Hurricanes

Every year between June 1 and November 30 (commonly called hurricane season), hurricanes threaten the eastern and gulf coasts of the United States, Mexico, Central America and the Caribbean. In other parts of the world, the same types of storms are called typhoons or cyclones. Hurricanes wreak havoc when they make landfall, and they can kill thousands of people and cause billions of dollars of property damage when they hit heavily populated areas.

Photo courtesy Weather.com, photographer Stuart Livingston

Destructive waves from Hurricane Opal (1995) at the State Pier in Gulf Shores, AL

In this article, we'll discuss how hurricanes form and move, and look at the destruction and damage they can cause. We'll also examine how meteorologists track hurricanes. You'll be amazed at the power and impact of these storms!

Defining a Hurricane

According to the National Hurricane Center, "hurricane" is a name for a tropical cyclone that occurs in the Atlantic Ocean. "Tropical cyclone" is the generic term used for low-pressure systems that develop in the tropics.

Storm Prep: A-Z

How do you prepare for landfall? After last year's onslaught, have you made any changes to your hurricane plan? Let us know.

"Tropical cyclones with maximum sustained surface winds of less than 17 meters per second (39 mph / 62.7 kph / 34 knots) are called tropical depressions. Once the tropical cyclone reaches winds of at least 17 meters per second (m/s), it is typically called a tropical storm and assigned a name. If winds reach 33 m/s (74 mph / 119 kph / 64 kt), then it is called a "hurricane."

Source: NASA Observatorium

"Hurricane"

According to the National Hurricane Center, the word "hurricane" comes from the name "Hurican," the Caribbean god of evil.

Hurricanes are defined by the following characteristics:

They are tropical, meaning that they are generated in tropical areas of the ocean near the Equator.

They are cyclonic, meaning that their winds swirl around a central eye. Wind direction is counterclockwise (west to east) in the Northern Hemisphere and clockwise (east to west) in the Southern Hemisphere (more about this later).

They are low-pressure systems. The eye of a hurricane is always a low-pressure area. The lowest barometric pressures ever recorded have occurred inside hurricanes.

The winds swirling around the center of the storm have a sustained speed of at least 74 mph (119 kph / 64 kt).

How a Hurricane Forms

Hurricanes form in tropical regions where there is warm water (at least 80 degrees Fahrenheit / 27 degrees Celsius), moist air and converging equatorial winds. Most Atlantic hurricanes begin off the west coast of Africa, starting as thunderstorms that move out over the warm, tropical ocean waters. A thunderstorm reaches hurricane status in three stages:

Tropical depression - swirling clouds and rain with wind speeds of less than 38 mph (61.15 kph / 33 kt)

Tropical storm - wind speeds of 39 to 73 mph (54.7 to 117.5 kph / 34 to 63 kt)

Hurricane - wind speeds greater than 74 mph (119 kph / 64 kt)

Photo courtesy NOAA

Hurricane Ivan over the Gulf Coast of the United States

2:45 p.m. EDT, September 15, 2004

It can take anywhere from hours to several days for a thunderstorm to develop into a hurricane. Although the whole process of hurricane formation is not entirely understood, three events must happen for hurricanes to form:

A continuing evaporation-condensation cycle of warm, humid ocean air

Patterns of wind characterized