Super Outbreak: 174 twisters, 284 dead, 1 mile wide at base

Update 6:00pm

The numbers continue to change and pour in. Pending final number it looks like this could be the #1 or #2 ranked tornado outbreak in U.S. history.

Latest numbers & analysis below.

Storm surveys from Birmingham Al NWS here.

Update 2:45pm:

We're still getting new numbers in this morning (afternoon), and they continue to rise and astound.

174 preliminary SPC tornado tally (and still counting)

284 dead (and still counting)

184 dead in Alabama alone

350 number of miles travelled by the Tuscaloosa tornado's "parent tornadic supercell"

400+ injured in Tuscaloosa

100+ number of miles debris was carried across Alabama according to reports.

Why did it happen?

A good write up here from the Twin Cities NWS.

"Reasons for the Severe Weather

The frequent severe weather in the south has been due to a persistent weather pattern that on the larger scale is also responsible for our cooler and cloudy, more March-like weather. The jet stream has been much stronger than normal across the central and southern part of the country, steering in at times what has been a parade of low pressure systems. To the north of these tracks, the northern U.S. states have seen cooler than normal temperatures, especially in the past two to two and a half weeks. In the south, warm and moisture rich air has continued surging northward ahead of each low pressure. The clash between the air masses, along with strong atmospheric winds associated with the jet stream over the area, has helped to blossom severe weather outbreaks. A further combination of dry air impinging from the western Plains and Texas, where there have been many fires, has potentially led to even more enhanced severe weather towards the Ozarks and Texarkana areas. Such persistent patterns can establish themselves because of continent or hemispheric scale air or ocean circulations. Examples of this are the El Niño and La Niña in the eastern Pacific, which can have impacts on established weather patterns worldwide."

Does this mean Minnesota & Wisconsin will have an active tornado year again?

A big maybe. Again, here's some good data from our local NWS.

"Tornadoes are spawned from individual thunderstorms, which last on the scale of minutes to hours. These thunderstorms are driven by low pressure systems and associated fronts which occur on the scale of days. So making a direct connection to the recent tornadic episodes and the upcoming thunderstorm season in Minnesota and April is not truly possible. However, as mentioned above, larger scale persistent patterns responsible for the current severe weather are often based on global scale patterns. Such patterns last on the scale of months and thus do offer an opportunity to compare past years with similar patterns. Here are some quick correlations made from 1950-2010:

A year that has had an April with a top ten number of tornadoes in the country has led to an above normal number of tornadoes in MN and WI six of those ten years.

Years that have had a La Niña (cooler than normal eastern Pacific waters) of similar strength and in a similar trend of gradually waning, have had an equal amount of active and non-active tornado seasons in MN and WI."

Minnesota's tornado numbers have nearly doubled since 1950:

I crunched some tornado numbers including 2010 for Minnesota for a presentation to our local AMS in February. You can see how Minnesota's average tornado numbers have nearly doubled since 1950.

Here's the slide from my power point.

This slide shows how Minnesota's tornado numbers have risen when compared to Oklahoma since the 1950's. The two lines crossed for the first time last year, as Minnesota surpassed Okalhoma in the annual tornado tally for the first time on record.

Will this be one of the top tornado outbreaks in USA history?

It appears so. Here are some good numbers courtesy of local SKYWARN storm spotter John Wetter. I have worked with John at various SKYWARN & AMS events in the past year.

"Though it will take some time to compile the tornadoes from today, and figuring the 5 year running average of final verification being about 70% of the number of reports of tornadoes, we'll likely fall somewhere short of the Super Outbreak, but seeing some of the video one could maybe think that there would be at least a few to possibly several violent tornadoes (EF-4+). This could rank it fairly high in the significant tornado outbreak tally. There is no doubt it was a historic outbreak none-the-less.

Below are totals of (E)F-4 or higher tornadoes in a 24-hour period for the top outbreaks:

(from SPC database, 1950-2010):

30: April 3, 1974 (AL, GA, IN, KY, NC, OH, TN)

14: April 11, 1965 (IA, IL, IN, MI, OH)

10: March 21, 1952 (AR, MO, MS, TN)

7: March 28, 1984 (NC, SC)

7: May 31, 1985 (NY, OH, PA)

7: June 2, 1990 (IL, IN, OH)

7: March 1, 1997 (AR, TN)

Turning to Grazulis for pre-1950 tornadoes, we can add to the list:

10: Match 21, 1932 (AL, GA, TN)

8: March 28, 1920 (AL, GA, IL, IN, MI, OH)

7: April 27, 1912 (NE, OK, TX)

7: March 16, 1942 (IL, IN, KY, MS, TN)"

It will take some time to get final numbers as NWS survey teams and rescue crews work in the field. But we do know this will end up as one of the most significant tornado outbreaks in U.S. history.

PH

***Original post 11:15pm Wednesday***

Wednesday will go down as one of the worst days in U.S. tornado history.

A massive swarm of killer tornadoes churned across the southeast. Dozens are dead. Hundreds are injured or homeless. Devastation is widespread.

This could be biggest tornado outbreak in 37 years. The numbers may eventually rival the 1974 "Super Outbreak" ...the biggest tornado outbreak in U.S. history, with 148 tornadoes in a 24 hour period.

Some of the staggering numbers:

161 preliminary tornado reports Wednesday.(and still counting)

178 dead. (and still counting)

128 dead just in Alabama.

400+ injured in Tuscaloosa

100 number of miles debris was carried across Alabama according to reports.

Anatomy of a "super outbreak:"

Check out the interactive Google map below. Tornado symbols represent individual touchdowns. Click on each to reveal data.

View Tornado Outbreak April 27, 2011 in a larger map

Tuscaloosa Terror:

This unbelievable video was shot by Chris England of the University of Alabama as the tornado tore through Tuscaloosa.

Watch as the massive violent vortex sends whole trees and other debris high into the air. Transformer flashes are visible as the twister tears through power lines. Mini vortices spin around the giant funnels core.

4-27-11 Tornado Tuscaloosa, Al from Crimson Tide Productions on Vimeo.

Classic "Debris Ball" captured on Doppler:

You can't make this stuff up.

Look at the doppler refectivity image below and you can see the "debris ball" churned up ahead of the massive twister near Birmingham.

Chunks of homes, cars, trees, anyhting that the twister "rototilled" and ejected into the air is bouncing back the radar beam with "high reflectivity."

True "Super Outbreak:"

SPC reports show at least 141 tornado sightings Wednesday. Keep in mind these are preliminary numbers and there are duplicate sighting of the same massive tornadoes.

Throw in Tuesday's tornado tally of 61 twister reports and you have a true "Super Outbreak."

Deadly Squall Line:

Tornado watch boxes and warnings still bracket the tornadic squall line as midnight rolls into Thursday.

Listen for much more on this potentially record breaking tornado outbreak on MPR News Thursday.

PH