Are tornadoes more difficult to form over several sqr miles of concrete vs bare land?

Question

They seem to form over cities at a much smaller rate than outside of hughly developed areas.

My hypothesis is that the tempature over developed areas is different than over bare land. I don't know. please enlighten me.

Answer 1

You say "several sqr miles of concrete", but then there is a reference to large cities, so I think you mean cities rather than flat expanses of concrete, such as at a very large airport...

Large cities occupy only a tiny fraction of the earth's surface. As far as Tornado Alley is concerned, tornadoes occur there pretty much randomly. Any one spot is about as vulnerable to being struck by a tornado as any other. Therefore, if open farmland accounts for, say, 95% of The Alley, then approximately 95% of the paths of tornadoes is on open farmland.

Sometimes a tornado's path is 5 or 10 miles long. If a quarter mile of that path was part of a town, then that is what you will hear about on the news; "Tornado hits town", even if the damage path was 96% on open fields.

Cities are pretty much always warmer than the surrounding open lands. They are a "heat island". Warmth generally enhances the likelihood and severity of tornadoes (although the dewpoint depression would be greater, but I won't get into that right here...), which would make cities a more favorable spot for a tornado to develop, but the friction of the buildings, as well as all the trees that people like to have in their yards, etc. in cities, on the flow of surface winds probably negates that effect. Tornadogenesis is enhanced, though to what extent would be contentious, by flat, featureless, treeless land under a thunderstorm. That's because inflow winds into the base of a storm are crucial to tornadogenesis.

To summarize, tornadoes are just about as likely to occur over cities as anywhere else, but they don't occupy much of the total land area. Ergo, most tornadoes occur outside cities. The higher temperature in a city is mostly irrelevant, but if it WERE to make a difference, it would likely increase the chance of a tornado.

Answer 2

Your theory is irrelevant. The temperature between bare land and the city has nothing to do with tornadoes forming. It has something to do with more space for tornadoes to roam and the dynamics favorable for them. However, several sqr. miles of concrete doesn't make a differnce between farmland, what matters is how much density is surrounding the land.

Answer 3

Toyota plant parking lot of asphalt and concrete in SE America
Versus
Open Farmland in Kansas

Heat is heat, they will form over both, its the moisture and wind conditions NOT the ground

Answer 4

Tornadoes can form anywhere on the planet, so long as the conditions are correct.
More complete info at the reference

Answer 5

Weather conditions flat lands and trailer parks. I've seen a lot of tornado's around here boy it gets really breezy.

Answer 6

Read this:

http://encarta.msn.com/encyclopedia_761554892/Tornado.html

Answer 7

i think they don't form in citys b/c all the buildings create dead spots in the wind. That's just a guess thou.