【单选题】

Hurricane (飓风)Hurricane is a name given to violent storms that originate over the tropical (热带的) or subtropical waters of theAtlantic Ocean,Caribbean Sea, Gulf of Mexico, or North Pacific Ocean east of the InternationalDate Line. Such storms over the North Pacific west of the InternationalDate Line are called typhoons (台风); those elsewhere are known as tropical cyclones (热带气旋), which is the general name for all such storms including hurricanes and typhoons. These storms can cause great damage to property and loss of human life due to high winds, flooding, and large waves crashing against shorelines. The deadliest natural disaster in the United States history was caused by a hurricane that struck the coast of Texas in 1990.The costliest natural disaster in U.S. history stemmed from Hurricane Katrina in 2005.How hurricanes formOceans can become warm enough in the summer for hurricanes to develop, and the oceans also retain summer heat through the fall.As a result, the hurricane season in theAtlanticBasin, which comprises theAtlantic Ocean,Caribbean Sea, and the Gulf of Mexico, runs from June 1 through November 30. At least 25 out-of-season storms, however, have occurred from 1887 through 2003, and 9 of these strengthened into hurricanes for at least a few hours.Hurricanes weaken and die out when cut off from warm, humid air as they move over cooler water or land but can remain dangerous as they weaken. Hurricanes and other tropical cyclones begin as disorganized clusters of showers and thunderstorms. When one of these clusters becomes organized with its winds making a complete circle around a center, it is called a tropical depression (热带低气压).When a depression’’s sustained winds reach 63 km/h or more, it becomes a tropical storm and is given a name.By definition, a tropical storm becomes a hurricane when winds reach 119 km/h or more.For a tropical depression to grow into a hurricane, winds from just above the surface of the ocean to more than 12,000 m in altitude must be blowing from roughly the same direction and at the same spee

D、Winds that blow in opposite directions create wind shears-different wind speeds or direction at upper and lower altitudes (海拔)—that can prevent a storm from, growing. Characteristics of hurricanes
A、hurricane consists of bands of thunderstorms that spiral (盘旋) toward the low-pressure center, or "eye" of the storm. Winds also spiral in toward the center, speeding up as they approach the eye. Large thunderstorms create an "eye wall" around the center where winds are the strongest. Winds in the eye itself are nearly calm, and the sky is often clear.Air pressures in the eye at the surface range from around 982 hectopascals (百帕) in a weak hurricane to lower than 914 hectopascals in the strongest storms.In a large, strong storm, hurricane-force winds may be felt over an area with a diameter of more than 100 km. The diameter of the area affected by gale winds and torrential rain can extend another 260 km or more outward from the eye of the storm. The diameter of the eye may be less than 16 km in a strong hurricane to more than 48 km in a weak storm. The smaller the diameter of the eye, the stronger the hurricane winds will be.
A、hurricane’’s strength is rated fromCategory 1, which has winds of at least 119 km/h, toCategory 5, which has winds of .more than 249 km/h. These categories, known as the Saffir-Simpson hurricane scale, were developed in the 1970s.In the tropics, hurricanes move generally east to west, steered by global-scale winds. Hurricane, typhoons, and cyclones usually "recurve" in the direction of either the South Pole in the Southern Hemisphere or the North Pole in the Northern Hemisphere.Eventually the storms move toward the east in the middle latitudes, but not all storms recurve. Hurricanes travel at varying rates. In the lower latitudes the rate usually ranges from 8 to 32 km/h, and in the higher latitudes it may increa