CYCLONE: An atmospheric closed circulation rotating counter-
clockwise in the Northern Hemisphere and clockwise in the
Southern Hemisphere. EYE: The relatively calm center of the
tropical cyclone that is more than one half surrounded by wall
cloud. This clear, calm area is the result of sinking air in the
center of a tropical cyclone. EYE WALL/WALL CLOUD: An organized
band of cumuliform clouds immediately surrounding the center of
a tropical cyclone. Eye wall and wall cloud are used
synonymously. The eye wall typically contains the strongest
winds and most violent weather within a tropical system.
EXTRATROPICAL: A term used in advisories and tropical summaries
to indicate that a cyclone has lost its "tropical"
characteristics. This usually happens once a system moves from
mid latitudes to high latitudes and changes from a "warm core"
to a "cold core" system. FUJIWHARA EFFECT: An interaction where
tropical cyclones within a certain distance (300 - 750 nautical
miles, depending on the sizes of the cyclones) of e