TROPICAL WAVE :    A cluster of thunderstorms in the tropics that has the potential to become a tropical depression.


TROPICAL DEPRESSION :  A tropical cyclone with maximum sustained winds less than 39mph at the surface.


TROPICAL STORM :  A tropical cyclone with maximum sustained winds ranging from 39-74 mph.


HURRICANE :  A severe tropical cyclone with maximum sustained winds over 74 mph at the surface. They are called hurricanes in the Atlantic & Eastern Pacific Oceans. In an average hurricane just one percent of it's energy released could meet energy needs of the United States for a full year. The force of the winds near the center are equivalent to an atomic bomb exploding every 10 seconds.


EYEWALL :  Thunderstorms that separate the eye from the feeder bands. Theses intense thunderstorms are where the most intense rains and most violent winds are located. In the northern hemisphere the worst winds can be found in the right front quadrant.  This is relative to forward motion of the storm.


EYE :  The calm center of a hurricane where the winds are calm and skies are virtually rain free. This is where the Hurricane Hunters aircraft fly to record the minimum central pressure of the hurricane. The eye of a mature hurricane can range from 3-65 miles wide.


OPEN EYEWALL :  A hurricane eyewall with one or more deformities such as open spaces in the structure. This shows a weakness in the storm and possible weakening.  


CLOSED EYEWALL :  A hurricane that is well structured and has no gaps within the eyewall. This could mean the hurricane is or could grow even stronger. 


FEEDER BAND :  Low level clouds that move into a thunderstorm or hurricane.


SPIRAL BANDS :  Clouds and thunderstorms that spiral inward toward the center and can be 3 to 30 miles wide and 50 to 300 miles long.


STORM SURGE :  Rapidly rising ocean water usually associated with tropical cyclones. In the past this was a hurricane's most deadly affect. But with radar and satellite we are aware of the situation well in advance of the event to head all of the watches and warnings.


HURRICANE WATCH :  An advisory issued stating that hurricane force winds MAY affect coastline within 36 hours.


HURRICANE WARNING :  An advisory issued that maximum sustained winds of 74 mph or greater are likely in 24 hours or less.


CONVECTION :  This is the transport of moisture and heat from the lower layers of the atmosphere to upper layers through updrafts of air sometimes as a thunderstorm inside of a hurricane.

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