A tornado is a violently swirling column of air, a “funnel cloud” that stretches from the base of a thunderstorm down to the ground. In mere minutes, it can level a swath as large as one mile wide and fifty miles long. Winds up to 300 miles per hour can crush sturdy structures, uproot trees, and turn heavy objects like cars or utility poles into unguided missiles.
Although tornadoes are more common on the Great Plains, they have been reported in every state. They tend to touch down rarely (only once in every five to ten years) and in no particular sector of the New River Valley more than another. But they have been nonetheless severe. A 1987 twister caused nearly 3 million dollars worth of damage in Montgomery County. The risk of tornados is greatest around Blacksburg from April through June, but they can occur from March through October.
It is vital to understand that forecasts of extreme weather can be helpful but will never be absolutely perfect. Actual conditions may turn out better or worse than predicted, and they may change too late to broadcast.
Tornado Watch: Conditions favor the development of a tornado. Be prepared. Tornadoes are possible in and near the watch area. Be ready to act quickly if a warning is issued or if you see a tornado approaching. Review plans; check supplies and your safe room. Acting early helps to save lives!
Tornado Warning: A tornado has been sighted or indicated by weather radar. Tornado warnings indicate imminent danger to life and property. Go immediately under ground to a basement, storm cellar or an interior room (closet, hallway or bathroom).
Levels of severity
Tornado intensities are classified on the Fujita Scale with ratings between F0 (weakest) to F5 (strongest).
|Category||Category Description||Level of Damage|
|F-0||Gale Tornado, 40-72 MPH||Chimneys damaged; branches broken off trees; shallow-rooted trees uprooted; sign boards damaged.|
|F-1||Moderate Tornado, 73-112 MPH||Roof surfaces peeled off; mobile homes pushed off foundations or overturned; moving autos pushed off roads.|
|F-2||Significant Tornado, 113-157 MPH||Roofs torn off frame houses; mobile homes demolished; box cars pushed over; large trees snapped or uprooted; light-object projectiles generated.|
|F-3||Severe Tornado, 158-206 MPH||Roofs and some walls torn off well-constructed houses; trains overturned; most trees in forest uprooted; heavy cars lifted off the ground and thrown.|
|F-4||Devastating Tornado, 207-260 MPH||Well-constructed houses leveled; structures with weak foundations relocated; cars thrown and large projectiles generated.|
|F-5||Incredible Tornado, 261-318 MPH||Strong frame houses lifted off foundations and carried considerable distance to disintegrate; automobile-sized projectiles hurtle through the air in excess of 100 yards; trees debarked; other incredible phenomena expected.|