wind,storms and hurricanes

Class #7: Monday, September 13, 2010

HurricanesChapter 15

1Class #7, Monday. September 13, 2010

Review for test #1

• Chapter 2, pp. 30-49• Chapter 3, pp. 58-64; 73-75• Chapter 7, p. 174• Chapter 9, pp. 224-5; 232-4, 238-44• Chapter 10, pp. 260-266; 268• Chapter 15, pp. 412-436• Chapter 17, pp. 470-483

Class #7, Monday. September 13, 2010 2

Fig. 15-CO, p. 4103Class #7, Monday. September 13, 2010

Tropical Weather

• Noon sun is always high, seasonal temperature changes small

• Daily heating and humidity = cumulus clouds and afternoon thunderstorms

• Non-squall clusters, tropical squall line, tropical wave

• Seasons defined by precipitation (higher sun season/ITCZ) as opposed to temperature


Anatomy of a Hurricane

• Intense storm of tropical origin with winds greater than 64kts; typhoon (N. Western Pacific), cyclone (Indian Ocean), tropical cyclone (Aust.)

• Eye, center, break in clouds, sinking air, lowest p• Eye wall, intense thunderstorms, upward motion• Spiral rain bands, principal rain band to northeast• Anticyclonic divergence aloft over the storm• Latent heat comes from ocean surface

evaporation in strong winds, warm Temperatures


Fig. 15-2, p. 4137Class #7, Monday. September 13, 2010

Stepped Art


Hurricane Formation and Dissipation

The Right EnvironmentTropical waters with light wind, high humidity26.5°C sea surface temperatures (June-November)Surface convergence trigger (tropical wave)Coriolis effect: 5-20º latitudeWeak vertical wind shear, weak winds aloft

The Developing StormCluster of thunderstorms around a rotating low

pressure centerRelease of latent heat, divergence aloft



• The Storm Dies Out– Cold water, land

• Hurricane Stages of Development– Tropical Disturbance– Tropical Depression (22-34kts)– Tropical Storm (35-64kts)– Hurricane (> 65kts)


Fig. 1, p. 41919Class #7, Monday. September 13, 2010


Topic: Hurricanes and Mid-latitude StormsHurricane warm core lowMid-latitude cold-core lowArctic hurricanesHurricane + upper level trough = mid-latitude

cyclone Hurricane movement

General track: west, northwest, northeastMuch variation


Stepped Art


Naming Hurricane and Tropical Storms

• Process has changed over the years:– Latitude and longitude– Letters of the alphabet– Alphabetical female names– Alphabetical, alternating female and male names– Retirement (Katrina, Camille)


Devastating Wind, Storm Surge, and Flooding

• Highest winds on the eastern side of storm (wind + speed of storm)

• Swell• Storm surge on north side of storm (tide)• Coastal flooding• River flooding• Hurricane spawned tornadoes• Saffir-Simpson scale – 1 weakest, 5 strongest


Table 15-1a, p. 42329Class #7, Monday. September 13, 2010

Table 15-1b, p. 42330Class #7, Monday. September 13, 2010

Some Notable Storms

• Camille 1969• Hugo 1989• Andrew 1992• Ivan 2004• Katrina 2005


Some Notable Storms

Observation: Atlantic Hurricanes 2004-2005Abnormally warm ocean water and weak vertical

sheer allowed for high frequency of hurricanes Environmental Issue: Hurricanes in a Warmer

WorldNo clear answer, need more dataIntensity and frequency most likely to be

impacted.


Table 15-2, p. 42639Class #7, Monday. September 13, 2010

Table 15-3, p. 42740Class #7, Monday. September 13, 2010

Stepped Art


Hurricane Watches, Warnings, and Forecasts

• Watch issued 24-48 hours before hurricane expected to make landfall

• Warning issued when storm expected to strike coast within 24 hours and probability of strike in a given location provided.


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Modifying Hurricanes

• Operation STORMFURY: seed clouds to create rain, weaken hurricane, and reduce winds; no conclusive evidence it was effective

• Oil or film on water to reduce evaporation and latent heat available to storms


wind,storms and hurricanes

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