Hurricane Hugo, 1989

Hurricane Hugo, 1989

The hurricane season in the Atlantic, the Caribbean and the Gulf of Mexico begins on June 1 each year and lasts until November 30. Tropical cyclones have played extremely important social and economic roles in the region. These phenomena have been known in the region since pre-Columbian times.

A cyclone is a circulation of wind around a center. It is counter-clockwise in the northern hemisphere and clockwise in the southern hemisphere. Its center is an area of low pressure that is accompanied by heavy clouds, producing an area of inclement weather. There are two main classes of cyclones: tropical cyclones and extratropical cyclones.

Tropical cyclones

This is the name given to organized systems of low pressure cyclonic circulation in the tropics that move across the surface of the earth. Tropical cyclones are classified based on the intensity of their sustained winds.

Tropical depression: is the first stage of a tropical cyclone. It is an organized system of clouds with a defined circulation and whose maximum winds are less than 39 mph (62.7 kmh). It is considered the formative phase of a tropical cyclone.

Tropical storm: is a well defined and well organized tropical cyclone in which the maximum sustained winds are between 39 and 73 mph. It is assigned a woman’s or man’s name based on a list prepared by the World Meteorological Organization.

Hurricane: is a tropical cyclone in which the intensity of winds exceeds 74 mph. The winds are organized in a circle around a relative calm. The word hurricane is used in the Caribbean, the Gulf of Mexico and the Atlantic Ocean. The word is derived from the gods Juracán or Hurakan who the Taino Indians believed created the Earth by breathing on the chaotic waters at the beginning of the universe. In the tropical region of the western Pacific Ocean, the word typhoon is used instead of hurricane. In other regions where tropical cyclones form, such as in the Indian Ocean, they are simply called severe cyclones, and in Australia they are called a willy willy.

In the center of a hurricane is an area of relative calm called the eye. In the eye, the sky is partly cloudy or quite clear. The eye is defined by a wall of clouds and has a diameter of 10-30 miles (16-48.28 kilometers). The strongest winds and most intense rain are located around the eye.

How are tropical cyclones named?

A tropical system is named once it reaches the category of tropical storm. They were originally assigned the name of the saint corresponding to the day the hurricane passed over the island. But this caused confusion because the cyclones passed over different countries on different days and so the same phenomenon had several names. Thus it was decided to assign a woman’s name, but feminist groups protested tying these destructive phenomena to women. It was finally decided to alternate men’s and women’s names from the three main languages in the Caribbean region (English, Spanish and French).

Strong winds on a beach

Strong winds on a beach

Hurricanes are classified in categories based on a scale developed in the 1970s by the Herbert Saffir, an engineer, and Robert Simpson, the director of the National Hurricane Center. This scale is based on the intensity of the winds.

Category 1 

Minimal damage: winds of 118 to 152 km/h (74 to 95 mph). Minimum barometric pressure of 980 millibars or above. Light damage to other structures. Partial or total destruction of signs. Waves of 1.32 to 1.65 meters above normal.

Category 2

Moderate damage: winds from 153 to 178 km/h (96 to 110 mph). Minimum barometric pressure of 965 to 979 millibars. Considerable damage to trees and shrubbery. Extensive damage to signs. Waves from 1.98 to 2.64 meters above normal affecting the structure of the coasts.

Category 3 

Extensive damage: winds of 179 to 209 km/h (111 to 130 mph). Minimum barometric pressure of 945 to 964 millibars. Many branches are torn from trees. Some damage to roofs of buildings, to bridges and highways. Waves from 2.97 to 3.96 meters above normal that flood extensive areas of the coastal zones with broad destruction of buildings located near the shore.

Category 4 

Extreme damage: winds from 211 to 250 km/h (131 to 155 mph). Minimum barometric pressure of 920 to 944 millibars. Trees are destroyed by the wind. Roofs and some walls of small residences are completely collapsed. Waves can reach between 4.29 to 5.94 meters above normal, destroying structures and ships along the coast.

Category 5

Catastrophic damage: winds of more than 250 km/h (155 mph). Minimum barometric pressure of less than 920 millibars. Trees are totally blown down by the winds, with many large trees torn up by the roots. Waves of 4.29 to 5.94 meters above normal.

 
Author: Rafael Méndez Tejada
Published: May 20, 2012.

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