There are about 1,800 thunderstorms in progress around the world at any given time, according to the National Weather Service.
Only a small fraction are classified as severe.
Severe thunderstorms are thunderstorms that produce hail 1 inch in diameter (about the size of a quarter), or larger, and or strong wind gusts of 58 mph or greater.
A small fraction of these thunderstorms produce tornadoes.
All thunderstorms are capable of producing deadly lightning. But the heavy rains or the lightning activity in a thunderstorm do not necessarily mean a thunderstorm is severe.
The National Weather Service's responsibilities include issuing watches, warnings and other information to help keep individuals safe when hazardous weather threatens. They say the best defense against dangerous storms is to have multiple plans of action, depending on the circumstances, and consistently monitor local weather information.
An individual's chances of receiving a severe weather warning depend on where you are, what you're doing and the time of day the warning is issued.
A single warning could turn out to be the most important warning in your life. Knowing how to get information and having multiple ways to hear a warning can help increase the chances you'll hear the warning when it matters most.
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How to develop a plan
Use the guidelines below to develop a personal tornado safety plan for you and your family. Remember you need to have a plan for wherever you may be when a tornado strikes — at home, at school, at work, on the road or in a public building.
Developing a tornado safety kit
These items would be extremely useful to have in your storm shelter, or to take with you to your storm shelter, when severe weather strikes.
• Disaster supply kit: You should store your emergency supplies as close to your shelter as possible.
• Battery-operated weather radio: You will want to be able to monitor the latest information directly from the National Weather Service.
• A map to track storms: You will need to be able to track the progress of the storm. Because warning texts include county names, a county outline map of your area is a great thing to keep handy. You might also keep a state highway map, which includes most of the cities and towns referred to in National Weather Service warnings and statements.
• Shoes: This will be very important if your home is damaged and you must walk across broken glass or other debris.
• Identification: You may need identification to move around in the area should significant damage occur.
• Your car keys.
Other things to consider
• Papers: If you have a safe room or other shelter area, you might consider storing important papers and other irreplaceable items in the shelter if space permits.
• Batteries: Check and replace batteries in your weather radio, flashlights and other devices in your safety kit often, preferably twice a year. Do this at the same time you set clocks back/ahead in the spring and fall.
• Maintain: Check your disaster supplies kit often to maintain fresh food and water.
• Cover: Make sure you have something to cover up with. Pillows, blankets, sleeping bags or a mattress could help to protect you from falling/flying debris.
SOURCE: NATIONAL WEATHER SERVICE
Hazardous Weather Outlooks are designed to give you information on any hazardous weather that is expected over the next seven days. This includes severe thunderstorms and tornadoes. For severe thunderstorm outlooks, the National Weather Service characterizes the risk as “slight,” “moderate” or “high.”
Watches may be issued hours before a storm. Remember a watch just means that conditions are favorable for severe thunderstorms and/or tornadoes.
Severe thunderstorm warnings
Severe thunderstorm warnings often precede tornado warnings, providing you with extra time to prepare. In addition, severe thunderstorm warnings issued by the National Weather Service will almost always contain details about the expected hail size and wind speeds. Severe thunderstorms can produce destructive hail — ranging in size from dime to softballs or larger — winds in excess of 100 mph, flooding rains and deadly lightning.
Tornado warnings cannot be issued for every single tornado that occurs. This is why you must take responsibility for your personal safety any time storms threaten. Do not wait until you get an official warning, through TV, radio or siren. If you feel threatened, you should take your tornado precautions. It is better to be safe than sorry. Tornado warnings contain information that lists the cities and towns in the path of a tornado. While the National Weather Service strives to provide the most detailed and accurate information possible, a small town or community may be in the path of a dangerous storm but not listed in the warning text. This also holds true for television path forecasts. You should be cautious when using detailed forecasts of time and location.
Severe weather statements
Severe weather statements are issued to update warnings, and include new information about an ongoing severe storm.