tornado frequency of hitting cities

[DrPizza]

Unlucky year, or overdue? I know the number of tornadoes is up this year.

But, has anyone done the math? What percentage of the area affected by frequent tornadoes is considered urban? What's the average area covered by a tornado? Avg number of tornadoes per year? And after a few calculations, what's the probability of the average number of tornadoes per year that "should" be hitting urban areas. (By should, I mean statistically. Of course we all agree that none would be wonderful.)

 

[wuliheron]

I don't have the numbers for you, but you might also want to know how many of those tornadoes actually cause damage and loss of life. I'll never forget the video of several tornadoes passing right through downtown Miami, right between the skyscrapers, without any casualties or real damage.

I lived in tornado alley in the Ozarks myself and we would have several tornadoes jump right over the property every year. I've even looked up in time to watch them flying by overhead hundreds of feet in the air. Everyone where we lived knew that the tornadoes tended to skip off the tops of the mountains and the bottom of the valleys, so you build your house somewhere on the hillside. Joplin Missouri is a few hours drive from where I lived and right on the border of the plains and the mountains. Out on the plains there's no telling where a tornado might go.

Once in central Virginia I looked out the window when the light from a storm turned a little green, a sign of tornadoes, and saw the rain coming down so hard you'd swear you could drown just breathing. That's another sign of a tornado because they tend to throw down water ahead of them, and then just pick up again on their way out. I grabbed my wife and kids and made them stand in an interior doorway. They thought I was being silly and scaring them for no reason but, sure enough, a tornado broke an 80 lob lolly in half not 30 feet away and just on the other side of the wall.

 

[DrPizza]

I receive an email each morning with a list of recent science stories. By coincidence, one of those stories this morning was this:
http://www1.umn.edu/news/expert-alerts/2011/UR_CONTENT_340242.html
(you have to scroll down a bit.)
So, my intuition was more or less correct - urban areas should be hit; but apparently they are with a reasonable frequency and I just haven't noticed it or downplayed it simply because of the unusual strength of a couple of tornadoes that hit cities this year so far.

 

[Modelworks]

I think this is just an anomaly . One thing that always irked me somewhat with reports of record weather is that we haven't been keeping the records that long. 200 years , is that all ? So when people get upset about floods, storms, etc I try to remember that what we view as weather changes doesn't even make up 1% of weather history for the planet.

 

[dullard]

I think this is just an anomaly . One thing that always irked me somewhat with reports of record weather is that we haven't been keeping the records that long. 200 years , is that all ? So when people get upset about floods, storms, etc I try to remember that what we view as weather changes doesn't even make up 1% of weather history for the planet.

That has always bothered me too. I live in the midwest where many cities are maybe 150 years old. Weather records here go back about 120 years. If the weather was completely randomly distributed (i.e. no systematic shifts like global warming) then on any given day there is a 1 out of 120 chance of hitting a record high, record low, record wind, record rain, record snow etc for that day of the year. Since a year averages 365.2 days, that means we should get about three record highs per year, three record lows, etc. Maybe one year we get none and the next we get six because that is how random things work.

Then everyone is up in arms that any given year has record warm days, record droughts, record tornadoes, etc. That alone doesn't necessarilly mean anything.

A large majority of all of the worlds tornadoes occur in the midwest. Thus, we have maybe 100 years of good records on tornadoes (less if you consider radar wasn't invented until WW2 so many tornadoes went unnoticed or at least unreported). Any given year should then have more than 1% chance of setting a record number of tornadoes in properly recorded history.

As cities get bigger, I'd assume the number of tornadoes hitting urban areas should keep going up (slowly). If I remember correctly, in a normal post-radar year we have under 50 tornado deaths. The sad part is that we are set to far, far exceed that number this year. It may mean a systematic change (rapture, global warming, etc). Or, it may just be a random fluke.