Tornadoes

Tornadoes are nature’s most violent storms. Spawned from powerful thunderstorms, tornados can cause fatalities and devastate a neighborhood in seconds. A tornado appears as a rotating, funnel-shaped cloud that extends from a thunderstorm to the ground with whirling winds that can reach 300 miles per hour. Damage paths can be in excess of one mile wide and 50 miles long.

Some tornadoes are clearly visible, while rain or nearby low-hanging clouds obscure others. Occasionally, tornadoes develop so rapidly that little, if any, advance warning is possible.

Before a tornado hits, the wind may die down and the air may become very still. A cloud of debris can mark the location of a tornado even if a funnel is not visible. Tornadoes generally occur near the trailing edge of a thunderstorm. It is not uncommon to see clear, sunlit skies behind a tornado.

Tornado Facts

They may strike quickly, with little or no warning.

They may appear nearly transparent until dust and debris are picked up or a cloud forms in the funnel.

The average tornado moves Southwest to Northeast, but tornadoes have been known to move in any direction.

The average forward speed of a tornado is 30 MPH, but may vary from stationary to 70 MPH.

Tornadoes can accompany tropical storms and hurricanes as they move onto land.

Waterspouts are tornadoes that form over water.

Tornadoes are most frequently reported east of the Rocky Mountains during spring and summer months.

Peak tornado season in the southern states is March through May; in the northern states, it is late spring through early summer.

Tornadoes are most likely to occur between 3 p.m. and 9 p.m., but can occur at any time.

Tornadoes are nature's most violent storms.

What Causes Tornadoes?

Thunderstorms develop in warm, moist air in advance of eastward-moving cold fronts. These thunderstorms often produce large hail, strong winds, and tornadoes. Tornadoes in the winter and early spring are often associated with strong, frontal systems that form in the Central States and move east. Occasionally, large outbreaks of tornadoes occur with this type of weather pattern. Several states may be affected by numerous severe thunderstorms and tornadoes.

During the spring in the Central Plains, thunderstorms frequently develop along a "dryline," which separates very warm, moist air to the east from hot, dry air to the west. Tornado-producing thunderstorms may form as the dryline moves east during the afternoon hours.

Along the front range of the Rocky Mountains, in the Texas panhandle, and in the southern High Plains, thunderstorms frequently form as air near the ground flows "upslope" toward higher terrain. If other favorable conditions exist, these thunderstorms can produce tornadoes.

Tornadoes occasionally accompany tropical storms and hurricanes that move over land. Tornadoes are most common to the right and ahead of the path of the storm center as it comes onshore.

How Tornados are Formed

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, 2-6 miles wide, now extends through much of the storm. Most strong and violent tornadoes form within this area of strong rotation.

Tornado Sizes

Weak Tornados

69% of all tornadoes

Less than 5% of tornado deaths

Lifetime 1-10+ minutes

Winds less than 110 mph

Strong Tornados

29% of all tornadoes

Nearly 30% of all tornado deaths

May last 20 minutes or longer

Winds 110-205 mph

Violent Tornados

Only 2% of all tornadoes

70% of all tornado deaths

Lifetime can exceed 1 hour

Winds exceed 205 mph

What to do During a Tornado

If Indoors

Go to a pre-designated shelter area such as a safe room, basement, storm cellar, or the lowest building level. If there is no basement, go to the center of an interior room on the lowest level (closet, interior hallway) away from corners, windows, doors, and outside walls. Put as many walls as possible between you and the outside. Get under a sturdy table and use your arms to protect your head and neck. Do not open windows.

If in a Car

Get out immediately and go to the lowest floor of a sturdy, nearby building or a storm shelter. Mobile homes, even if tied down, offer little protection from tornadoes.

If Outdoors

Lie flat in a nearby ditch or depression and cover your head with your hands. Be aware of the potential for flooding. Do not get under an overpass or bridge. You are safer in a low, flat location. Never try to outrun a tornado in urban or congested areas in a car or truck. Instead, leave the vehicle immediately for safe shelter. Watch out for flying debris. Flying debris from tornadoes causes most fatalities and injuries.

(The information contained on this page comes from the Federal Emergency Management Administration)