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 SeALWx:
TomT-Good post, man.


I think the max winds area might be a little subjective though. They certainly appear to me to be more concentrated near the surface low than 'at a distance'.

edit-Not showing many westerlies here for a 'proof' pic for classification.
I said it before and I guess I'll say it again, "You can't just pick the pieces you want from the definition."

Yep true about the Westerlies. One thing to keep in mind is this pass probably wasn't at peak intensity since it was from Thursday. The only reason I used this pass is because it was the most recent clean pass I could find
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Quoting Jedkins01:


Yeah that's very true! Good point and thanks!
Did you see the CMC Jed...It looks real bad...Link
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Quoting aquak9:
I do that all the time, when I get wrong answers it is on stuff that I know easily and I somehow don't realize the mistake till its over then I immediately know what I did wrong.

hey jed? even if you don't get the grade you want, it's not really about the grade. It's about what you've learned, what you retain. Making simple mistakes is not so bad- you learn from that, too.

The letter grade is not nearly as important as how well you can APPLY what you've learned in the future. Keep up the good work.


Yeah that's very true! Good point and thanks!
Member Since: August 21, 2008 Posts: 0 Comments: 7434
Afternoon all. That is some impressive damage from those tornados last night. It's very fortunate that no deaths were reported [so far].

Weather here today is mostly cloudy, but not rainy so far. Nothing about this



seems to suggest we will still get lucky rainwise, but I live in hopes... :o)
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TomT-Good post, man.


I think the max winds area might be a little subjective though. They certainly appear to me to be more concentrated near the surface low than 'at a distance'.

edit-Not showing many westerlies here for a 'proof' pic for classification.

I said it before and I guess I'll say it again, "You can't just pick the pieces you want from the definition."
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Quoting SeALWx:
This system is typically an upper-level cold low with circulation extending to the surface layer and maximum sustained winds generally occurring at a radius of about 100 miles or more from the center.

Guess you're right then.

But looking at a Windsat pass


The maximum winds extend out about 4 degrees of latitude in either direction. There are 69 miles per degree of latitude, so 69 x 4 = 276 miles N/S wise. Which is ~135 miles N/S wise in each direction from the center.

Going longitudinally, its about 3 degrees. At 30N, each degree of longitude is about 60 miles, so 60 x 3 = 180 miles. So E/W wise, max winds extend out about 90 miles in each direction.

In the definition it says "generally" and "about 100 miles", I think we can all agree this is close enough...
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alfabob-I know you are a really smart guy and I do love your posts here. We are just differing on the pronunciation of tomato and potato.

edit-Everyone knows the NHC is conservative on naming borderline systems, normally. Trying to force an almost round peg into a perfectly round hole is sometimes difficult.
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Quoting alfabob:


What exactly made it not meet the criteria for sub-tropical? (Strong central winds has nothing to do with it)

This part:
In comparison to tropical cyclones, such systems have a relatively broad zone of maximum winds that is located farther from the center.

It had winds near the surface low. That isn't part of a sub-t storm definition. Its more of a tropical type which I certainly don't think you are advocating here.
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Quoting alfabob:


Well there are multiple stages to a subtropical system. Some may form in colder waters (22-24C) which doesn't really support core convection. But it is still considered subtropical when it moves into 24-26C waters and begins to have core convection (which it did for a while). After this if it hits 26.5C then it will start to become tropical if conditions are correct. The only cyclone which is distinctly different is extra-tropical. Subtropical and tropical both have surface features and the only difference is really the availability of high level cold air and the SST.

But even in the transition, it is still considered sub-tropical. It can be labeled as one once it reaches the first stage, but the second it is one for sure. Only way for it to become tropical would be organized and consistent convection at the core.
I understand the mechanics involved, that's not the issue here.

I'm simply stating that the ex-91L did not meet the established definitions for either tropical or sub-tropical storms. You guys are trying to pull pieces out of the definitions to support naming and that's not how the NHC plays the game.
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Quoting SeALWx:
Hmmm...sure got quiet all of a sudden. :)
no more invest back to hurry up and wait
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(delete)
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Quoting TomTaylor:
I don't have the exact definition, but I believe it said "within" or "up to" 100 miles from the center. Which 91L certainly did have
Nope; "about 100 mi or more"

Link to NHC Glossary
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Best of ESL Hurricane Archived Imagery

Rita 05
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Quoting alfabob:


That is the first stage of subtropical formation, winds begin to pickup near the center if SST are above 23-24C. It is currently in 26C waters.


From the NHC Glossary:

Subtropical Cyclone:
This system is typically an upper-level cold low with circulation extending to the surface layer and maximum sustained winds generally occurring at a radius of about 100 miles or more from the center.


I'm thinking you're mixing in some sub-t to tropical transitioning in there with your SST argument.
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Quoting SeALWx:
It also didn't have winds focused at the ~100 mile from center area that sub-t storms have in the definition either. You can't just pick pieces out of the definitions.
I don't have the exact definition, but I believe it said "within" or "up to" 100 miles from the center. Which 91L certainly did have
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Quoting alfabob:


A forming subtropical system doesn't need organized consistent convection, it's not tropical. It also had consistent convection going at the core, although yes shear and dry air did inhibit any major formation. And what you stated is exactly why I think NHC didn't classify it, to avoid any media hype. How many April storms have formed in the past?
It also didn't have winds focused at the ~100 mile from center area that sub-t storms have in the definition either. You can't just pick pieces out of the definitions.
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Alas,,lad's,,dey be shear & dry air ahead beaucoup!!


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Quoting SeALWx:
Persistent organized convection was lacking due to shear; I applaud the NHC for NOT over-hyping and over-warning the public about a non-event.

Whoever said anything about over warning he public (although I am sure that is exactly why they didnt name it)? The storm met the written standards and therefore deserved a name.

It's not about appealing to weather enthusiasts who want the storm to be named, its about scientific statistical accuracy and reliability.
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Quoting alfabob:
Lame, NHC deactivated visuals on 91L while it seemed to be reorganizing. Think we should just name it ourselves since the NHC failed at doing so (can't use any official names due to confusion though). Also I don't know what pressures they were giving earlier in development, but I'm pretty sure it was around 1006-1007 mb at some point.
That system is obviously no longer a threat to develop into a tc
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So is any of the models predicting a tropical storm to form towards the late part of may?
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xx/xx/swirl
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Quoting alfabob:


I thought 40 mph is usually classified and named no? I mean you have maybe 1 or 2 people calling the shots here; but I guarantee that regardless of what they think or say, what actually happened is what happened. There were 40 mph winds earlier, very strong vorticity, and clearly subtropical (and also a decent low pressure relative to the surroundings). If this was simply a low chance invest, it would not still be spinning and building low level structure while under 50 kt shear and a lot of dry air. Sorry but NHC dropped the ball on this one and I couldn't care less of what they think relative to 91L.
Persistent organized convection was lacking due to shear; I applaud the NHC for NOT over-hyping and over-warning the public about a non-event.
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Quoting alfabob:


I thought 40 mph is usually classified and named no? I mean you have maybe 1 or 2 people calling the shots here; but I guarantee that regardless of what they think or say, what actually happened is what happened. There were 40 mph winds earlier, very strong vorticity, and clearly subtropical (and also a decent low pressure relative to the surroundings). If this was simply a low chance invest, it would not still be spinning and building low level structure while under 50 kt shear and a lot of dry air. Sorry but NHC dropped the ball on this one and I couldn't care less of what they think relative to 91L.
it was meeting the conditions to warrant a classified system but future forecasts were showing otherwise and conditions as well and the system responsed to that forecast therefore allowing the deactivation of said 91L because of that outcome system is still an AOI and will be watch for any or such redevelopment over the next 48 to 72 hrs
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Quoting hydrus:
I was kidding around Taz..Good afternoon..:)



oh ok

thank olny about 11AM here so its still AM or mid AM if you would call it
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34. IKE

Quoting alfabob:


Just cause NHC didn't classify it doesn't mean it wasn't a storm.
It wasn't a storm. We go through this every year on here....multiple times. I figured this debate would happen with this one and it did.
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Quoting Tazmanian:



?????
I was kidding around Taz..Good afternoon..:)
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Quoting alfabob:


Just cause NHC didn't classify it doesn't mean it wasn't a storm.

it was invest 91L nothing more nothing less
if it was a storm it would have been posted a storm and right now its not even an invest
its just a aoi at the moment
if we are going to do it
we are going to do it right
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Quoting aquak9:
same here, hydrus. We get so used to tackling simple problems, we often don't pay enough attention to them, and get sloppy. Then we concentrate on the big problems, not realizing we've already screwed up the simple stuff.

Not just math lessons, but life lessons overall.

and on a weather-related note- oh DEAR- if this so-called spring is any prelude to the heat we're gonna be seeing this summer? I don't even wanna imagine.
I am somewhat nervous about this years hurricane season..I have family and property in S.W.Florida( whats left of it ) and hope that the lull of landfalling storms continues...I have been getting stomped up here though...And more is on the way....
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Quoting hydrus:
The NCEP has a tropical storm forming in the Caribbean Sea 2124 hours out.



?????
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Is naki



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Quoting FirstCoastMan:
Is the gfs still predicting a tropical storm to form towards the end of may?
The NCEP has a tropical storm forming in the Caribbean Sea 2124 hours out.
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same here, hydrus. We get so used to tackling simple problems, we often don't pay enough attention to them, and get sloppy. Then we concentrate on the big problems, not realizing we've already screwed up the simple stuff.

Not just math lessons, but life lessons overall.

and on a weather-related note- oh DEAR- if this so-called spring is any prelude to the heat we're gonna be seeing this summer? I don't even wanna imagine.
Member Since: August 13, 2005 Posts: 165 Comments: 25909
Quoting aquak9:
I do that all the time, when I get wrong answers it is on stuff that I know easily and I somehow don't realize the mistake till its over then I immediately know what I did wrong.

hey jed? even if you don't get the grade you want, it's not really about the grade. It's about what you've learned, what you retain. Making simple mistakes is not so bad- you learn from that, too.

The letter grade is not nearly as important as how well you can APPLY what you've learned in the future. Keep up the good work.
So true.
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Quoting alfabob:
Lame, NHC deactivated visuals on 91L while it seemed to be reorganizing. Think we should just name it ourselves since the NHC failed at doing so (can't use any official names due to confusion though). Also I don't know what pressures they were giving earlier in development, but I'm pretty sure it was around 1006-1007 mb at some point.

sure
lets call it "never was" storm 91L
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Quoting Jedkins01:


nahh its ok, I did sound that way but it wasn't intended! haha

I already got the grade for it, I got a B on it. I knew the stuff like an A. I'm just a poor tester with math. I had 15 minutes left to look back over my material cause I finished before the time limit. Yet I still didn't notice 2 very easy and stupid mistakes I made that cost me 2 wrong that I didn't need to get wrong at all. I do that all the time, when I get wrong answers it is on stuff that I know easily and I somehow don't realize the mistake till its over then I immediately know what I did wrong.

Oh well, at least I haven't gotten any lower than a B on any tests for the class. Heck I also know the material just as good as the only 3 to 4 people who get A's in the class. What matters most is knowing the material. I still could pull off an A in the class though, there is still the final and I always do better on the final unlike most people.


Most people hate final exams and do much worse on them the rest of the semester. Its not that I like them, but the final exam is your best way to prove your capability, plus its the final test why not put your best effort into it? I don't get it.
I must say, I do like your attitude toward your studies. I know what you mean about the simple mistakes. For reasons I dont really know, I would get the harder problems correct and the easier ones wrong..This was a long time ago however, and I probably attacked some of the tests improperly.
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I do that all the time, when I get wrong answers it is on stuff that I know easily and I somehow don't realize the mistake till its over then I immediately know what I did wrong.

hey jed? even if you don't get the grade you want, it's not really about the grade. It's about what you've learned, what you retain. Making simple mistakes is not so bad- you learn from that, too.

The letter grade is not nearly as important as how well you can APPLY what you've learned in the future. Keep up the good work.
Member Since: August 13, 2005 Posts: 165 Comments: 25909
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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.