. Aerographer's Mate 3 & 2. United States. Navy; Meteorology; Oceanography. AEROGRAPHER'S MATE 3 & 2 Structure The fundamental structural element of the thunderstorm is the unit of convective circula- tion known as a convective cell. A mature thunderstorm contains several of these cells, which vary in diameter from 1 to 6 miles. By radar analysis and measurement of drafts, it has been determined that, generally, each cell is independent of surrounding cells of the same storm. Each cell progresses through a cycle which lasts from 1 to 3 hours. In the initial stage (cumulus development),
. Aerographer's Mate 3 & 2. United States. Navy; Meteorology; Oceanography. AEROGRAPHER'S MATE 3 & 2 Structure The fundamental structural element of the thunderstorm is the unit of convective circula- tion known as a convective cell. A mature thunderstorm contains several of these cells, which vary in diameter from 1 to 6 miles. By radar analysis and measurement of drafts, it has been determined that, generally, each cell is independent of surrounding cells of the same storm. Each cell progresses through a cycle which lasts from 1 to 3 hours. In the initial stage (cumulus development), the cloud consists of a single cell; but as the development pro- gresses, the new cells form and older cells dissipate. The life cycle of the thunderstorm cell con- sists of three distinct stages; they are the cumulus stage, the mature stage, and the dis- sipating or anvil stage. (See fig. 15-13.). RAIN DECREASING FIRST RAIN AT SURFACE ' ' AT SURFACE V< CUMULUS STAGE MATURE STAGE ANVIL OR DISSIPATING STAGE Figure 15-13. — Life cycle of a thunderstorm cell. CUMULUS STAGE. —Although most cumulus clouds do not become thunderstorms the initial stage of a thunderstorm is always a cumulus cloud. The chief distinguishing feature of this cumulus or building stage is an updraft, which prevails throughout the entire cell. Such up- drafts vary from a few feet per second to as much as 100 feet per second in mature cells. MATURE STAGE. —The beginning of surface rain, with adjacent updrafts and downdrafts, ini- tiates the mature stage. By this time the apex of the average cell has attained a height of 25,000 feet or more. As the raindrops begin to fall, the frictional drag between the raindrops and the surrounding air causes the air to begin a downward motion. Since the lapse rate within a thunderstorm cell is more than the moist adia- batic rate, the descending saturated air soon reaches a level where it is colder than its environment; consequently, its rate of downward mot
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