Section 3 Severe Weather Severe weather conditions called storms occur when pressure differences cause rapid air movement. Thunderstorms are storms with thunder, lightning, heavy rains and strong winds; form within large cumulonimbus clouds; usually form along a cold front but can form within an air mass

Section 3 Severe Weather Thunderstorms Lightning is an electric discharge that occurs between a positively charged area and a negatively charged area. Thunderstorms are very active electrically. Thunder is the sound that results from the rapid expansion of air along the lightning strike.

Section 3 Severe Weather Severe Thunderstorm By definition, a severe thunderstorm is a thunderstorm that contains any one or more of the following three weather conditions: -Hail that is 3/4 of an inch or greater in diameter -Winds 58 miles per hour or greater -Tornadoes

Section 3 Severe Weather Tornadoes A tornado is a small, spinning column of air that has high wind speeds and low central pressure and that touches the ground. It forms from a severe thunderstorm. A tornado starts out as a funnel cloud that pokes through the bottom of a cumulonimbus cloud and hangs in the air. The funnel cloud becomes a tornado when it makes contact with Earth’s surface.

Section 3 Severe Weather Tornadoes, continued

Tornadoes, continued Enhanced Fajita Scale EF 0 EF 1 EF 2 EF 3 EF 4 Section 3 Severe Weather Enhanced Fajita Scale EF 0 EF 1 EF 2 EF 3 EF 4 EF 5 Gale Weak Strong Severe Extreme Incredible Tornadoes, continued

Section 3 Severe Weather Tornadoes, continued

Section 3 Severe Weather Hurricanes How a Hurricane Forms A hurricane begins as a group of thunderstorms moving over tropical ocean waters. Winds traveling in two different directions meet and cause the storm to spin. The lower the air pressure at the center, the faster the winds blow toward the center of the storm.

Section 3 Severe Weather Hurricanes, continued

Section 3 Severe Weather Hurricanes Damage Caused by Hurricanes Hurricanes can cause a lot of damage when they move near or onto land. Wind speeds of most hurricanes range from 120 to 150 km/h.

Section 3 Severe Weather Hurricanes

Section 3 Severe Weather Severe Weather Safety Thunderstorm Safety Lightning is one of the most dangerous parts of a thunderstorm. If you are outside, stay away from trees, which can get struck down. If you are in the open, crouch down. Tornado Safety If there is a tornado warning for your area, find shelter quickly. The best place to go is a basement or cellar.

Severe Weather Safety, continued Section 3 Severe Weather Severe Weather Safety, continued Flood Safety The best thing to do during a flood is to find a high place to wait out the flood. Hurricane Safety If you live in an area where hurricanes strike, your family should have a disaster supply kit that includes enough water and food to last several days.