When conditions are favorable for severe weather to develop, a severe thunderstorm or tornado watch is issued.
Weather Service personnel use information from weather radar, spotters, and other sources to issue severe thunderstorms and/or tornado warnings for areas where severe weather is imminent.
Severe thunderstorm watches and/or warnings are passed to local radio and television stations to be broadcast over local NOAA Weather Radio stations serving the warned areas. These watches and/or warnings are also relayed to local emergency management and public safety officials who can activate local warning systems to alert communities.
Watch for Developing Thunderstorms:
Thunderstorms are most likely to develop on warm summer days and go through various stages of growth, development and dissipation. On a sunny day, as the sun heats the air, pockets of warmer air start to rise in the atmosphere. When this air reaches a certain level in the atmosphere, cumulus clouds start to form. Continued heating can cause these clouds to grow vertically upward in the atmosphere into "towering cumulus" clouds. These towering cumulus may be one of the first indications of a developing thunderstorm.
What is the difference between WATCH and WARNING????
SEVERE THUNDERSTORM WATCH : Severe thunderstorms are possible in your area.
SEVERE THUNDERSTORM WARNING : Severe thunderstorms are occurring.
*Remember, tornadoes occasionally develop in areas in which a severe thunderstorm watch or warning is in effect. Remain alert to signs of an approaching tornado and seek shelter if threatening conditions exist.
Other Thunderstorm Hazards :
Flash Floods : Number 1 weather killer
Lightening : Kills 75 - 100 people each year
Damaging Straight-line Winds : Can reach 140 mph
Hail : Can reach to the size of a grapefruit - causes several hundred million dollars in damage annually to property and crops.
WHAT YOU CAN DO
Before the storm:
Develop a plan for you and your family for home, work, school and when outdoors. Have frequent drills.
Know the county/parish in which you live, and keep a highway map nearby to follow storm movement from weather bulletins.
Have a NOAA Weather Radio with a warning alarm tone and battery back-up to receive watches and/or warnings.
Listen to radio and television for information.
If planning a trip outdoors, listen to the latest forecasts and take necessary action if threatening weather possible.
Environmental Clues (What to look for) :
Dark, often greenish sky
Wall Cloud
Large hail
Loud roar; similar to a freight train
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.
If a warning is issued or if threatening weather approaches :
In a home or building, move to a pre-designated shelter, such as a basement.
If an underground shelter is not available, move to an interior room or hallway on the lowest floor and get under a sturdy piece of furniture.
Stay away from windows.
Get out of automobiles. Do not try to outrun a tornado in your car; instead, leave it immediately. Overpasses are not safe - An overpass's under-the-girder-type construction can cause a dangerous wind tunnel effect. This may cause the winds to be stronger and more focused underneath. This can also cause the overpass to be collector of debris.
Mobile homes, even if tied down, offer little protection from tornadoes and should be abandoned.
If you are outside, remember to cover your head with your arms, coat or blanket to protect yourself from flying debris.
Occasionally, tornadoes develop so rapidly that advance warning is not possible. Remain alert for signs of an approaching tornado. Flying debris from tornadoes causes most deaths and injuries.
Caution :
Some tornadoes appear as a visible funnel extending only partially to the ground. Look for signs of debris below the visible funnel.
Some tornadoes are clearly visible while others are obscured by rain or nearby low-hanging clouds.