GEO 125

Physical Geography

Tropical Cyclonic Storms

Types of Tropical Cyclonic Storms

  • Hurricanes (North Atlantic Ocean, Gulf of Mexico, and Eastern Pacific Ocean)

  • Typhoons (Western Pacific)

  • Cyclones (Indian Ocean)

Generic Characteristics of Tropical Cyclonic Storms

  • Intense low barometric pressure (record low pressure for an Atlantic hurricane is 26.22 inches of mercury for Hurricane Gilbert in 1988)

  • Cyclonic wind circulation

  • Counter clockwise in the northern hemisphere
  • Clockwise in the southern hemisphere
  • Diameter of storms range between 100 to 600 miles
  • Diameter of the eye of hurricanes range between 10 to 30 miles
  • Wind speeds may reach 160 miles per hour for Atlantic hurricanes and over 200 miles per hour for Pacific typhoons

Structure of Tropical Cyclonic Storms

  • Energy derived from the evaporation of warm ocean water

  • Energy released by the process of convection

  • Bands of cumulonimbus clouds surround the eye

  • Hurricanes are made up of thunderstorms

Origins of Hurricanes in the North Atlantic Ocean Basin

  • Off the west coast of Africa between 5 to 15 degrees north latitude

  • Caribbean Sea

  • Gulf of Mexico

Hurricane Tracks

  • Influence of the northeast trade winds

  • Influence of the Bermuda High

  • Influence of the prevailing westerlies

  • Influence of the Gulf Stream

Temporal Distribution of Hurricanes Affecting the Atlantic and Gulf Coasts of the United States

  • Hurricane season extends from May through November

  • The majority and most violent storms occur in August and September with the occurrence of seasonally warmer water

Spatial Distribution of Hurricanes Striking

  • Gulf and Atlantic Coasts of the United States

  • Storms more frequently strike the Gulf and Southeastern coasts of the United States because of the warmer ocean water temperatures

  • Less strikes occur along the Mid-Atlantic and New England coastlines due to colder ocean water temperatures

Stages in the Development of Tropical Cyclonic Storms

  • Equatorial air mass

  • Tropical depression (wind speeds less than 45 miles per hour)

  • Tropical storm (wind speeds between 45 and 74 miles per hour)

  • Hurricane (wind speeds 75 miles per hour or greater)

  • Great hurricanes (wind speeds of 125 miles per hour or greater)

  • Dissipation of tropical cyclonic storms (Movement over land or movement over the cold waters of the North Atlantic)

Naming of Tropical Cyclonic Storms

  • Tropical cyclonic storms are named when they reach tropical storm strength

  • Prior to 1953, Atlantic Ocean Basin hurricanes were given generic names such as the Galveston storm of 1900

  • Named after women in alphabetical order from 1953 to 1978

  • Hurricanes in the Atlantic Ocean have been named after both men and women since 1979 (in even numbered years the first storm is named after a man and in odd numbered years the first storm is named after a woman)

Damage Associated with Hurricanes

  • Normally the greatest amount of damage is associated with where the northeast quadrant of the storm makes landfall because of higher wind speeds and wave heights

  • Elevated storm water associated with coastal flooding associated with tide level, storm surge, and height of the wind waves

  • Tornadoes

  • Inland flash flooding

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