Blog Archive

Thursday, April 28, 2011

Jeff Masters: "Tornadoes, floods, and fires continue to pound U.S.";

Tornadoes, floods, and fires continue to pound U.S.

by Jeff Masters, wunderblog, April 27, 2011
The nation's unprecedented April tornado-fest continued full force last night, with NOAA's Storm Prediction Center logging 57 tornado reports, 295 cases of damaging thunderstorm winds, and 254 reports of large hail. The 2-day tornado count from this latest huge April tornado outbreak is already 102. With another "high risk" forecast for tornadoes today, the tornado total for this week's outbreak may rival the April 14-16, 2011, tornado outbreak (155 confirmed tornadoes) as the greatest April tornado outbreak in history. It is unprecedented to have two such massive tornado outbreaks occur so close together, and the April preliminary tornado count of 654 is truly stunning. Even adjusting this number downwards 15% (the typical over-count in preliminary tornado reports) yields a probable April tornado total of 550. This easily crushes the previous April tornado record of 267, set in 1974. An average April has "only" 163 tornadoes, so we are already 300% over average for the month, and may approach 400% after today's outbreak. According to a list of tornado outbreaks maintained by Wikipedia, only two other tornado outbreaks have had as many as 150 twisters -- the May 2004 outbreak (385), and the May 2003 outbreak (401). One positive note -- there has only been one violent EF-4 or stronger tornado this year, despite the fact we've already had about two-thirds of the 1,200 tornadoes one typically gets for the entire year. Over the past 20 years, we've averaged 7 violent EF-4 or EF-5 tornadoes per year, so we should have had 4 or 5 of these most dangerous of tornadoes so far this year.

Figure 1. Satellite image of last night's storm at 8 p.m. EDT, April 26, 2011. Image credit: NASA/GSFC.

Fortunately, no one was killed in last night's tornado frenzy, but four twisters caused injuries, with 7 injuries in Hesterman, Mississippi, and 3 in Beekman, Louisiana. Over 100 homes were damaged when a tornado struck Edom, Texas, approximately 75 miles east of Dallas. One woman was injured when her mobile home was destroyed. The only killer tornado of the current outbreak occurred on Monday night at 7:30 p.m. CDT when a 1/2 mile-wide, EF-2 tornado struck the small town of Vilonia, Arkansas. Four people died in the town, where 50-80 buildings were destroyed. Tornado warnings were issued 30 minutes before the storm hit, contributing to the relatively low loss of life.

Figure 2. Storm chaser video of a tornado yesterday in Ben Wheeler, Texas.

Another very dangerous tornado outbreak expected today
The busiest April in history for tornadoes continues full-force today, as NOAA's Storm Prediction Center has issued their highest level of severe weather potential, a "High Risk" forecast, for Northern Alabama, Southern Tennessee, and adjoining portions of Georgia and Mississippi. This is the second day in a row, and third time this year, that SPC has issued a "High Risk" forecast. The devastating North Carolina tornado outbreak of April 16, which generated 52 confirmed tornadoes that killed 24 people in North Carolina and 2 people in Virginia, was the other "high risk" day. Numerous tornado warnings have already been issued in Tennessee, Kentucky, Georgia, Mississippi, Arkansas, Ohio, and Alabama this morning, but today's main action is expected to erupt late this afternoon as the cold front from a low-pressure system currently over Arkansas moves eastwards over the "high risk" area. Strong daytime heating in a very moist, unstable airmass will allow a tremendous amount of energy to build up ahead of the front. The arrival of the cold front will force the warm, moist air upwards, allowing the pent-up energy to burst out and fuel supercell thunderstorms.

Related post: Are tornadoes getting stronger and more frequent?

Figure 3. Severe weather threat for Wednesday, April 27, 2011.

From commenters:

are Sight (Freakofnature1)
I haven't seen a storm like this in quite some time. Still no rain in Seguin, Tx. Pic taken in Seguin storm near Martindale.
Rare Sight
Mississippi @ Burlington (BURGuy)
Taken within minutes after the storm cell had passed directly overhead.
Base of Anvil Cloud 4/26/11

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