Hurricanes are huge heat engines. Something has to start the system. Often this involves the Intertropical Convergence Zone, the area near the equator where the air from the two hemispheres collides and rises. This area acts like a front, and low pressure systems can form where the line of convergence buckles. The global air circulation has air moving towards the Intertropical Convergence Zone from the east, and angling in from the two hemispheres. If the Intertropical Convergence Zone is far enough away from the equator, and it does drift north during the northern hemisphere’s summer and south during the winter, the Earth’s rotation will cause the easterlies to change to a westerly direction, having air pass each other as it moves into the Intertropical Convergence Zone. The collision of the air from the two hemisphere causes the air to rise, and triggers severe thunderstorms.
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