Weather Extremes in 2010 Shattered Slew of Records.
(Nov. 5) — Government forecasters highlighted the potential for “another winter of extremes” in the U.S. in their recently issued 2010-11 winter outlook, and that seems an appropriate assessment coming off a year in which numerous all-time records have been set, ranging from winter cold and snow to summer heat to thousand-year rainfall events.
Winter Snow and Cold
The combination of an active southern storm track and occasional arctic blasts from Canada resulted in a remarkable 2009-10 winter across much of the eastern two-thirds of the United States.All-time seasonal snowfall records were established in the mid-Atlantic region, including in Washington (56.1 inches at Reagan National Airport and 78.7 inches at Dulles International Airport), Philadelphia (78.7 inches) and Atlantic City, N.J. (58.1 inches). February alone resulted in nearly two dozen all-time monthly and single-storm snowfall records.The snow was not limited to the mid-Atlantic region. On Feb. 12, every state except Hawaii reported at least a trace of snow on the ground.
While snow was the focus in February, it was widespread cold that stole the weather headlines from December into early January, when arctic blasts from Canada resulted in bouts of extreme cold.
In early January, high temperatures remained below zero in parts of the northern Plains, and low temperatures plummeted well below freezing even into central Florida. West Palm Beach, Fla., experienced its coldest 12-day stretch since at least 1940, according to the National Weather Service.
The winter was one of the top 10 coldest on record in many Southern states, and it was the coolest December through March on record in Key West, Fla.
The cold and snow were followed by intense summer heat, the result of a persistent and strong high-pressure system in the upper levels of the atmosphere, which was centered farther to the east than during a typical summer. In a dramatic turnaround, many of the places that had extreme winter cold experienced extreme summer heat.
June through August was the hottest on record in 11 states, from Mississippi to Rhode Island, and 35 of the 48 continental U.S. states had one of the top 16 hottest summers on record. Cities with all-time record-breaking summer heat included Washington, Baltimore, Philadelphia and New York.
The summer was normal or cooler than average in the Pacific Northwest and California, but a fall Western heat wave resulted in the hottest day on record in downtown Los Angeles. The temperature soared to 113 degrees on Sept. 27, breaking the old record of 112 set on June 26, 1990.
Flooding is a common weather hazard in the U.S. every spring and summer, but a couple of events in the past year were particularly noteworthy.
The epic flood in Tennessee in early May is considered to be a 1,000-year event, which means the type of weather event that should occur only once per millennium. Nashville, having sustained more than $1 billion in damage on its own, is the defining location of the two-day storm that dumped about 40 percent of the average annual rainfall in two days. Massive flooding also occurred in much of western and central Tennessee, as well as in parts of Kentucky, northern Mississippi and Arkansas.Arkansas was also the site of a deadly flood a couple of weeks later, when over 10 inches of rain, most of which fell during the overnight hours, resulted in a torrent of water sweeping through campsites. It’s believed that 20 people were killed in the flood.
Possible Winter 2010 Extremes
The National Oceanic and Atmospheric Administration based its winter prediction of more extremes largely on the presence of a La Nina, which is a cooling of sea-surface temperatures in the equatorial Pacific that influences global weather patterns.
Across the United States, the most common extremes during a winter with a La Nina include heavier than normal rain and mountain snow in the Pacific Northwest and northern Rockies, drought conditions in the southern tier of the country and colder and stormier than normal weather in the northern Plains.