This diverging air aloft actually produces a

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of its moisture, begins to flow outward away from the center. This diverging air aloft actually produces a clockwise (Anti-cyclonic in the Northern Hemisphere) flow of air several hundred kilometers from the eye. As this outflow reaches the storm’s periphery, it begins to sink and warm, including clear skies. In the vigorous thunderstorms of the eye wall, the air warms due to the release of large quantities of latent heat. This warming produces slightly higher pressure aloft, which initiate downward air motion within the eye. As the air subsides, it warms by compression. This process helps to account for the warm air and the absence of thunderstorms in the center of the storm. As surface air rushes in toward the region of much lower surface pressure, it should expand and cool, and we might expect to observe cooler air around the eye, with warmer air further away. Apparently so much heat is added to the air from the warm ocean surface that the surface air temperature remains fairly uniform throughout the hurricane. Hurricane Formation and Dissipation Hurricanes do not form spontaneously, but require some kind of trigger to start the air converging. Surface winds converge along the inter-topical convergence zone (ITCZ), an area of low pressure develops, convection becomes organized, and the system grows into a hurricane. Weak convergence also occurs on the eastern side of a tropical wave, where hurricanes have been known to form. In fact, many if not most Atlantic hurricanes can be traced to tropical waves that form over Africa. However, only a small fraction of all of the tropical disturbances that form over the course of a year ever grow
into hurricanes. Studies suggest that major Atlantic hurricanes are most numerous when the western part of Africa is relatively wet. Hurricane Stages of Development Hurricanes go through a set of stages from birth to death. Initially, the mass of thunderstorms with only a slight wind circulation is known as a tropical disturbance, or tropical wave, The tropical disturbance becomes a tropical depression when the winds increase to between 20 and 34 knots and several closed isobars appear about its center on a surface weather map. When the isobars are packed together and the winds are between 35 and 64 knots, the tropical depression becomes a tropical storm. The tropical storm is classified as a hurricane only when its winds exceed 64 knots ( 74 miles per hour ) Naming Hurricanes Before naming hurricanes became common practice the hurricanes were identified by lat long. During WWII the hurricanes were identified by Able, Baker….. to reduce confusion. In 1953 the National Weather Service began using female names to identify hurricanes. Since 1978 hurricanes now are assigned both male and female names including names of Spanish and French origin.

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