thunderstorms.notebook October 29, 2010

A thunderstorm is a storm with lightning and thunder. It's produced by a cumulonimbus cloud, usually producing gusty winds, heavy rain and sometimes hail. A typical thunderstorm is 15 miles in diameter and lasts an average of 30 minutes.

Thunderstorms can happen, at any time of year, and any time of day. But, they are most likely to happen in the spring and summer months and during the afternoon and evening hours. There are an estimated 1,800 thunderstorms that occur across our planet every day.

Thunderstorms

thunderstorms

The basic ingredients used to make a thunderstorm are:1) moisture ­ to form clouds and rain2) unstable air ­ relatively warm air that can rise rapidly, and 3) lift ­ fronts, sea breezes and mountains are capable of lifting air to help form thunderstorms.

Thunderstorm Recipe

thunderstorms.notebook October 29, 2010

The National Weather Service (NWS) declares that a thunderstorm is severe if:­ wind gusts reach 57.5 mph or faster­ hail is 1 inch (quarter­size) in diameter or bigger, OR ­ the thunderstorm produces a tornado or tornadoes.

Air that's moving up, called an updraft, feeds warm, humid air into a thunderstorm. Some updrafts can reach speeds of 40 mph or faster. These updrafts carry a huge amount of air up, which means large amounts of air are going to be coming down (downdrafts). Normally, a thunderstorm has both updrafts and downdrafts.

Severe Thunderstorms

Downdrafts in severe thunderstorms can create gusty winds as high as 160 mph. Downdraft winds can smash buildings, uproot trees, and are often mistaken for tornadoes. If the downdraft is concentrated in an area less than 2.5 miles in diameter, it is called a microburst.

Thunderstorm Dangers

thunderstorms.notebook October 29, 2010

Hail is created when small water droplets are caught in the updraft of a thunderstorm. These water droplets are lifted higher until they freeze into ice. Once they become heavy, they will start to fall. If the smaller hailstones get caught in the updraft again, they will get more water on them and get lifted higher in the sky and get bigger. Once they get lifted again, they freeze and fall. This happens over and over again until the hailstone is too heavy and then falls to the ground.

All thunderstorms are dangerous, because every thunderstorm produces lightning. Lightning can strike people and buildings, and kills more people each year than tornadoes. Heavy rain from thunderstorms can also lead to flash flooding. Strong winds, hail, and tornadoes are other dangers associated with some thunderstorms.

thunderstorms.notebook October 29, 2010

Severe Thunderstorm Watch ­ A severe thunderstorm (damaging winds of 58 miles per hour or more, or hail 1 inch in diameter or greater) is likely to develop in your area.

Severe Thunderstorm Warning ­ A severe thunderstorm (damaging winds of 58 miles per hour or more, or hail 1 inch in diameter or greater) is taking place in your area.

Thunder is caused by lightning. When a lightning bolt travels from the cloud to the ground it opens up a channel in the air. Once then light is gone, the air collapses back in and creates a sound wave that we hear as thunder. The reason we see lightning before we hear thunder is because light travels faster than sound!

You can estimate how many miles away a storm is by counting the number of seconds between the flash of lightning and the clap of thunder. Divide the number of seconds by five to get the distance in miles.

Lightning

thunderstorms.notebook October 29, 2010

Lightning is an electric current produced by a thunderstorm. High in the thundercloud, many small bits of ice (frozen raindrops) bump into each other as they move around in the air. All of those collisions create an electric charge which eventually fills the cloud.

The positive charges form at the top of the cloud and the negative charges form at the bottom of the cloud. Since opposites attract, that causes a positive charge to build up on the ground beneath the cloud. The ground's electrical charge concentrates around anything that sticks up, such as mountains, people, or single trees. The charge coming up from these points eventually connects with a charge reaching down from the clouds.

lightning

thunderstorms.notebook October 29, 2010

* The average lightning bolt is about an inch wide and five miles long, although the longest lightning bolt was 118 miles.

* Lightning kills and injures more people each year than hurricanes or tornadoes; between 75 to 100 people.

* The temperature of lightning is approximately 55,000 degrees, which is hot enough to fuse sand into glass!

* Yes, lightning can strike the same place twice ­ the Empire State Building in New York City is struck an average of 25 times a year.

Lightning Facts

from: news.nationalgeographic.com/news/2004/06/0623_040623_lightningfacts.htmlwww.usatoday.com/weather/resources/askjack/walightn.htmatmo.tamu.edu/weather­and­climate/weather­whys/616­todays­topic­lightning­temperature

* When a flash of lightning is seen, but no thunder is heard, this "heat lightning" is actually from a storm that is too far away to be heard. Since sound waves are bent and dispersed as they travel through the air, thunder is typically heard from storms that are closer than 10 miles, though, under the right conditions, storms can be heard as far as 20 miles away.

* Lightning comes from a parent thunderstorm, but the storm can sometimes be more than 25 miles away from the lightning strike. So, if you can hear thunder, you are within 10 miles of a storm—and can be struck by lightning.

* Your chances today of being struck by lightning in your lifetime is about 1 in 3,000!

* Roy Cleveland Sullivan was a U.S. Park Ranger in Virginia. Between 1942 and 1977, Sullivan was hit by lightning on seven different occasions and survived all of them.