Parameter Tree:
EARTH SCIENCE > ATMOSPHERE > ATMOSPHERIC PHENOMENA > CYCLONES

Definition:
A weather system charcterised by relatively low surface air pressure at a
given level and a closed cyclonic wind circulation. Also the regional name
for a severe tropical cyclone with sustained surface wind speeds greater
than 64 knots (74 mph) in the western South Pacific and Indian Oceans,
equivalent of a hurricane or typhoon. 


Reference:
Glossary of Weather and Climate, American Meteorological Society, 1996.