The terms "hurricane" and "typhoon" are regional names for tropical cyclones. All tropical cyclones are alike in that they draw heat from warm water at the ocean's surface to power horizontal, rotating wind. Although similar in size, tropical cyclones have a different energy source than synoptic cyclones, which are storm systems that draw their energy from weather fronts and jet streams.
Most hurricanes begin in the Atlantic as a result of tropical waves that move westward off the African coast.
As rising water vapor condenses and latent heat is released, surrounding air is warmed and made less dense, causing the air to rise. The thunderstorms that make up the hurricane’s core are strengthened by this process. As air rises within the storms, pressure at the surface decreases and moister, tropical air is drawn to the center of the circulation, providing even more water vapor to fuel the hurricane. A hurricane has sustained wind gusts of at least 74 mph.
A tropical depression forms when a low pressure area is accompanied by thunderstorms that produce a circular wind flow with maximum sustained winds below 39 mph. An upgrade to a tropical storm occurs when cyclonic circulation becomes more organized and maximum sustained winds gust between 39 mph and 73 mph.
A thunderstorm is formed when a combination of moisture and warm air rise in the atmosphere and condense. While over land, thunderstorms are most likely to occur at the warmest, most humid part of the day, which is usually the afternoon or evening. Over the ocean they are most likely to occur in the early hours of the morning before dawn.
