What are hurricanes?

Hurricanes are born over tropical oceans when the water is warmer than about 80 degrees. They all start as areas of disturbed weather. Blobs of clouds and falling pressure are given a spin by the Coriolis force. Once they mature into hurricanes, they can remain constant for days or peak and quickly die. One sure way to kill a hurricane: Take away its warm water source, which is what happens when a storm moves over land.

Hurricanes and other cyclones that form in the tropics during summer are very different from the extratropical storms that often form during winter even though both may produce very strong winds and possible flooding. The seven main differences between hurricanes and extratropical storms are:

• Hurricanes and tropical systems have no fronts.

• Hurricane winds weaken with height

• The centers of hurricanes are warmer than their surroundings

• Hurricanes and tropical systems form under weak high-altitude winds.

• Air sinks at the center of a hurricane

• Hurricanes' main energy source is the latent heat of condensation

• Hurricanes weaken rapidly over land

Tropical systems are classified into four categories according to its degree of organization and maximum sustained wind speed.

Tropical disturbance, tropical wave: Unorganized mass of thunderstorms, very little, if any, organized wind circulation.

Tropical depression: Has evidence of closed wind circulation around a center with sustained winds from 37-62 km/h.

Tropical storm: Maximum sustained winds are from 63-117 km/h. The storm is named once it reaches tropical storm strength.

Hurricane: Maximum sustained winds exceed 117 km/h.

Hurricanes are classified into different categories according to the Saffir-Simpson scale. Hurricanes can also spawn severe weather such as tornadoes as they move inland.

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