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An occluded front is formed during the process of cyclogenesis when a cold front overtakes a warm front. When this occurs, the warm air is separated (occluded) from the cyclone center at the Earth's surface. The point where the warm front and the occluded front meet (and consequently the nearest location of warm air to the center of the cyclone) is called the ''triple point''.〔Djurić, D: "Weather Analysis". Prentice Hall, 1994. ISBN 0-13-501149-3.〕 The trowal (short for TROugh of Warm air ALoft) is the projection on the Earth's surface of the trough of warm air aloft formed during the occlusion process of the depression. == Description == Occluded fronts usually form around mature low pressure areas. There are two types of occlusion, warm and cold: * In a cold occlusion, the air mass overtaking the warm front is cooler than the cool air ahead of the warm front, and plows under both air masses. * In a warm occlusion, the air mass overtaking the warm front is not as cool as the cold air ahead of the warm front, and rides over the colder air mass while lifting the warm air. The occluded front symbol should thus be plotted at the position where the cold air is intersecting the surface, as on the image to the right. It thus varies between warm and a cold occlusions. The ''trowal'' on the other hand, being the projection of the warm air trough aloft, is at the same position in both cases. The position of the occluded front is often misplaced with the associated weather on a weather map but this is the position of the ''trowal''. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「occluded front」の詳細全文を読む スポンサード リンク
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