Hurricanes

• large tropical cyclones

• also called typhoons (North Pacific Ocean) or cyclones (Indian Ocean and South Pacific Ocean)

• basically heat engines

  • convert heat energy of the tropical oceans into winds and waves

  • distribute heat from the tropics northwards

Terminology

• tropical cyclone: a storm formed over tropical waters characterized by huge rotating mass of low-pressure air with strong winds and torrential rains

  • tropical disturbance: low-pressure system in the tropics with weak wind circulation and thunderstorms

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

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

    • this is when the storm is named

  • hurricane: tropical cyclone with wind speeds >74 mph

Hurricane Formation

• long, hot summers in the tropics build up heat

• hurricanes export the heat to mid-latitudes

• for a hurricane to form:

  1. seawater in the upper 200ft of the ocean must be at least 80 degrees F

     1. maximum is about 20 degrees latitude

  2. warm, humid, and unstable air

  3. storm must be around 300 miles away from the equator

     1. Coriolis effect needs to be strong enough to spin the system

  4. weak, upper-level winds blow the same direction the storm is moving