2. Tornadoes can occur at anytime of the day or night and in almost any month of the year. However, most tornadoes occur in the months of April, May, June and July in the late afternoon and evening hours usually between 3-7pm.
3. Tornadoes usually come from the western horizon and have been known to travel at speeds of up to 70 mph.
4. Tornadoes that develop from thunderstorms that occur early in the season have a tendency to be the most intense.
5. The average tornado is on the ground less than 10 minutes and travels a distance of about 5 miles. However, they have stayed on the ground for more than three hours and traveled more than 200 miles.
6. The width of the tornado as it touches the ground averages 200 to 400 yards but may be wider, up to one mile across.
7. Tornadoes usually turn counter-clockwise with wind speeds that vary from under 100 mph to approaching 300 mph.
8. Tornadoes develop from dark thunderstorm clouds and research has shown that many tornadoes occur toward the southwestern edge of the thunderstorm cloud.
9. The greatest frequency of tornadoes occurs during temperatures between 70 and 75 degrees with high relative humidities.
10. Tornadoes do their destructive work through the combined action of their strong rotary winds, flying debris, and the partial vacuum in the center of the vortex.
A Tornado/Severe Thunderstorm Warning is issued by the local Weather Service Office whenever a tornado or severe thunderstorm has actually been sighted or strongly indicated by radar. Warnings are for smaller areas, such as portion of a county, and are usually 30 minutes to 1 hour long. You must act immediately when you first hear the warning. If the severe weather is reported near you, seek shelter immediately. If not, keep a constant lookout for severe weather and stay near shelter.
The following table shows the different steps in the warning process and the time required for each step.
|TIME FOR EACH STEP|
(minimum to maximum)
|TOTAL ELAPSED TIME|
(minimum to maximum)
|Identification||5 sec - 2 min||5 sec - 2 min|
|Report to First Level Warning Center - Police, Fire, CD||30 sec - 3 min||30 sec - 5 min|
|Sound Sirens||30 sec - 2 min||1 min - 7 min|
|Report to Weather Service||30 sec - 4 min||1.5 min - 11 min|
|Warning Decision||30 sec - 5 min||2 min - 16 min|
|NOAA Weather Radio||30 sec - 3 min||2.5 min - 19 min|
|Teletype to TV and Radio Stations||3.5 min - 5 min||6 min - 24 min|
|Broad cast from TV & Radio to Public||1 min - 6 min||7 min - 30 min|
This table illustrates that, even under ideal conditions, a tornado may be on the ground for 7 minutes before commerical radio or TV could begin to warn the population. Even more astonishing is the fact that, currently it requires about 30 minutes to warn half the population through the electronic media. Since the average tornado lasts approximately 10 minutes chances are it could strike your home without warning. Therefore, individuals and communities should be prepared to warn themselves. How can you improve the odds of being warned in time?
Support an active and well-organized community spotter program. This can minimize the delay between severe weather developent and its identification and reporting. Spotters are the only sure means available for identifying tornadoes, for even radar has its weaknesses.
Develop close communications between designated first-level warning centers and the National Weather Service. This would provide spotter information to both nearly simultaneously.
Determine if you are within coverage of a NOAA weather radio, which provides watch and warning information direct from the National Weather Service. If so, obtain an alarm receiver for home or office.
Acquire a healthy respect for Severe Thunderstorm Warnings. Tornadoes often develop without warning from severe or rapidly intensifying thunderstorms. Radar can detect these thunderstorms and the National Weather Service issues Severe Thunderstorm Warnings when they develop. However, radar can seldom detect the tornadoes which they spawn. The Severe Thunderstorm Warning, then, is likely to be the public's only warning of a short-lived but none the less dangerous tornado.
Severe weather can strike unexpectedly anytime. It is impossible for warnings to be issued before each storm strikes. Therefore, individuals and communities may have to warn themselves.
A basement offers the greatest safety. Seek shelter under sturdy furniture if possible. In homes without basements take cover in the center of the house on the lowest floor in a small room such as a closet or bathroom, or under sturdy furniture.
During warnings, go to a prearranged substantial shelter. Do not stay in a mobile home during a tornado warning.
DRIVING A VEHICLE
Get out of the vehicle into a basement, ditch or ravine -- away from the vehicle.
AT WORK OR AT SCHOOL
Follow advance plans to move to interior hallways or small rooms on the lowest floor. Avoid areas with glass and wide, freespan roofs. (Schools, factories, and office buildings should designate someone to look out for severe weather and initiate an alarm.)
IN OPEN COUNTRY
Get into a sturdy building if possible, or lie flat in a nearby ditch or depression and hold onto something on the ground if possible.
Your County Emergency Program Manager and staff will work with you in your time of need, as will the American Red Cross, Salvation Army and other volunteer groups. These organizations will work with state and federal relief agencies to assist your community in its recovery.
Do NOT go to the tornado scene. The area must be kept clear and secure for the victims and for emergency personnel. REMEMBER -- TORNADOES CAN STRIKE ANYWHERE, ANYTIME, AND MORE THAN ONCE!
Lightning is another potential killer associated with thunderstorms. Most lightning deaths are singular in nature as opposed to the multiple deaths often caused by tornadoes or floods. When a thunderstorm threatens, get inside a home or large building as quickly as you can.
NOAA Weather Radio is a service of the National Oceanic and Atmospheric Administration (NOAA) of the U.S. Department of Commerce. It provides continuous broadcasts of the latest weather information directly from National Weather Service offices. Taped weather messages are repeated every four to six minutes and are routinely revised every one to three hours, or more frequently if needed. Most of the stations operate 24 hours daily.
NOAA Weather Radio broadcasts are made on one of three high-band FM frequencies - 162.40, 162.475, or 162.55 megahertz (MHz). These frequencies are not found on the average home radio now in use. However, a number of radio manufacturers offer special weather radios to operate on these frequencies, with or without the emergency warning alarm. Also, there are now many radios on the market which offer standard AM/FM frequencies plus the so-called "weather band" as an added feature.
If more information on NOAA Weather Radio is required, please write: National Weather Service (ATTN: W112), National Oceanic and Atmospheric Administration, Silver Springs, MD 20910.