Tropical cyclone development criteria

Necessary conditions for the development of tropical storms and hurricanes (from observations) (Gray, 1979):

• Presence of converging surface horizontal winds.

• Location north (south) of 4 - 5^o of latitude in the tropics or subtropics.

• An underlying ocean with surface temperatures above 26^oC (80^oF) to a depth of 60m (150 feet).

• Upper and lower level horizontal winds with small shear.

• Temperature of the atmosphere favoring the formation of clouds.