M e t e o r - o l o g y

Hurricanes are tropical cyclones with winds that exceed 64 knots (74 mi/hr) and circulate counter-clockwise about their centers in the Northern Hemisphere (clockwise in the Southern Hemisphere).

Hurricane Formation

This is a sea surface temperature map. The yellow, orange, and red colors show water temperatures warm enough to sustain hurricanes (> 26.5°C).

Here is avery brief general description of how hurricanes are formed: 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. -Jack Williams USA TODAY

Hurricanes grow to their maximum strength with help from both the atmosphere and the ocean. First of all, the ocean water itself must be warmer than 26.5 degrees Celsius (81°F). The heat and moisture from this warm water is the source of energy for hurricanes. Hurricanes will weaken rapidly when they travel over land or colder ocean waters -- locations with insufficient heat and/or moisture. This is why hurricanes will affect more costal areas then inland areas..

Hurricanes start small and get big. To further enhance the previous statement, hurricanes start as a period of disturbed weather in the ocean, a thunderstorm etc.

Hurricane Life Cycle


Once a group of thunderstorms has come together under the right atmospheric conditions for a long enough time, they may organize into a tropical depression. Winds near the center are constantly between 20 and 34 knots (23 - 39 mph).	Once a tropical depression has intensified to the point where its maximum sustained winds are between 35-64 knots (39-73 mph), it becomes a tropical storm. It is at this time that it is assigned a name. During this time, the storm itself becomes more organized and begins to become more circular in shape -- resembling a hurricane.	As surface pressures continue to drop, a tropical storm becomes a hurricane when sustained wind speeds reach 64 knots (74 mph). A pronounced rotation develops around the central core.
A tropical depression is designated when the first appearance of a lowered pressure and organized circulation in the center of the thunderstorm complex occurs.	The rotation of a tropical storm is more recognizable than for a tropical depression. Tropical storms can cause a lot of problems even without becoming a hurricane. However, most of the problems a tropical storm cause stem from heavy rainfall.	Hurricanes are Earth's strongest tropical cyclones. A distinctive feature seen on many hurricanes and are unique to them is the dark spot found in the middle of the hurricane. This is called the eye. Surrounding the eye is the region of most intense winds and rainfall called the eye wall. Large bands of clouds and precipitation spiral from the eye wall and are thusly called spiral rain bands.

A Question we all have: How does a hurricane get its counterclockwise rotation?

Hurricanes spin counterclockwise (like all low pressure centers in the northern hemisphere) because of the Coriolis Effect. Because the equator rotates faster than other areas of the Earth's surface, anything moving in a straight line on a North to South axis will eventually curve.

-Ean Stewart Meteorologist for SkyMAX 13 New Orleans.

-Since air spins into a low pressure center (like water going into a drain), it makes the hurricane rotate.

Click here for Hurricane home page [here]

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Copyright 2001 Nate, and Kavi. This website was created using Dreamweaver 4, Microsoft FrontPage 2000, and Eversoft 1st page 2000 (free verstion). This website was created for Thinkquest.org, for a website competition. More information about this contest can be found here. We are team C0120505.