For a hurricane to breed, the conditions must be exactly right. The sea has to be relatively calm, and the air above humid and cool at high altitudes. Too much turbulence causes the air circulation to break before the storm is formed, and if the air is too dry, the moisture condenses too quickly and forms small storms. If conditions conform to the formation of a tropical cyclone, the rotating circulation draws more moisture and energy from the lower atmosphere, building a powerful storm system over time.
Hurricanes become stronger over warm waters and begin to die when those conditions change. Typically, a hurricane builds in force constantly as it approaches land, but begins to dissipate quickly once the storm leaves the ocean.
Hurricanes usually appear near the equator. The storms that affect the Americas are formed in the calm waters between Africa and South America, and sometimes meet in the Caribbean. Asian storms generally form in the Eastern Pacific before continuing westward. The Indian Ocean also serves as a spawning ground for hurricanes that threaten the Indian subcontinent.
