The Stages and Categories of Hurricanes

8/22/2022 (Permalink)

During Hurricane Season, you tend to hear TV meteorologists talking about different terms and categories to classify the storm.  What do they actually mean?

Where do hurricanes actually begin?  As a storm builds from a thunderstorm to a hurricane, it passes through 4 distinct stages:

Tropical Disturbance: a mass of thunderstorms that have wind speeds of less than 23 mph.

Tropical Depression: consistent wind speeds of 23-39 mph and circulation of wind in the center of the thunderstorm mass is detected.

Tropical Storm: forms when the maximum sustained winds have intensified to 39-73 mph. Storms are typically given a name at this stage and are characterized by problems caused from very heavy rainfall.

Hurricane: finally forms when surface pressures continue to drop, and winds reach 74 mph. There is now a clear and definite rotation around a calm center or eye. 

Hurricanes have their own categories which are defined by the Saffir Simpson Hurricane Wind Scale: 

Category 1: Winds 74 to 95 mph (Minor damage)

Category 2: Winds 96 to 110 mph (Extensive damage — Can uproot trees and break windows)

Category 3: Winds 111 to 129 mph (Devastating — Can break windows and doors)

Category 4: Winds 130 to 156 mph (Catastrophic damage — Can tear off roofs)

Category 5: Winds 157 mph or higher (Can level houses and destroy buildings)

This scale only estimates property damage that could occur with the maximum sustained wind speed of a particular hurricane; it does not consider the potential for other dangerous events that often accompany hurricanes, like tornadoes, flooding, and storm surge.