Wednesday's tornado was roughly 1/4 - 1/2 mile wide and travelled at least 1 1/2 miles on the ground, moving east into the avenues and memory grove. It lasted for approximately 9 min. and is being considered a once-in-a-lifetime event.

tornado:
Source: www.infoplease.com

Dark, funnel-shaped cloud containing violently rotating air that develops below a heavy cumulonimbus cloud mass and extends toward the earth. The funnel twists about, rises and falls, and where it reaches the earth causes great destruction. The diameter of a tornado varies from a few feet to a few miles; the rotating winds attain velocities of 200 to 300 mi (320–480 km) per hr, and the updraft at the center may reach 200 mi per hr.

The atmospheric conditions required for the formation of a tornado include great thermal instability, high humidity, and the convergence of warm, moist air at low levels with cooler, drier air aloft.

It travels in a generally northeasterly direction with a speed of 20 to 40 mi (32–64 km) per hr. The length of a tornado's path along the ground varies from less than one mile to several hundred.

	F0   72 mph F1   73 - 112 mph F2   113 - 157 mph F3   158 - 206 mph F4   207 - 260 mph F5   261 - 318 mph

About 1% of the tornados reported during any given year are categorized as a F4 or F5. However, 70% of all deaths reported are attributed to either an F4 or F5.

Meteorologists will tell you that tornadoes can occur anywhere if the conditions are right. But they are extremely rare in the Salt Lake City area.

High mountains make the air less dense, which makes it harder for a cloud base to spin out of control and touch the ground.