Violent EF-4 tornado causes severe damage at St. Louis' airport

By: Dr. Jeff Masters , 3:25 PM GMT on April 23, 2011

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A violent EF-4 tornado ripped through St. Louis near 8pm local time Friday night, severely damaging Lambert International Airport. The airport, the world's 30th busiest, may be closed for several days. The tornado ripped off the roof from Concourse C, blew out more than half of the windows in the main terminal, and moved an aircraft that was parked at a gate twenty feet. So far, only minor injuries due to flying glass have been reported from the tornado. The tornado also passed over nearby residential areas, causing severe damage. The National Weather Service office in St. Louis has rated the damage from the St. Louis tornado EF-4, making the twister the first violent EF-4 tornado of the year. Softball-sized hail also pelted three towns in Missouri--Hermann, Big Spring, and Warrenton--during Friday night's severe weather outbreak. NOAA's Storm Prediction Center logged 24 tornado reports Friday in Oklahoma, Arkansas, Missouri, Illinois, and Kentucky. The cold front responsible for triggering last night's severe weather will remain draped over the nation's mid-section for the next three days, and a slight risk of severe weather is predicted along a swath from Texas to Ohio both Saturday and Sunday. A more substantial risk of severe weather is likely on Tuesday through Wednesday, as a new, more powerful spring storm system gathers strength over the Midwest.


Figure 1. Radar reflectivity image of the EF-4 St. Louis tornado taken near 8pm local time on Friday, April 22, 2010. This image is from the high-resolution Terminal Doppler Radar (TDR) at the St. Louis Airport, and shows very fine details of the tornado, which displays a classic hook echo here.


Figure 2. Radar Doppler velocity image of the St. Louis tornado taken near 8pm local time on Friday, April 22, 2010. This image is from the high-resolution Terminal Doppler Radar (TDR) at the St. Louis Airport, located at the "+" sign on the image. Green colors denote areas where precipitation is moving towards the radar, and red and yellow colors show where precipitation is moving away from the radar. Pink colors are bad data regions. The small couplet of greens right next to reds is where the tornado was, since the tight vortex had winds moving towards the radar and away from the radar. The area marked "RFD" shows where a Rear-Flank Downdraft (RFD) was occurring behind the tornado. The downdraft hit the ground to the west of the radar site and spread out in all directions, creating a diverging area of winds moving both towards and away from the radar. An area of air flowing into the tornado on the SE side is marked "Inflow." Thanks go to Dr. Rob Carver, wunderground's tornado expert, for annotating this image.


Figure 3.
Remarkable video from a security camera at the St. Louis airport showing the roof being torn off Concourse C.


Figure 4. Severe damage characteristic of at least a strong EF-2 tornado is apparent from this helicopter view of residential St. Louis neighborhoods taken by KMOV.

Jeff Masters

Lambert St. Louis Tornado Damage (WindyCityBob)
Taken after the good friday tornado at Lambert Field St.Louis, MO
Lambert St. Louis Tornado Damage

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Quoting Jedkins01:


I know there will training of systems, but seriously I think the HPC is going a little overkill there. If it rains that much it may be historic flooding. It could happen but it seems more in the possible category rather than probable. Lets hope rainfall does fall well short of that. Because if that forecast is right lives may be lost from flooding in the coming days.


Its been very consistent for the past couple of days. Models are for sure showing a lot of rain. IF this does occur as you said LIVES WILL BE CHANGED!
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The Sub Tropical Jet is on it's way... It's April mind you. We won't see AEW's until the jet sags. It's right in the wheel house ATM, don't expect anything until the jet moves out of the way...

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Quoting TampaSpin:




I know there will training of systems, but seriously I think the HPC is going a little overkill there. If it rains that much it may be historic flooding. It could happen but it seems more in the possible category rather than probable. Lets hope rainfall does fall well short of that. Because if that forecast is right lives may be lost from flooding in the coming days.
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Quoting KEEPEROFTHEGATE:



Keeper nice job on your blog!
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Member Since: July 15, 2006 Posts: 186 Comments: 57626
Quoting trHUrrIXC5MMX:
HAPPY EASTER EVERYONE!!!

You too! 6 minute countdown initiated... Nite all... very tired, be back in the morning...
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HAPPY EASTER EVERYONE!!!

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Quoting KoritheMan:
Here is an immensely useful site for the anatomy of tropical waves.


Excellent Info.. thanks
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407. JRRP
.
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Lots of train affect raining will occur.
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QUIET TROPICA AROUND THE GLOBE

Long gone 91L!!!


"A 1013 MB LOW CENTERED
NEAR 24N66W WITH A WELL DEFINED CIRCULATION PER VISIBLE
SATELLITE IMAGERY CONTINUES TO MOVE W AT 10-12 KT. DATA FROM
NOAA BUOY 41043 STILL INDICATES A CLOSED LOW AT THE SURFACE.
THE LOW IS EMBEDDED WITHIN A BROAD AREA OF STRONG UPPER LEVEL
SUBSIDENCE TO THE NW OF A TROUGH AND SHEAR AXIS WHICH EXTENDS
FROM 32N50W THROUGH 26N60W TO 24N66W. THE STRONG SUBSIDENCE
ALOFT HAS INHIBITED ANY DEEP CONVECTION ASSOCIATED WITH THE LOW
WITH ONLY ISOLATED TO LOCALLY SCATTERED SHOWERS LOCATED WITHIN
150 NM OF THE CENTER OF THE LOW BUT MAINLY IN THE EAST AND
SOUTHEAST QUADRANTS. THE LOW IS FORECAST TO WEAKEN TO A SURFACE
TROUGH WITHIN THE NEXT 24 HOURS AS IT PUSHES TOWARD THE BAHAMAS. "
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402. JRRP


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401. beell
Anyway, the time height series charts are probably the easiest way to spot a wave as they leave the coast of Africa. These are not much more than a look up through the atmosphere over a given point.

A wave signature shows a sharp wind shift from NE to SE as the wave passes at 600-700mb. And there is usually an increase in moisture/RH as well.

Bookmark this one if you want.

Upper Air Time Section Analyses
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Quoting spathy:


Tampa
Actually!
Thanks for the question and pursuing it.
The following give and take was very informative.
Spathy learning moment.


its actually good to have these moments now during down times. I have learned all i know (which is still little) from this blog.
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Quoting TampaSpin:


Honestly if a potential spins does not detach it is rarely classified as a storm until it makes its way out of the ITCZ! It must sustain its own dynamics and spin!


Tomas of 2010 knew how to intensify and deal with the ITCZ at some point without weakeing for a shot time
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Back to simply surfing!
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395. beell
Quoting TampaSpin:


Bell in understand the dynamics of what causes a spin and land heat effects. I was simply trying to understand what is considered the first wave and what the definition of the first wave is as i might have considered the ones coming off Africa now as Wave. I will shut up and just simply observe!


It's cool, Tampa. I remember last year we were sitting around arguing against the NHC about the first tropical wave. Nope. "Not yet", we all said.

NHC refrenced a time/height series from Dakar on the coast of Africa in the next TWD and there it was. Big as Dixie! So even if you think you know what it is-it don't mean you can find it!
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Quoting KoritheMan:
It should also be noted that if a tropical wave ultimately detaches from the ITCZ, it loses a large supply of moisture and instability and can struggle thereabouts, at least until it can manage to become self sufficient. This is why the incipient wave that spawned Danielle last August had so much darned trouble intensifying once it detached from the ITCZ.


Honestly if a potential spins does not detach it is rarely classified as a storm until it makes its way out of the ITCZ! It must sustain its own dynamics and spin!
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Look at this weird thing (since waves are begining to roll off) chances are we might...



A wave eventually came Bertha.. am early Cape Verde type hurricane.

Chaces are we can get one like this soon if right conditions are present.

We had already 90L and 91L, chances for Arlene are increasing
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Quoting Levi32:


They can be embedded within the ITCZ but they aren't always. Often we wait for them to become independent from the ITCZ before giving them good chances to develop. I gave their basic definition in #380.


Levi thanks i fully understand that already! Thank you!
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It should also be noted that if a tropical wave ultimately detaches from the ITCZ, it loses a large supply of moisture and instability and can struggle thereabouts, at least until it can manage to become self sufficient. This is why the incipient wave that spawned Danielle last August had so much darned trouble intensifying once it detached from the ITCZ.
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Quoting beell:


The AEJ and waves are a consequence of the temperature gradient between equatorial Africa and the much warmer Saheel/Saharan Desert.


Bell i understand the dynamics of what causes a spin and land heat effects. I was simply trying to understand what is considered the first wave and what the definition of the first wave is as i might have considered the ones coming off Africa now as Wave. I will shut up and just simply observe!
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Quoting trHUrrIXC5MMX:


I said it will NOT develop.
I know, but know one was talking about formation of a tropical wave, Tampaspin is a bit confused about tropical waves, and were helping him out.
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Quoting TampaSpin:
Sorry for my confusion as i really don't honestly track anything unless it is of meaning and possible for development. Sorry to be so dumb on this one. I actually did not realize tho that a Wave must be contained within the ITCZ to be considered a wave if i understand this correctly. Sorry all and thanks for clearing my mind!


They can be embedded within the ITCZ but they aren't always. Often we wait for them to become independent from the ITCZ before giving them good chances to develop. I gave their basic definition in #380.
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full northern hemisphere
enhanced infared red animation
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386. beell
Quoting TampaSpin:


So, basically as the ITCZ climbs out of the Southern Hemisphere is when the first cluster of storms is considered a Wave.


The AEJ and waves are a consequence of the temperature gradient between equatorial Africa and the much warmer Sahel/Saharan Desert. That gradient does not exist quite yet.
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Quoting HurricaneDean07:
Who said it would develop, there's not any kind of wave to talk about anyway, and you don't look for CV development until Late July to Early October.


I said it will NOT develop.
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Quoting trHUrrIXC5MMX:
Severe weather for Nortern Texas and Oklahoma Tuesday???

Yep
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Sorry for my confusion as i really don't honestly track anything unless it is of meaning and possible for development. Sorry to be so dumb on this one. I actually did not realize tho that a Wave must be contained within the ITCZ to be considered a wave if i understand this correctly. Sorry all and thanks for clearing my mind!
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Severe weather for Nortern Texas and Oklahoma Tuesday???

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Quoting TampaSpin:


So, basically as the ITCZ climbs out of the Southern Hemisphere is when the first cluster of storms is considered a Wave.


No. Tropical waves are not clusters of thunderstorms within the ITCZ. They are literally waves within the African Easterly Jet at about the 650mb level with defined potential vorticity maxima and zonal wind shifts.

In fact, quite a few tropical waves per season come off Africa and continue across the eastern Atlantic with little or no convection whatsoever.
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Quoting trHUrrIXC5MMX:


not just that... they have to be in a shear/dry air free environment w/ warm waters
I'm not talking about how they develop, im talking about what a tropical wave is.
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Quoting trHUrrIXC5MMX:
Wave or not... it won't develop
Who said it would develop, there's not any kind of wave to talk about anyway, and you don't look for CV development until Late July to Early October.
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Quoting HurricaneDean07:
The tropical waves, aren't just balls of convection, they have(when they're strong) Structure, T-storms attempting to Organize, Convection(of Coarse), and a good amount of vorticity.


not just that... they have to be in a shear/dry air free environment w/ warm waters
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Quoting beell:


You won't find a wave today. A wave heralds the advance of the African Easterly Jet out into the eastern ATL and the slow northward march of the ITCZ.


So, basically as the ITCZ climbs out of the Southern Hemisphere is when the first cluster of storms is considered a Wave.
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Quoting TampaSpin:


Just asking a question? But, the above dates are waves that came off Africa and developed into something. Otherwise i could find a Wave coming off Africa today and say that is the first wave. I don't mean to come across combative but, asking a question as to what a first wave off Africa really means and when one can say this is the first wave. Hope you understand what i saying and asking!


I think you are misunderstanding. None of those above tropical waves developed into anything that I am aware of (maybe one got into the southwest Caribbean, but I don't know).

There is a very clear definition of a tropical wave, and we have had none so far. The blobs of convection that start coming off are not yet tropical waves. There is a reason why the NHC leaves the surface map blank.
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Quoting TampaSpin:



Guess my point is, Why couldn't this wave be considered the First Wave and what defines the first wave?
The tropical waves, aren't just balls of convection, they have(when they're strong) Structure, T-storms attempting to Organize, Convection(of Coarse), and a good amount of vorticity.
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Wave or not... it won't develop
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what would actually happen if the loop current broke off into a loop eddy?
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371. beell
Quoting TampaSpin:


Just asking a question? But, the above dates are waves that came off Africa and developed into something. Otherwise i could find a Wave coming off Africa today and say that is the first wave. I don't mean to come across combative but, asking a question as to what a first wave off Africa really means and when one can say this is the first wave. Hope you understand what i saying and asking!


You won't find a wave today. A wave heralds the advance of the African Easterly Jet out into the eastern ATL and the slow northward march of the ITCZ. These disturbances are found near the 600-700mb level. You may find a surface feature today or tomorrow but you will not find a true easterly wave.
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Quoting beell:


The assertion was: It is time to start looking for tropical waves off Africa in a few weeks.

Development is another issue.


Tropical wave formation.



Easterly Waves
Long waves occur in bands of geostrophic wind flowing above the friction layer. Long waves may flow toward the west or toward the east depending on which of the major global wind belts they occur in. Easterly waves are "long waves" that occur within the trade wind belt, start over north western Africa, and propagate toward the west in the lower tropospheric tradewind flow across the Atlantic Ocean. They are first seen usually in April or May and continue until October or November. They occur between 5-15 degrees N. They have a wavelength of about 2000 to 2500 km, a period of ~3-4 days, and move at approximately 18 - 36 km/h. Approximately two easterly waves per week travel from Africa to North America during hurricane season. Passing from the African continent onto the cool Eastern Atlantic, the waves generally decay, but remnants mostly survive to the Western Atlantic and Caribbean where they regenerate. Only 9 out of 100 easterly waves survive to develop into gale-force tropical storms, or full-fledged hurricanes.

About 60% of the Atlantic tropical storms and minor hurricanes (Saffir-Simpson Scale categories 1 and 2) originate from easterly waves. However, nearly 85% of the intense (or major) hurricanes have their origins as easterly waves. The majority of synoptic scale systems from Africa propagate beyond the Caribbean and the Central American Isthmus into the Eastern Pacific, where some intensify into Tropical Storms. It has been suggested that nearly all of the tropical cyclones that occur in the Eastern Pacific Ocean can also be traced back to Africa. Many Typhoons in the Western Pacific are also believed to develop from Easterly Waves, although more work is needed on the relationship of Easterly Waves in the Western and Eastern Pacific.

Fig.1. Approximate location, amplitude and wavelength of easterly waves.

At first, an easterly wave has a small amplitude, and produces mild rain showers. Powerful thunderstorms and the force of high-altitude winds amplify the wave when atmospheric conditions are favourable. Several severe thunderstorms begin to form, and eventually a tropical storm may develop.

Fig. 2. The development of easterly waves off the west coast of Africa.


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369. xcool
Ana April 20–April 24 Tropical Storm 60 994
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Guess my point is, Why couldn't this wave be considered the First Wave and what defines the first wave?
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Quoting sunlinepr:
Getting Stronger, should see the first actual wave in the next week or two.
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Quoting beell:
Post 328, 345,Levi and Pat...
Is there that much difference in the location of the loop between the initial velocity run and IR?

Ya'll looking at apples and oranges?


It's weird Beell, a lot of the navy's model runs look very different from the initial conditions sometimes.

Compare the NLOM initialization with the (I think more accurate) HYCOM initialization:

NLOM:



HYCOM:




And then Pat's image says HYCOM on it, but there's no way it moves the loop that far west in 120 hours. That's not realistic.
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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