I'm not surprised. This is the beginning of tornado season in the U.S., and it's gotten off to a violent start. You need several ingredients for tornadic thunderstorms-
1)Two air masses that differ vastly in temperature and humidity.
2) A fast-moving jet stream above.
3) Winds blowing in different directions at different altitudes.
The reason spring is such an apt time for tornadoes in the U.S. is due to the contrasts in warm and cold air masses, as I indicated above. In the middle of the U.S., topography (the Rocky Mountains) is an added ingredient for creating deadly tornadoes-in particular, F3s F4s and the deadliest-F5s, which contain winds of up to 318 mph. The F-scale was created by Dr. T. Theodore Fujita. The instability that results from the cold and warm air masses colliding creates violent supercell thunderstorms. The winds going at different speeds in the atmosphere create a twist, which cause the thunderclouds to spin. The jet stream acts as a bottle opener, allowing the rising moist warm air that feeds the thunderclouds to rise explosively. Combine all that, and you get a tornado.
With the Rocky Mountains, they add a further bit of imbalance. Cold air usually goes under warm air, causing it to rise. When cold dry air comes off of the Rocky Mountains, it can sometimes come off at such a speed that when it collides with the warm air, part of the cold air mass goes over a section of the warm air, creating an even greater imbalance. When the jet stream removes this cap, the results are even more explosive, leading to large tornado outbreaks and some monster tornadoes that can be up to 2 miles wide.
For those folks who live in Tornado Alley, make sure you have a weather radio. I own one-I've owned them for over 30 years. Last summer, I had a tornado-warned thundercloud go right over my house!!
It was Doppler-radar indicated, but it didn't drop any funnels. It did put out a LOT of lightning, though. In the past, tornadoes were very rare in my area, but in recent years, I've been noticing an increasing number of them. And they are not just increasing in number-they are also getting more ferocious. Last summer, twin tornadoes struck Brooklyn, New York, causing extensive damage. Tornadic winds were determined by the National Weather Serice to be around 150 mph!!
Edited by Analog Kid, 17 April 2011 - 06:42 PM.