1 Hurricane characteristics Sustained winds of 120 km or more Sustained winds of 120 km or more Sea level pressure < than 990 mb Sea level pressure < than 990 mb Varying sizes but cloud shield usually > 400 km diameter Varying sizes but cloud shield usually > 400 km diameter Warm tropical waters > 27°C (~80) Warm tropical waters > 27°C (~80) Atlantic Season Atlantic Season June – November June – November Peak: Mid August – Early October Peak: Mid August – Early October

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3 Hurricane movement & dissipation Controlled by large surface pressure systems Controlled by large surface pressure systems Steered by orientation and position of subtropical high Steered by orientation and position of subtropical high Controlled by upper- level flow Controlled by upper- level flow Vary by time of year Vary by time of year Will dissipate over land or colder water Will dissipate over land or colder water

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6 Hurricane genesis

7 Hurricane Development Coriolis Force Coriolis Force Atlantic Formation usually between 10 – 20°N Atlantic Formation usually between 10 – 20°N Water above 27°C Water above 27°C Little wind shear Little wind shear

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9 Tornadoes

10 Levels of storm One closed isobar: Tropical Depression (receives number) One closed isobar: Tropical Depression (receives number) 60 km/h winds: Tropical Storm (receives name) 60 km/h winds: Tropical Storm (receives name) 120 km/h winds: Hurricane 120 km/h winds: Hurricane These vary worldwide These vary worldwide

11Landfalls

12 Storm surge and wind variability

13 Climate change and hurricanes ???? A sign of the future Or natural variability

14 Problems with the Saffir Simpson Scale Pre-landfall Warning Scale Pre-landfall Warning Scale Was the storm as strong as advertised? Was the storm as strong as advertised? Uniform Rating Uniform Rating Focuses on wind speed and accompanying surge Focuses on wind speed and accompanying surge SURGE discrepancies! SURGE discrepancies! Duration? Duration? Size? Size? Precipitation? Precipitation? Gusts Gusts Surface friction, topography Surface friction, topography