What made the Palm Sunday Outbreak so violent?

[Robert Dewey]

You know I wonder based on the knowledge we have today what they would have rated the Tri State Tornado or even Xenia,OH.

Considering the fact that structures wern't built as strong as they are today, I would say it's safe to assume an F3/F4 rating :lol: :wink:

 

[Michael Auker]

I was surprised none of those long-track tornadoes on May 4, 2003 in southwestern Missouri got rated higher. Nov 10, 02 also had numerous F-3's. What would they have been rated fifty years ago? I wonder, if in some circumstances, the death count of some historic tornadoes might be a better indication of their violence than attempting to rate their damage?

 

[Joe Nield]

I wonder, if in some circumstances, the death count of some historic tornadoes might be a better indication of their violence than attempting to rate their damage?

A possibility, but the decline in tornado death rates over the last 50-75 years is largely a function of vastly increased public awareness and improved warning capability. It would be difficult, in my opinion, to use casualty counts as a proxy for rating historic tornadoes.

 

[Blake Naftel]

Just as a side-note to this thread; I've recently updated the Palm Sunday Outbreak homepage with a refreshed new look, new (very in-depth) article by Ronald Wilbanks covering the full geographic extent of the outbreak, and other arguments here and there.

http://homepages.wmich.edu/~b1naftel/outbreak65.html

..Blake..

 

[mikegeukes]

NOAA REMEMBERS THE MIDWEST'S DEADLY
1965 PALM SUNDAY TORNADO OUTBREAK
http://www.noaanews.noaa.gov/stories2005/s2418.htm

Mike

 

[Dave Carroll]

complicated damage

It would appear that tornado size matters as far as damage/F-scale ratings go. A short, 10 second blast of winds 261mph+ would certainly inflict damage, but a large, slow moving tornado with winds of 180mph could certainly do the job too. A large tornado might take a minute to pass over a home, subjecting the home to high winds for a substantial amount of time. It seems that once a roof/wall is compromised on a home (possible in F2-F3), winds less than F4/F5 would be needed to bring the structure to the ground, and perhaps even blow some of the now loose debris away. In essence, could a large, slow moving F3 tornado actually produce damage that would normally be assigned a higher rating?

-DC

 

[Michael Auker]

I remember the slow movement of the Jarrell, Texas tornado made some question it's F-5 status. The damage was pretty extreme though. Didn't it skin cattle?

 

[Jeff Snyder]

Re: complicated damage

Originally posted by Dave Carroll
In essence, could a large, slow moving F3 tornado actually produce damage that would normally be assigned a higher rating?

-DC

Technically, no, since if it did produce damage normally associated with a high-scaled tornado, then it would indeed be a high-scaled tornado. I mean, it's contradictory to say than an F3 tornado did F4 damage... If it does F4 damage, then it's an F4 tornado...

Now, I know the point you are trying to make -- if a tornado with WINDS in the typical F3 range sits over a structure for an extended amount of time and does catastrophic damage (F4 or F5), would it be rated F4 or F5? Remember, the F-scale is a damage scale, not a wind-speed scale. Yes, there are winds associated with each rating, but those winds are sketchy. Without being able to accurately measure ground-level wind speeds in most tornadoes, the F-scale will continue to be based upon damage produced rather than wind speeds contained. But yes, I can certainly see where a tornado with 175mph winds can do F4 damage if there is (a) a ton of debris swirling around the tornado (a roof flying at that speed does much more damage should it hit a house than air alone) or (B) an extended residence time over the structure. I think this happens quite often. I also think that there are many more violent tornadoes each year in the U.S. than climo dictates, but the vast majority of the time that a particular tornado spends with winds >220mph is likely over structure-less area. Well, now even structures aren't enough, since they need to hit WELL-BUILT structures. Given this, I'm sure there are more tornadoes with winds >220mph each year in the U.S., but most only get classified as F1-F2-F3 since they don't hit any well-built structures.

For what it's worth, there is a movement to modify the Fujita scale to take into account damage inflicted on many more types of objects (different types of trees, lightpoles, TV/radio towers, electrical transmission lines, service station canopies, etc). More information on the Fujita Scale Enhancement Project can be found at http://www.wind.ttu.edu/F_Scale/default.htm . In fact, Tim Marshall did a presentation at the 22nd Conference on Severe Local Storms regarding the EF-scale , and his presentation can be viewed online by click on "Recorded Presentation" at the bottom of http://ams.confex.com/ams/11aram22sls/tech...paper_81090.htm .

The full 95-page report titled "A Recommendation for an Enhanced Fujita Scale (EF-Scale)" submitted to the National Weather Service and "Other Interested Users" (dated June 2004) can be accessed directly at http://www.wind.ttu.edu/F_Scale/images/efsr.pdf . This is a rather interesting read...

 

[Dave Carroll]

Jeff, you hit the point I was aiming for but failed to connect! Lower, but longer duration windspeeds over a structure could produce damage that doesn't necessarily correspond to the F-Scale's windspeed guidelines....but since it is a damage-based scale, a higher rating would apply. If the well-built house is leveled, an F4 is assigned...

-DC

 

[Jeff Snyder]

Originally posted by Dave Carroll+--><div class='quotetop'>QUOTE(Dave Carroll)</div>

Jeff, you hit the point I was aiming for but failed to connect! Lower, but longer duration windspeeds over a structure could produce damage that doesn't necessarily correspond to the F-Scale's windspeed guidelines....but since it is a damage-based scale, a higher rating would apply. If the well-built house is leveled, an F4 is assigned...

-DC[/b]

I did mention this mid-way through the second paragraph:

<!--QuoteBegin-I
But yes, I can certainly see where a tornado with 175mph winds can do F4 damage if there is (a) a ton of debris swirling around the tornado (a roof flying at that speed does much more damage should it hit a house than air alone) or (B) an extended residence time over the structure. I think this happens quite often

A tornado with 175mph winds is mid-range F3 by the windspeed estimates (which they are, despite the falsely-implied precision by going to the singles digit), but certainly could do F4 damage if it sits over a house for some longer time (or if there's a lot of debris in the tornado), and thus be rated F4. I see what you are saying, and I completely agree with you! The EF-scale seems to be a step in the right direction, that's for sure! Tornado "strength" and damage produced is much more than a sole function of wind speed... It seems to also be a function of residence time (the amount of time a tornado affects any particular location), debris concentration, structural integrity, etc, etc, etc.

 

[Dave Carroll]

Agreed!

Jeff, in my earlier posting I was referring to MY failure to connect and get the point across...YOU were right on target! The entire process seems almost too difficult to overcome, as so many variables contribute to the damage and it may be next to impossible to trace which one(s) caused it. I agree wholeheartedly that the EF Scale is a step in the right direction.

-Dave