Hurricanes form in the tropics where extremely moist air and heat are concentrated over the ocean, near the equator. The water temperature must be at least 80? Fahrenheit both day and night. Evaporation of the warm water into the atmosphere over the ocean makes the air very moist. Winds blowing across the ocean in different directions begin to push masses of warm, moist air toward each other. When the air masses collide, the air in the center starts to rise, forming an updraft. The moist air of the updraft begins to cool and water droplets form. These water droplets form clouds. This weather event becomes large enough to be influenced by forces created from the Earth's rotation. The energy of a hurricane comes from the heat released when water vapor condenses to liquid water. The atmosphere above a tropical ocean is the only place enough warm, moist air is available to produce the energy necessary to create a hurricane. The movement of a hurricane is somewhat predictable. It is so large that it moves with the Earth's wind currents that surround it. These wind currents are very large and steady and don't change course abruptly. Therefore, hurricanes usually travel in one of these wind currents until they meet another wind current, then they may change direction.
Hurricanes generally form in the southern Atlantic Ocean, the Caribbean Sea, the Gulf of Mexico, and the entire tropical Pacific Ocean and the Indian Ocean. They are called different names in different parts of the world; hurricane is the term used in the Americas, cyclones in the Indian and South Pacific Oceans, and typhoons in the west Pacific Ocean.
One very dangerous part of a hurricane is the eye-wall, which is near the center of the storm. Hurricanes move in a counter-clockwise direction around the eye of the storm. At some point, a hurricane may hit land. When this happens, the strong winds and heavy rains can cause serious damage. When the hurricane comes on land, the mound of water pushed ashore by the wind is known as a storm surge, another quite dangerous part of a hurricane.
Hurricanes are placed into one of five categories. Once a storm reaches a wind speed of at least 74 miles per hour it can be classified as a hurricane. The categories are set up based on the storm wind speed and how it progresses. Wind speed and the chance to cause damage are factors that are looked at when deciding how to rate the storm, which helps people plan and be more prepared. Hurricane season is typically between June 1 and November 30.
Hurricanes are given names in order to help storm meteorologists track and identify them as they move across the ocean. Often a given ocean will have more than one hurricane moving across it at a time.