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Reasons for the Unusually Destructive 2004 Atlantic Basin Hurricane Season Phil Klotzbach and William Gray Department of Atmospheric Science Colorado State University Climate Diagnostics Workshop October 25, 2005. Outline. 2004 Atlantic Hurricane Summary Activity-Enhancing Features
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Reasons for the Unusually Destructive 2004 Atlantic Basin Hurricane Season Phil Klotzbach and William Gray Department of Atmospheric Science Colorado State University Climate Diagnostics Workshop October 25, 2005
Outline • 2004 Atlantic Hurricane Summary • Activity-Enhancing Features • Westward Track-Enhancing Features • Conclusions
Outline • 2004 Atlantic Hurricane Summary • Activity-Enhancing Features • Westward Track-Enhancing Features • Conclusions
2004 Storm Tracks Figure taken from http://www.nhc.noaa.gov/tracks/2004atl.gif
2005 Storm Tracks Figure taken from http://www.wunderground.com/hurricane/at2005.asp
Outline • 2004 Atlantic Basin Statistics • Activity-Enhancing Features • Westward Track-Enhancing Features • Conclusions
? 1860 1900 1940 1980 2020 Adapted from Goldenberg et al. 2001
August-September 2004 V Anomalies Anomalous Northerlies 200 mb Anomalous Southerlies 850 mb
Genesis Parameter (GP) Definition GP = ΔV + U850mb + SSTA Where: ΔV = 850 mb – 200 mb average August-September V wind component from (7.5°N – 7.5°S, 20°-45°W) U850mb = 850 mb average August-September U wind component from (5°-15°N, 20°-60°W) SSTA = Average August-September sea surface temperature anomaly from (5°-15°N, 20°-60°W)
Genesis Parameter (GP) Component Locations SSTA + U 1.5 km V 12 km 1.5 km
Upper-Level Wind Parameter (UP) Definition UP = -ZWA Where: ZWA = 200 mb average August-September U wind component from (5°-15°N, 20°-60°W)
Upper-Level Wind Parameter (UP) Location - ZWA 12 km
Outline • 2004 Atlantic Basin Statistics • Activity-Enhancing Features • Westward Track-Enhancing Features • Conclusions
FRAN OPAL BRET 1995-2003 Intense Hurricane Tracks (32 tracks)
Westward Track Parameter (WP) Definition WP = Zone 1 – Zone 2 – Zone 3 Where: Zone 1 = 500 mb average August-September 500 mb height from (40°-50°N, 65°-75°W) Zone 2 = 500 mb average August-September 500 mb height from (50°-60°N, 20°-30°W) Zone 3 = 500 mb average August-September 500 mb height from (40°-50°N, 100°-110°W)
L L H
United States Tropical Cyclone Landfall Parameter (LP) Definition LP = GP + UP + WP Where: GP = Genesis Parameter UP = Upper-Level Wind Parameter WP = Westward Track Parameter
United States Landfall Parameter (LP) Values (in Standard Deviations)
Outline • 2004 Atlantic Basin Statistics • Activity-Enhancing Features • Westward Track-Enhancing Features • Conclusions
Conclusions • The 2004 hurricane season was very active both in terms of overall tropical cyclone activity and in terms of United States landfalls • A strong Intertropical Convergence Zone, weaker trade winds, and warm Atlantic sea surface temperatures contributed to the very active season • A mid-level ridge predominated over the East Coast of the United States with mid-level troughs to the west and east which helped push storms westward into the longitudes of the United States