Warm fall, record disasters across U.S.
December 7th, 2011, 1:35 pm · · posted by Pat Brennan, O.C. Register science, environment editorThe lower 48 experienced a warmer-than-average fall season, and the country set a record for weather-related disasters causing over $1 billion in damage in 2011, the nation's climate agency says.
While coastal Southern California had its share of wild weather, however, we bucked the national trend and saw a colder-than-average fall.
The seasonal climate snapshot from the National Climatic Data Center fits a years-long trend, said Jake Crouch, a climatologist with the agency.
"We have seen an upward trend in fall temperatures, and in most seasons for the U.S.," he said.
But fitting that into the larger, global increase in average temperature over decades is trickier.
"When you're looking at these smaller time scales, a lot of things come into play, such as La Niña," he said. "Climate variables tend to have a larger role in what we see month to month."
La Niña, a periodic cooling of the waters of the equatorial Pacific, likely played a role in the the nation's warmer-than-normal fall, he said.
"That tends to create warmer than average conditions across the Southern U.S. this time of year," Crouch said. "It also tends to create a wetter pattern across the Midwest."
Nationwide, precipitation was higher than normal in November but about average for the fall season, September through November.
The average fall temperature in the contiguous United States was 55.5 degrees, 1.3 degrees above the long-term average from 1901-2000.
La Niña — combined with another phenomenon known as a "negative Pacific decadal oscillation" — also likely played a role in temperature and rainfall trends for coastal Southern California, said Bill Patzert, a climate and ocean researcher at the Jet Propulsion Laboratory in Pasadena.
"Those two things generally, statistically speaking, mean cool and dry," Patzert said.
Much of California has seen lower than average rainfall, including Orange County, although downtown Los Angeles is a bit above normal.
Orange County and the South Coast also are seeing a second cooler-than-normal year, Patzert said, despite weather extremes this year such as the recent bout of powerful winds — which left Patzert himself with wind damage as well as a three-day loss of power in Sierra Madre.
"L.A. is 20 percent above-normal rainfall, Irvine is 20 percent below normal," he said. "One thing we all shared the last two years was basically cooler temperatures locally in a warming world."
Meanwhile, 2011 saw 12 weather-related disasters costing $1 billion or more, for a preliminary total of $52 billion. That breaks the previous record of nine billion-dollar disasters in a single year, set in 2008.
The 12 disasters caused 646 deaths.
The 2011 disasters were:
Wildfires in Texas, New Mexico and Arizona in spring and fall, with more than $1 billion in damage, at least five deaths.
Hurricane Irene, Aug. 20-29, more than $7.3 billion, at least 45 deaths.
Upper Midwest flooding, summer, more than $2 billion, at least five deaths.
Mississippi River flooding, spring and summer, $3 to $4 billion, at least seven deaths.
Southern plains and Southwest drought, heatwave and wildfires, spring and fall, approaching $10 billion.
Midwest and Southeast tornadoes and severe weather, June 18-22, more than $1.3 billion, at least three deaths.
Midwest and Southeast tornadoes, May 22-27, more than $9.1 billion, 177 deaths.
Southeast Ohio Valley and Midwest tornadoes, April 25-30, more than $10.2 billion, 321 deaths.
Midwest and Southeast tornadoes, April 14-16, more than $2.1 billion, 38 deaths.
Southeast and Midwest tornadoes, April 8-11, more than $2.2 billion.
Midwest and Southeast tornadoes, April 4-5, more than $2.8 billion, nine deaths.
Groundhog Day blizzard in central, eastern and northeastern states, Jan 29-Feb. 3, more than $1.8 billion, 36 deaths.
Source: http://sciencedude.ocregister.com/2011/12/07/warm-fall-record-disasters-across-u-s/165263/--
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