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Definitions of Terms Commonly Used in Hurricane Reports

  1. ADVISORY - A message released by the National Hurricane Center, Usually at six (6) hour intervals, updating information on a storm or hurricane, including watches and warnings whenever they are in effect. A Special Advisory is a message given any time there is a significant change in weather conditions, or change in warnings previously released. An Intermediate Advisory updates information in advisories at two-three (2-3) hour intervals, whenever a watch or warning is in effect.

  2. SMALL CRAFT WARNING - When a hurricane or tropical storm threatens a coastal area, small craft are advised to remain in port and not to venture into the open sea.

  3. TROPICAL DEPRESSION - A circulation of air, at the surface of the water, with a sustained wind speed of 38 MPH or less.

  4. TROPICAL STORM - Distinct circulation with sustained wind speeds of 39 to 73 MPH.

  5. HURRICANE - A tropical cyclone that rotates counterclockwise, in the Northern Hemisphere, with sustained winds of 74 MPH or greater.

  6. TROPICAL STORM WATCH - An alert is given to an area when a tropical storm poss a threat within 36 hours.

  7. TROPICAL STORM WARNING - An alert issued when a tropical storm is expected to strike with 24 hours, with sustained winds of 39 to 73 MPH.

  8. HURRICANE WATCH - The alert given when a hurricane poses a threat to an area within 36 hours.

  9. HURRICANE WARNING - A hurricane is expected to strike within 24 hours with sustained winds of 74 MPH or more, accompanied by heavy rain, and high waves in coastal areas.

  10. STORM SURGE - A rise in tide caused by a hurricane as it moves over or near the coastline. It can be much higher than the normal tidal rise, with breaking waves on top.

  11. SAFFIR/SIMPSON SCALE - Hurricanes are classified by wind strength. This classification system is known as the Saffir/Simpson Scale:

    I ........... 74 - 95 MPH
    II .......... 96-110 MPH
    III ....... 111-130 MPH
    IV ....... 131-155 MPH
    V ............. 156+ MPH

  12. BUYS BALLOT'S LAW - If you are in the Northern Hemisphere, a hurricanes's center and direction of travel can be determined by useing Buys Ballot's Law. To do this, face the wind and extend yhour right arm out at about 100 degrees from the direction you are facing. Your arm is now pointing approximately at the center of the storm. Periodic determinations like this will indicate the storm's relative movement and on which side of the hurricane's track line you are located.

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