Pertanyaan

Tornados occur when the conditions that cause thunderstorms are unusually violent. Winds blow in opposite directions around a strong updraft start a narrow, violent whirl. This is much like stirring water in a cup, thus forming a vortex-like dip I the surface This low-pressure core acts as a partial vacuum, sometimes helping to lift the roofs off houses. Most of the damage, though, results from the force of the wind itself. At first, the tornado’s funnel is whitish-gray because it is composed of minute water droplets formed as the air in the funnel expands and cools. After touching down, the funnel becomes dark because of all of the debris it has picked up. This debris can include soil, tree limbs, and parts of buildings; tornado has been known to pick up automobiles, horses, and whole trees. A tornado usually moves toward the east (or often northeast in the Northen Hemisphere and southeast Hemisphere) at 25 to 40 miles (40 to 65 kilometer) per hour. Fortunately, most tornados are less than half a mile (800 meters) wide; the edge of one may destroy all of the houses on one side of a while leaving those on the other side completely undamaged. Deaths from tornados in the US averaged 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 deaths from Tornado in the US decreased in the recent decades?