National Weather Service Definitions

  • Tropical Disturbance:  A moving area of thunderstorms in the tropics.
  • Tropical Depression:  An area of low pressure, counter-clockwise rotation of clouds, and winds to 38 mph.
  • Tropical Storm:  A low pressure area with wind speeds increasing to 39-73 mph. A storm is given a name at his point.
  • Hurricane:  When a tropical storm reaches winds of 74 mph or greater, it is classified as a hurricane.
  • Advisory:  A dissemination of hurricane and storm data issued every 6 hours.
  • Special Advisory:  A notice given anytime there is a significant change in weather conditions or warnings.
  • Intermediate Advisory:  A report updating a regular advisory information every 2 to 3 hours, as necessary.
  • Gale Warning:  Wind speeds of 39-54 mph expected
  • Storm Warning:  Wind speeds of 55-73 mph expected.
  • Hurricane Watch:  A hurricane may threaten your area within 36 hours.
  • Hurricane Warning:  A hurricane expected do strike your area within 24 hours or less.
  • Tornado Watch:  Tornadoes and severe thunderstorms are possible for your area.
  • Tornado Warning:  Tornadoes and severe thunderstorms are possible for your area.
  • Storm Surge:  The low pressures and strong winds associated with hurricanes and tropical storms cause the sea level to rise above normal tidal heights, giant waves, and unpredictable currents over a 50 mile area.

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