Tornado season … be alert

A tornado is defined as a violently rotating column of air extending from a thunderstorm to the ground.

The most violent tornadoes are capable or tremendous destruction with wind speeds of 20\50 MPH or more. Damage can be in excess of one mile wide and 50 miles long. In an average year, 800 tornadoes are reported nationwide. Only a small percentage actually strike occupied buildings, but every year a number of people are killed or injured.

In 2001, 74 tornadoes touched down in Minnesota; one in Morrison County. (From 1950 through 2001 16 tornadoes were reported in Morrison County).

How do tornadoes form? According to the National Oceanic and Atmospheric Administration (NOAA), before thunderstorms develop, a change in wind direction and an increase in wind speed with increasing height creates an invisible, horizontal spinning effect in the lower atmosphere. Rising air within the thunderstorm updraft tilts the rotating air from horizontal to vertical; an area of rotation 2-4 miles wide, now extends through much of the storm. Most strong and violent tornadoes form within this area of strong rotation.

Some tornadoes may form during the early stages of rapidly developing thunderstorms. This type of tornado is most common along the front range of the Rocky Mountains, the Plains and the Western States.

Tornadoes may appear nearly transparent until dust and debris are picked up. Occasionally, two or more tornadoes may occur at the same time.

Often times people disregard or are confused by the terminology used by media to describe the approaching storm.

A Tornado Watch means weather conditions are favorable for the formation of tornadoes. One should be alert and stay informed of changing weather conditions.

A Tornado Warning means a tornado has been sighted and one should seek shelter immediately. Do not wait for a warning signal. One should have a portable radio to take with them to keep informed of changing weather conditions. Important things to remember during this time include:

•Stay away from windows, doors and outside walls.

•In homes or small buildings, go to the basement or to an interior part of the building on the lowest level. Closets, bathrooms or other small rooms offer the best protection in many cases.

• In schools, hospitals, nursing homes, office buildings, shopping malls and other public buildings, go to predesignated shelter areas. The basement or interior hallways on the lowest floor are usually best. Avoid auditoriums, gymnasiums or large areas with poorly supported roofs.

• In mobile homes or vehicles, leave them and go to more substantial shelter.

• If outdoors, with no shelter viable, lie flat in a nearby ditch and shield head with arms.

Two other weather warnings one should know is the meaning of a severe thunderstorm watch and a severe thunderstorm warning.

A Severe Thunderstorm Watch means weather conditions are favorable for severe thunderstorms, including high winds, hail, heavy rain, lightening and tornado formation. One should be alert and stay informed of the changing weather conditions.

A Severe Thunderstorm Warning means severe thunderstorms have been sighted or indicated on radar. One should stay tuned to a radio or television for the latest advisory information and be prepared to seek shelter. Tornadoes may accompany severe thunderstorms. One should also be aware that heavy rains causing flash flooding, large hail, winds and lightening may accompany severe thunderstorms.


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