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

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