HURRICANES, TORNADOES & THUNDERSTORMS

HURRICANES Large, rotating tropical weather system w/wind speeds of at least 120 km/h The most powerful storms on Earth. Pacific Ocean—typhoons Indian Ocean---cyclones Form in areas between 5o to 20o north latitude & 5o to 20o south latitude over warm, tropical areas.

HURRICANES At higher latitudes, water is too cold for hurricanes to form. Vary in size from 160 to 1,500 km in diameter Can travel for thousands of kilometers. Begins as a group of thunderstorms over tropical ocean water.

HURRICANES Winds traveling in two different directions meet and cause the storm to spin. Because of the Coriolis effect, storm turns counterclockwise in N. Hem & clockwise in the S. Hem. Gets energy from condensation of water vapor. Once formed, fueled by warm ocean water.

HURRICANES As warm, moist air rises, water vapor condenses & releases large amounts of energy. When moving into cold water or land, it begins to die as it has lost its source of energy.

HURRICANES Wind speeds range from 120-150 km/h, some reaching speeds as high as 300 km/h. Knock down trees, telephone poles, damage and destroy buildings and homes. Most damage is caused by flooding associated with heavy winds & storm surges.

HURRICANES SAFETY May need to evacuate the area. Disaster supply kit that includes enough food and water for several days. Cover windows w/plywood Stay indoors during the storm.

TORNADOES Happen in only 1% of thunderstorms. Small, spinning column of air that has high wind speeds & low central pressure. Touches the ground. Starts out as a funnel cloud that pokes through a cumulonimbus cloud & hangs in the air

TORNADOES Funnel cloud becomes a tornado when it makes contact with Earth’s surface. 75% occur in the U.S. Spring & early summer Cold, dry air from Canada meets the moist, warm air from the tropics.

TORNADOES Path of destruction is about 8 km long and 10 to 60 km. wide. Last only a few minutes; cause lots of damage Strong spinning winds; average wind speeds are between 120-180 km/hr. More violent tornadoes can have spinning winds up to 500 km/h.

TORANDOES Winds have been known to uproot trees, destroy buildings, can pick up heavy objects (cars; mobile homes) and hurl them through the air. SAFETY! Watches—lets people know that a tornado may happen Warning-lets people know that a tornado has been spotted

TORNADOES Go to the basement or cellar or to a windowless room in the center of the building (bathroom, closet, or hallway) Outside---lie down in a large, open field or a deep ditch.

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THUNDERSTORMS Small, intense weather systems that produce strong winds, heavy rain, lightning and thunder. Occur along cold fronts. Two atmospheric conditions required: warm & moist air near Earth’s surface & an unstable atmosphere (surrounding air is colder than rising warm air mass).

THUNDERSTORMS Forms cumulus/cumulonimbus clouds Electrically active (lightning!) Lightning---electric discharge that occurs between a positively charged area & a negatively charged area. Happens between clouds, between Earth and cloud or within a cloud.

THUNDERSTORMS Energy is released when lightning strikes. Energy transferred to the air and causes air to expand rapidly, sending out sound waves (thunder). Severe thunderstorms---produce high winds, hail, flash floods & tornadoes. SAFETY! Stay inside! Stay away from trees as lightning is attracted to tall objects. Stay out of water!