Nova had a special tonight on the tornadoes in april in 2011. I live just East of the Mississippi valley in Illinois, just on the lea side of the bluffs that flank the river on either side. Through many years of observation, it seems to me that if a tornado forms in the river bottoms, by the time it gets near us that it skips over us and lands 5-10 miles to the East NE,SE, depending on the direction of the storm. Is this just my imagination, or am I protected in some way by the topography of the land and its relation to the storm? I am of the mind that if a tornado was to form directly above us and drop down right here we’d be toast. Excepting that, I’m just wondering,“does a tornado hug the ground, or does it skip and jump according to the terrain?”
There seems to be some strange “vortex” involving Nashville that causes weather systems to detour around it or skip over it often enough to be noticeable to me.
Not long ago I ran across some details on tornado histories but I’m not sure if it was this one http://www.tornadohistoryproject.com/ or some other like it.
Maybe that sort of source could help you decide the odds in your specific area.
though tornadoes mostly follow the winds that cause the storms and come from the southwest, they can go any direction. the farther north of the gulf then the less strongly they might be steered.
i saw evidence of a small tornado having coming over a hill causing damage on the down side to trees.
Don’t bet your life or home on it; folks used to say that about Omaha and Oklahoma City.
I certainly won’t and don’t. I pay close attention to our weather. That 2010 flood spooked me big time, and the tornados nearby have had my nerves shot for days. I even take cover for severe thunderstorms, of which we have more than enough.
But it’s still the case that a good percentage of bad weather events skip over us. Not long ago (maybe 10 years) one of the big hurricanes swept across Florida and headed up through Georgia and Alabama, dropping much rain and carrying stiff winds. I watched it on the radar on my computer as it headed straight for us. It stopped cold at the county line. I shit you not.
Tornados form well above the land in the atmosphere. Masses of moving air move past each other in the right conditions creating a vortex, which may reach down to the ground. The high winds from the vortex are very damaging whether or not they form the classic funnel shape. The atmospheric conditions maintain the vortex. The land topography affects the atmospheric conditions that create and maintain tornados, and has some affect on maintaining the vortex at ground level. I’d wager that with the right atmospheric conditions, a tornado can touch down anywhere. But topography probably produces zones of likely and unlikely tornado formation.
Hills and cliffs don’t affect anything, tornadoes can even form in mountains. Tetsuya Fujita, who created the Fujita scale, once documented a tornado go a couple thousand feet up the side of a mountain in Yellowstone.
The one good thing you sort of have going for you is the river. If a tornado crosses, it will pick up tons of water which will slow it’s rotation. But that doesn’t mean one can’t make it across and still be strong, form on top of you or come from another direction. Tornadoes generally tend to follow the general track of their parent storm, but rotating storms tend to wobble, don’t always go west to east, and they have a lot of dynamics going on that can affect the tornado’s path.
Tornadoes do skip and jump but it isn’t because of terrain because they can do it on flat ground. I’m not sure if there is any research or theories on lifting.
You may be interested in this site.
Thanks for the link. I’ll add it to the several I use depending on what level of detail I’m needing at the moment.
My go-to places worth sharing are
Intellicast
and
Wunderground
The Wunderground link in my Favorites Bar is customized to my ZIP code and I can zoom the radar to my neighborhood.
Until recently Channel 2’s weather blog had been my go-to for forecasts, but they just redid their site and now it’s harder to get around in.
I have another four or five places I check periodically, but these are where I go when I need quick pictures of stuff.
Mr. Neville claims topography can make some areas immune to tornadoes. I am very skeptical of this, given the history of that kind of claim. Anyway, he’s an astronomer, not a meteorologist.
There is some truth to that. Topography does affect the number of tornadoes seen in some areas, but it’s due to things that affect the local climate and make conditions for tornadoes unfavorable like deserts and mountains. But even then, large scale topography doesn’t make tornadoes impossible, they just make for lower average numbers of them. All 50 states have had tornadoes and there is nowhere that they are impossible. But cliffs or rivers won’t stop them from forming or stop them once formed.
The fallacy is that geography can make a region or city “tornado proof.”
My observation from having spent some significant time doing research on sites and data like the Tornado History Project is that there appears to be less of a tendency for small tornadoes (EF0-EF2) to not form in cities, and also a tendency to skirt around or die out quickly upon entering a heavily developed area. Not a guarantee, but just a tendency. And only with weak tornadoes.
My theory is that the conditions which allow formation of (relatively) weak tornadoes are such that the local climate is more heavily influenced by wind pattern disturbances and heat island effects of cities. Again, I am not claiming nor alleging anyplace being tornado proof, not saying that it seems to impact stronger tornadoes.
I’ve been exploring how to do a proper statistical analysis of this on my own for The Straight Dope, but I am not sure I have the horsepower to do it.
Is there any hard data on this? I’ve seen this before but there are actually a lot of tornadoes in cities, and the National Severe Storms Laboratory tends to disagree that they are hit any less. But the dissenting viewpoint seems to be driven by simple numbers. Any given area is expected to have X tornadoes and downtown areas have around X that have actually happened. The heavy populated downtown areas are always so small that they are hard to hit, but seemingly have no less tornadoes than a small area anywhere else. Is there anything that actually shows a city having an effect on certain storms? Maybe the wind patterns around large buildings could affect the lower side of the wind shear vortex as it begins to tilt up and form a tornado or something.
I realize it’s understudied. One study on the downtown Atlanta tornado of 2008 actually says the opposite, that the city landscape helped it form, but I’m skeptical of it for other reasons.
I don’t know. As I tried to stress above, this is an observation of mine as a result of research, leading to a theory which I would like to test. I do not assert anything at this juncture. And as I said upon investigating the issue, I don’t know that I have the ability to test my theory, yet.
Yes, albeit a rather old (1978) study for St. Louis (which also happens to be where I live):
Most recently, there was a huge hailstorm, or rather, two hailstorms, and they seemed to intensify as they moved across the area. On the other hand, I too see plenty of people making claims that storms die out or move around the area for whatever reason (but people everywhere say that; a thunderstorm is far smaller and shorter-lived than, say, a hurricane, so it isn’t surprising that they seem to “miss”).
I was going to bring up the Atlanta tornado of 2008 (wow, was it really FOUR years ago!) as a counter-example of a tornado-proof city. Atlanta has a significant ‘heat island’ effect that causes storms to tend to pass north or south of the city. Large fronts will ignore this, but the smaller ‘popcorn’ variety of afternoon and evening thunderstorms definitely follow the pattern. That leaves the eastern suburbs with lower precipitation and smaller storms.
Aha, I’ve been reading interesting stuff. I think there’s two things going on here, heat islands and the city structure itself. Heat islands behave like I assumed, they actually cause bad weather. The rising air causes precipitation or localized storms to form over and/or downwind of the city. The city and areas downwind actually get a lot more precipitation than they should. A storm that approaches a heat island can be pulled toward it because the rising air leaves an area of low pressure beneath it. A heat island can also intensify a storm because storms love updrafts. Also, pollution from a city provides a lot of condensation nuclei for cloud formation. So altogether, heat islands are generally rainmakers.
But apparently there’s something called “urban bifurcation” which means that precipitation will lessen over the city center due to the “building-barrier effect”, a low level difluence from surface roughness. I.e., buildings scatter the wind. If I read it right, this is only possible when the city isn’t acting as a heat island, which makes sense because rising air from a heat island would cause a convergence, or winds going toward the center.
But, there are urban heat island days and bifurcation days. Generally, UHI has more effect when everything is calm and bifurcation happens when there are strong regional winds. But bifurcation is somewhat rare and there is indication that certain upper level conditions may be important.
Some cities don’t seem to bifurcate, possibly because of their layout, and some don’t have a heat island effect that does much. None of this effects tornadoes, but I wouldn’t rule it out. I would look more towards the same things that cause bifurcation though, the buildings. Maybe there’s an aspect that could affect something but, In my mind, a tornado would love the heat island effect.
There’s plenty more examples, and that’s apparently just a cherry picked list of tornadoes that hit the central business districts. NYC has had 10 inside the city since 1950, 5 of those since 2003.
One went through downtown Ft Worth TX in 2000
http://en.wikipedia.org/wiki/2000_Fort_Worth_tornado
I saw the damage first hand the next day, unreal
A bit OT, but say I’m driving down the road and oh shit! I got no cover. Do I dive into a ditch or a ravine or something? Stay in the car and push the pedal–does speed help? And there’s that hail… and you in the cawntry…
You can usually outrun a tornado, although they say not to. If you’re stuck in the car, you’re probably dead, but point the nose toward the twister anyway. It will give you a lower wind profile and the windshield is the strongest glass in the car and will afford some protection. Lay down and expect the windows to blow out. Cover your head, most deaths come from head injury.
If possible, get out and away from the car. I think the second leading number of deaths happen in cars. A highway overpass is not as good as it seems, the winds are intensified underneath and debris flies under it without any trouble. Get to a sturdy building if possible and get to the lowest point, away from windows and/or with the most walls between you and outside.
Outdoors, wind speed at the ground level can still be approaching 0 in a tornado while it may be 200mph a few feet up. The best thing is to lay flat in a ditch or depression and protect your head. Yeah, that doesn’t sound good at all, but it’s your best bet.
The killer is debris. It doesn’t lazily pass overhead giving you time to duck like in the movie Twister. Instead, imagine every object within a mile, thousands of them, suddenly flying toward you at 200 mph. Then away from you. Then side to side. And back and forth for seconds or minutes. There are some amazing tornado videos from surveillance cameras where you realize that if you stuck a finger outside for 5 seconds, something would cut it off. The sound of debris hitting a house is like raindrops in number, too many to count, and all potentially deadly missiles.
ETA: there are surely many resources in the web that will be better than my advice. Everyone should spend a few minutes reading up on what to do in case your area’s number comes up.
if a tornado is very close then get out of the car. an auto is little protection against debris, you will get peppered by its glass. straw gets nailed into buildings and trees. get into the ditch along side the road and hang onto the grass. debris and wind will pass over your head.