Saturday, April 30, 2011

How Powerful Were These Tornadoes?

From Fox News, Smithville, MS
I'm always glad to try to answer questions from my readers but I wish to mention again that all of the surveys of damage and tornado paths are not completed so it is very difficult to make definitive statements about this month's tornadoes versus, say, the Superoutbreak of 1974 (where the surveys obviously are completed).  Again, I have been asked why is the death toll was so very high, now ranking with the 1974 "Superoutbreak."

Here is an illustration: the Smithville, MS tornado (above) has been rated EF-5. This tornado was so strong it pulled up the pavement and tore out a culvert. This type of damage is extremely rare. Maybe one tornado in 1,000 reaches this destructive power. When you are dealing with tornadoes of this violence, there are very few places that offer adequate shelter (i.e., even a basement would be unsafe), thus the extremely high death toll. As far as I am able to determine (again with the caveat that the studies are nowhere near complete) the forecasts and warnings were very good.

6 comments:

  1. To be fair, the death toll is a result of the combination of this sheer destructive power that renders basement shelters vulnerable, the lack of basements in soil with high clay content, and the power outages from earlier storms.

    I don't know how many home builders will consider including a dedicated storm shelter (not just a basement) deep enough, and with a sufficiently strong door, to not be damaged even by an EF-5. But I have a portable AM/FM/WB radio that can run off batteries as well as recharge via cranking its dynamo. I strongly encourage anyone who lives between the Rockies and Appalachians to have at least one of these (perhaps pre-positioning one inside the storm shelter), so that they can make an informed decision about when the threat is clear.

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  2. I'd like to see an index of tornado and tornado outbreak destructiveness. I'm thinking something like Fujita * width * track length. Add it up for an outbreak.

    For example, suppose the most recent outbreak included 10 F5s, with 1/2 mile width and 200 mile track. That would be:

    5 (Fujita) * 0.5 (width) * 200 (track) * 10 (number) = 5000 tornado destructive index.

    I'd bet this outbreak is the highest recorded.

    Even ignoring the strength, 10 tornados, 0.5 miles wide, 200 mile tracks = 1000 square miles. That's an area the size of Rhode Island!!!

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  3. There was an attempt to do this called the "Fujita-[Allen] Pearson Scale" where the F-number was the intensity and the second two numbers were width and path length. Unfortunately, it never caught on.

    You are correct that this was a very major outbreak.

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  4. I remember the 1974 Outbreak from a 9 year old point of view and my most vivid memory is local radio dj's urgently telling people to take cover. I watched the beginning of the 2011 Outbreak in Mississippi at work on both a computer and tv. All the local TV stations had broke from regular programming and did an excellent job covering the storms. As I left work, I knew there was a tornado on the ground within 50 miles north and east of me. During the 20 minute drive I scanned the radio and local radio stations were playing piped in music with some breaks for the watches and warnings from the NWS. After the 15 seconds of fog horn it took the mechanical voice another 30 seconds to tell me that the NWS office in Memphis had issued a Tornado Watch for my county- (my county was the 13th county listed). From TV and radar I was pretty sure a couple of really bad tornadoes had already been through and the local TV weatherman had warned me to "take cover now" an hour before. Once I got home, the Birmingham tornado was being broadcast live and I've seen video of the local coverage. I own a weather radio, but if a person is driving or even listening to a local station while at work-that is a weak link in the warning system right now. One first hand story I have heard from a survivor is that they had a radio on listening to music on a local station while at work but were warned by someone who came into their place of business. Those old radio dj's scared the crap out of a 9 year old in 1974- but they did a much better job of getting the word out quickly than radio does today.

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  5. "Those old radio dj's scared the crap out of a 9 year old in 1974- but they did a much better job of getting the word out quickly than radio does today."

    You are correct: There are radio stations today that do a good job (KMOX, St. Louis; KDFI, Wichita, etc.) but these tend to be the news/talk format. The rest are often automated and do a fair to even terrible job. In 1974 (and I was in the radio business then) there was no such thing as a fully automated station. There are lots of automated stations now.

    That is why I increasingly believe tapping into GPS and cell phones is the way to go for people on the move. Radio, in too many cases, has given up its advantage for that audience.

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  6. Another interesting idea I read in the past couple of days would be to have the big online gaming companies (Microsoft's XBox Live, Sony Playstation Network, etc.) actually break into games with alerts. Might be good to have Facebook and other social networking sites broadcast warnings also.

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