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 with 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 does 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 depends 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.
And since it’s important to understand that information, the National Weather Service provides these explanations:
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 dimes 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 may not listed in the warning text. This also holds true for television 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.
Source: National Weather Service