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Extratropical Storms

Extratropical Storms
An extratropical storm is a popular name for two different seasonal events. One begins with a clash of warm and cold air and results in the typical winter storm. The second is born when a hurricane leaves the tropics and transforms itself into a super powerful version of a winter storm.
The common winter storm is born when a cool mass of air, dropping down from the Arctic, clashes with a warmer mass of air. The area where these air masses meet is called a front, named after the battle grounds of World War I, because it is usually a place of violent weather commonly associated with fierce wind, rain, snow, and hail. As these fronts move across the mid-latitudes of the United States, they produce far ranging winter storms.

Palm tree in storm.A hurricane may grow to resemble a powerful winter storm, but begins life as a tropical storm. Hurricanes tend to move along specific seasonal paths, known as storm tracks, which relate to long-standing patterns in atmospheric circulation. One common storm track begins in the warm waters of the tropics and then courses up along the eastern seaboard of the United States.

Tropical storms tend to be small and violent, spinning in a counter-clockwise motion, and measuring about 60 to 300 miles in diameter, with powerful wind gusts. The faster they spin, measured by the speed of the gusting air, the more violent and dangerous they become. The most violent of these storms, when the wind speeds surpass 74 miles per hour, are identified by scientists as hurricanes. They are called typhoons in the North Pacific and the South China Sea, and cyclones in the Indian Ocean.

When hurricanes leave the warm tropical waters that spawned them, they become known as extratropical storms. They also tend to lose their cyclonic spinning action, and spread into enormously large storms ranging from 620 to 2,500 miles across, with wind gusts that can reach 50 miles per hour.

The Storm of the Century
In early March, 1993, weather satellite photos showed a large mass of cold air moving across North America, down from the North Pole. This cold mass of air eventually collided with a warmer mass in the region above the Gulf of Mexico.

Satellite photo of Superstorm.A line of powerful thunderstorms formed along the front, drawing energy from the temperature differentials. The size of the thunderstorms alarmed many of the meteorologists watching the developing storm, and they began issuing storm alerts as they watched the thunderclouds combine into an enormous spinning winter storm.

The winter storm moved onto land during the early hours on Friday morning, March 12, killing dozens of people, and devastating parts of the Florida coast. As the storm approached land, high winds and low pressures carried the sea along with it. High winds and low pressures can raise the water level in the ocean. This effect is known as storm surge, and if it gets trapped against a cove or bay, it can raise the water 10 to 20 feet higher than normal. Large waves, some up to 40 feet high, can ride on top of the surge, and come crashing over the shores and deep inland.

The storm then began to climb along the East Coast. As the storm moved across the eastern seaboard, torrential rains turned into heavy snows falling from Alabama to New York, virtually paralyzing the eastern third of the country. The storm eventually spread and covered more than 2,000 miles. Strong winds, created by rapidly dropping pressures, blew up and down the East Coast. Local authorities were totally unprepared for the intensity of the assault. The interstate highways became impassable and millions of people lost electrical power. New York City was brought to a standstill. A foot of snow fell from Alabama to Maine, and freezing temperatures set new records across the eastern seaboard.

The final accounting included 243 deaths, and about two billion dollars in damage. The storm had forced the closure of all the airports in the eastern United States, and created great chaos. Nearly 100 million people in 26 states had their lives affected in ways both great and small by the Storm of the Century.

-- By Micah Fink


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