2011-04-27 MISC: AL,TN,MS,KY,OH,IN,WV,GA

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Dec 8, 2003
712
7
6
51
Calera, AL
anyone know if the University of Alabama was hit? I haven't heard anything on it, so just wondering if anyone knew.
The UA campus was not directly hit. Most of the damage from the tornado appears to have occurred south of the campus along 15th Street heading eastward into Alberta City. This is the area where University Mall and DCH are located as well. Several student are confirmed among the fatalities though as there are many who live in apartments and houses in this area.
 

Jeff Duda

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I would like to know where the 287mph wind speed came from. Some of the damage definitely looks like EF4 and EF5 damage. But 287 mph is incredible. The big one on May 3 1999 was similar and higher in spots and the grass was ripped from the ground, trees completely bare of limbs/leaves and bark. I've not seen anything quite that impressive yet, which makes me question the 287mph wind speed. But I've definitely seen pics that justify the EF5 rating.
Anyone have any thoughts on this?
I have yet to see EF5 damage in any of the pictures I've seen, but I probably haven't seen all of the images released, and I'm sure new stuff will continue to be released throughout the next few days. I'm pretty sure the wind speed measurement is being obtained from the gate-to-gate velocity signature from a radar scan a few minutes after the tornado exited Tuscaloosa:



The two bins in the oval had velocities of +133.8/-109.8 = 243.6 kts of shear = 280 MPH OF SHEAR. This is not a ground wind speed measurement, nor is it an aerial speed measurement. The rotational velocity is the average of the two maxima, or 121.8 kts = 140 MPH, which would be a better estimate of wind speed. However, the radar beam was hitting this feature at 2700 ft ARL, so at that distance from the radar and at that height, it probably was only resolving the low-level mesocyclone, not the tornado. Also, winds aloft do not correlate well with winds at the surface, especially in areas of high surface roughness (like in Alabama). There were still very high velocities, but not quite this high, when the signature was in Tuscaloosa. I saw a max delta-V of 175.2 kts from the 2210Z scan when the storm was over Tuscaloosa.

I wonder how the towns of Holt and Peterson fared with this as it went right between the two.
 
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Jeff Duda

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This is going to push the super outbreak damned close. I think you're looking at at least a half dozen violent class tornadoes yesterday with death tolls nearing what we saw in the super outbreak. I think the actual count takes a backseat to those two items.

And even then... is an event any less of an event because one long track violent tornado stayed on the ground two hours and thusly generated one report vs a cyclical supercell that keeps dropping violent tornadoes intermittently and generated 10 reports over the same path? A more telling metric might be to tally up total path area of tornadoes on a given outbreak with strength of tornado in any given area figured in. (perhaps a simple multiplier would do EF0 = path area X 1, EF1 = PA x 2, etc...) Though one issue with that calculation may be valuation of area... weak tornadoes with wide paths gaining too much value.
I think the two better ways of measuring that would be sum(average tornado width*length) or sum(average tornado width*length*EF-scale-rating).
 
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jeremy wilson

And even then... is an event any less of an event because one long track violent tornado stayed on the ground two hours and thusly generated one report vs a cyclical supercell that keeps dropping violent tornadoes intermittently and generated 10 reports over the same path? A more telling metric might be to tally up total path area of tornadoes on a given outbreak with strength of tornado in any given area figured in. (perhaps a simple multiplier would do EF0 = path area X 1, EF1 = PA x 2, etc...) Though one issue with that calculation may be valuation of area... weak tornadoes with wide paths gaining too much value.

Great points Derek and great idea on one point of comparison.
 

Trey Thee

EF2
Mar 29, 2010
191
29
11
Tulsa metro
True... much better data to be collected here. Though, I wonder what sort of advancements we can really make off of this information.... I can't imagine the handling of this situation being much better. The was recognized from the get go as an extremely volatile and dangerous situation. The watches and the wording pre-storm initiation reflected this. (I've never seen a 95%/95%) Media coverage was giant -- weather channel and local. Storms had huge lead times warning wise.

I feel as though we're nearing a point in meteorology where we can't better most warn times. The greatest gains in human safety are going to be advancements in engineering of homes -- really, great engineering exists, it's just not common enough -- and in actually human observance of severe weather. Basically... people taking note of the information that is at their disposal. This will save more lives than anything.
Great post, I agree completely, this was handled fantastically well by SPC, NWS and local media outlets. I think improvements can be made in the prediction of when/where/strength of storms out into the future. By future I mean minutes and hours.

For example, we knew it was going to be bad, but we couldn't tell you for sure that storm X which initiated at lets say 3pm would have a confirmed large tornado on the ground by 4pm. We knew the potential was there, once the big tor was on the ground obviously warnings went out well in advance. But I do feel much improvement can be made on the technical side of things.

Hope I'm making sense.
 

Jeff Duda

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True... much better data to be collected here. Though, I wonder what sort of advancements we can really make off of this information.... I can't imagine the handling of this situation being much better. The was recognized from the get go as an extremely volatile and dangerous situation. The watches and the wording pre-storm initiation reflected this. (I've never seen a 95%/95%) Media coverage was giant -- weather channel and local. Storms had huge lead times warning wise.

I feel as though we're nearing a point in meteorology where we can't better most warn times. The greatest gains in human safety are going to be advancements in engineering of homes -- really, great engineering exists, it's just not common enough -- and in actually human observance of severe weather. Basically... people taking note of the information that is at their disposal. This will save more lives than anything.
I think a big reason for why the death toll will be so high is due to the fact that many places in Alabama had no NWR and no warning sirens because the storms that moved through in the morning took out a lot of power and infrastructure. As I was watching the ABC 33/40 stream yesterday, early in the outbreak they mentioned several times that at least 6 people in Alabama had died in the morning from earlier storms and that the warning sirens and weather radio transmitters and INTERNET were down across many areas, including those that got hit (Cullman, AL was the first big area they talked about and it was one of the first areas to get hit). Later on in the outbreak they were telling people to use their cell phones to call anyone they knew in warned areas because they were probably not going to get the warning any other way. If you remove the effects of the morning storms, many more people would probably have gotten the warnings and many more lives may have been saved. Speculation, sure, but I don't think it has no merit.
 
On my way to work this morning there were power poles snapped off about an 1/8 of the way up, gas pump at the local gas station blown off its base, a 18 wheeler on its side, tree branches and random debris here & there over the course of my 23 mile drive.
 
Jan 28, 2005
234
4
0
Haslett, Michigan
I have yet to see EF5 damage in any of the pictures I've seen, but I probably haven't seen all of the images released, and I'm sure new stuff will continue to be released throughout the next few days. I'm pretty sure the wind speed measurement is being obtained from the gate-to-gate velocity signature from a radar scan a few minutes after the tornado exited Tuscaloosa:



The two bins in the oval had velocities of +133.8/-109.8 = 243.6 kts of shear = 280 MPH OF SHEAR. This is not a ground wind speed measurement, nor is it an aerial speed measurement. The rotational velocity is the average of the two maxima, or 121.8 kts = 140 MPH, which would be a better estimate of wind speed. However, the radar beam was hitting this feature at 2700 ft ARL, so at that distance from the radar and at that height, it probably was only resolving the low-level mesocyclone, not the tornado. Also, winds aloft do not correlate well with winds at the surface, especially in areas of high surface roughness (like in Alabama). There were still very high velocities, but not quite this high, when the signature was in Tuscaloosa. I saw a max delta-V of 175.2 kts from the 2210Z scan when the storm was over Tuscaloosa.

I wonder how the towns of Holt and Peterson fared with this as it went right between the two.
I think the storm was moving ENE at around 55 mph so I assume you would add the forward movement vector in with your 140 mph rotational speed example..giving an estimate of closer to 200 mph which would put that tornado at the EF-4/EF-5 threshold. Looking at the damage photos that I've seen so far..that seems about right and I doubt I have seen the worse yet.
 
Dec 25, 2006
618
0
5
Iowa City, Iowa
Great post, I agree completely, this was handled fantastically well by SPC, NWS and local media outlets. I think improvements can be made in the prediction of when/where/strength of storms out into the future. By future I mean minutes and hours.

For example, we knew it was going to be bad, but we couldn't tell you for sure that storm X which initiated at lets say 3pm would have a confirmed large tornado on the ground by 4pm. We knew the potential was there, once the big tor was on the ground obviously warnings went out well in advance. But I do feel much improvement can be made on the technical side of things.

Hope I'm making sense.
Ah, yeah, predicting initiation from a space and time standpoint, agree we could possibly improve that a good deal. Honestly wonder how far we'll be able to get there -- I haven't put the time and research in -- but something to shoot for.
 

Jeff Duda

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I think the storm was moving ENE at around 55 mph so I assume you would add the forward movement vector in with your 140 mph rotational speed example..giving an estimate of closer to 200 mph which would put that tornado at the EF-4/EF-5 threshold.
No, Mike, this is base velocity, which measures the instantaneous inbound and outbound velocities. Thus, if anything, you'd want to remove that 55 mph forward move speed to get an idea of how the vortex itself was rotating. Not to mention, the EF scale doesn't care about propagation speed of a tornado, just about how much damage was done, which is then correlated to a wind speed estimate. For example, if a tornado that was rotating at 80 MPH was moving forward at 100 MPH, the damage done (on the one half side of the tornado where speeds added) would still be equivalent to that of a stationary tornado rotating at 180 MPH, but that wouldn't change the EF-scale rating.
 
Something to keep in mind about tornado dynamics is that the azimuthal (tangential) velocities are not as strong as the vertical velocities in a maximum tornado. Research by Brian Fiedler (OU) and David Lewellen (WVU) has shown that the vertical velocities in an optimal tornado exceed the horizontal velocities by at least a factor of two. When one considers the KBMX imagery, this is a stunning thought.

Another thing I found remarkable is that pretty much every tornado video I've seen from yesterday exhibited strong to violent vertical velocities in the lower part of the funnel. It seems that every tornado in this outbreak acquired an optimal configuration for producing violent tornado damage. I would not be surprised if this outbreak gives the '74 outbreak (can we still call it "The" Super Outbreak?) a run for its money, in terms of the number of violent tornadoes.
 
Dec 25, 2006
618
0
5
Iowa City, Iowa
I think a big reason for why the death toll will be so high is due to the fact that many places in Alabama had no NWR and no warning sirens because the storms that moved through in the morning took out a lot of power and infrastructure. As I was watching the ABC 33/40 stream yesterday, early in the outbreak they mentioned several times that at least 6 people in Alabama had died in the morning from earlier storms and that the warning sirens and weather radio transmitters and INTERNET were down across many areas, including those that got hit (Cullman, AL was the first big area they talked about and it was one of the first areas to get hit). Later on in the outbreak they were telling people to use their cell phones to call anyone they knew in warned areas because they were probably not going to get the warning any other way. If you remove the effects of the morning storms, many more people would probably have gotten the warnings and many more lives may have been saved. Speculation, sure, but I don't think it has no merit.
That would be a huge issue if true. Communication infrastructure could always be better... may have cost us here. Satellite feeds would be nice.
 
Jan 28, 2005
234
4
0
Haslett, Michigan
No, Mike, this is base velocity, which measures the instantaneous inbound and outbound velocities. Thus, if anything, you'd want to remove that 55 mph forward move speed to get an idea of how the vortex itself was rotating. Not to mention, the EF scale doesn't care about propagation speed of a tornado, just about how much damage was done, which is then correlated to a wind speed estimate. For example, if a tornado that was rotating at 80 MPH was moving forward at 100 MPH, the damage done (on the one half side of the tornado where speeds added) would still be equivalent to that of a stationary tornado rotating at 180 MPH, but that wouldn't change the EF-scale rating.
I would think you would add it one side..and subtract it on the other.

I was looking at this:

http://books.google.com/books?id=3z...&resnum=2&ved=0CB8Q6AEwAQ#v=onepage&q&f=false


Gives an excellent discussion on how to add tornado vectors..probably should throw in the fact that it appear to be multi-vortex from the videos which would have increased the damage potential from the internal suction vortices.
 
Jan 28, 2009
119
0
5
Conrad, Iowa
No, Mike, this is base velocity, which measures the instantaneous inbound and outbound velocities. Thus, if anything, you'd want to remove that 55 mph forward move speed to get an idea of how the vortex itself was rotating. Not to mention, the EF scale doesn't care about propagation speed of a tornado, just about how much damage was done, which is then correlated to a wind speed estimate. For example, if a tornado that was rotating at 80 MPH was moving forward at 100 MPH, the damage done (on the one half side of the tornado where speeds added) would still be equivalent to that of a stationary tornado rotating at 180 MPH, but that wouldn't change the EF-scale rating.
As I recall the Moore tornado had measured wind speeds of over 300mph well above ground level. What were the damage survey wind estimates?
 
Mar 26, 2009
174
13
5
Bismarck, ND
Let's do keep in mind that the super outbreak encompassed 6 F5 tornadoes and 24 F4's. Now I know its much harder to get an EF rating as opposed to an F rating, but numbers like that will be hard to surpass anywhere. Will this end up being considered worse than the super outbreak? Who knows, people will probably argue for years about it. All I know and care about is that it was an historic outbreak not likely to be matched any time soon and it is an extreme tragedy and it has been absolutely devastating. Do we really have to classify one as greater than the other? Can't we just call this Super Outbreak #2 and just let them both be once in a life time type events?
 
Dec 25, 2006
618
0
5
Iowa City, Iowa
I think the two better ways of measuring that would be sum(tornado path area*length) or sum(tornado path area*length*EF-scale-rating).
Not seeing why we'd want to multiply path area by length... shouldn't path area suffice?

Ideally you'd like to be able to segment a path and and do sub calculations on certain areas as the intensity of the tornado changes... but I doubt we have such data for all paths. So agree that summing path areas is probably a good baseline measure.
 

Jeff Duda

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Not seeing why we'd want to multiply path area by length... shouldn't path area suffice?

Ideally you'd like to be able to segment a path and and do sub calculations on certain areas as the intensity of the tornado changes... but I doubt we have such data for all paths. So agree that summing path areas is probably a good baseline measure.
Yes, that's correct. I have corrected that error in my post. Thanks for mentioning it.
 
Dec 8, 2003
1,526
0
0
38
Grand Forks, ND
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Ah, yeah, predicting initiation from a space and time standpoint
I'd argue that we will NEVER have perfect prediction of convection in both space and time. Even with PERFECT models, we will never have the funding and instruments required to properly observe the properties needed for input into our models.

If we are good meteorologists, this outbreak SHOULD go down as the best case-study for the societal aspects of the warning decision process.

Big questions:

Of the fatalities -
How many occurred in a proper shelter (interior of home, etc.)? <<Impossible to know... some could have been caught off guard from the speed/strength and weren't actively in a closet, etc.
How many occurred in vehicles?
How many occurred in mobile homes? etc.

Can't question the dead so we need to focus on learning as much as we can from the injured. How did they get warnings? Did they know? Did they ever hear mention of high risk/watches/etc. Did they go out to sight see and get caught off guard? etc.
 

Jeff Duda

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I would think you would add it one side..and subtract it on the other.

I was looking at this:

http://books.google.com/books?id=3z...&resnum=2&ved=0CB8Q6AEwAQ#v=onepage&q&f=false


Gives an excellent discussion on how to add tornado vectors..probably should throw in the fact that it appear to be multi-vortex from the videos which would have increased the damage potential from the internal suction vortices.
Thanks for pointing out that book. I may have to buy it.

I'm not going to argue the findings and methods of Tom Grazulis, but that doesn't change the fact that the radar measures instantaneous velocities with the tornado's move speed already factored in. Thus, you wouldn't add anything to the wind speed in the image to get a sense of the actual ground relative wind speed.
 

rdale

EF5
Mar 1, 2004
7,230
778
21
50
Lansing, MI
skywatch.org
I was kind of shocked at the number of "tornado emergency" type tornado warnings issued yesterday. I know there's some controversy in using the term tornado emergency, but the NWS has obviously adopted the term as official policy.
It was adopted last year - but it was used incorrectly by two offices this year. They are supposed to issue a "Tornado Warning" and put the TE in the text of the warning and/or followup SVSs. Several edited the header to replace "Warning" with "Emergency" which could have caused some major issues in dissemination.