Hurricanes
Definition
•A tropical cyclone with sustained one-minute winds of at least 74 mph (64 knots),at an elevation of 10 meters.
• Derived from the Spanish word "huracan" ,which was most likely inspired byHunraken, the name for the ancient Mayanstorm god or Hurakan, the Quiche god ofthunder
Hurricane Facts
•They are tropical cyclones (low pressure areas) withsustained winds at least 64 knots (74 mph). Strongesthurricane on record (Camille) had winds exceeding 200mph.
•Typically 500-1000 km in diameter (smaller thanmidlatitude cyclones).
•Can be associated with heavy rains (10-20 inches!),tornadoes, and storm surges on the coast.
•Also called typhoons and tropical cyclones
Katrina
•1833 deaths
•125 billion indamage
•Most destructivehurricane in U.S.history
![Hurricane%20Katrina%20Response2[1].jpg](data/images/img5.jpg)
Fig. 11-24, p. 320
1900 Galveston, TX Hurricane: The Greatest Loss of Life of AnyU.S. Meteorological Event (8000 died)
Typhoon Haiyan
Fig. 11-10, p. 307
Not on the equator!
Table 11-2, p. 313
Saffir-Simpson Hurricane Category
Fig. 11-16, p. 313
Atlantic Basin Hurricanes and Tropical Storms
Hurricane Structure
Fig. 11-20, p. 317
Major Features:
Eye (nearly clear)
Eye Wall Rainband
Spiral Rainbands
Fig. 11-18, p. 316
Fig. 11-8, p. 305
Eye slopes outward
In much the same way anice skater spins morequickly as her arms aretucked close into her body,a hurricane also spins at afaster pace near thecenter than near the outeredge.
Destruction most intense on rightside of cyclone (wind + stormspeed)
Eye wall replacement
•A shrinking eye indicatesstorm intensification.
•Some intense hurricanesdevelop double eye walls,as rain bands contract andintensify.
•Eye wall replacementleads to weakening of thehurricane winds, followedby renewed strengthening.
The Greatest Damage and Lossof Life from Hurricanes is Nearthe Coast Associated with StormSurges
Fig. 11-15, p. 312
Before and after Hurricane Iva, Sept 2004, coastal Alabama
Before ahurricane…
After ahurricane.
What is the energy source ofHurricanes?
Hurricanes
•Hurricanes get their energy from the warm,waters of the tropics.
•Require the water surface to be at least 80F
•Also need moist air through depth and weakwind shear.
•Generally develop as a weak tropicaldisturbance moves over the oceans.
Revving Up a Hurricanes: Two Positive FeedbacksInvolving Warm Water
Convergence-Convection (CISK—Conditional Instability of theSecond Kind)
Surface flux-Convection (WISHE—Wind Induced Surface HeatExchange)
Hurricane Origin
Many Atlantic Hurricanes Begin as Tropical WavesOver Africa
Hurricane Prediction: A MixedReport
•During the past thirty years there has been asubstantial improvement in hurricane trackforecasts as computer models improved andmore data became available to describetheir environment.
•Over the same period only minimalimprovement is hurricane intensityforecasts.
Katrina
48-h Before: Virtually a Perfect Forecast of Track
NOAA P3
“Hurricane Hunter”
Aircraft
Gulfstream IV-SP (G-IV) is a highaltitude, high speed, twin turbofan jetaircraft
Substantial Promise
•The use of higher resolution prediction andbetter data around and in hurricanes shouldresult in better intensity predictions.
15-km grid spacing
1.67 km grid spacing
U.S Hurricane Headquarters
