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Posted at 02:45 PM ET, 04/22/2011

Spring 2011 extreme weather going nuts

Tornadoes off the charts, wildfires rage, floods loom


The spring jet stream pattern, characteristic of La Nina, has resulted in warm, humid air clashing with cold, dry air east of the Plains, resulting in severe weather.

We warned you that this spring’s weather would be volatile. But who knew it would be as extreme as it’s been to date? And is the worst still to come?

AccuWeather’s Joe Lundberg aptly describes the weather pattern as “bipolar.” Discovery Magazine puts it this way: “Draw a line from Washington D.C. to Denver and down to Phoenix. North and west of that line, it has been cold and wet. To the south and east, it has been hot and dry.”

The bi-polar weather is a manifestation of an amped up jet stream, fueled by this spring’s moderate La Nina. Weather Nation meteorologist Paul Douglas told Discovery Magazine that jet stream winds are as strong as he can remember during April.

The jet, relentlessly surging south through the Midwest, has set up a volatile transition zone east of the Great Plains extending across the mid- South and Tennessee Valleys, occasionally reaching the Southeast. In this transition zone, where cold, dry air has persistently done battle with warm, moist air, seldom a day goes by without explosive, rotating thunderstorm development.


Severe weather reports to date this April (2011). Blue dots represent high winds (2593), green large hail (1901), and red tornadoes (509).
As discussed Tuesday, the U.S. is on pace for its most active tornado season on record, ahead of 2008. And next week, AccuWeather’s Henry Margusity predicts “an insane outbreak of severe weather”.

“Given the pattern next week, I can see 100-200 tornadoes over a four-day period starting Monday,” Margusity wrote.

Just to the northwest of regions impacted by severe thunderstorms and tornadoes, flooding poses major problems. The clockwise flow from high pressure off the Southeast coast, another characteristic feature of La Nina, is directing moisture-laden air northward from an unusually warm Gulf of Mexico.


Rainfall projected over the weekend by NOAA’s Hydrometeorological Prediction Center (NOAA HPC)
Increasingly, significant flooding appears to be a high risk across the Mississippi, Missouri, and Ohio River Valleys. For the upcoming weekend, the National Weather Service has cautioned:

Rainfall forecasts for many locations from the southern Great Lakes across the Midwest to southern Oklahoma and northern Texas are calling for 3-7 inches and possibly more. Much of that rain will fall on saturated soil that will absorb very little, if any, of the new water. Resultant runoff water will cause rapid rises and flash flooding as well as significant river and overland flooding in many areas.


Drought intensity over Texas and several surrounding states (U.S. Drought Monitor)
While flooding is a concern for these areas, the rain may well benefit areas on the southwest periphery of the heavy rain shield, currently in the midst of a drought, ranging from extreme to exceptional. It is this drought that has sparked the large wildfire outbreak across the state of Texas, where more than 1.4 million acres have burned.

Up until now, the orientation of the jet stream has resulted in storms passing east of this drought-stricken area. But with a slight shift to the west, the weekend storm system offers the possibility of some modest relief. The Associated Press reports Texas Gov. Rick Perry has “proclaimed a three-day period, from Friday to Sunday, as Days of Prayer for Rain.”

This hyperactive spring pattern shows no sign of letting up. WeatherBell meteorologist Joseph D’Aleo wrote today that “the month of May is likely to continue stormy” and his colleague, Joe Bastardi wrote yesterday: “April and May are liable to be the two most active [severe weather] months on record.”

By  |  02:45 PM ET, 04/22/2011

Categories:  U.S. Weather, Latest

 
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