Pertanyaan

Tornados occure when the condition that cause thunderstorms are usully violent. Winds blow in opposite directiona around a strong updraft start a narrow, violent whirl. Centrifugal force effectively throws the aor away from the center, leavinng a core of very low preasure. This is much like stirring water in a cup, thus formin a vortex-like dip in the surface. This low-presure core acts as a partial vacuum, sometimes helping to lift the roofs off houses. Most of the demage, though, result from the force of the wind itself. Around the edges of the whirl, wind speeds may reach 300 miles (480 kilometers) per hour. At first, the tornado's funnel is whitish-gray because it is composed o minute water droplets formed as the air in the funnel expand and cools. After touching down , the funnel becomes dark because of all oh the the debris it has picked up. this debris can include soil, tree limbs, and parts of buildings; tornados have been known to pick up automobiles, horses and whole trees. A tornado usually moves toward the east (or often northeast in the Northen Hemisphere an southeast Hemisphere) at 25 to 40 miles (40 to 60 kilometers) per hour. Fortunately, most torandos are less than half a mile (800 meters) wide; the edge of one may destroy all of the houses on one side of a street while leaving those on the other side compeletely undameged. Deaths from tornados in the United States avaraged roughly 100 per year over the last century. However, they have dropped somewhat in recent decades as better forecasting and warning system have been implemented Why have death from Tornados in the United States decreased in the recent decades?