Hurricanes

INTRODUCTION

The term "hurricane" is a name given to violent storms that originate over the tropical or subtropical waters of the Atlantic Ocean, Caribbean Sea, Gulf of Mexico, or North Pacific Ocean. Hurricanes need warm tropical oceans, moisture and light winds above them in order to maintain themselves active. Those storms other than the ones considered typhoons are known as tropical cyclones, which is the general name for all such storms including hurricanes and typhoons. Hurricanes are named based on certain aspects and location of where they first originate. With just the right conditions lasting long enough, a hurricane can cause violent winds, incredible waves crashing against shorelines, torrential rains and floods that produce great damage to properties and human life.

HOW HURRICANES FORM

Tropical cyclones form and grow in warm ocean water as a collection of storms in the tropic, receiving their energy from latent heat. Hurricanes and other tropical cyclones begin as clusters of showers and thunderstorms. When one of these showers becomes organized with its winds making a complete circle around the center, a tropical depression is formed. "The deepening low-pressure center takes in moist air and thermal energy from the ocean while simultaneously the high pressure higher in the atmosphere pushes it outward" ( Longshore 1). As the clouds turn into a tight curl, the depression becomes a tropical storm. Due to low central pressure air spiraling cyclonically, the diameter of what is known as the "eye" of the hurricane is anywhere from ten to twenty miles. Hurricanes and tropical cyclones form, maintain their strength, and grow only when they are over ocean water that is approximately 27oC (80oF). This type of warmth causes large amounts of water to evaporate, making the air very humid. Since water is slow to warm up and cool down, oceans do not become warm enough for tropical cyclones to occur in the spring. When hurricanes start to get weak and die out as they move over colder water or land, they can still remain dangerous as they slow down and weaken

CHARACTERISTICS OF HURRICANES

Hurricane-force winds coming from a large, strong storm may be felt over an area with a diameter of more than 60 miles. The diameter of the area affected by gale winds and torrential rain can extend another 120 miles outward from the eye of the storm. The diameter of the eye may be less than 10 miles in a strong hurricane to more than 30 miles in a weak storm. The smaller the diameter of the eye, the stronger the hurricane winds will be. A hurricane's strength is rated from Category 1, which has winds of at least 74 mph to Category 5, which has winds of more than 155 mph. These categories are known as the Saffir-Simpson hurricane scale and were developed in the 1970s. In the U.S., the official hurricane season is from June 1st to November 30th (F.E.M.A. 1).

Hurricanes originated in the tropics move generally east to west, steered by global-scale winds. Hurricanes, typhoons, and cyclones usually turn back in the direction of either the South Pole in the Southern Hemisphere or the North Pole in the Northern Hemisphere. The storms eventually move toward the east in the middle latitudes, but not all storms turn back. Hurricanes travel at varying rates. In the lower latitudes the rate usually ranges from 8 to 32 km/h (5 to 20 mph), and in the higher latitudes it may increase to as much as 80 km/h (50 mph).

Hurricanes generate large waves that travel out in all directions, and winds which pile up water. This piling up of water is known as a storm surge, and it can raise the sea level more than twenty feet when the storm hits land. During the last third of the 20th century, floods and landslides from heavy rain were the main cause for hurricane and tropical storm deaths. "In October 1998 Hurricane Mitch's torrential rain caused floods and landslides that killed more than 9,000 people with another 9,000 missing and presumed dead in Central America, according to the U.S. National Hurricane Center" ( Barnes 3 ). The U.S. natural disaster that has been the most costly was Hurricane Andrew, which hit Miami, Florida in 1992, causing $26.5 billion in damages, including both insured and uninsured losses.

HOW HURRICANES ARE DETECTED AND MONITORED

The National Hurricane Center is part of the U.S. National Weather Service and is the main forecast center for storms that originate over the Atlantic Ocean, the Caribbean Sea, the Gulf of Mexico, and the northeastern Pacific Ocean west to longitude 140 degrees west. A coordinated system for tracking hurricanes was developed in the mid-1950s and in addition to it, weather satellites and ocean buoys automatically measure and record and transmit data such as wave heights and wind speeds. The Hawaiian Hurricane Center at the Honolulu National Weather Service office handles storms from longitude 140o west to longitude 180o west. Hurricane Iniki happens to be the worst hurricane by far in Hawaii killing six people and doing an estimated $2.3 billion in damages on September 1992.

When a storm begins to formulate and threaten land, forecasters call on military or civilian aircraft

for detailed storm data that satellites cannot supply.

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