The terms "hurricane" and "typhoon" are regionally
specific names for a strong "tropical cyclone". A tropical cyclone is the
generic term for a non-frontal synoptic scale low-pressure system over
tropical or sub-tropical waters with organized convection (i.e.
thunderstorm activity) and definite cyclonic surface wind circulation
(Holland 1993).
Tropical cyclones with maximum sustained surface winds of less than 17 m/s
(34 kt, 39 mph) are called "tropical depressions". (This is not to be
confused with the condition mid-latitude people get during a long, cold
and grey winter wishing they could be closer to the equator ;-)) Once the
tropical cyclone reaches winds of at least 17 m/s they are typically
called a "tropical storm" and assigned a name. If winds reach 33 m/s (64
kt, 74 mph)), then they are called: a "hurricane" (the North Atlantic
Ocean, the Northeast Pacific Ocean east of the dateline, or the South
Pacific Ocean east of 160E); a "typhoon" (the Northwest Pacific Ocean west
of the dateline); a "severe tropical cyclone" (the Southwest Pacific Ocean
west of 160E or Southeast Indian Ocean east of 90E); a "severe cyclonic
storm" (the North Indian Ocean); and a "tropical cyclone" (the Southwest
Indian Ocean) (Neumann 1993).