Natural Hazards and Disasters Chapter 14 Hurricanes and Nor’easters
description
Transcript of Natural Hazards and Disasters Chapter 14 Hurricanes and Nor’easters
Natural Hazards and Disasters Chapter 14 Hurricanes and Nor’easters
Terminology
• Hurricanes: N. Atlantic and E. Pacific• Typhoons: W. Pacific, Japan, SE Asia• Cyclones: Indian Ocean
• All are low pressure systems in the tropics• Lower winds are tropical depressions or
storms
Formation of Hurricanes
• Rising air and condensation creates convective ‘chimney’ of thunderstorms
• Strong winds inhibit convection • Warm seawater promotes hurricanes• Winds exceed 119 km/hr
Formation of Hurricanes and Cyclones
• Warm air expands, cools and releases latent heat• Eye is 20oC warmer than surrounding air• Rising air pulls more air into center of hurricane• 160-800 km in diameter• Forward motion averages 25 km/hr• Winds drop abruptly in eye, pressure drops
Formation of Hurricanes and Cyclones
Hurricane is a big convection cell
Areas at Risk
Areas at Risk
• Northern hemisphere tropical cyclones:– Rotate counterclockwise, track clockwise
• Southern hemisphere tropical cyclones:– Rotate clockwise, track counterclockwise
Areas at Risk
Areas at Risk
Understanding Motion
• Hurricane track is controlled by Coriolus Effect
Storm Damages
Storm Damages
CAT 1 CAT 2 CAT 3 CAT 4 CAT 5
WIND SPEED
74-95 MPH
96-110 MPH
111-130 MPH
131-155 MPH
>156 MPH
STORM SURGE
4-5 FT 6-8 FT 9-12 FT 13-18 FT
>19 FT
PRESSSURE 980 MBARS
965-979 MBARS
945-964 MBARS
920-944 MBARS
<920 MBARS
SAFFIR-SIMPSON SCALE
Hurricane Related Hazards
• Storm surge• Wave damage• Wind damage• Rainfall and flooding• Disease and starvation
HURRICANE-PRODUCED CONDITIONS
• Storm surge - Tropical cyclones cause an increase in sea level, which can flood coastal communities. This is the worst effect, as hurricanes claim 80% of their victims when they first strike shore.