User:TECHADV AND EDU

Tropical wave: A tropical wave (also called easterly wave, tropical easterly wave, and African easterly wave), in and around the Atlantic Ocean, is a type of atmospheric trough, an elongated area of relatively low air pressure, oriented north to south, which moves from east to west across the tropics, causing areas of cloudiness and thunderstorms.

Tropical depression: A tropical depression is a tropical cyclone that has maximum sustained surface winds (one-minute average) of 38 mph (33 knots) or less.

Tropical storm: A tropical storm is a tropical cyclone that has maximum sustained surface winds ranging from 39-73 mph (34 to 63 knots).

Hurricane: A hurricane is a tropical cyclone that has maximum sustained surface winds of 74 mph or greater (64 knots or greater).