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Hurricanes It’s a day late in the summer. You hear the sounds of pounding hammers and buzzing saws. Some people are fixing roofs, others are cutting up trees. A hurricane struck last night. Wind ripped at the town for hours, objects were sent flying, and rain poured down. Fortunately people paid attention to the weather forecasts and left town. What causes such powerful storms? What are Hurricanes? •A hurricane is a type of storm with lots of energy. •These storms usually form in the tropics, the part of the Earth near the equator. •It gets the energy from air moving upward over warm ocean water. •A hurricane is a dangerous storm with wind speeds of at least 119 kilometers per hour. •Many bands of thunderstorms and rain wrap around the center. Hurricane Andrew •In august 1992, an area of low pressure formed over the Atlantic ocean. •It gained strength and became a tropical storm. •People gave it a name – Andrew •Hurricane Andrew moved West across the ocean. •It smashed into the Bahama Islands in the Caribbean Sea. Hurricane Andrew •The United Stated was next. Hurricane Andrew •On August 24th, the hurricane slammed into Florida. •Winds may have reached 250 kilometers per hour. Hurricane Andrew •In about 4 hours, Andrew swept across southern Florida. Hurricane Andrew •It weakened over land •but it regained strength as it moved over the warm water of the Gulf of Mexico. Hurricane Andrew •The hurricane then crashed into Louisiana Hurricane Andrew •Then Andrew moved northward over land. It’s winds quickly weakened, but it’s rains still flooded many areas. Hurricane Andrew approaching the Bahamas and Florida as a category 5 hurricane. An entire Miami Neighborhood flattened Storm surge measured 16.5 feet above sea level. Satellite image of Andrew approaching Louisiana A tropical storm needs special conditions before it can form. It needs wind blowing towards the low pressure It needs an area of low pressure It needs a large area of warm ocean water Tropical Depression Thunderstorms grow out of a tropical depression as the wind increases and begins to swirl. The wind speeds can reach 61 kilometers per hour. Tropical Storm Air pressure at the ocean’s surface drops. Surface winds blow faster and begin to swirl. A tropical storm develops. Hurricane Thunderstorms begin to move in spiral bands. Air pressure drops lower, and surface winds blow faster. The tropical storm is now a hurricane. What’s in a Name? •To tell listeners about several different storm systems, the National Hurricane Center uses a list to name the storms. •Female and male names follow one another in alphabetical order. • A tropical storm gets a name when its winds reach 63 kilometers per hour. •If the storm becomes a hurricane, it keeps that name. •The name may be used again unless the storm causes severe damage. Then another name that starts with the same letter is used. •All hurricanes have strong thunderstorms and fast, swirling winds. • As you can see in the table, hurricanes are classified by their wind speed. The strong winds of hurricanes cause incredible damage and can be compared to other types of storms. Hurricanes A hurricane can be hundreds of kilometers across. It has many thunderstorms. A hurricane forms over the ocean. It can last for many days. Both Strong storms. Both spin around a center of low air pressure. has high winds and can cause great damage. affect all of Earth’s systems. Tornadoes A tornado is usually hundreds of meters across. It forms within a single thunderstorm. Almost all form over land. Most last only a few minutes. winds can be much faster Let’s see how much you remember! Try the quiz. Hurricane Tornado Storm surge The ocean water that a hurricane can push onto land is a ______. Tropical storm Tropical depression Vortex Hurricane Tornado Storm surge A ______ has wind speeds of at least 119 kilometers per hour. Tropical storm Tropical depression Vortex Hurricane Tornado Storm surge A hurricane keeps the name it was given when it became a ______. Tropical storm Tropical depression Vortex Hurricane Tornado Storm surge A low pressure air mass with storms that have winds that begin to spin over warm ocean water is a ______. Tropical storm Tropical depression Vortex Hurricane Tornado Storm surge A rapidly spinning column of air that comes out of a thunderstorm and touches the ground is a ______. Tropical storm Tropical depression Vortex