Chapter 15

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 as opposed to temperature

Anatomy of a Hurricane

Intense storm of tropical origin with winds greater than 64kts; typhoon, cyclone, tropical cyclone

Eye Eye wall Spiral rain band Anticyclonic divergence Latent heat

Hurricane Formation and Dissipation The Right Environment

Tropical waters with light wind26.5°C sea surface temperatures (June-

November)Surface converge trigger (tropical wave)Coriolis effect: 5-20º latitude

The Developing StormCluster of thunderstorms around a rotating

Low pressureRelease of latent heat, divergence aloft

Hurricane Formation and Dissipation The Storm Dies Out

Cold water, land

Hurricane Stages of DevelopmentTropical DisturbanceTropical Depression (22-34kts)Tropical Storm (35-64kts)Hurricane (> 65kts)

Hurricane Formation and Dissipation 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

Fig. 15-12, p. 421

Naming Hurricane and Tropical Storms Process has changed over the years:

Latitude and longitudeLetters of the alphabetAlphabetical female namesAlphabetical, alternating female and male

namesRetirement (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

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.

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.

Stepped Art

Fig. 15-27, p. 433

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