the growth of a thunderstorm

the growth of a thunderstorm is impeded by a stable layer sometimes a temperature inversion—that serves as a lid over the cloud top. Asia thunderstorm matures, a draftsman develops adjacent to the updraft core. Both drafts arc composed of churning high-speed air resembling a tumbling stream of rushing water. This pattern of air motion accounts for the turbulence: experienced by an airplane flying through a thunderstorm. The drafts may carry an airplane up or down while eddies in air velocity buffet it and, in extreme cases, muse structural damage. Most thunderstorms pass through their lifetimes in less than an hour, yielding a few lightning strokes and rain. Provided no one is struck by lightning, these storms do a great deal more good than harm. The rain is usually very beneficial, particularly to farms. The cool air that precedes an arriving thunderstorm on a hot summer day is the result of air from high altitudes being cooled by the evaporation of water drops; the air descends to the ground and spreads out, mostly in the direction of the storm motion. Some thunderstorms, because of their large sizes and long duration, arc called "supermodel" thunderstorms. They can last for many hours and have strung, persistent updrafts and downdrafts. They commonly occur as parts of a squall line, a line of thunderstorms, often oriented northeast-southwest, that sweeps across the Great Plains ahead of an advancing cold front. Super cell storms an produce violent weather. They are the sources of tornadoes and hail. As these storms move over the flatland of Kansas, Nebraska, Iowa, Illinois, and surrounding states, they sometimes lay down swaths of hail that devastate wheat, corn, and soybeans (Figure 3-16). In an average year, hail damage to agriculture in the United States amounts to more than 5700 million. Hailstorms also cause widespread damage in many other parts of the world: the fruit orchards of northern Italy, the grapevines of the Caucasus region of the Soviet Union, the tea plantations in Kenya, the farmlands of South Africa and Argentina. In India, 246 people were killed during a severe hailstorm near New Delhi in April 1888.