AIM: Types of severe storms Do Now: In your notes answer the following question. 1) Which pressure system do you think is the cause for severe weather?

I. Severe Storms caused by intense low pressure rotate Counterclockwise pull air in towards the center.

A. Thunderstorms - caused by moist, warm air rising quickly (cold front). 1) Nor'easters are massive cyclones that make land fall in the North East due to winds blowing from the NE. Cumulonimbus clouds (takes on an anvil shape)

2) Thunder and Lightning - Friction between raindrops and the cloud builds an electric charge causing lightning. - lightning causes the air to expand and then collapse back on itself creating thunder clap.

B. Tornadoes (Spring Early Summer) 1. Most powerful storms on Earth. - violently rotating columns of air (vortex) - in contact with both a cumulonimbus cloud and the surface of the earth. - they occur when a cold air mass meets a warm air mass. Winds can exceed 300 mph!

The mid-west region where tornados occur in great numbers is called “Tornado Alley”.

2. Strength is measured with the fujita scale, which measures wind speeds and destruction.

II. El Nino Conditions: seasonal shift in global weather patterns (about every 5 years) causes changes in precipitation, winds and sea levels along pacific coasts.

III. Monsoons - In winter, the water is warmer than the land causing a land-breeze to occur, pushing storms out into the ocean creating period of drought. Large seasonal changes in winds due to the differences in specific heat of land and water. Mostly seen in the Indian Ocean. - Summer temperatures cause the land to heat up faster than the water causing a sea-breeze to occur, pushing storms onto the land creating floods.

B. Hurricanes (late summer early fall) 1) Begin as tropical storms and gain energy from warm water (Gulf of Mexico and Caribbean sea. - Energy is lost moving over land or cool water.

2) Tropical storms travel west along the equator. - Their rotation carries them Northward. - At 300N, they are influenced by the westerlies (travel up the U.S. east coast)

3) Small area of sinking air in the center called the eye 3) Small area of sinking air in the center called the eye. This marks the half way point of the hurricane.

4) Hurricanes are categorized based on their wind speed 4) Hurricanes are categorized based on their wind speed. At 76 mph a tropical storm is now called a hurricane. 5) Storm Surge is caused as strong winds pile water up against the coast, causing flooding.