Formation- Tropical Depression, Tropical Storm, and Hurricane

Formation-Tropical Depression

• surface winds strengthen, flow more efficiently around and into the core of the system

  • tropical depression: tropical cyclone with wind speeds <39 mph

• Coriolis effect spins the storm counterclockwise

• surface winds converge with the central core and warm, moist air is pushed rapidly upwards (like a chimney)

• warm air reaches the dew point which leads to water vapor condensing which leads to latent heat being released

• surrounding air heated, strong updrafts created, rate of upward flow of warm air increased

Formation-Tropical Storm and Hurricane

• converging winds continue to spiral the core

• rotating rising and falling air masses generated by the heat (fuel) they acquire from the ocean

  • often called “heat engines”

• tropical storm: tropical cyclone with wind speeds of 39-74 mph

• once surface wind speeds are very high (>74 mph), the wind can’t reach the center of the storm anymore

  • eye of the storm develops

  • hurricane has formed

Characteristics

• can be 620 miles wide, 9.3 miles high

• eyes as wide as 8-10 miles

• characterized by:

  • high (>74 mph), sustained winds

  • heavy rainfall

  • storm surges up to 20 ft higher than sea level