55 Hurricanes

They occur with monotonous regularity every year, usually commencing in August and fading away in early November. They have names like Fran and Bonnie and Andrew and Camille—friendly, everyday sorts of names. But these gigantic, often monstrous storms—hurricanes—are the farthest thing from friendly, as anyone who has endured the fury of one will attest.

Though typhoon and cyclone are essentially synonyms describing the same formations, the word hurricane refers only to violent wind-and-rain-filled storms that develop over the western Atlantic and strike North America and the Caribbean. A storm becomes a hurricane only if its winds exceed 72 miles per hour; however, the worst hurricanes may be twice that strong.

Warm ocean waters and low atmospheric pressure are essential conditions for hurricanes. Low pressure—when the atmosphere does not bear down too hard on the earth—pulls warm air up from the water’s surface; the lower the pressure in an area, the more air that will enter it and rise. In fact, low-pressure areas function as a chimney: the warm air ascends, cools, condenses into rain, and spreads, forming a thunderstorm that gets larger as more air is drawn in.

At the hurricane’s center is the eye, an area of intensely low pressure where, surprisingly, the air is calm and the sky is clear. Around this eye, however, winds are raging—blowing in one direction on one side and in the opposite direction on the other. Property may be destroyed by the sheer velocity of the winds, by the terrible flooding they provoke as they raise the ocean’s waters and those of nearby rivers to abnormally high levels, or, in the worst cases, by both.

55 飓风

它们每年都会以单调的规律性出现，通常从8月开始，11月初消退。它们有着像弗兰、邦妮、安德鲁和卡米尔这样的名字——都是亲切的日常名字。但这些巨大的、常常是狂暴的风暴——飓风——却一点也不亲切，任何经历过飓风狂怒的人都能证明这一点。

虽然“台风”和“气旋”本质上是描述同一类气象形成的同义词，但“飓风”一词仅指在西大西洋形成、袭击北美和加勒比地区的狂风暴雨型风暴。只有当风速超过每小时72英里时，风暴才会成为飓风；而最严重的飓风风速可能是这个数值的两倍。

温暖的海水和低气压是形成飓风的必要条件。低气压——即大气对地球的压力不太大时——会将暖空气从水面向上吸起；一个区域的气压越低，进入该区域并上升的空气就越多。事实上，低气压区域的作用就像烟囱：暖空气上升、冷却、凝结成雨并扩散，形成雷暴，随着更多空气被吸入，雷暴会变得更大。

飓风的中心是风眼，这是一个气压极低的区域，令人惊讶的是，这里空气平静、天空晴朗。然而，在风眼周围，狂风肆虐——一侧的风朝一个方向吹，另一侧则朝相反方向吹。狂风的巨大速度可能会摧毁财产，飓风还会将海水和附近河流的水位抬升至异常高度，引发可怕的洪水，在最严重的情况下，两者共同造成破坏。