What does it take to create such a huge atmospheric phenomena? What are some of the parameters forecasters use to predict the upcoming hurricane season activity?
When it looks like a tropical cyclone is developing, scientists and aviators gear up for long flights into the suspect area. Data gathered helps meteorologists predict the path. Early watches and warnings help emergency management officials prepare and plan evacuations. Aircraft observations enhance our understanding of tropical cyclones.
Hurricane FormationHurricanes can develop in the Gulf of Mexico, in the Caribbean Sea or in the North Atlantic. Some may even begin thousands of miles away off the west coast of Africa.
Tropical cyclones are born in moist tropical air. About each 4-5 days, a tropical wave of low pressure moves west in the trade winds. Some tropical waves develop into tropical depressions, tropical storms, and hurricanes.
In developing tropical cyclones, deep thunderstorms develop. Air pressure drops at the surface, forming low pressure. Low pressure attracts warm moist air near the ocean's surface. The coriolis force causes these low level winds to spiral in a counterclockwise direction around the center of the low in the Northern Hemisphere. Winds swirl clockwise in the Southern Hemisphere.
Typically, an "eye" forms when the tropical cyclone reaches hurricane strength, but an eye is not necessary for a tropical cyclone to be a hurricane.
Think of a hurricane as a large heat engine. The fuel is moisture from warm ocean water. The moisture is converted to heat in the thunderstorms that form. Spiral rain bands that surround the tropical cyclone's core help feed the circulation more heat energy.
As air nears the center, it rises rapidly and condenses into clouds and rain. The condensation releases tremendous amounts of heat into the atmosphere. The result is lower surface pressure and strengthening winds.
In this way, the tropical cyclone's engine refuels itself, concentrating its power in a donut-shaped area, called the eye wall, surrounding the center. The eye wall typically contains the strongest surface winds.
Sinking air at the center clears the tropical cyclone of clouds and forms the "eye."
Falling surface pressure can only occur if air mass is removed from the circulation center. This is accomplished by wind flowing out away from the circulation in the upper atmosphere.