Hazards: Hurricane and Tropical Storm Terminology

Hurricane icon

Hurricanes  aren’t the only tropical storm systems that warrant caution. Tropical Depression Gaston (2004) and Tropical Storms Jeanne (2004) and Floyd (1999) all caused major damage and prompted federal disaster declarations.

Tropical depressions, tropical storms and hurricanes are low pressure areas that develop in the tropical regions of the ocean (between 20 degrees N latitude and the equator). These storms, called tropical cyclones, are masses of thunderstorms that organize and begin to rotate.

Tropical cyclone systems, in order of intensity, are called:

  • Tropical Depression (winds between 25 and 38 mph)
    • A tropical depression, the lowest intensity, is given a number once it has a counterclockwise spin and winds of 38 mph or less.
  • Tropical Storm (winds between 39 and 73 mph)
    • When wind speeds reach 39 mph and the storm is given a name from a pre-determined list, a tropical storm is born. While a tropical storm does not produce a high storm surge, its thunderstorms can still pack a dangerous and deadly punch.
  • Hurricane (winds of 74 mph or greater)
    • A hurricane is the most intense tropical event, with five categories and winds ranging from 74 mph to 155 mph or greater.
      1. Category One – Winds 74-95 mph
      2. Category Two – Winds 96-110 mph
      3. Category Three – Winds 111-130 mph
      4. Category Four – Winds 131-155 mph
      5. Category Five – Winds greater than 155 mph
    • Storm surge is a major concern with hurricanes. The extremely high winds cause ocean water to pile up, creating higher than normal sea levels with waves up to 40 feet in open water.
    • The eye is the calm center of a hurricane. Don't be fooled if wind and rain stop during a hurricane. You may just be in the eye of the storm. Listen to the radio to find out when the storm has really passed.

Hurricane Names

Names are selected by the World Meteorological Organization’s hurricane committee. Six lists of names are used in rotation. If a storm had extraordinary impact, its name is retired.

In 2011, the name Irene was retired because of the deaths and damage it caused. In 2008, three hurricane names in the Atlantic were retired from the official name rotation: Gustav, Ike and Paloma will not be used again. The names Hugo, Andrew, Floyd and Isabel also have been retired.

A storm is named when its winds travel counterclockwise and reach 39 mph, tropical storm strength. For more information, visit NOAA’s hurricane naming page.

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