- The typical thunderstorm has a diameter of 15 miles and lasts 30 minutes.
- Almost 1,800 thunderstorms are occurring at any given moment around the world.
- All thunderstorms have lightning.
- In the US, 100,000 thunderstorms happen in a year. 10% of these, or 10,000, are classified as severe.
- A thunderstorm gets classified as severe if winds reach 58 mph or higher, if it produces hail of 3/4 inches in diameter or more, or if it also produces tornadoes.
Three stages of a thunderstorm
(Diagram from bouqueteweather.com)
- Here are the stages of a thunderstorm (I've been taught this a million times, but it's never stuck entirely):
- Developing stage:
- Warm air rises quickly and makes a big fat cumulus cloud, like a big hump in the sky.
- The cloud is usually not more than 20,000 feet high.
- Sometimes it will start to rain at this stage, but only a little bit and maybe for about 10 minutes. There might be some lightning, but not much.
- Mature stage:
- The big fat cloud gets really tall, about 40,000 feet or higher. The cloud takes on a sickly green or sometimes even black shade.
- The warm air is getting cooled pretty fast, and as it cools it condenses, forming rain.
- Heavy rain falls, which also pushes out strong winds ahead of it. Sometimes the wind is so strong it travels for miles ahead of the storm. This is why when it gets good and windy, you can count on a storm coming.
- If the air in the cloud pushes high enough and the moisture in the cloud cools enough, the rain turns instead into ice crystals at the top of the cloud. If you get enough air pushing high enough, the ice will fall. In other words, it might hail.
- At this stage of the storm, you definitely get lightning, booming thunder, and possibly tornadoes.
- This stage usually lasts 10 to 20 minutes, but in stronger storms, it could last longer.
- Dissipating stage:
- As the moisture drops out of the cloud, the big knob at the top flattens out, almost like a deflated balloon.
- Rain is still falling, but it is less intense.
- Bursts of strong winds may occur as the cloud is basically releasing its air.
- Some lightning may also happen.
- Lightning happens because the storm cloud contains warm air that is rising quickly and cool air that is descending. The movement of this air in different directions separates positive and negative charges. When these charges build up enough, the electrical energy is released, making lightning.
- The average flash from a lightning bolt could light a 100-watt bulb for more than 3 months.
- The air near a lightning strike is heated to 50,000 degrees F, which is hotter than the surface of the sun.
- When lightning flashes, it heats the air super-fast. This makes a shock wave in the air that we hear as thunder.
- This just in (01/2011): Thunderstorms also create and release antimatter. Researchers aren't exactly sure of the process, except that the electric fields build up and when the lightning flashes, electrons are accelerated almost to the speed of light, essentially making gamma rays and blasting antimatter into space. Read more here.
- The most lightning flashes that occurred in a given year (1991) happened in the peninsula part of Florida. In fact, this part of Florida saw lightning flashes almost 4 times more than any other part of the country. (I wonder if this is related to the fact that they get a lot of hurricanes?)
People get this mixed up a lot, so I'll include this too:
- Storm Watch means conditions are right, so watch for a possible storm
- Storm Warning means look out! there's an actual storm coming.
P.S. Have you identified your top ten favorite apples yet?
NOAA, Thunderstorms and Lightning...the underrated killers!
The above graphic, originally from the Times-Picayune, but reproduced at Loyola's Center for Environmental Communications' page on the Ecology of the Mississippi River Delta Region