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All-Time Heat Records Broken in . . . Alaska?!

2013-06-18T15:20:11+00:00

A massive dome of high pressure, sometimes referred to as a "heat dome," has set up shop over Alaska, bringing all-time record temperatures just a few weeks after parts of the state had a record cold start to spring. In some cases, towns in Alaska were warmer on Monday and Tuesday than most locations in the lower 48 states.

Forecast temperature anomalies on June 19 from the GFS computer model.
Click image to enlarge. Credit: WeatherBell.com.

For example, Talkeetna set an all-time high temperature record of 96°F on Monday, smashing its previous mark of 91°F set a day earlier, and previously set in June of 1969. In fact, it was warmer in Talkeetna, which is about 110 miles north of Anchorage, than it was in Miami, based on data from the National Weather Service (NWS). (As Weather Underground's Christopher Burt notes, there was an unofficial observation of 98°F on Monday, which would rank among the hottest all-time temperature records for the state.)

In Valdez, which sits along the cool waters of Prince William Sound, the temperature reached a remarkable 90°F Monday, beating the previous all-time mark of 87°F. And in Seward, another coastal port, the temperature hit 88°F, breaking the previous all-time high of 87°F that was set on July 4, 1999.

Here is how the National Weather Service described the Valdez record (the ALL CAPS style is from the original public statement):

EXCITEMENT ABOUNDED THIS AFTERNOON ACROSS NORTHEASTERN PRINCE WILLIAM SOUND AS UNUSUALLY HOT TEMPERATURES WERE FELT ACROSS THE REGION. FOR THE PAST SEVERAL DAYS . . . HIGH TEMPERATURE RECORDS HAVE BEEN TIED OR BROKEN . . . BUT TODAYS TEMPERATURES SOARED BEYOND ANYTHING PREVIOUSLY SEEN IN THIS AREA.

IN VALDEZ . . . THE DAILY HIGH TEMPERATURE RECORD OF 75 DEGREES SET IN 1997 WAS SHATTERED WHEN . . . AT 45 MINUTES AFTER 3 PM...THE MERCURY IN OUR THERMOMETER SHOT UP TO 90 DEGREES. AFTER A BRIEF DIP BACK INTO THE UPPER 80S . . . THE MERCURY AGAIN REGISTERED 90 DEGREES AT 15 MINUTES BEFORE 6 PM.

THIS ALSO CRUSHED THE ALL-TIME RECORD HIGH TEMPERATURE FOR ANY DAY OF THE YEAR . . . AND FOR THE MONTH OF JUNE . . . WHICH WAS 87 DEGREES AND WAS ACHIEVED TWICE . . . ON BOTH THE 25TH AND THE 26TH OF JUNE IN 1953. A LOCAL WEATHER SPOTTER IN TOWN RECORDED A HIGH TEMPERATURE OF 87 DEGREES NEAR THE HOSPITAL DURING THE MID-AFTERNOON HOURS TODAY AS WELL. SUN-WORSHIPERS WERE OUT IN FORCE THROUGH THE MID TO LATE EVENING HOURS . . . AS THE TEMPERATURE AT 10 PM WAS STILL AN ASTOUNDING 77 DEGREES.

Extreme heat was also felt across the interior of Alaska, where hot temperatures are expected to continue this week until the large high pressure area, or ridge in the jet stream, weakens and moves away. The heat, combined with low relative humidity and the chance for thunderstorms, is raising the risk of wildfires across parts of Alaska.

A map of the upper level air flow at about 18,000 feet. The bright red area over Alaska corresponds to an unusually strong area of High Pressure bringing warmer-than-average temperatures.
Click image to enlarge. Credit: WeatherBell.com.

On Tuesday June 18, McGrath set a record high of 91°F, beating the old record of 84°F set in 1962. Record highs were also broken or tied at Eielsen Air Force Base and Tanana, the NWS said.

On Sunday, Tanana, Delta Junction, Northway, and McGrath all set set record-high temperatures.

The 90°F and 91°F readings in McGrath, a small town located about 220 miles northwest of Anchorage, are extremely unusual, and it comes on the heels of record cold that occurred during late May.

On May 18, McGrath set a record for the coldest temperature recorded there so late in the season, at 15°F. Fairbanks had an average temperature for the month of May that was 5.1°F below average.

In Nome, the high temperature reached 84°F Monday, breaking the record for June. The highest recorded temperature there for any month is 86°F, which could be within reach Tuesday.

Alaska is one of the fastest-warming states in the U.S., largely because the nearby Arctic region is warming rapidly in response to manmade global warming and natural variability. In recent years, Alaska has had to content with large wildfires, melting permafrost, and reduced sea ice, among other climate-related challenges.

Tropical Storm Andrea Brings Heavy Rain to East Coast

2013-06-07T14:19:14+00:00

Tropical Storm Andrea is barrelling up the eastern seaboard after bringing heavy rain, high winds, a modest storm surge, and nearly a dozen tornadoes to Florida on Thursday. The storm is mainly a rain producer now, and is losing its tropical characteristics as it moves from the Carolinas northeastward to a position near Nantucket Island by Saturday morning, according to the National Hurricane Center.

Tropical Storm Andrea covered most of the East Coast on Friday morning.
Click on the image to enlarge. Credit: NASA via CIMSS.

The storm is sending a plume of tropical moisture up the East Coast, hugging the I-95 corridor, and 2 to 4 inches or more of rainfall is falling from South Carolina to Maine. The rainfall is already causing flash flooding, and may result in river flooding as well, particularly in the Mid-Atlantic and Northeast. The National Weather Service forecast office in New York City warned of potential rainfall rates of 1 inch per hour for several hours on Friday afternoon and Friday night.

Forecast total rainfall from Tropical Storm Andrea, showing the bullseye right along the Mid-Atlantic and Northeast coastline.
Click on the image to enlarge. Credit: NOAA/HPC.

The storm’s strongest winds are mainly confined to the immediate coastline of the Carolinas, and as the remnants of Andrea move northeast, the wind field is likely to stay offshore, sparing the I-95 corridor of tropical storm force winds, although it will still be windy.

Minor storm surge flooding is possible from the Carolinas to Virginia, but is not a threat for the Chesapeake Bay or New Jersey coastline, which is good news after the devastation wrought by Hurricane Sandy last year.

Satellite animation of T.S. Andrea as it made landfall in Florida's Big Bend region on June 6. Credit: NOAA.

In Florida, Tropical Storm Andrea spawned nearly a dozen tornadoes, dumped 3 to 6 inches of rain, and caused a maximum storm surge of 4.55 feet at Cedar Key. The peak wind gust recorded in the Sunshine State was 58 mph in St. Petersburg.

NASA’s Beautiful Animation of Hurricane Sandy’s Winds

2013-06-06T18:57:55+00:00

NASA never fails to capture dazzling images of our home planet, and on Thursday it released an animation of 2012's Hurricane Sandy that almost — almost — makes you forget how devastating that storm actually was. It's a stunningly beautiful 43-second video, replete with its own soundtrack, albeit a soundtrack that evokes Yanni on Xanax.

Musical notes aside, the video shows the output of a computer model known as NASA's GEOS-5 global atmosphere model, which was one of many computer models to project the storm's unusual path, strength, and structure.

Don't Have Flash? Watch this video on your iPad or iPhone here

Credit: NASA's Goddard Space Flight Center and NASA Center for Climate Simulation. Video courtesy of NASA/GSFC/William Putman.

The NASA model not only produced an accurate track of Sandy, but also captured fine-scale details of the storm’s changing intensity and winds, NASA said. The video provides insight into the storm's near-surface wind field, and the weather systems that were around it, forcing it to make a never-before-seen left turn straight into the New Jersey coastline, causing severe damage along the New Jersey Shore and flooding parts of New York City.

Hurricane Sandy pummeled the East Coast late in 2012’s Atlantic hurricane season, causing 159 deaths and between $50 and $100 billion in damage.

If you like this video, you should check out these other NASA Sandy visuals, and these loops that were made by a separate team of researchers.

Tornadoes Rake Okla., Kansas as Storm Threat Continues

2013-05-20T14:39:22+00:00

A tornado outbreak on Sunday left at least two people dead in Oklahoma and nearly two dozen injured after the busiest day in what had been an unusually tame 2013 tornado season.

The Shawnee, Okla., tornado that caused major damage southeast of Oklahoma City on May 19.
Credit: TornadoTitans.com/Brett Wright via Facebook.

Severe thunderstorms struck from Oklahoma all the way to Minnesota as a strong cold front edged eastward, plowing into warm and humid air. Strong upper-level winds provided support for supercell thunderstorms, which are thunderstorms that have persistent rotation associated with them, and can cause tornadoes and damaging large hail.

Video footage of the Shawnee, Okla., tornado from Brandon Sullivan/Wicked Wind Media

Several cities narrowly missed direct hits, including Oklahoma City and Wichita, Kan. In Wichita, a tornado touched down near the Mid-Continent Airport, and a “tornado emergency” was declared for the city. On the livefeed of KSN-TV’s storm coverage, the sound of large hail striking the studio’s rooftop was audible, and the TV meteorologists hastily retreated to the station’s storm shelter, leaving an eerily silent radar image on the screen.

A total of 24 tornado reports were received by the Storm Prediction Center in Norman, Okla. The Weather Channel broadcast at least two large tornadoes live as they formed and strengthened, including one of the most damaging twisters, which struck near Shawnee, Okla. The National Weather Service gave the Shawnee tornado a preliminary rating of EF-4 on the Enhanced Fujita Scale, with winds of up to 200 mph.

Footage from KSN-TV in Wichita as the news team moved to their storm shelter.

According to news reports, the worst of the damage in Oklahoma was centered on the Steelman Estates Mobile Home Park, which is located about 35 miles southeast of Oklahoma City.

CBS News provided this report from a mobile home park resident:

"It took a dead hit," resident James Hoke said. Emerging from a storm cellar where he sought refuge with his wife and two children, Hoke found that their mobile home had vanished. "Everything is gone."

Hoke said he started trying to help neighbors and found his wife's father covered in rubble.

"My father-in-law was buried under the house. We had to pull sheetrock off of him," Hoke said.

More severe thunderstorms were expected Monday, with Oklahoma City, Tulsa, and Springfield, Mo., at the highest risk for severe storms, according to the Storm Prediction Center. The threat for severe weather also extends south to Dallas, and northward into the Midwest, including Chicago, Indianapolis, and Detroit.

The tornado outbreak over the weekend follows a deadly outbreak in Texas on May 15, when six people were killed by more than a dozen tornadoes.

So far, there’s simply not enough information to say anything definitive about the future of tornadoes under climate change. Studies of how the environment that gives rise to severe thunderstorms and tornadoes may change as global warming continues shows that the number of thunderstorm days may increase in parts of the U.S. — owing to an upward trend in heat and humidity — but wind shear may decrease, which could curtail tornado numbers.

Deadly Texas Outbreak May Mark End of Tornado Drought

2013-05-16T14:49:45+00:00

After months with record-low activity, the 2013 tornado season roared back with a vengeance on Wednesday as at least 10 twisters touched down across portions of north-central Texas, killing at least 6 and injuring dozens more. An even broader outbreak of severe weather, including the threat of more tornadoes, is forecast this weekend from North Texas to Missouri, gradually shifting eastward with time.

Eyewitness video of one of the Texas tornadoes on Wednesday.

The hardest-hit community on Wednesday evening was Granbury, about 40 miles southwest of Fort Worth. Hood County Sheriff Roger Deeds told the media that an entire neighborhood, consisting of 100-plus homes, was “heavily damaged to destroyed.”

There were reports that the Granbury tornado was as large as 1-mile wide, and aerial footage on Thursday morning revealed a broad swath of destruction. The town received a tornado warning 20 minutes in advance, according to Reuters. Preliminary reports from the National Weather Service show the tornado was at least an EF-4 on the Enhanced Fujita Scale, with winds of between 166 to 200 mph. Damage surveys have found homes that were completely swiped aside, and reduced to mere concrete slabs.

The Texas tornado fatalities were the second in the Lone Star State since 2007 — an unusually long stretch for a state that typically sees 8 deaths per year, based on statistics from 1961-1990.

For the U.S., the deadly outbreak shatters the relative calm of the 2013 tornado season, which was following an apparent record in 2012 for the fewest tornadoes during any 12-month period, dating back to 1954. But the country is just two years removed from one of the deadliest and busiest tornado seasons on record.

Aerial image of the damage near Granbury, Texas on Wednesday night.
Credit: Twitter via Kristin Walls.

The National Severe Storms Laboratory (NSSL) in Norman, Okla., estimated that between May 2012 and April 2013, there were just 197 tornadoes ranked EF-1 or stronger. That tops the previous 12-month low of 247 tornadoes from June 1991 and May 1992.

Tornado researcher Harold Brooks wrote on NSSL’s blog that the death toll from tornadoes during the past 12 months was also flirting with a record low, with seven tornado fatalities during that period. That's the lowest 12-month tornado death toll on record dating to 1950, but research has shown that the 12-month period starting in September 1899 may have been even quieter, with five fatalities.

The U.S. did set a record for the longest streak of days without a tornado-related fatality — at 220 days — between June 24, 2012 and Jan. 26, 2013. And July 2012, which was the hottest month on record in the U.S., saw the fewest tornadoes on record for any July.

Doppler Radar image showing the classic "hook echo" signature of the Granbury tornado.
Credit: RadarScope.

The severe drought that has gripped much of the U.S. for more than a year was the most likely leading cause of the plunge in tornado activity, since it helped squelch thunderstorms by robbing the atmosphere of necessary moisture. In addition, this spring, a persistent dip, or trough, in the jet stream across the West, Midwest, and South Central states has also inhibited widespread severe thunderstorm activity, instead resulting in record cold and record-breaking spring snowfall.

April 2013 contrasted sharply with April 2011, which set the record for the most tornadoes of any month on record, with 358. The weather pattern then, though, consisted of a westerly air flow across the U.S., with low-pressure systems that brought slow-moving cold fronts that collided with warm, moist air from the Gulf of Mexico, yielding major severe weather outbreaks. Now that weather patterns are changing, with the drought shifting to encompass mainly the Western U.S., and the unusually cold air retreating back to the north, severe weather in the Plains and Midwest is becoming more likely, forecasters said.

The U.S. may see more tornadoes this weekend as a storm system draws moisture north from the Gulf of Mexico, where it will meet a cold front with an energetic jet stream aloft. These jet stream winds will help give the thunderstorms a key ingredient necessary for tornadoes to form — wind shear — which occurs when winds blow in different directions with height.

Rare May Snowstorm Annihilates Records in Midwest

2013-05-03T14:37:41+00:00

A late spring snowstorm in the Midwest has shattered longstanding state snowfall records, with all-time state records for the month of May falling in Iowa, Minnesota, and Wisconsin. The snowstorm, which walloped the region with snowfall rates of more than an inch per hour at times on May 1-2, delivered 18 inches of snow in Blooming Prairie, Minn., 17.5 inches in Goodhue, and 15.5 inches in Owatonna.

Snowfall measurement in Eau Claire, Wis.
Credit: NWS.

According to the Minnesota Climate Working Group, the state daily May snowfall record had stood at 12 inches, which was most recently set on May 3, 1954. The Working Group said that the snowstorm was extremely rare for southern parts of the state.

“While May snowfalls are not uncommon in northern Minnesota, heavy May snowfall in southern Minnesota is rare. A quick scan of all historical Minnesota May daily snowfall totals greater than or equal to 3 inches indicates that May 1938 may have been the last time any southern Minnesota observer reported snowfall totals of similar magnitude,” the Working Group said on its website.

In Iowa, the 11 inches recorded at the town of Britt, which is in the north central part of the state, is also likely a state record. The 6.7 inches that fell in Des Moines was the city's biggest May snowstorm on record. In Wisconsin, 16.2 inches fell at Ashland, which also set a state record for the heaviest May snowstorm on record.

Also, up to 3 inches of snow fell in Arkansas, where measurable snow had never before been recorded in May.

One of the major impacts of climate change on the U.S. has been an increase in extreme precipitation events, such as record daily rain and snowstorms, according to a forthcoming federal climate assessment. As air and water temperatures warm, the more moisture is added to the atmosphere, where it can be tapped by storms to produce heavier amounts of rain or snow.

The storm resulted from a sharp dip in the jet stream across the West and Midwest, which drove cold air southward from Canada, causing record-cold temperatures as far south as Texas. Meanwhile, to the east, an area of high pressure over the eastern seaboard, and an area of low pressure in the upper layers of the atmosphere over the Western Atlantic, effectively blocked the eastward progress of the storm, keeping it in place for more than 24 hours and allowing it to dump heavy amounts of precipitation.

Map of upper-level winds, with annotations to show upper level Lows (L) and Highs (L) along with the general direction of upper level winds.
Click image to enlarge. Credit: Weatherbell.com/Climate Central.

Meteorologists refer to this type of weather pattern as an Omega Block, since the upper air flow’s twists and turns resemble the Greek letter omega.

The frontal boundary that dumped the snowfall is moving eastward, and it is expected to bring potentially flooding rains to the Lower to Middle Mississippi and Tennessee River Valleys

As the National Weather Service reported in an online forecast discussion, “The sluggish progression of the front . . . combined with plenty of moisture streaming out of the Gulf and Atlantic . . . should fuel an organized band of moderate to heavy rains along the front. Flooding and flash flooding will be a concern with this system . . . especially as it dumps rain on the already swollen rivers of the Mississippi."

The weather pattern has contributed to overall colder-than-average and wetter-than-average conditions during the past month across the West, parts of the Plains, and Midwest. Between April 3 and May 2, for example, 4,133 daily record-low temperatures were set across the lower 48 states, compared to just 656 daily record highs. In addition, 1,166 daily snowfall records were set during this period, according to the National Climatic Data Center in Asheville, N.C.

Twin Cities Narrowly Escape Record May Snowstorm

2013-05-02T14:20:02+00:00

Minneapolis-St. Paul narrowly missed a crushing, record-smashing snowstorm on Wednesday night into Thursday, as a band of extremely heavy snow stalled over the eastern suburbs of the Twin Cities. As of Thursday morning, some locations in southeast Minnesota had received more than 15 inches of snow, which is unprecedented this late in the year. Western Wisconsin was also seeing heavy snow, with more than a foot already on the ground and more to come throughout the day.

Records have likely been broken for single-day May snowfall in Iowa, Minnesota, and Wisconsin, and state snowfall records for the month of May have also been threatened in these states. The snow has been causing power outages by weighing down tree branches and power lines.

The snowy scene in Owatonna, Minn., on Thursday.
Credit: Twitter/Christian McKenzie

Had the storm hit only 50 miles or so further northwest, the Twin Cities would have been in the bullseye for at least a foot of snow, which would have shattered the all-time May snowfall record there, which stands at just 3 inches. That record, which was expected to be broken, may not be exceeded after all, since most of the snow has remained to the east of the Minneapolis-St. Paul International Airport, where official weather records are taken.

The freakishly heavy May snow totals in Minnesota, along with a barrage of similar storms during April, have helped to erase the long-term drought in the area, and in fact, have raised flooding concerns. As WeatherNation TV meteorologist Paul Douglas described the situation on his blog: “This is the price we're paying for a rapid easing of drought conditions," he wrote. Douglas noted a big dip in the jet stream across the Midwest and West, saying it is functioning "like a storm incubator . . . pulling moisture north out of the Gulf of Mexico, turning many Midwest counties from drought to flood in the meteorological blink of an eye.”

The weather whiplash seen in parts of the Midwest and Mississippi River Valley in recent years is consistent with climate change projections for more frequent and severe extreme weather events, including heavy precipitation events.

The snow in Minnesota comes courtesy of the same weather system that brought frigid conditions and significant snowfall to Colorado and Wyoming on Tuesday and Wednesday. The biggest snowfall in Colorado was Buckhorn Mountain, which received 28.2 inches. Fort Collins had 16 inches, Breckenridge ski area reported 15.3 inches of snow, and the Denver metro area saw 5 to 12 inches of snow.

24-hour temperature change in Oklahoma, showing drops of 30°F or more in some spots.
Credit: Oklahoma Mesonet.

In Wyoming, Warren Air Force Base, which is home to an Intercontinental Ballistic Missile squadron, received a foot and a half of snow, and Cheyenne picked up 15 inches.

Heavy snow also fell in Iowa, where numerous reports of 6 inches were noted, along with one report of 11 inches.

As Climate Central reported on Wednesday, the rare May snowstorm has been accompanied by an unusual surge of cold air that has reached all the way to southeast Texas. In Oklahoma on Thursday morning, temperatures were as much as 30°F colder than they were 24 hours earlier. According to the Capital Weather Gang blog, Boulder, Colo. saw a low temperature on Wednesday night of 17°F, which was both a daily and monthly record low. And in Laramie, Wyoming, the temperature fell to 7 degrees, its coldest May temperature on record.

Record-low temperatures are also forecast for parts of Texas, possibly including the Houston metro area, through the weekend.

Watch 62 Years of Global Warming in 13 Seconds

2013-05-02T13:41:30+00:00

Don't Have Flash? Watch this video on your iPad or iPhone here

From our friends at NASA comes this amazing 13-second animation that depicts how temperatures around the globe have warmed since 1950. You’ll note an acceleration of the temperature trend in the late 1970s as greenhouse gas emissions from energy production increased worldwide and clean air laws reduced emissions of pollutants that had a cooling effect on the climate, and thus were masking some of the global warming signal.

The data come from NASA's Goddard Institute for Space Studies in New York (GISS), which monitors global surface temperatures. As NASA notes, “All 10 of the warmest years in the GISS analysis have occurred since 1998, continuing a trend of temperatures well above the mid-20th century average."

Winter is Coming: Texas, Midwest Bracing for Cold

2013-05-01T17:22:14+00:00

Winter is coming . . . back, that is.

A sharp cold front is ushering in some of the coldest temperatures on record for the month of May in the southern Plains and into Texas, with temperatures plummeting from the mid-90s on Tuesday in Amarillo, Texas, to the upper 20s on Wednesday night. Houston may be in line to set a record for the coldest May day on record if the low temperature on Friday or Saturday morning falls to 43°F.

These before and after images showing the profound temperature change as the cold air sags south, toward the Gulf of Mexico. Thee images come from computer-model projections:

Surface temperatures on Wednesday afternoon.
Credit: Weatherbell.com.

Forecast surface temperatures on Friday morning for the same region.
Credit: Weatherbell.com.

As an example of the cold front's strength, consider that as of 1 p.m. Central time on Wednesday, it was snowing and in the mid-30s in northwestern Iowa, while in southeast Iowa, on the warm side of the front, it was partly cloudy and near 80°F.

According to Houston Chronicle science reporter Eric Berger, Houston has only had one May day in recorded history with a temperature below 45°F.

The cold front may even be accompanied by light snow and sleet in parts of Oklahoma and the Texas Panhandle. Here's how the National Weather Service forecasters in Tulsa, Okla,. described the cold front in an online discussion (the all-caps format is NWS style): "AN ALMOST UNBELIEVABLY STRONG COLD FRONT FOR EARLY MAY WILL BLAST THROUGH THE AREA WED NIGHT AND VERY EARLY THURSDAY MORNING . . . AS FAR AS I KNOW . . . SNOW HAS NOT FALLEN IN MAY IN OUR FORECAST AREA IN THE PERIOD OF RECORD SO WE ARE TALKING ABOUT AN UNPRECEDENTED EVENT."

Heavier snows were falling Wednesday across the Denver metro region, where 6 inches or more of snow may fall, with more than 2 feet likely in the Rocky Mountains. Colorado residents are no doubt tired of the cold and snow after the snowiest April on record in some spots, and low temperatures that frequently dipped into the teens to single digits. A major plus to the snow, though, is that it is lessening the drought and at least temporarily dampening the wildfire risk across much of the Rocky Mountain State.

Computer-model projections show that a narrow strip of accumulating snow may extend across parts of Nebraska, Minnesota and northwest Wisconsin through Friday. Minneapolis may break its record for the biggest May snowstorm, which is 3 inches, recorded in 1946.

The snowy scene in Boulder, Colo. on Wednesday morning.
Credit: Claudia Tebaldi, Climate Central.

According to Paul Douglas of WeatherNation TV, since 1891 there have only been five 2-inch-or-greater snowfalls in the Minneapolis-St.Paul.

“Numbing air over central Canada, displaced unusually far south, is responsible for this March-like time warp — enough cold air in the lowest mile of the atmosphere for an historic slush-storm,” Douglas wrote on his blog. “The ground is warm (it was 81°F Sunday) so any snow will melt on contact this afternoon but we may still wake up to a slushy 2-5" by Thursday AM. A plowable 3-7" snow may fall on some suburbs. Unreal.”

The cold and snow is the result of a persistent dip in the jet stream across the Midwest and parts of the West, which has allowed cold, Canadian air masses to move southward into those regions. The weather pattern has been largely stuck during the past month, courtesy of a "blocking high" over Greenland that is acting like a stoplight, preventing storm systems from progressing from west to east across the country.

More than 1,100 snowfall records and 3,400 cold records were set during April, and May is likely to average out to be cooler than average across the South Central states, according to the most recent climate outlooks from the National Oceanic and Atmospheric Administration.

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Winter Is Finally Releasing Its Chilly Grip on the U.S.

2013-04-03T18:44:37+00:00

After more than a month of colder-than-average weather in the U.S., warmer days are finally on the way. According to the Climate Prediction Center, which is part of the National Oceanic and Atmospheric Administration (NOAA), above-average temperatures are expected across the eastern U.S. from April 8-16, and above-average temperatures are also favored in the East, South, and Southwest for the April-June time period.

Click image to enlarge. Credit: NASA.

The warmth will be especially welcome after an unusually cold March gripped much of the U.S., and affected Europe and parts of Asia as well. The above graphic from NASA tells the story, showing the colder-than-average temperatures between March 14-20 (compared to average of the same dates from 2005 to 2012). The image is based on data from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite, and shows land surface temperature anomalies .

Areas with above-average temperatures appear in red and orange, and areas with below-average temperatures appear in shades of blue. Much of Europe, Russia, and the U.S. saw unusually cool temperatures, while Greenland was surprisingly warm for the time of year.

As Climate Central has reported, the long-lasting cold was related to a strong blocking High pressure system over Greenland, which was associated with a particular configuration of an atmospheric pressure pattern known as the Arctic Oscillation, or AO. The AO is a measure of the difference in relative air pressure between the Arctic and the mid-latitudes, and the configuration of air pressure patterns can have profound impacts on weather patterns in the Northern Hemisphere.

During March, the AO hit rock bottom.

Plot of the Arctic Oscillation Index during the 2012-2013 winter season.
Credit: Image adapted from NASA's Earth Observatory.

When the AO index is in its “negative” phase, air pressure over the Arctic is higher than average, while pressure over the mid-latitudes is relatively low, and prevailing winds allow extremely cold air to spill out of the Arctic, as if opening the Northern Hemisphere's refrigerator door.

Warmer times ahead! NOAA's latest temperature outlook for the April-June period.
Credit: NOAA.

The AO Index fell all the way to -5.6, which was one of its lowest readings on record, dating back to 1950. As this occurred, near record-breaking cold broke out in the U.K., which had its fourth-coldest March since 1962. Germany saw its coldest March since 1883, and Moscow had its coldest March since the 1950s, according to NASA and news reports.

The AO, which is still in negative territory, is expected to return to its positive phase by mid-April, raising the odds of a major weather pattern shift, possibly to warmer-than-average conditions.

Ferocious Storm Set to Explode in North Atlantic

2013-01-25T20:43:56+00:00

Some of the most powerful storms on earth form in the North Atlantic Ocean during wintertime, spelling peril for sailors unfortunate enough to encounter them. For the past few days, the meteorologists at the Ocean Prediction Center (OPC) in College Park, Md., whose job it is to warn vessels of weather hazards, have been highlighting the likelihood of a treacherous storm event that is taking place in the open ocean, to the south of Iceland.

Satellite image of the intense North Atlantic storm, taken by the NASA MODIS imager on Saturday Jan. 26.
Click to enlarge the image. Credit: NASA.

A storm that was rather inoccuous when it affected the U.S. is exploding, through a process known to meteorologists as “bombogenesis,” into a ferocious storm over the North Atlantic. The storm has intensified enough to become stronger than Hurricane Sandy was, as measured by the minimum central air pressure. That storm devastated the northern Mid-Atlantic coast in late October and the lowest pressure recorded during it was 940 mb. The current storm intensified all the way to 933 mb, if not even lower than that, based on information from the OPC on Saturday.

In a Facebook post on Friday, the OPC said the storm is expected to undergo “incredible, explosive cyclogenesis” during the next 24 hours, with the central pressure plummeting from 988 mb on Friday down to 927 mb by late Sunday. (In general, the lower the central air pressure, the stronger the storm.)

At its maximum intensity, the storm will be capable of producing winds to 90 mph, and waves of greater than 50 feet, the OPC said.

Fortunately, the storm is expected to weaken considerably before it interacts with northwestern Europe, but it could still produce strong winds in Ireland and parts of the U.K.

The storm comes about 10 days after a different storm underwent a similar process of rapid intensification over the North Pacific Ocean, pummeling the western Aleutian Islands of Alaska with hurricane force winds and high waves, but sparing the rest of the state from any major impacts.

Computer model forecast for early Sunday of significant wave heights over the N. Atlantic. (Some waves will actually be higher than indicated here, since this shows the average of the top one-third of waves.)
Credit: Facebook/Stu Ostro.

The North Pacific storm's minimum central pressure plunged by 48 to 49 mb in just 24 hours, making it one of the most rapidly intensifying storms at a mean latitude of 34°N since 1979, according to a data analysis by Ryan Maue of Weatherbell Analytics..

As strong as the upcoming Atlantic storm is expected to get, it is not likely to set any records. The strongest extratropical storm on record in the North Atlantic occurred in 1993, when a minimum central pressure of 913 mb was recorded near Scotland’s Shetland Islands, according to Weather Underground. That was the lowest sea-level adjusted barometric pressure reading observed on the earth’s surface, with the exception of lower readings measured during tropical cyclones and tornadoes.

Climate studies have shown that extratropical storms in the Northern Hemisphere are shifting their paths northward as the climate warms, and there has been a trend toward stronger Arctic storms in recent years. However, the question of whether characteristics of storms like the one this weekend are changing in response to the warming climate is unclear, given the fact that these events have a long history in the region.

Monster Storm Lashing Outer Reaches of Alaska

2013-01-16T16:09:45+00:00

An extraordinarily powerful ocean storm, packing hurricane-force winds and waves towering up to 62 feet, has been spinning its way toward Alaska's Aleutian Islands after undergoing a phenomenally rapid intensification process in the Western North Pacific Ocean since Sunday. This satellite image, which captured the storm near its peak intensity on Tuesday, offers a rare glimpse at a storm system of this magnitude.

This visible satellite image shows a massive and intense low pressure system swirling over the Western North Pacific Ocean on Tuesday, Jan. 15.
Click to enlarge the image. Credit: Facebook/Stu Ostro via. University of Dundee, Scotland.

At its most intense point, the storm had an air pressure reading of about 932 mb, roughly equivalent to a Category 4 hurricane, and more intense than Hurricane Sandy as that storm moved toward the New Jersey coastline in October. (In general, the lower the air pressure, the stronger the storm.) The storm's central pressure plunged by 48 to 49 mb in just 24 hours, making it one of the most rapidly intensifying storms at a mean latitude of 34°N since 1979, according to a data analysis by Ryan Maue of Weatherbell Analytics.

On Tuesday, the storm spanned a staggering 1,440 miles, according to David Snider, a meteorologist at the National Weather Service in Alaska. That's equivalent to the distance between Denver and New York City.

Satellite image with notes provided by NOAA's Ocean Prediction Center, pointing out the center of the storm and its associated features.
Click to enlarge the image. Credit: Facebook/Ocean Prediction Center.

In Alaska, the National Weather Service has issued high wind warnings and hurricane force wind warnings for the sparsely populated, but strategically important central and western Aleutian Islands and surrounding coastal waters starting on Wednesday. “Tonight winds may howl up to 85 miles-per-hour over the western tip of Alaska in the Aleutian Islands,” the NWS said. Sustained winds are expected to be near hurricane force, or 74 mph, and waves of 40 feet or greater are expected to pound the western Aleutian Islands.

As of Wednesday morning, winds were already blowing as high as 72 mph at Eareckson Air Station on the island of Shemya, about 1,500 miles southest of Anchorage. That island is no stranger to extreme weather, considering that it sticks out far into the North Pacific, making it vulnerable to polar storms and storms coming northward from the Western Pacific. (The U.S. Air Force outpost located there isn't exactly the most coveted assignment in the U.S. military.)

The storm was well-forecast by computer models. This image shows the modeled wave heights from a computer model simulation on Jan. 13, valid for Jan. 15. The projection shows a large area of 50-60 foot waves associated with the storm.
Click to enlarge the image. Credit: Facebook/Ocean Prediction Center.

Fortunately for Alaska, the Pacific superstorm is weakening as it moves northeast, and it is not expected to significantly impact the rest of the state. Alaska had a frigid start to the winter, but it has experienced a significant January thaw. An “atmospheric river” event brought tropical moisture to the state during the past week, with warm air turning snow to rain and freezing rain as far inland as Fairbanks. The 0.10 inches of rain that fell in Fairbanks on Monday was the most rain to fall there in a single January storm since 1963, the NWS said.

In the satellite animation above, from NASA's Rob Simmon, the intense storm is seen in the upper left corner as it weakens and approaches Alaska.

As Alaska's temperatures soar, however, Arctic air is getting ready to sneak into the lower 48 states, beginning this weekend and continuing through next week, possibly making for an extremely cold Presidential Inauguration in Washington, D.C. on Monday.

Heat and Threat of Wildfires Blaze on in Australia

2013-01-11T20:08:45+00:00

As Climate Central reported on Wednesday, a delayed monsoon is helping to heat Australia to record levels, with weather forecasters adding new colors onto weather maps to indicate temperatures up to 129°F. While the wildfires have diminished some, the heat is forecast to return to Queensland and other areas during the weekend into early next week, and the fire danger remains "extreme" in some places, such as the capital region surrounding Canberra. In addition, a photogenic, otherworldy dust storm swept into the town of Onslow in Western Australia, leading to some amazing images.

5 Charts Help Illustrate 2012 As Warmest Year on Record

2013-01-09T16:00:18+00:00

According to the National Oceanic and Atmospheric Administration (NOAA), 2012 was far and away the warmest year on record in the lower 48 states, beating 1998 by a full degree Fahrenheit.

These charts put that warmth into historical perspective for the country as a whole, and for a few select cities.

The 1°F margin between 2012 and 1998 may not seem like much at first, but usually such temperature records are set by just a few fractions of a degree. As seen in this NOAA chart, 2012 towers above the pack of warm years.

Temperature departures from average throughout 2012 as compared to the previous 5 warmest and 5 coolest years.
Click to enlarge the image. Credit: NOAA.

Every state in the continental U.S. had temperatures that were above average, and 19 states, from Utah to Massachusetts, had record warm annual average temperatures. In South Dakota, annual average temperatures were 4.4°F above average, putting 2012 in the top spot on the list of warmest years there.

A total of 45 states had annual average temperatures that ranked among their top 10 warmest on record. The three exceptions in the lower 48 were Georgia, which had its 11th-warmest year, Oregon, where 2012 was the 12th-warmest year, and Washington, which was the coldest state in the contiguous U.S. this year, with its 30th-warmest year. (Here is a list of the annual temperatures for each of the lower-48 states, as well as a Climate Central interactive on 2012 state temperatures.)

Statewide ranks of 2012 average temperatures. Any state marked "118" had its warmest year on record in 118 years of recordkeeping.
Credit: NOAA/NCDC.

NOAA’s National Climatic Data Center (NCDC) in Asheville, N.C., has a treasure trove of climate data, and on Tuesday they released a slew of city-by-city data showing the extraordinary climate of 2012. Each state in the lower 48, except Washington, had at least one location experience its warmest year on record.

Des Moines, Iowa, wins the award for the largest gap between its average temperature during 2012 and the typical annual average. The average annual temperature was 50.9°F, which was 5.2°F above the 30-year average, according to the NCDC. The NCDC computed an “unusualness” score for each city that is based on the entire period of record for that station. In 2012, Des Moines had an average annual temperature that was 3.5 standard deviations from its historical average.

This chart, known as a Haywood Plot, shows the evolution of Des Moines temperatures during 2012 when compared to all other years on record.

The evolution of temperatures during 2012 in Des Moines, Iowa. As you read from left to right, a particular year's trace represents the average of all previous days during that year. For this reason, these plots are often very noisy early in a period (towards the left), but they provide an outstanding representation of unusualness over the whole of the period.
Click to enlarge the image. Credit: NOAA/NCDC.

Rochester, Minn., was another extremely warm location during 2012, having experienced an unprecedented March heat wave and a hot and humid summer. The average annual temperature there exceeded the average value by 4.9°F, or 3.4 standard deviations from its historical average, according to NCDC.

The evolution of temperatures during 2012 in Rochester, Minnesota. As you read from left to right, a particular year's trace represents the average of all previous days during that year. For this reason, these plots are often very noisy early in a period (towards the left), but they provide an outstanding representation of unusualness over the whole of the period.
Click to enlarge the image. Credit: NOAA/NCDC.

Omaha, Neb., was another one of the warmest locations this year, mired at the epicenter of the massive drought. The average annual temperature this year was 4.7°F above average, which was 3.1 standard deviations from its historical average, according to NCDC.

The year was also characterized by extreme drought, and two states — Nebraska and Wyoming — also had their driest year on record. Eight more states had annual precipitation totals that ranked in the bottom 10.

Average annual precipitation in Nebraska, showing the record dry conditions during 2012 (bottom right).
Click to enlarge the image. Credit: NOAA/NCDC.

At its maximum extent in July, drought conditions encompassed 61 percent of the nation, with the most intense conditions in the Great Plains, West, and Midwest. The nationally averaged annual precipitation total was 2.57 inches below average, making 2012 the 15th-driest year, and the driest year since 1988, which also featured a major drought.

Tell Me Why: We Need ‘Normals’ and Long-term Trends

2013-01-07T13:00:41+00:00

What is “normal” when it comes to temperature and precipitation? The definition not only varies with location and time, but it changes from decade to decade. And it’s those decadal trends that interest climate scientists like Anthony Arguez. He explains the importance of “normals” in this version of Tell Me Why, a NOAA-funded series that explains key climate concepts.