Tornadoes Vs. Straight Line Winds

PHILADELPHIA (CBS) - Tornadoes usually form in the Midwest in an area dubbed "Tornado Alley."

This is where warm, moist air and cooler, drier air clash, causing lots of upward motion.

Wind speeds that vary in direction and speed from the ground well up into the atmosphere. This wind shear helps rotate those upward moving air parcels, causing tornadoes.

Straight line winds develop in a very different way. As thunderstorms mature, cool, dry air forms within clouds, and, over time, becomes much heavier than the surrounding warm air.

This causes the air to rush toward the ground and spread out at extremely fast speeds that can reach 100 mph.

It is often hard to tell whether a tornado or straight line winds will develop during a thunderstorm.

Meteorologists will then have to wait until the storms have passed, so they can go out and do a site survey.

What they investigate is the direction of the debris. In straight line winds, the debris will be pushed in a single direction while a tornado throws debris in various directions, due to the rotating winds.