrina and the 1988 drought. (Ricky Rood has an excellent book on the Dust Bowl that he recommends in a 2008 blog post).


Figure 2. The Annual Climate Extremes Index (CEI) for drought. The worst U.S. droughts on record occurred in the 1930s and 1950s. There has been no trend in the amount of the U.S. covered by drought conditions (blue bars) or by abnormally moist conditions (red bars) over the past century. About 10% of the U.S. is typically covered by abnormally dry or wet conditions (black lines). Image credit: National Climatic Data Center.

The good news is that the intensity and areal coverage of U.S. droughts has not increased in recent decades (blue bars in Figure 2). The portion of the U.S. experiencing abnormal drought and exceptionally wet conditions has remained nearly constant at 10% over the past century. A recent paper by Andreadis et al., 2006, summed up 20th century drought in the U.S. like this: "Droughts have, for the most part, become shorter, less frequent, and cover a smaller portion of the country over the last century. The main exception is the Southwest and parts of the interior of the West, where, notwithstanding increased precipitation (and in some cases increased soil moisture and runoff), increased temperature has led to trends in drought characteristics that are mostly opposite to those for the rest of the country especially in the case of drought duration and severity, which have increased."

Other portions of the globe have not not been so fortunate. Globally, Dai and Trenberth (2004) showed that areas experiencing the three highest categories of drought--severe, extreme, and exceptional--more than doubled (from ~12 to 30%) since the 1970s, with a large jump in the early 1980s due to an El Niño-related precipitation decrease over land, and subsequent increases primarily due to warming temperatures. According to the Global Drought Monitor, 98 million people world-wide currently live in areas experiencing the highest level of drought (exceptional).

References
Andreadis, K. M. Lettenmaier, D. P., "Trends in 20th century drought over the continental United States", Geo. Res. Letters 33, 10, L10403, DOI 10.1029/2006GL025711

Dai A., K.E. Trenberth, and T. Qian, 2004: A global data set of Palmer Drought Severity Index for 18702002: Relationship with soil moisture and effects of surface warming", J. Hydrometeorol., 5, 11171130.

Gleason, K.L., J.H. Lawrimore, D.H. Levinson, T.R. Karl, and D.J. Karoly, 2008: "A Revised U.S. Climate Extremes Index", J. Climate, 21, 2124-2137.

Groisman, P.Y., R.W. Knight, T.R. Karl, D.R. Easterling, B. Sun, and J.H. Lawrimore, 2004, "Contemporary Changes of the Hydrological Cycle over the Contiguous United States: Trends Derived from In Situ Observations," J. Hydrometeor., 5, 64-85.

Kunkel, K. E., D. R. Easterling, K. Redmond, and K. Hubbard, 2003, "Temporal variations of extreme precipitation events in the United States: 1895-2000", Geophys. Res. Lett., 30(17), 1900, doi:10.1029/2003GL018052.

A new Nor'easter for New England
A low pressure system currently centered along the Gulf Coast near New Orleans is bringing heavy rain to much of the south. Rains in excess of 3 inches have fallen over central Mississippi, and the rain is expected to change to snow over northern Mississippi, northern Alabama, and much of Tennessee late tonight. A swath of 2 - 4" of snow is expected in these regions, with higher amounts in the mountains. The low will move off the coast of North Carolina on Wednesday morning, then northeastward out to sea, potentially bringing heavy snows of 4 - 8" to inland portions of New England and the mid-Atlantic. At this time, it appears that the storm will track far enough from the coast and there will be insufficient cold air in place for snowfall amounts of a foot or more to fall. A nasty mix of rain, sleet, and snow is likely for much of the coast, with the heaviest snows expected to miss New York City, Washington D.C., and Boston (Figure 3.) As the low drags its cold front over Florida this afternoon, a slight risk of severe thunderstorms exists, and Florida could see a few tornadoes.


Figure 3. Probability of more than 8 inches of snow falling, for the 24 hour period ending 7am EST Thursday January 27, 2011. Image credit: National Weather Service HPC.


Jeff Masters

Climate Change Drought

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Is the U.S. climate getting more extreme?

By: JeffMasters, 2:37 PM GMT on January 24, 2011

Is the world's climate getting more extreme, with hotter heat waves, colder cold events, heavier rains, and more extreme droughts? After seeing the unprecedented weather events of 2010 and the equally impressive floods of 2011, it's an important question to be asking. Unfortunately, it's an almost impossible question to answer objectively, because we simply don't have good enough long-term global weather records to do so. However, in the U.S., we do have good enough records to attempt this, and the NOAA National Climatic Data Center (NCDC) has developed a Climate Extremes Index to do so. For 2010, the Climate Extremes Index (CEI) showed that the U.S. had a near-average area experiencing extreme weather conditions. Averaged over decades-long time scales, the U.S. climate has been getting more extreme since 1970, but has not changed significantly over a century-long time scale. The Climate Extremes Index (CEI) is based upon three parameters:

1) Monthly maximum and minimum temperature
2) Daily precipitation
3) Monthly Palmer Drought Severity Index (PDSI)

The temperature data is taken from 1100 stations in the U.S. Historical Climatology Network (USHCN), a network of stations that have a long period of record, with little missing data. The temperature data is corrected for the Urban Heat Island effect, as well as for station and instrument changes. The precipitation data is taken from 1300 National Weather Service Cooperative stations. The Climate Extremes Index defines "much above normal" as the highest 10% of data, "much below normal" as the lowest 10%, and is the average of these five quantities:

1) The sum of: (a) the percentage of the United States with monthly maximum temperatures much below normal, and (b), the percentage of the United States with monthly maximum temperatures much above normal.

2) The sum of: (a) the percentage of the United States with monthly minimum temperatures much below normal, and (b), the percentage of the United States with monthly minimum temperatures much above normal.

3) The sum of: (a) the percentage of the United States in severe drought each month (equivalent to the lowest tenth percentile) based on the Palmer Drought Severity Index (PDSI), and (b), the percentage of the United States with severe moisture surplus (equivalent to the highest tenth percentile) based on the PDSI.

4) Twice the value of the percentage of the United States with a much greater than normal proportion of precipitation derived from extreme (equivalent to the highest tenth percentile) 1-day precipitation events.

5) The sum of: (a) percentage of the United States with a much greater than normal number of days with precipitation, and (b), percentage of the United States with a much greater than normal number of days without precipitation.


Figure 1. The Annual Climate Extremes Index (CEI), updated through 2010, shows that U.S. climate has generally been getting more extreme since the early 1970s, but that the 2010 climate was just slightly more extreme than average. On average since 1910, 21% of the U.S. has seen extreme conditions in a given year (thick black line), and in 2010 this number was about 24%. Image credit: National Climatic Data Center.

As summarized by Gleason et al. (2008), the National Climatic Data Center concludes that based on the Climate Extremes Index, the percentage of the U.S. seeing extreme temperatures and precipitation generally increased since the early 1970s. These increases were most pronounced in the summer. No trend in extremes were noted for winter. The annual CEI index plot averaged for all five temperature and precipitation indices (Figure 1) showed that four of the ten most extreme years on record occurred since 1996. However, some very extreme years also occurred in the 1910s through 1950s, in association with widespread extreme drought and above-average temperatures. The most extreme year in U.S. history was 1998, with 1934 a close second. The year 1998 was the hottest year in U.S. history, with a record 78% of the U.S. experiencing minimum temperatures much above normal. That year also had a record 23% of the U.S. with much greater than normal precipitation from extreme 1-day precipitation events. The 1934 extreme in CEI was due in large part because of the most widespread drought of the century--a full 52% of the U.S. was affected by severe or extreme drought conditions. That year also saw a record 64% of the U.S. with much above normal maximum temperatures.

Maximum and minimum temperatures
It is very interesting to look at the five separate indices that go into the Climate Extremes Index. Today I'll look at temperature, and focus on drought and precipitation in my next post. The portion of the U.S. experiencing month-long maximum or minimum temperatures either much above normal or much below normal has been about 10% over the past century (black lines in Figures 2 and 3.) However, over the past decade, about 20% of the U.S. has experienced monthly maximum temperatures much above normal, and less than 5% has experienced maximum temperatures much cooler than normal. Minimum temperatures show a similar behavior, but have increased more than the maximums (Figure 3). Climate models minimum temperatures should be rising faster than maximum temperatures if human-caused emissions of heat-trapping gases are responsible for global warming, which is in line with what we are seeing in the U.S. using the CEI.

While there have been a few years (1921, 1934) when the portion of the U.S. experiencing much above normal maximum temperatures was greater than anything observed in the past decade, the sustained lack of maximum temperatures much below normal over the past decade is unique. The behavior of minimum temperatures over the past decade is clearly unprecedented--both in the lack of minimum temperatures much below normal, and in the abnormal portion of the U.S. with much above normal minimum temperatures. Remember that these data ARE corrected for the Urban Heat Island effect, so we cannot blame increased urbanization for the increase in temperatures.


Figure 2. The Annual Climate Extremes Index (CEI) for maximum temperature, updated through 2010, shows that about 10% of U.S. had maximum temperatures much warmer than average during 2010. This was right near the average from the past 100 years (thick black line.) Image credit: National Climatic Data Center.


Figure 3. The Annual Climate Extremes Index (CEI) for minimum temperature, updated through 2010, shows that about 35% of U.S. had minimum temperatures much warmer than average during 2010. This was the 7th largest such area in the past 100 years. The mean area of the U.S. experiencing minimum temperatures much warmer than average over the past 100 years is about 10% (thick black line.) Image credit: National Climatic Data Center.

I'll have a new post on Tuesday, when I'll talk about how extremes of drought and precipitation have changed in the U.S. (I may talk instead about the developing winter storm for the Appalachians and Northeast coming Wednesday and Thursday this week, though.)

References
Gleason, K.L., J.H. Lawrimore, D.H. Levinson, T.R. Karl, and D.J. Karoly, 2008: "A Revised U.S. Climate Extremes Index", J. Climate, 21, 2124-2137.

The National Climatic Data Center has a more in-depth discussion of the Climate Extremes Index for the U.S. on a regional and seasonal basis during 2010. In some regions, such as the Southeast U.S., 2010 was a remarkably extreme year.

Jeff Masters

Climate Change

Updated: 2:38 PM GMT on January 24, 2011

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2011: Year of the flood

By: JeffMasters, 3:21 PM GMT on January 21, 2011

The year 2010 was one the worst years in world history for high-impact floods. But just three weeks into the new year, 2011 has already had an entire year's worth of mega-floods. I'll recap here six remarkable floods that have already occurred this year.

Brazil
Brazil suffered its deadliest natural disaster in history on January 11, when torrential rains inundated a heavily populated, steep-sloped area about 40 miles north of Rio de Janeiro. Flash floods and mudslides from the heavy rains have claimed 902 lives, including at least 357 in Nova Friburgo and 323 in Teresópolis. Rainfall amounts of approximately 300 mm (12 inches) fell in just a few hours in the hardest-hit regions. Damage estimates are currently $1.2 billion, and 13,000 were left homeless. Latest rainfall forecasts from the GFS model show the heaviest rains during the coming week staying well south of the Rio de Janeiro area, which will give the flood region time to dry out and recover.


Figure 1. Flooded stream in Teresópolis. Image credit: Wikipedia.

Australia Queensland
Australia's most expensive natural disaster in history is now the Queensland flood of 2010 - 2011, with a price tag now as high as $30 billion. At least 31 have been killed since December in the floods, and another 40 are missing. According to the Australian Bureau of Meteorology, in 2010 Australia had its wettest spring (September - November) since records began 111 years ago, with some sections of coastal Queensland receiving over 4 feet (1200 mm) of rain. Rainfall in Queensland and all of eastern Australia in December was the greatest on record, and the year 2010 was the rainiest year on record for Queensland. Queensland typically has its rainiest years when La Niña events occur, due to the much warmer than average ocean temperatures that occur along the coast. The BOM noted, "Previous strong La Niña events, such as those of 1974 and 1955, have also been associated with widespread and severe flooding in eastern Australia. Sea surface temperatures off the Queensland coast in recent months have also been at or near record levels." The BOM's annual summary also reported, "Sea surface temperatures in the Australian region during 2010 were the warmest value on record for the Australian region. Individual high monthly sea surface temperature records were also set during 2010 in March, April, June, September, October, November and December. Along with favourable hemispheric circulation associated with the 2010 La Niña, very warm sea surface temperatures contributed to the record rainfall and very high humidity across eastern Australia during winter and spring." Queensland has an area the size of Germany and France combined, and 3/4 of the region has been declared a disaster zone. The latest GFS precipitation forecast for the coming week shows new heavy rains of 3 - 5 inches can be expected over the extreme northern portion of Queensland, but the majority of the state will receive lesser rains that should not further aggravate the flooding situation.


Figure 2. The airport, the Bruce Highway, and large swaths of Rockhampton, Australia, went under water due to flooding from the Fitzroy River on January 9, 2011. The town of 75,000 was completely cut off by road and rail, and food, water and medicine had to be brought in by boat and helicopter. Image credit: NASA.

Australia Victoria
From January 12 - 14, extremely heavy rains over the southern Australian state of Victoria caused major flooding that killed one person and caused hundreds of millions in damage. Kevin Parkyn, a senior forecaster with the Bureau of Meteorology said "Victoria is experiencing one of its worst flood events in its history" after "a week in which rainfall totals have been smashed in parts of Victoria". Bureau of Meteorology senior forecaster Terry Ryan said "It's the worst flood in western Victoria in their history as far as our records go in terms of the depth of water and the number of places affected." According to atmospheric moisture expert Dr. Kevin Trenberth of the National Center for Atmospheric Research, extratropical storm systems like the one that affected Victoria get 70% of their moisture from the surrounding atmosphere, and 30% due to evaporation from the surface. Since the airmass that supplied Victoria with its flooding rains traveled over the already-flooded portions of Queensland to the north before reaching Victoria, the moisture from the Queensland floods contributed significantly to the Victoria floods. Little rain is predicted over Victoria during the coming week, fortunately.

100-year flood in Sri Lanka
As I reported in my previous post, at least 43 are dead and damage estimates are at $500 million in Sri Lanka, which suffered a 1-in-100 year flood this month.

South Africa
Heavy rains of up 345 mm (13.6") have fallen in South Africa so far this month, resulting in deadly floods that have killed 40 people. Seven of the country's nine provinces have been declared disaster zones. Agricultural damage alone from the floods is estimated at $145 million. Heavy rains and severe flooding have also affected neighboring Mozambique, where 13 people are dead and 13,000 homeless or suffering damaged homes. Neighboring Zimbabwe has seen its heaviest rains in 30 years in recent weeks, according to the nation's Civil Protection Unit, but severe flooding has not yet hit that nation. La Niña events commonly cause heavy rains in southern Africa. Sea surface temperatures off the east coast of South Africa were 0.2 - 0.4°C above average during December 2010--nowhere near record levels, but warm enough to contribute to enhanced rainfall.

Philippines
Very heavy rains since late December have triggered a major flooding disaster in the Philippines, where 40 are dead, 453,000 people displaced, and 1.2 million people affected. The heavy rains were caused when a cold front moved over the eastern Philippines and lingered for many days. Heavy rains are common in the Philippines during La Niña events, as unusually warm waters accumulate by the islands. This winter, the waters in the central Philippines (10N to 15N, 120E to 130E) were at the warmest levels in history--1.0°C above average during December. The exceptionally warm waters allowed more moisture than usual to evaporate into the air, enhancing rainfall.

Commentary
The year 2011 has begun with a remarkable number of high-impact floods world-wide, and much of the blame for this can be placed on the current La Niña event occurring in the Eastern Pacific. NOAA's Climate Prediction Center currently puts the La Niña event in the "strong" category, and whenever a La Niña or El Niño event reaches the strong category, major perturbations to global weather patterns occur. This typically results in record or near-record flooding in one or more regions of the globe. When one combines the impact of La Niña with the increase of global ocean temperatures of 0.5°C (0.9°F) over the past 50 years, which has put 4% more water vapor into the atmosphere since 1970, the result is a much increased chance of unprecedented floods. A 4% increase in atmospheric moisture may not sound like much, but it turns out that precipitation will increase by about 8% with that 4% moisture increase. Critically, it is the extreme rainfall events that tend to supply the increased rainfall. For example, (Groisman et al., 2004) found a 20% increase in very heavy (top 1%) precipitation events over the U.S. in the past century, and a 36% rise in cold season (October - April) "extreme" precipitation events (those in the 99.9% percentile--1 in 1000 events. These extreme rainfall events are the ones most likely to cause floods.

References
Groisman, P.Y., R.W. Knight, T.R. Karl, D.R. Easterling, B. Sun, and J.H. Lawrimore, 2004, "Contemporary Changes of the Hydrological Cycle over the Contiguous United States: Trends Derived from In Situ Observations," J. Hydrometeor., 5, 64.85.

Milly, P.C.D., R.T. Wetherald, K.A. Dunne, and T.L.Delworth, Increasing risk of great floods in a changing climate", Nature 415, 514-517 (31 January 2002) | doi:10.1038/415514a.

Santer, B.D., C. Mears, F. J. Wentz, K. E. Taylor, P. J. Gleckler, T. M. L. Wigley, T. P. Barnett, J. S. Boyle, W. Brüggemann, N. P. Gillett, S. A. Klein, G. A. Meehl, T. Nozawa, D. W. Pierce, P. A. Stott, W. M. Washington, and M. F. Wehner, 2007, "Identification of human-induced changes in atmospheric moisture content", PNAS 2007 104: 15248-15253.

Trenberth, K.E., J. Fasullo, and L. Smith, 2005: "Trends and variability in column-integrated atmospheric water vapor", Climate Dynamics 24, 741-758.

Jeff Masters

Flood

Updated: 3:14 AM GMT on December 19, 2011

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Another flooding mega-disaster: Sri Lanka recovers from extreme flooding

By: JeffMasters, 1:14 PM GMT on January 19, 2011

At least 43 are dead and thousands still in refugee camps due to extreme flooding in eastern Sri Lanka caused by record monsoon rains. According to the United Nations, the rains in recent weeks in Sri Lanka have been the heaviest in nearly 100 years of record keeping, and the flood that resulted was a 1-in-100 year event, according to The U.N. Global Disaster Alert and Coordination System. Rainfall at Batticaloa, Sri Lanka, during the 42-day period December 1 - January 12 was 1606 mm (63"), which is about how much rain the station usually receives in an entire year (1651 mm, or 65".) Sri Lanka's previous most devastating flooding disaster was the 2004 tsunami, but as The Economist commented, "in terms of the numbers of people displaced and farmland inundated, the floods have been even more devastating than the tsunami of December 2004." Damage estimates start at $500 million, and much of Sri Lanka's agriculture has been severely damaged by the disaster. Also of concern is the large number of land mines from the recent Sri Lanka civil war that may have been unearthed by the floods. Water is also a major concern in the flood-hit area, as fighting between government forces and Tamil Tigers rebels from mid-2007 to May 2009 damaged or destroyed almost all of the water facilities.


Figure 1. A family affected by the 2011 Sri Lanka floods braves the flood waters. Image credit: United Nations.

Sri Lanka is now the fifth nation in the past six month to suffer a flooding disaster unprecedented in its history. As I reported in a previous post, the other four mega-impact floods--the July 2010 Pakistan floods, the December - January Queensland Australia floods, the November 2010 Colombia floods, and the January 2011 Rio de Janeiro floods--were all accompanied by an atmosphere laden with moisture, due, in part, due to sea surface temperatures over nearby ocean areas that were the 2nd or 3rd warmest on record. However, that was not the case for the Sri Lanka floods. Ocean temperatures during December 2010 were 0.2°C below average in the 5x5 degree square of ocean adjoining the island (5N - 10N, 80E - 85E). The floods appear to be due to the normal monsoon rains that typically affect the region this time of year, enhanced by the strong La Niña event occurring in the Eastern Pacific.


Figure 2. Satellite-estimated precipitation over Sri Lanka for January 3 - 9. Up to 18 inches (525 mm) fell over eastern Sri Lanka. Image credit: NASA Earth Observatory.

Jeff Masters

Flood

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Globe cools slightly in December 2010: 11th - 17th warmest on record

By: JeffMasters, 2:43 PM GMT on January 18, 2011

December 2010 was the globe's 17th warmest December on record, according to the National Oceanic and Atmospheric Administration (NOAA) National Climatic Data Center (NCDC). NASA's Goddard Institute for Space Studies rated December 2010 the 11th warmest December on record. December 2010 global ocean temperatures were the 10th warmest on record, and land temperatures were the 30th warmest on record. Global satellite-measured temperatures for the lowest 8 km of the atmosphere were the 7th warmest on record, according to both Remote Sensing Systems and the University of Alabama Huntsville (UAH). The global cool-down from November, which was the warmest November on record for the globe, was due in large part to the on-going moderate strength La Niña episode in the Eastern Pacific. The large amount of cold water that upwells to the surface during a La Niña typically causes a substantial cool-down in global temperatures. Still, December 2010 temperatures were warm enough to make 2010 tied with 2005 as Earth's warmest year in history, as I reported in yesterday's post.

For those interested, NCDC has a page of notable weather highlights from December 2010.


Figure 1. Departure of temperature from average for December 2010. Eastern Canada and Greenland were very warm, relative to average, and much of Siberia and Europe were abnormally cold. Image credit: National Climatic Data Center (NCDC).

An average December for the U.S.
For the contiguous U.S., December was near-average in temperature, ranking as the 44th coldest December in the 116-year record, according to the National Climatic Data Center. The year 2010 was the 23rd warmest on record. A strong "Arctic Oscillation" pattern allowed cold air to spill southward over the Southeast U.S., resulting in the coldest December on record in Florida and Georgia. Nine other states in the Southeast U.S. had top-ten coldest Decembers. Five states in the Southwest U.S. had top-ten warmest Decembers. A series of major snowstorms brought the 7th-largest December snow cover to the U.S. as a whole. December 2010 precipitation in the contiguous U.S. was also near average, ranking 54th driest in the 116-year record. Montana and Utah had their wettest Decembers on record, and six other states had top-ten wettest Decembers--Minnesota, North Dakota, South Dakota, Oregon, Maine, and California. Six states had top-ten driest Decembers--Louisiana, Mississippi, Alabama, Arkansas, Kansas, and Delaware.

La Niña in the "moderate" to "strong" category
The equatorial Eastern Pacific Ocean is currently experiencing moderate to strong La Niña conditions. Sea surface temperatures (SSTs) over the tropical Eastern Pacific in the area 5°N - 5°S, 120°W - 170°W, also called the "Niña 3.4 region", were 1.5°C below average as of January 10, according to NOAA. The Australian Bureau of Meteorology put this number at 1.45°C below average (as of January 9.) Moderate La Niña conditions are defined as occurring when this number is 1.0°C - 1.5°C below average. Temperatures colder than 1.5°C below average qualify as strong La Niña conditions. NOAA is maintaining its La Niña advisory, and expects La Niña conditions to last through through spring.

Both El Niño and La Niña events have major impacts on regional and global weather patterns. La Niña typically causes warm, dry winters over the southern portion of the U.S., with cooler and wetter than average conditions over the Pacific Northwest. The Ohio and Mississippi Valleys states typically have wetter winters than usual during La Niña events.

December 2010 Arctic sea ice extent lowest on record
Northern Hemisphere sea ice extent in December 2010 was the lowest in the 31-year satellite record, according to the National Snow and Ice Data Center. Ice volume in December was also the lowest on record for this time of year, according to University of Washington Polar Ice Center. At the end of December, the eastern portion of Canada's Hudson Bay remained unfrozen, the first time in recorded history that Hudson Bay has not been completely frozen over at the end of the year. The unusual amount of open water led to temperatures that averaged 20°C (36°F) above normal over a region larger than Texas during the first ten days of January.

Jeff Masters

Climate Summaries

Updated: 2:46 PM GMT on January 18, 2011

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2010: tied with 2005 for warmest year in history

By: JeffMasters, 5:23 PM GMT on January 16, 2011

The year 2010 was tied with 2005 as Earth's warmest year in history, according to separate calculations performed by NASA and the National Oceanic and Atmospheric Administration (NOAA). Temperatures during 2010 were 1.12°F (0.62°C) above the 20th century average. Reliable global temperature records go back to 1880. NOAA reported that the Northern Hemisphere had its warmest year on record in 2010, the Southern Hemisphere its 6th warmest, land areas their 2nd warmest, and the oceans their 3rd warmest. Global satellite-measured temperatures of the lowest 8 km of the atmosphere during 2010 were virtually tied with 1998 for warmest on record, according to the University of Alabama Huntsville (UAH). The 1998 temperatures were 0.01°C warmer than 2010, but the difference is so small that the two years should be considered tied for first place. These measurements are very sensitive to the effect of major El Niño events that warm the waters and atmosphere over the Eastern Pacific. Thus the 1998 El Niño--the strongest such event ever recorded--set a global lower atmospheric temperature record that had been impossible to match until 2010.


Figure 1. Departure of temperature from average for 2010. Image credit: NOAA's National Climatic Data Center.

Earth's warmest temperatures in 2010, relative to average, occurred in western Greenland and eastern Canada, where record-duration sea ice loss contributed to temperatures that were 9°F (5°C) above average for the year (Figure 1.) The coolest temperatures, relative to average, were in central Siberia, 5.4°F (3°C) below average. In addition to being the warmest year on record globally, it was also the wettest (Figure 4.)


Figure 2. The latest rankings by NOAA of the hottest years globally since 1880. Earth's ten hottest years have all come since 1998, and the decade of the 2000s was by far the warmest decade in the historical record. Image credit: NOAA's National Climatic Data Center.


Figure 3. Global departure of temperature from average for 1880-2010, as computed by NASA.


Figure 4. Global departure of precipitation from average for 1900 - 2010. The year 2010 set a new record for wettest year in Earth's history. The difference in precipitation from average in 2010 was about 13% higher than that of the previous record wettest year, 1956. Image credit: NOAA's National Climatic Data Center.

A record warm year during a deep solar minimum: an unusual occurrence
The 2010 record warmth was unusual in that it occurred during a period when energy from the sun was at its lowest levels since satellite measurements began in the 1970s. The 11-year sunspot cycle causes a 0.1% variation in the amount of energy reaching the Earth. White et al. (1997) found that sea surface temperatures varied by about 0.04 - 0.07°C on time scales of 11 - 22 years due to this change in solar energy, with temperatures lagging the sunspot cycle by 1.5 - 3 years (because the ocean is slow to heat up and cool down in response.) So, although solar activity began to pick up somewhat in 2010, the 1.5 - 3 year lag in ocean temperature response meant that the record low solar activity of 2008 - 2009 was what affected global temperatures in 2010. Given that the departure of Earth's temperature from average during 2010 was 0.62°C, this difference would have been perhaps 10% greater had we been 2 - 3 years past the peak of the 11-year sunspot cycle. The previous global temperature record, set in 2005, occurred 3 - 5 years after the twin-peaked previous solar cycle. It is very difficult to get a record warm year during a deep solar minimum, making the 2010 record one likely to be broken later this decade as the sun begins to exert a greater warming influence on the planet.


Figure 5. During 2008 - 2009, the energy from the sun arriving at the top of Earth's atmosphere (Total Solar Irradiance, or TSI) as measured by satellites fell to its lowest value since satellite measurements began in 1978. Image credit: Physikalisch-Meteorologisches Observatorium Davos World Radiation Center.

References
Skepticalscience.com has an in-depth discussion of Solar activity & climate: is the sun causing global warming?

Wunderground climate change blogger Dr. Ricky Rood has a comprehensive 5-part series on how the sun affects climate.

Gray, L.J., J. Beer, M. Geller, J.D. Haigh, M. Lockwood, 2010, "Solar Influences on Climate", Accepted in Rev. Geophys, 2010.

White, W.B., J. Lean, D.R. Cayan and M.D. Dettinger (1997), Response of global upper ocean temperature to changing solar irradiance, J. Geophys. Res., 102, 3255-3266.

Thunderstorms hurl antimatter into space
NASA announced this week that mature thunderstorms can produce antimatter when exceptionally powerful lightning bolts occur. The antimattter beams were detected by the Fermi Gamma-ray Space Telescope. The amount of antimatter produced is tiny, though, and probably not enough to help power a starship.

"Cap'n, we're running low on antimatter to power the warp engines. Can you fly in low over those thunderstorms to replenish our reserves? We'll use the transporters to gather the antimatter and funnel it into the antimatter containment vessel."

"OK, Scotty!"

I'll have a new post on Tuesday.

Jeff Masters

Climate Change Climate Summaries

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At least 611 dead in Brazilian floods: Brazil's deadliest natural disaster in history

By: JeffMasters, 5:05 PM GMT on January 14, 2011

Torrential rains inundated a heavily populated, steep-sloped area about 40 miles north of Rio de Janeiro on Tuesday and Wednesday, triggering flash floods and mudslides that have claimed at least 611 lives. Rainfall amounts of approximately 300 mm (12 inches) fell in just a few hours in the hardest-hit regions, Teresopolis and Nova Friburgo. Many more people are missing, and the death toll is expected to go much higher once rescuers reach remote villages that have been cut off from communications. The death toll makes the January 2011 floods Brazil's worst single-day natural disaster in its history. Brazil suffers hundreds of deaths each year due to flooding and mudslides, but the past 12 months have been particularly devastating. Flooding and landslides near Rio in April last year killed 246 people and did about $13 billion in damage, and at least 85 people perished last January during a similar event.


Figure 1. Flooding at Sao Jose do Vale do Vale do Rio Preto in Brazil, photographed on Thursday, January 13, 2011.

Role of near-record sea surface temperatures in Brazil's flood
This week's heavy rains occurred when a storm system crossing from west to east over southern Brazil drew in a moist southerly flow air off the Atlantic Ocean over southern Brazil at the surface. At higher levels, the storm drew in very moist air from the Amazon. Sea surface temperatures along the Brazilian coast are at near-record warm levels, which likely contributed to the heavy rains. Record rains are more likely when sea surface temperatures over the nearby moisture source regions are at record high levels. This occurs because increased amounts of water vapor evaporate into the atmosphere from a warm ocean compared to a cold one, due to the extra motion and energy of the hotter water molecules. According to an analysis I did of the UK Met Office Hadley Centre sea surface temperature data set, December 2010 sea surface temperatures in the 5x5 degree region of Earth's surface along the Brazilian shore nearest the disaster area, 20S to 25S and 45W to 40W, were the second warmest on record since 1900. Temperatures were 1.05°C (1.9°F) above average in this region last month. Only 2007, with a 1.21°C departure from average, had warmer December ocean temperatures.

Meteorologist Eugenio Hackbart, with the Brazilian private weather forecasting company Metsul, wrote in his blog today, "Heavy rains early this year coincide with the strong warming of the Atlantic along the coasts of southern and southeastern Brazil. With waters up to 2°C warmer than average in some places, there is a major release of moisture in the atmosphere essential for the formation of storms."


Figure 2. Newspaper front page story in Brazil after the March 18, 1967 flooding disaster, Brazil's previous deadliest single-day natural disaster. Image credit: Metsul.

Brazil's previous worst natural disaster: the March 18, 1967 flood
The previous worst natural disaster in Brazilian history occurred on March 18, 1967 when a tsunami-like flood of water, mud and rocks swept down a hillside in the coastal city of Caraguatatuba, near Sao Paulo, killing 300 - 500 people. According to meteorologist Eugenio Hackbart with the private Brazilian weather company Metsul, a rainguage at nearby Sao Sebastao measured 115 mm (4.5") on March 17, and 420 mm (17") on March 18. Hackbart puts the death toll from the 1967 disaster at 300 - 500, and refers to it as Brazil's deadliest single-day natural disaster in history. Heavy rains at other locations in Brazil that month caused additional mudslides and flooding deaths, and Wikipedia lists the total death toll for the Brazil March 1967 floods at 785.

I looked at the sea surface temperatures for March 1967 to see if unusually warm ocean waters may have contributed to that year's flooding disaster. Sea surface temperatures in the 5x5 degree region of Earth's surface nearest the disaster site (20S to 25S, 50W to 45W) were 0.24°C (0.4°F) above average, which is not significantly different from normal. So, we can get record rains and flooding when sea surface temperatures are near normal, and it is possible that this week's catastrophe was not significantly impacted by the exceptionally warm water near the coast. However, heating up the oceans loads the dice in favor of extreme rainfall events, and makes it more likely we will have an unprecedented flood. If we look at the departure of temperature from average for the moisture source regions of the globe's four most extreme flooding disasters over the past 12 months, we find that these ocean temperatures ranked 2nd or 3rd warmest, going back through 111 years of history:

January 2011 Brazilian floods: 2nd warmest SSTs on record, +1.05°C (20S to 25S, 45W to 40W)
November 2010 Colombia floods: 3rd warmest SSTs on record, +0.65°C (10N to 0N, 80W to 75W)
December 2010 Australian floods: 3rd warmest SSTs on record, +1.05°C (10S to 25S, 145E to 155E)
July 2010 Pakistani floods: 2nd warmest SSTs on record, +0.95°C (Bay of Bengal, 10N to 20N, 80E to 95E)

The size of the ocean source region appropriate to use for these calculations is uncertain, and these rankings will move up or down by averaging in a larger or smaller region of ocean. For example, if one includes an adjacent 5x5 degree area of ocean next to Brazil's coast that may have also contributed moisture to this week's floods, the SSTs rank as 7th warmest in the past 111 years, instead of 2nd warmest. It would take detailed modeling studies to determine just how much impact these near-record sea surface temperatures had on the heavy rains that occurred, and what portion of the ocean served as the moisture source region.


Figure 3. Predicted total precipitation amounts in South America for the 7-day period ending at 7am EST January 21, 2011, as forecast by the 06Z run of the GFS Ensemble model made January 14, 2011. Image credit: Florida State University.

More rain in the forecast
The coast of Brazil is embedded in a warm, moist tropical airmass that is expected to continue to bring heavy rains over he Rio de Janeiro area for at least the next week. Heavy rains in excess of five inches in the next seven days (Figure 3) are predicted by the GFS Ensemble computer model for the disaster region, just north of Rio de Janeiro. The additional heavy rains are likely to cause more life-threatening mudslides and floods.

2010 tied for warmest year in Earth's history
Earth's warmest year in history occurred in 2010, NASA reported this week. The globe's temperature beat the previous record set in 2005 by just .01°C, so we should consider 2010 and 2005 tied for the warmest year on reecord. Reliable global temperature records go back to 1880. The National Oceanic and Atmospheric Administration (NOAA) also announced this week that 2010 was tied with 2005 as the warmest year on record, with temperatures during 2010 1.12°F (0.62°C) above the 20th century average. When the planet stops producing record weather catastrophes to blog about, I'll discuss the 2010 global temperature record in more detail.

Anniversary of the Haitian earthquake
Yesterday was the 1-year anniversary of the great Haitian earthquake of 2010. I want to thank all of you who offered donations to such great charities as the Lambi Fund of Haiti and Portlight.org. The people of Haiti need our continued financial support and prayers in the difficult rebuilding years to come.

I'll have a new post on Monday.

Jeff Masters

Flood

Updated: 2:26 AM GMT on January 19, 2011

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Record snows hit New England; Brazilian floods kill 350; Brisbane underwater

By: JeffMasters, 4:16 PM GMT on January 13, 2011

The Northeast U.S. is digging out today from the winter's third major snowstorm, and the nation's South continues to deal with travel disruptions caused by the nasty coasting of ice, snow and sleet the storm left behind early this week. Yesterday's Nor'easter has exited into Canada, and the storm is over for the U.S. It was a pretty average Nor'easter as far as intensity goes--the storm's central pressure bottomed out at 982 mb, and just the Massachusetts coast was subject to high winds that merited blizzard warnings. The storm did generate one hurricane-force wind gust--Provincetown airport on the tip of Cape Cod had sustained winds at 43 mph, gusting to 79 mph, at 6:35am EST yesterday, and a personal weather station at Humarock Beach in Scituate, southeast of Boston, recorded a wind gust of 64 mph at 5:51am EST yesterday.


Figure 1. A bit of work today needed before one can step out of the door in Southborough, Massachusetts! Image credit: wunderphotographer Megmdp.

But what was remarkable about the January Nor'easter of 2011 were its snow amounts. This rather ordinary-strength Nor'easter managed to assemble the perfect mix of conditions needed to transport moisture to a region of the storm highly favorable for heavy snow formation. Many heavy snow bands with snowfall rates up to 3 inches per hour formed over New England, with some of these bands intense enough to generate lightning and thunder. Connecticut, Massachusetts, and Vermont all came within an inch of setting all-time state 24-hour snowfall records yesterday. North Haven, Connecticut received 29.5", falling just short of the 30.2" 24-hour snowfall record for the state, set at Fairfield in February 2006. Savoy, Massachusetts received 34.5", falling just short of that state's all-time 24-hour snowfall record, the 36" recorded at Milton in February 1997. Wilmington, Vermont got 36" in yesterday's storm, just missing the state record of 37", set at Peru in March 1984. The capital of Connecticut, Hartford, had its greatest snowstorm in history yesterday, with 24". The old record was 23.5", set in a February 1899 storm.

Some selected storm total snowfall amounts, taken from the latest NOAA storm summary:

New York City, NY 9.1"
Albany, NY 13.2"
Worcester, MA 21.1"
Boston, MA 14.6"
Augusta, ME 14.5"
Portland, ME 9.2"
Concord, NH 22"
Somerset, PA 15"
Philadelphia, PA 5.2"
Providence, RI 9.5"
Brattleboro, VT 19"
Elkin, WV 10"
Danbury, CT 17.9"
Wilmington, DE 4.3"

According to our weather historian, Christopher C. Burt, in his latest blog post titled, "Snowstorms in the South: A Historical Perspective", the 8.9" that fell on Huntsville, Alabama from this week's storm was that city's third heaviest snow on record. The post has a nice summary of the remarkable heavy snow storms that have hit the South in the past.


Figure 2. Flooding at São José do Vale do Rio Preto in Brazil photographed on Thursday, January 13, 2011.

Brazilian floods, landslides kill at least 350
The globe's parade of massive flooding disasters in recent months continued yesterday in Brazil, where heavy rains of up to 10 inches in 24 hours inundated the region about 60 miles north of Rio de Janeiro. At least 350 are dead and 50 people missing, and the death toll is expected to go much higher once rescuers reach remote villages that have been cut off from communications. Brazil suffers hundreds of deaths each year due to flooding and mudslides, but the past 12 months have been particularly devastating. Flooding and landslides near Rio in April last year killed 246 people and did about $13 billion in damage, and at least 85 people perished last January during a similar event.


Figure 3. A woman trapped on the roof of her car awaits rescue during the Toowoomba flash flood on Monday. Image credit: Wikipedia.

New floods ravage Australia's 3rd largest city
Flood waters swept today into Brisbane, Australia's 3rd largest city, inundating 14,400 homes and businesses, partially submerging another 17,200, and cutting power to 118,000, as the Brisbane River peaked at its highest level since 1974. Queensland Premier Anna Bligh, who has called the recent floods in Queensland the greatest natural disaster in their history, said, "What I'm seeing looks more like a war zone in some places. All I could see was their rooftops...underneath every single one of those rooftops is a horror story. We are facing a reconstruction effort of post-war proportions." Much of Brisbane's infrastructure has been damaged or destroyed, including 55,000 miles of roads. The Port of Brisbane, one of Australia's busiest, has been closed because of debris, and the city's largest sports stadium is under several feet of water.

The search for bodies continues in Toowoomba, about 60 miles west of Brisbane, where freak rains of 6 inches in just 30 minutes triggered a flash flood that killed 12 and left 61 missing on Monday. The flood waters from the Toowoomba disaster poured into the Brisbane River, contributing to its rampage through Brisbane yesterday. The Australian Bureau of Meteorology (BOM) reported that only scattered light rains less than 1/3" fell in the Brisbane area over the past 24 hours, and no further significant rains are forecast in the Brisbane area until Tuesday next week, so the worst of the flooding is now over for Queensland. According to the Australian Bureau of Meteorology, the December - January floods in Queenland are the most significant flooding event in Australia since at least 1974. In 2010, Australia had its wettest spring (September - November) since records began 111 years ago, with some sections of coastal Queensland receiving over 4 feet (1200 mm) of rain. Rainfall in Queensland and all of eastern Australia in December was the greatest on record, and the year 2010 was the rainiest year on record for Queensland. Queensland typically has its rainiest years when La Niña events occur, due to the much warmer than average ocean temperatures that occur along the coast. The BOM notes, "Previous strong La Niña events, such as those of 1974 and 1955, have also been associated with widespread and severe flooding in eastern Australia. Sea surface temperatures off the Queensland coast in recent months have also been at or near record levels." The BOM's annual summary also reported, "Sea surface temperatures in the Australian region during 2010 were the warmest value on record for the Australian region. Individual high monthly sea surface temperature records were also set during 2010 in March, April, June, September, October, November and December. Along with favourable hemispheric circulation associated with the 2010 La Niña, very warm sea surface temperatures contributed to the record rainfall and very high humidity across eastern Australia during winter and spring." Beginning in December, the Queensland floods have killed at least 22, and damage estimates are now as high as $20 billion. Queensland has an area the size of Germany and France combined.

2010 tied for warmest year in Earth's history
Earth's warmest year in history occurred in 2010, NASA reported yesterday. The globe's temperature beat the previous record set in 2005 by just .01°C, so we should consider 2010 and 2005 tied for the warmest year on record. Reliable global temperature records go back to 1880. The National Oceanic and Atmospheric Administration (NOAA) also announced yesterday that 2010 was tied with 2005 as the warmest year on record, with temperatures during 2010 1.12°F (0.62°C) above the 20th century average. I'll have a full blog post on the subject Friday morning.

Jeff Masters

Flood Winter Weather

Updated: 7:42 PM GMT on January 13, 2011

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Major Nor'easter pounds New England; icy mess in the South; record floods in Australia

By: JeffMasters, 2:10 PM GMT on January 12, 2011

A classic Nor'easter continues to intensify this morning off the New England coast, bringing heavy snow and strong winds from New Jersey to Maine. The snow has ended in New York City, which received 9.1" at Central Park as of 7am EST. Heavier snows of just over a foot fell on nearby regions, with 12.1" in Bedford Park, 13.2" in Levittown, and 12.5" in East Rutherford, NJ. The heaviest snow is occurring in Connecticut, where a storm-high 23" has fallen so far at North Haven. Twenty-two inches fell at Ridgefield on the Connecticut/New York border. The storm is at peak intensity this morning in Rhode Island and Massachusetts, and blizzard warnings are now posted for Boston and the surrounding coast of Massachusetts. Blizzard conditions occur when a storm has frequent wind gusts over 35 mph or sustained winds over 35 mph, plus visibility less than 1/4 mile for at least three consecutive hours. Today's Nor'easter intensified a little more than expected, reaching a central pressure of 983 mb at 8am EST. The storm is currently centered along the Southeast Massachusetts coast, and is bringing very high winds to all of coastal Massachusetts. Winds at the Provincetown airport on the tip of Cape Cod were sustained at 43 mph, gusting to 79 mph, at 6:35am EST. A personal weather station at Humarock Beach in Scituate, southeast of Boston, recorded a wind gust of 64 mph at 5:51am EST this morning. Snow fall rates of 1 - 2 inches per hour are common over Rhode Island, western Connecticut, and much of Massachusetts this morning. Some of the heaviest bands are producing three inches of snow per hour, accompanied by thunder. The highest snowfall amounts in Massachusetts as of 6am EST were 14" at Goshen and Worthington. A few locations in the state may see as much as 20" from the storm.


Figure 1. Morning satellite image taken at 8:30am EST of the Nor'easter of January 12, 2011. Image credit: NASA/GSFC.

Winter misery continues in the South
Meanwhile, travel over much of the nation's South remains difficult this morning due to the winter storm that left up to a foot of snow and dangerous ice accumulations in its wake. Atlanta had all of its interstate highways open this morning, but continued icy conditions resulted in numerous crashes on area roads. With temperatures expected to remain below freezing in Atlanta and surrounding regions today, the area will be slow to shed its coasting of snow and ice. Temperatures will struggle to reach freezing on Thursday, and it is not until Friday that much of the South will see significant melting of their ice and snow. The South's storm began Sunday in northeast Texas and tracked eastward, bringing snow amounts as high as 7 - 8 inches to northeastern Texas and southern Arkansas, 9 - 11 inches to northern Mississippi, northern Alabama, South Carolina, North Carolina, and southern Tennessee. The heaviest snow as reported in the NOAA Storm Summary occurred in the Smoky Mountains at Bakersville, North Carolina--20 inches. The worst freezing rain was reported in central Georgia at Wrightsville, which received 1.5" of ice. Aiken, South Carolina received 1" of ice, and numerous locations in South Carolina, Central Georgia, and Central Alabama received over 1/2" of ice. Freezing rain amounts of 1/4" were also reported in northern Louisiana, central Mississippi, and western Arkansas.

According to our weather historian, Christopher C. Burt, in his blog post this morning titled, "Snowstorms in the South: A Historical Perspective", the 8.9" that fell on Huntsville, Alabama from this week's storm was that city's third heaviest snow on record. The post has a nice summary of the remarkable heavy snow storms that have hit the South in the past.


Figure 2. A unusually heavy snow storm for North Carolina dropped 20" on Bakersville in the Smoky Mountains, and 7 inches in Asheville, near where this photo was taken. Image credit: wunderphotographer jettking..

Extreme flooding continues in Australia
Flood-weary Queensland, Australia suffered a new flooding disaster on Monday when freak rains of six inches fell in just 30 minutes near Toowoomba. The resulting flash flood killed twelve people, and 40 are still missing. The flood waters poured into the Brisbane River, causing it to overflow, and significant flooding of low-lying areas in Brisbane, Australia's third largest city with some 2 million people, is expected on Thursday. At least 20,000 homes and businesses are expected to be inundated when the Brisbane River crests at a record 18 feet, according to media reports. The Australian Bureau of Meteorology (BOM) reports that an additional 100+ mm (4") of rain has fallen in the Brisbane area in the 24 hours ending at 9am local time this morning, further adding to the city's flood woes. No further significant rains are forecast in the Brisbane area until next week, though. According to the Australian Bureau of Meteorology, this is the most significant flooding event in Australia since at least the 1970s. In 2010, Australia had its wettest spring (September - November) since records began 111 years ago, with some sections of coastal Queensland receiving over 4 feet (1200 mm) of rain. Rainfall in Queensland and all of eastern Australia in December was the greatest on record, and the year 2010 was the rainiest year on record for Queensland. Queensland typically has its rainiest years when La Niña events occur, due to the much warmer than average ocean temperatures that occur along the coast. The BOM notes, "Previous strong La Niña events, such as those of 1974 and 1955, have also been associated with widespread and severe flooding in eastern Australia. Sea surface temperatures off the Queensland coast in recent months have also been at or near record levels." The BOM's annual summary also reported, "Sea surface temperatures in the Australian region during 2010 were the warmest value on record for the Australian region. Individual high monthly sea surface temperature records were also set during 2010 in March, April, June, September, October, November and December. Along with favourable hemispheric circulation associated with the 2010 La Niña, very warm sea surface temperatures contributed to the record rainfall and very high humidity across eastern Australia during winter and spring." Beginning in December, the Queensland floods have killed at least 22, and damage estimates are now as high as $13 billion. Queensland has an area the size of Germany and France combined.


Figure 3. Still frame from a remarkable 6-minute YouTube video showing the sad fate of a row of parked cars when a flash flood in Toowoomba, Queensland sweeps away dozens of the cars. A note to the wise: Two minutes into the video, we see a man enter the flash flood to save his car. He is successful, but his actions were extremely risky--most flash flood deaths occur when cars with people inside get swept away. I would not have attempted to save my car in that situation.

Jeff Masters

Flood Winter Weather

Updated: 2:34 PM GMT on January 12, 2011

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Snow, ice paralyze South; Nor'easter aims at New England; deadly floods in Australia

By: JeffMasters, 2:49 PM GMT on January 11, 2011

Much of the nation's South remains paralyzed today by a major winter storm that left up to a foot of snow and dangerous ice accumulations in its wake. Six states have declared states of emergency, and travel is extremely hazardous in the affected region, including Atlanta, where at least five closures of major interstates occurred this morning due to severe icing. The storm began Sunday in northeast Texas and tracked eastward, bringing snow amounts as high as 7 - 8 inches to northeastern Texas and southern Arkansas, 9 - 11 inches to northern Mississippi, northern Alabama, South Carolina, North Carolina, and southern Tennessee. As of 3am CST, the heaviest snow as reported in the NOAA Storm Summary occurred at Cashiers, North Carolina, 12.5 inches. The worst freezing rain was reported in central Georgia at Wrightsville, which received 1.5" of ice. Aiken, South Carolina received 1" of ice, and numerous locations in South Carolina, Central Georgia, and Central Alabama received over 1/2" of ice. Freezing rain amounts of 1/4" were also reported in northern Louisiana, central Mississippi, and western Arkansas. Dangerous travel conditions will persist across the affected region the rest of today, as temperatures will struggle to reach 40°.


Figure 1. Snow and ice at North Carolina's Charlotte airport caused travel delays yesterday, and thousands of flights were canceled Sunday and Monday across the Southeast U.S. due to the severe winter storm that hit the region. Image credit: wunderphotographer robb04047.

Major Nor'easter expected for New York City and Boston
Today's snow storm has pushed off the coast of North Carolina, and is expected to "bomb" into a classic Nor'easter off the coast of New England tonight through Wednesday. Up to a foot of snow is possible for New York City, Boston, Connecticut, and Rhode Island. The heaviest snow--up to 16 inches--will likely fall across central Massachusetts, eastern Connecticut, western Rhode Island, and Long Island. Today's Nor'easter will not be as intense as the December 26 blizzard, however. The winds from today's storm are expected to remain less than 35 mph, resulting in only minor coastal flooding and an absence of blizzard conditions (frequent wind gusts over 35 mph or sustained winds over 35 mph, plus visibility less than 1/4 mile for at least three consecutive hours.)

Deadly flash flood hits Australia
Flood-weary Queensland, Australia suffered a new flooding disaster yesterday when freak rains of six inches fell in just 30 minutes near Toowoomba. The resulting flash flood killed nine people and left 59 missing. The flood waters poured into the Brisbane River, causing it to overflow, and significant flooding of low-lying areas in Brisbane, Australia's third largest city with some 2 million people, is expected on Thursday. As I discussed last week, Australia had its wettest spring (September - November) since records began 111 years ago, with some sections of coastal Queensland receiving over 4 feet (1200 mm) of rain. Rainfall in Queensland and all of eastern Australia in December was the greatest on record, and the year 2010 was the rainiest year on record for Queensland. The ocean waters surrounding Australia were the warmest on record during 2010, and these exceptionally warm waters allowed much higher amounts of water vapor to evaporate into the atmosphere, helping fuel the heavy rains. The record warm ocean temperatures were due to a combination of global warming and the moderate to strong La Niña event that has been in place since July. Queensland typically has its rainiest years when La Niña events occur, due to the much warmer than average ocean temperatures that occur along the coast. Beginning in December, the Queensland floods have killed at least 19, and done $5 billion in damage. Queensland has an area the size of Germany and France combined.


Figure 2. Remarkable 5-minute YouTube video showing the sad fate of a row of parked cars when a nearby small stream experiences a flash flood, sweeping away dozens of the cars. A note to the wise: Two minutes into the video, we see a man enter the flash flood to save his car. He is successful, but his actions were extremely risky--most flash flood deaths occur when cars with people inside get swept away. I would not have attempted to save my car in that situation.

Jeff Masters

Flood Winter Weather

Updated: 8:17 PM GMT on January 11, 2011

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Dangerous winter storm slams South, heads to New England; Indiana sets snow record

By: JeffMasters, 3:14 PM GMT on January 10, 2011

A powerful winter storm has brought heavy snow and dangerous amounts of freezing rain to much of the South, in a swath stretching from northeastern Texas to southern North Carolina. The storm began Sunday in Texas, then tracked almost due east, bringing snow amounts of 8 - 11 inches to southern Arkansas, northern Mississippi, northern Alabama, and southern Tennessee. As of 9am CST, the heaviest snow amounts as reported in the NOAA Storm Summary were 11 inches at Lawrenceburg, TN and 10 inches at Baldwyn, MS. The worst freezing rain was reported in central Georgia at Fort Valley, where 3/4" of ice had accumulated. Texarkana, Arkansas, had 1/2" of ice. Freezing rain amounts of 1/4 inch were also reported over much of northern Louisiana, central Alabama, and central Mississippi. A nasty mix of up to four inches of snow, sleet, and freezing rain hit the Atlanta, Georgia area, causing the cancellation of thousands of flights at the world's busiest airport. The storm will bring an additional 2 - 6 inches of snow to eastern Tennessee, central South Carolina, and central North Carolina today, with significant freezing rain possible in northern Georgia and portions of North and South Carolina. Below-freezing temperatures are expected to remain over the region through Wednesday morning, resulting in a long period of dangerous travel conditions.

Major Nor'easter expected for New York City and Boston
Today's snow storm is expected to push off the coast of North Carolina tonight, then "bomb" into a classic Nor'easter off the coast of New England on Tuesday and Wednesday. Up to a foot of snow is possible for New York City, Boston, and coastal Connecticut and Rhode Island beginning on Tuesday night. The Nor'easter will not be as intense as the December 26 blizzard, however. The winds from the new storm are expected to remain less than 35 mph, resulting in only minor coastal flooding and an absence of blizzard conditions (winds in excess of 35 mph and visibility less than 1/4 mile.)

South Bend nearly sets all-time Indiana snowfall record
An epic lake effect snow storm hit South Bend, Indiana Friday and Saturday, burying the city under a remarkable 36.6" of snow. It was the heaviest two-day snow storm in South Bend's history, breaking a record that had stood since 1909 (a 29" snow storm on January 30 - 31.) The 32.6" that fell in a 24-hour period between 4pm EST 1/7 and 4pm EST 1/8 came just 0.4" short of matching Indiana's heaviest 24-hour snow storm on record. Indiana's heaviest 24-hour snow event was the 33.0" that fell at Salem in December 2004, according to wunderground's weather historian, Christopher C. Burt.


Figure 1. Snow from Saturday's record lake effect snow storm in South Bend, Indiana piles up. Photo by slowhiker.

While the current snow event is over, new snows are expected in South Bend beginning Wednesday, when a renewed strong northwesterly flow of air off of Lake Michigan will develop in the wake of the strong winter storm currently pounding the Southern U.S. Another 8+ inches of snow may fall in the South Bend area in the new storm.


Figure 2. True color satellite image of the South Bend, Indiana lake effect snow storm of Saturday, January 8, 2010 at 1:45pm EST. A well-defined band of heavy snow developed over Lake Michigan and anchored itself over South Bend, giving the city its heaviest snow storm on record. Image credit: NASA.

Jeff Masters

Winter Weather

Updated: 3:17 PM GMT on January 10, 2011

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Globe's coral reefs take second worst beating on record during 2010

By: JeffMasters, 4:50 PM GMT on January 07, 2011

Record warm ocean temperatures across much of Earth's tropical oceans during the summer of 2010 created the second worst year globally for coral-killing bleaching episodes. The warm waters, fueled in part by the El Niño phenomena, caused the most coral bleaching since 1998, when 16 percent of the world's reefs were killed off. "Clearly, we are on track for this to be the second worst (bleaching) on record," NOAA coral expert Mark Eakin in an interview last month. "All we're waiting on now is the body count." The summer 2010 bleaching episodes were worst in Southeast Asia, where El Niño warming of the tropical ocean waters during the first half of the year was significant. In Indonesia's Aceh province, 80% of the bleached corals died, and Malaysia closed several popular dive sites after nearly all the coral were damaged by bleaching. However, in the Caribbean's Virgin Islands, coral bleaching was not as severe as experienced in 2005, according to National Park Service fisheries biologist Jeff Miller. I'll discuss the reasons for this in a future blog post. In other portions of the Caribbean, such as Venezuela and Panama, coral bleaching was worse than that experienced in 2005.


Figure 1. An example of coral bleaching that occurred during the record-strength 1997-1998 El Niño event. Image credit: Craig Quirolo, Reef Relief/Marine Photobank, in Climate, Carbon and Coral Reefs

What is coral bleaching?
Coral bleaching is a whitening of the corals that occurs when stresses such as high water temperatures, increased water acidity, or pollution disturbs the symbiotic relationship between the corals and the algae that live inside them. Bleaching episodes occur when ocean temperatures rise above 85 - 87°F (29.5 - 30.5°C.) Peak warming events took place in the western Indian Ocean and north-western Pacific in 1997/98, in the north of Australia and central Pacific during 2003/04, and in the Caribbean in 2005. About half of the reefs affected by bleaching in these episodes have recovered, and one recent study cautions that non-lethal bleaching episodes and subsequent recovery of corals is often under-reported.

Australia's Great Barrier Reef at risk
With summer now in full swing in the Southern Hemisphere, coral bleaching concern now shifts to Australia's Great Barrier Reef. Ocean temperatures along the reef are currently up to 1°C above average, due, in part, to the current moderate to strong La Niña event. NOAA's Coral Reef Watch has issued its highest level of coral bleaching alert for the northern 2/3 of the Great Barrier Reef, since the La Niña event is predicted to persist into at least April. Also of concern is the tremendous run-off occurring in the wake of the record flooding that has affected the neighboring Australian province of Queensland. While the floods have now peaked and the rivers of Queensland are now falling, the $5 billion disaster dumped a large amount of sediments, pollutants, fertilizers, and pesticides into the southern portion of the Great Barrier Reef, and this will act to increase the stress on the corals. However, the floods may end up indirectly benefiting some portions of the Great Barrier Reef. The cloud cover and strong winds that accompanied the flooding rain storms also acted to cool the waters along the reef. According to an analysis I did of the UK Met Office Hadley Centre global ocean temperature data, sea surface temperatures along the southern portion of the reef, between 15°S and 20°S latitude, were the warmest ever for September, 1.27°C above average. These waters cooled significantly, relative to average, during October and November, and were just 0.12°C warmer than average during November. Cooler waters will mean less potential for coral bleaching, though the pollution in the flood run-off water may end up killing some corals.


Figure 2. Forecast stress on coral due to warm ocean temperatures for Australia, Jan - Apr 2011. The northern 2/3 of the Great Barrier Reef are under the highest alert level for coral bleaching. Waters are cooler along the southern portion of the reef, due, in part, to the storms that have brought record flooding to portions of Queensland, Australia. Image credit: NOAA Coral Reef Watch.

Long term outlook for world's coral reefs: grim
The large amount of carbon dioxide humans have put into the air in recent decades has done more than just raise Earth's global temperature--it has also increased the acidity of the oceans, since carbon dioxide dissolves in sea water to form carbonic acid. Corals have trouble growing in acidic sea water, and the combined effects of increasing ocean temperatures, increasing acidity, pollution, and overfishing have reduced coral reefs globally by 19 percent since 1950. Another 35 percent could disappear in the next 40 years, even without the impact of climate change, according to a report released in October 2010 by the World Meteorological Organization and the Convention on Biological Diversity. Coral loss has been the most severe in Earth's hottest ocean, the Indian Ocean. Up to 90% of coral cover has been lost in the Maldives, Sri Lanka, Kenya and Tanzania and in the Seychelles. Global warming has heated up most of the tropical ocean surface waters by about 0.5°C (0.9°F) over the past 50 years, and the remarkable bleaching episodes of 1998 and 2010 both occurred when strong (natural) El Niño episodes heated up Pacific tropical waters to record levels. If the Earth continues to heat up this century as expected, coral bleaching episodes will grow more frequent and intense, particularly during strong El Niño episodes. The twin stresses of ocean acidification and increasing ocean temperatures will probably mean that by 2050, it will be difficult for any coral reefs to recover when subject to additional stresses posed by pollution or major storms, according to a talk presented by Stanford climate scientist Ken Caldeira at last month's American Geophysical Union (AGU) meeting.


Figure 3. Departure of sea surface temperature in the Australian region over the past one hundred years, year-by-year (red line), and decade-by-decade (grey bars.) The 2010 value is preliminary and does not include data for December 2010. If ocean temperatures and ocean acidity continue to rise in Australian waters at the same pace as has occurred over the past 100 years, the Great Barrier Reef will be in significant danger by 2050. Image credit: Australian Bureau of Meteorology.

Coral expert J.E.N. Veron, former chief scientist of the Australian Institute of Marine Science, had this to say in an excellent interview he did with Yale Environment 360 last year: "the science is clear: Unless we change the way we live, the Earth's coral reefs will be utterly destroyed within our children's lifetimes.

"You may well feel that dire predictions about anything almost always turn out to be exaggerations. You may think there may be something in it to worry about, but it won't be as bad as doomsayers like me are predicting. This view is understandable given that only a few decades ago I, myself, would have thought it ridiculous to imagine that reefs might have a limited lifespan on Earth as a consequence of human actions. It would have seemed preposterous that, for example, the Great Barrier Reef--the biggest structure ever made by life on Earth--could be mortally threatened by any present or foreseeable environmental change. Yet here I am today, humbled to have spent the most productive scientific years of my life around the rich wonders of the underwater world, and utterly convinced that they will not be there for our children's children to enjoy unless we drastically change our priorities and the way we live."

Reefs are the ocean's canaries and we must hear their call. This call is not just for themselves, for the other great ecosystems of the ocean stand behind reefs like a row of dominoes. If coral reefs fail, the rest will follow in rapid succession, and the Sixth Mass Extinction will be upon us--and will be of our making.


I might add that not only are reefs the ocean's canaries, they are incredibly valuable in their own right. According to the World Meteorological Organization, coral reefs provide economic services--jobs, food and tourism--estimated to be worth $30 billion per year. NOAA put this figure at twelve times higher, $375 billion each year. Corals cover just 0.2% of the world's oceans, but contain about 25% of all marine species.

Next post
I'll be back with a new post on Tuesday at the latest.

Check out wunderground weather historian Christopher C. Burt's post on the notable weather extremes of December 2010. It was truly an extreme month!

Jeff Masters

Climate Change

Updated: 4:55 PM GMT on January 07, 2011

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Top U.S. weather event of 2010: Snowmageddon

By: JeffMasters, 4:44 PM GMT on January 05, 2011

As we ring in the new year, it's time to look back on 2010 and reflect upon what a remarkable weather year it was. Today, I'll focus on the U.S. While 2010 certainly had its share of violent and destructive weather events in the U.S., I am thankful for two things:

1) The sustained period of northerly winds needed to blow oil from the Deepwater Horizon catastrophe into the Loop Current never materialized, and the Florida Keys and U.S. East Coast were spared oil damage.

2) The 3rd busiest Atlantic hurricane season on record resulted in minimal damage to the U.S., with only one minimum strength tropical storm (Bonnie) making direct landfall in the U.S.

Here, then, is my list of the top three most significant weather events in the U.S. in 2010:

#1: Snowmageddon
The top U.S. weather story of 2010 has to be "Snowmageddon", the remarkable February blizzard that buried the mid-Atlantic under 2 - 3 feet of snow. Snowmageddon set the all-time record for heaviest snowfall in Delaware history, thanks to the 26.5" that fell in Wilmington (old state record: 25" in the President's Day storm of 2003). "Snowmageddon" dumped the second heaviest at Philadelphia 28.5"), second heaviest at Atlantic City (18.2"), third heaviest at Baltimore (24.8"), and the 4th heaviest at Washington D.C. (17.8"). Several locations in Maryland saw over three feet of snow, with the northern Washington D.C. suburb of Colesville receiving 40", and the southern Baltimore suburb of Elkridge receiving 38.3". While the blizzard was not an exceptionally strong storm--the central pressure was a rather unimpressive 986 mb at the height of the blizzard--it was an exceptionally wet storm. The melted equivalent precipitation for the blizzard exceeded three inches along its core snow belt. That's an phenomenal amount of moisture for a winter storm. The blizzard formed a very unstable region aloft where thunderstorms were able to build, and there were many reports of thundersnow during the height of the storm. These embedded thunderstorms were able to generate very heavy snow bursts of 2 - 3 inches per hour.

"Snowmageddon" was followed just three days later by a second massive snowstorm which dumped another 1 - 2 feet of snow on the mid-Atlantic. By the time the flakes stopped flying, Washington D.C., Philadelphia, Wilmington, and Atlantic City all had their snowiest winters on record. The February snowstorms killed 41 people and did up to $2.4 billion in damage, according to the Insurance Information Institute.


Figure 1. There's a car under here somewhere! Maryland resident digs out after Snowmageddon. Image credit: wunderphotographer chills.

#2: The Tennessee and Nashville floods
An atmospheric river of moisture originating in the East Pacific subtropics surged northwards into the southeast U.S. during the first two days of May, unleashing unprecedented rains that caused a 1000-year flood in Tennessee, Kentucky, and northern Mississippi. The floods killed 31 people, making it the deadliest non-tropical storm or hurricane flood disaster in the U.S. since the October 1998 Central Texas floods that killed 31 when a cold front stalled over Texas. The 2010 flood did more than $1.5 billion in damage, much of it in Nashville, Tennessee, where ten fatalities were reported. The city had its heaviest 1-day and 2-day rainfall amounts in its history. A remarkable 7.25" of rain fell on May 2, breaking the record for most rain in a single day (6.60", set September 13, 1979.) Nashville's third greatest day of rainfall on record occurred on May 1, 2010, when 6.32" fell. Nashville also eclipsed its greatest 6-hour and 12-hour rainfall events on record during the May 2 deluge, with 5.57" and 7.20", respectively. By the end of May 2, it was already the rainiest May in Nashville's history. Rainfall records were smashed all across Tennessee and Kentucky, with amounts as high as 17.73" recorded at Camden, TN, and 17.02" at Brownsville, TN. According to Christopher C. Burt, the author of the excellent book Extreme Weather, the 13.30" that fell on Camden in 24 hours just missed eclipsing the state's all-time 24-hour precipitation record, the 13.60" inches that fell on Milan on September 13, 1982.


Figure 2. Parking via Mother Nature. A scene in Nashville after the May, 2010 flood. Image credit: wunderphotographer jannash.

#3: May 10 tornado outbreak
On May 10, a massive tornado outbreak affected large areas of Oklahoma, Kansas, and Missouri, with the bulk of the activity in central and eastern Oklahoma. Over 60 tornadoes, including two violent EF-4 twisters and six strong EF-3s, hit the region. The tornadoes and associated severe thunderstorms caused approximately $2 billion in damage, according to Swiss Re Insurance Company. The most destructive tornadoes caused severe damage in southern suburbs of the Oklahoma City metropolitan area and just east of Norman, Oklahoma. Three people were killed by the tornadoes.


Figure 3. Video of the May 10, 2010 tornado near Norman, OK. Dr. Rob Carver's blog has many more videos from this spectacular outbreak linked.

I'll be back with a new post on Friday.

Our extreme weather blogger, Christopher C. Burt, has an interesting post on historic episodes where large numbers of dead birds have fallen from the sky.

Jeff Masters

Climate Summaries Winter Weather

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Massive flooding in Australia cuts off city of 75,000

By: JeffMasters, 1:52 PM GMT on January 03, 2011

The arrival of the new year has brought continued misery to northeast Australia, where unprecedented flooding continues in the wake of weeks of torrential rains. The floods have killed at least ten people and covered an area the size of France and Germany combined, cutting off the coastal city of Rockhampton. Today, the military was forced to fly in food, water, and other supplies into Rockhampton, a city of 75,000, due to the lack of unflooded roads into the city. The local airport, all access roads, and all rail lines into the city are closed. The flooding has affected at least 21 other towns, and 200,000 people in northeast Australia. Australian Prime Minister Julia Gillard stated last week, "Some communities are seeing flood waters higher than they've seen in decades, and for some communities flood waters have never reached these levels before [in] the time that we have been recording floods." According to the National Climatic Data Center, springtime in Australia (September - November) had precipitation 125% of normal--the wettest spring in the country since records began 111 years ago. Some sections of coastal Queensland received over 4 feet (1200 mm) of rain from September through November. Rainfall in Queensland and all of eastern Australia in December was the greatest on record, and the year 2010 was the rainiest year on record for Queensland. The heavy rains are due, in part, to the moderate to strong La Niña event that has been in place since July. The relatively warm waters that accumulate off the northeast coast of Australia during a La Niña typically cause heavy rains over Queensland.


Figure 1. Comparison of river conditions in Queensland from today to December 30, 2010. While some rivers have fallen below major flood stage, the Fitzroy River at Rockhampton is rising, and may peak at levels not seen since 1918 on Wednesday. Image credit: Australian Bureau of Meteorology.


Figure 2. Rainfall in Queensland, Australia for December, 2010. Image credit: Australian Bureau of Meteorology.

The rains over Queensland continued yesterday and today, with many of the flooded regions receiving 1/2 - 1 inch (about 12 - 25 mm) of rain. Total rainfall amounts in the flood region over the past month are generally in the 16 - 24 inch range (400 - 600 mm). Predicted rainfall amounts for the next two days in the flooded region are less than 1/2 inch (12 mm), which should allow for river levels to peak by Tuesday or Wednesday, then slowly fall. However, heavy rains are predicted to affect the area again by Thursday, and it may be several weeks before the summer rains ease enough to allow all of Queensland's rivers to retreat below flood stage. Damage to infrastructure in Australia has been estimated at over $1 billion by the government, and economists have estimated the Australian economy will suffer an additional $6 billion in damage over the coming months due to reduced exports, according to insurance company AIR Worldwide. Queensland is Australia's top coal-producing state, and coal mining and delivery operations are being severely hampered by the flooding. Damage to agriculture is currently estimated at $400 million, and is expected to rise.

Jeff Masters

Flood

Updated: 12:24 PM GMT on January 04, 2011

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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.