How do Tornados Form?
High in the atmosphere, cool air pushes against warm air. The place where the two kinds of air meet is called a front. A front can stretch over 100 miles (161 kilometers). On warm days, the air near the ground is much warmer than it is at higher elevations. Warm air rises by bubbling up from the ground, just like the bubbles in a pot of boiling water. If the air has enough moisture in it, the moisture condenses and forms cumulus clouds. Sometimes, the rising air is trapped by a layer of cooler air above it. As the day continues, the warm air builds up. If this pocket of warm air rises quickly, it can break through the cap of cooler air like water shooting up from a fountain and a thunderhead or cumulonimbus (kyu-mya-lo-NIM-buhs) cloud, grows, topped by an anvil cloud. The thunderheads most likely to cause tornadoes are those that form along and ahead of fronts. Strong, fast winds tend to blow along and above fronts. If slower surface winds blow opposite to the direction of the higher w
Tornadoes can travel at any speeds. The average foreward motion of a tornado is between 25-35 mph, however, speeds can vary from stationary to as much as 65-70 mph! The average direction a tornado travels is from Southwest to Northeast but again tornadoes can travel in any direction. Tornadoes are most likely to strike areas to the East of the Rocky Mountains and to the West of the Appalachians. However, tornadoes can strike anywhere in the United States and in the world (except Antarctica and North Pole). For tornadoes to form you need warm moist air at the surface and cold dry air aloft. The warm moist air rides Northward from the Gulf of Mexico and the cool dry air comes in from Canada or from air traveling over the Rocky Mountains. You also need lots of speed shear (change of wind speeds with height) and directional shear (change in wind direction with height). You don’t want wind speeds to be too strong though as this can actually kill off tornadoes b/c the updraft gets tilted too
