They begin between the latitudes of 5 and 20 degrees north or south of the equator, in the areas where the ocean temperatures reach 80 during summer and fall. Hurricanes begin as an unstable air mass, often when the convergence zone created by the trade winds of the two hemispheres is displaced over unusually warm areas of sea. It must be far enough from the equator for rotational forces to cause to winds to spiral, counterclockwise in the northern hemisphere, and clockwise in the southern hemisphere. The hurricane gets its energy supply from the ocean, drawing energy as heat is transferred from water to air. Large amounts of water vapor are evaporated and carried upwards in strong spiraling winds.
Clouds increase when the latent heat is released as the vapor condenses into clouds.
As warm air and moisture rise, a low pressure area is created near the surface. This pulls in more air and moisture and the system grows. This process continues until the system reaches 90 to 400 miles across. When wind speed reaches 39 miles per hour, the storm is classified as a tropical storm and the storm system is given a name. The old tradition of giving storms feminine names was abandoned in 1979, now they receive both male and female names.