How Does a Hurricane Develop?

Image from the National Weather Service’s JetStream – Online School for Weather

In order for a hurricane to develop, an atmospheric disturbance that causes convection must occur over ocean waters that have a temperature of at least 80 degrees Farenheit. These conditions usually occur all together at the same time in only seven regions of the ocean. Therefore, these seven regions are where hurricanes typically form.

Convection means that as warm, moist air moves across the ocean, water evaporates and rises up to form thunderclouds.

More moist air moves in to take the place of the rising air. This new air also rises up, and once again more moist air moves in. More thunderclouds develop, and the wind, which is the movement of the air in and up, grows more and more strong.

Image from The National Weather Service’s JetStream – Online School for Weather.

As this convection cycle continues, a different cycle begins. Because the Earth is rotating, these storms and winds begin to move in a spiral pattern—counterclockwise in the northern hemisphere and clockwise in the southern hemisphere. The force that causes this pattern is called the Coriolus effect.

A NASA imagine of Hurricane Wilma in October 2005 as it moves across the ocean.

The whole spiraling system is propelled across the ocean by the winds and pressure fronts that exist at the time.