Meteorology

Question

How do hurricaines form? Asked by Sanchita

Answer

Hi, Hurricane formation requires a couple of key ingredients: warm sea surface temperatures (> 25 deg C) and relatively weak winds at high levels of the atmosphere (that is, at heights where jet planes fly). The warm sea surface temperatures provide fuel for the hurricane in terms of large supply of moisture (that is, warmer sea surface temperatures allow for more evaporation of sea water and thus more mositure in the air). The weak winds in the upper atmosphere allow the hurricane to stay together instead of "shearing apart": if there are strong upper level winds, the top of the hurricane will be pushed away from the bottom part and the disturbance will eventually fall apart. In the Atlantic, hurricane formation is usually associated with disturbnaces in the atmosphere that originate in Africa. These initial disturbances over Africa may be weak and may not be visible until it crosses the ocean (heading westward) over warm water. If conditions are favorable, the disturbance can deepen (that is, the sea level pressure in the central part will decrease) so that winds will rush in to try and fill the lower pressure. Because the Earth is rotating, those winds don't actually rush into the center of the storm: they get deflected to the right in the northern hemisphere. Thus, a counter clockwise circulation sets up. If the storm continues to deepen and winds increase, the storm can become a tropical depression, a tropical cyclone or a hurricane.