How Hurricanes are Formed
by Patrick

There are three major areas of hurricane formation on the earth. They typically form in the Northwest Pacific Ocean, the South Pacific and Indian Oceans, and the Mid Atlantic and Gulf of Mexico.

In the Atlantic Ocean, a hurricane normally begins forming off the coast of West Africa. Storms begin to rotate, counterclockwise in the Northern Hemisphere (or clockwise in the Southern Hemisphere) due to converging winds. The storm grows because of the warm ocean water and violent seas. Rising water vapor begins to rotate adding to the already increasing wind speed. As the storm gets stronger, it moves in a west-north-west direction until it reaches land. It weakens as it goes inland, and usually drops heavy rain for hundreds of miles.

• The earliest stage in a hurricane being developed is a tropical wave. This is an area of low pressure with showers and thunderstorms, but it does not have a defined circulation.
• For a tropical disturbance to form, a group of thunderstorms has to stay together for at least 24 hours. Winds are usually light and there may be heavy rain.
• A tropical depression is an area that has low pressure and wind speed of 38mph or less.
• A tropical storm is a strong area of low pressure with winds of 39 mph to 73 mph. It has very heavy rains. When a tropical storm is formed, it is given a name.

If the winds are higher than 74 mph, you have a hurricane. The hurricane season in the Atlantic and Caribbean occurs during the months of June through November with September being the most active month. Hurricanes are usually about 200–250 miles in diameter.

To develop and intensify, a tropical system needs these five conditions:

1. The surface water has to be at least 26.5° C.
2. The system must be at 5° latitude or greater.
3. There must be no wind shear.
4. The divergence in the upper part of the system is greater than the convergence in the lower part of the system.
5. There must have been a low-level disturbance before it developed.

Hurricanes that are forming can be compared to giant heat engines because they gather heat and energy through contact with warm waters from the ocean. Then the moisture powers them.

The eye, or center, of the hurricane is calm and the sun may be shining. The most intense part of a hurricane is the area immediately around the eye. This is called the eyewall.  The size of the eye or center can range from practically nonexistent to several miles wide!  Once an eye is established, it usually maintains its size.  The size does not necessarily predict the power of the storm.  For example, Hurricane Camille in 1969, one of the most destructive hurricane ever to hit the southern part of the United States, had an eye of only a few miles in diameter.