Important information on Tornado's

How are Tornado's 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

 

A lower cloud base in the center of the photograph identifies an area of rotation known as a rotating wall cloud. This area is often nearly rain-free. Note rain in the background.

 
Moments later a strong tornado develops in this area. Softball-size hail and damaging "straight-line" winds also occurred with this storm.

Weak Tornadoes

• 69% of all tornadoes
• Less than 5% of tornado deaths
• Lifetime 1-10+ minutes
• Winds less than 110 mph

Strong Tornadoes

• 29% of all tornadoes
• Nearly 30% of all tornado deaths
• May last 20 minutes or longer
• Winds 110-205 mph

Violent Tornadoes

• Only 2% of all tornadoes
• 70% of all tornado deaths
• Lifetime can exceed 1 hour

Tornado Myths:

MYTH: Areas near rivers, lakes, and mountains are safe from tornadoes.
FACT: No place is safe from tornadoes. In the late 1980's, a tornado swept through Yellowstone National Park leaving a path of destruction up and down a 10,000 ft. mountain.
MYTH: The low pressure with a tornado causes buildings to "explode" as the tornado passes overhead.
FACT: Violent winds and debris slamming into buildings cause most structural damage.

MYTH: Windows should be opened before a tornado approaches to equalize pressure and minimize damage.
FACT: Opening windows allows damaging winds to enter the structure. Leave the windows alone; instead, immediately go to a safe place.

Tornadoes Occur Anywhere

Carolinas Outbreak:

• March 28, 1984, afternoon-evening
• 22 tornadoes
• 57 deaths
• 1,248 injuries
• damage $200 million
• 37% of fatalities in mobile homes

 

Pennsylvania-Ohio Outbreak:

• May 31, 1985, late afternoon-evening
• 41 tornadoes, including 27 in PA and OH
• 75 deaths in U.S.
• 1,025 injuries
• damage $450 million

 

Plains Outbreak:

• April 26-27, 1991, afternoon of 26th through early morning 27th
• 54 tornadoes
• 21 deaths
• 308 injuries
• damage $277+ million
• 15 deaths in/near mobile homes, 2 deaths in vehicles

Frequency of Tornadoes

Tornadoes can occur at any time of the year.

• In the southern states, peak tornado occurrence is in March through May, while peak months in the northern states are during the summer.
• Note, in some states, a secondary tornado maximum occurs in the fall.
• Tornadoes are most likely to occur between 3 and 9 p.m. but have been known to occur at all hours of the day or night.
• The average tornado moves from southwest to northeast, but tornadoes have been known to move in any direction. The average forward speed is 30 mph but may vary from nearly stationary to 70 mph.
• The total number of tornadoes is probably higher than indicated in the western states. Sparce population reduces the number reported.

NOAA WEATHER RADIO IS THE BEST MEANS TO RECEIVE WARNINGS FROM THE NATIONAL WEATHER SERVICE

The National Weather Service continuously broadcasts updated weather warnings and forecasts that can be received by NOAA Weather Radios sold in many stores. The average range is 40 miles, depending on topography. Your National Weather Service recommends purchasing a radio that has both a battery backup and a tone-alert feature which automatically alerts you when a watch or warning is issued.

What To Listen For...

• TORNADO WATCH: Tornadoes are possible in your area. Remain alert for approaching storms.
• TORNADO WARNING: A tornado has been sighted or indicated by weather radar. If a tornado warning is issued for your area and the sky becomes threatening, move to your pre-designated place of safety.
• SEVERE THUNDERSTORM WATCH: Severe thunderstorms are possible in your area.
• SEVERE THUNDERSTORM WARNING: Severe thunderstorms are occurring.