Hurricanes

Introduction to Tropical Cyclones

  • Tropical Cyclones: Can form over land or water.

  • Hurricanes: Always develop over warm oceans.

  • Storm Definition: Defined by wind speed.

Classification of Storms by Wind Speed

  • Tropical Depression: Winds below 40 mph.

  • Tropical Storm: Winds between 40-74 mph.

  • Hurricane: Winds exceed 74 mph.

Formation Conditions

  • Warm Water: Necessary temperature of at least 80°F or 27°C.

  • Disturbances: Requires disturbances over the ITCZ or mid-latitude cyclones moving over warm water.

  • Coriolis Force: Needed for deflection and spinning.

  • Weak Upper Air Winds: Required to prevent destruction of the forming storm.

Tropical Storm Locations

  • Occur in the Atlantic and Eastern Pacific with very high winds.

  • Creation depends on a combination of:

    • Warm ocean surface

    • High evaporation rates

    • Favorable upper air winds

    • High pressure aloft.

Anatomy of a Hurricane

  • Eye of the Hurricane: Center where air flows downwards; high pressure area.

  • Eyewall: Surrounding the eye; area of severe low pressure and strongest winds.

  • Airflow Patterns:

    • Inward and upward flow around the eye.

    • Descending air in the eye.

  • Structure Visualization: Diagrams show airflow and circulation patterns, illustrating rising air in the eyewall and calm in the eye.

Saffir-Simpson Hurricane Wind Scale

  • Categories:

    • Category 1: Winds 74-95 mph

    • Category 2: Winds 96-110 mph

    • Category 3: Winds 111-129 mph

    • Category 4: Winds 130-156 mph

    • Category 5: Winds above 157 mph.

  • Visual Reference: 80 mph wind compared to feeling wind at high speed from a moving vehicle.

Hurricane Formation Regions

  • Hurricane Alley: Generally formed from warm air moving off Africa across the Atlantic.

  • Hurricane Season: From June to November; peak season is mid-August to October.

  • Storm Pathways: Storms can also form off South America's warm waters, influencing Central America and the Gulf of Mexico.

Human Interaction with Hurricanes

  • Notable Hurricanes: Recent examples include Hurricane Ian, Sandy, and Katrina.

  • Impact of Hurricanes: Massive rainfall, strong winds, and storm surges can lead to severe flooding and destruction.

  • Storm Surge Definition: The rise in sea level caused by wind pushing water onshore, significantly contributing to flooding during hurricanes.

  • Katrina's Context: The hurricane's impact exacerbated by socioeconomic and political issues, highlighting the complexity of disaster responses.

Conclusion

  • The interaction between hurricanes and human structures remains a crucial aspect in disaster preparedness and response.