Reasons for the Unusually Destructive 2004 Atlantic Basin Hurricane Season Phil Klotzbach and...
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Transcript of Reasons for the Unusually Destructive 2004 Atlantic Basin Hurricane Season Phil Klotzbach and...
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
Forecast Parameter and 1950-2000 Climatology (in parentheses)
Observed
Activity
Named Storms (NS) (9.6) 14
Named Storm Days (NSD) (49.1) 90
Hurricanes (H) (5.9) 9
Hurricane Days (HD) (24.5) 46
Intense Hurricanes (IH) (2.3) 6
Intense Hurricane Days (IHD) (5.0) 22
Net Tropical Cyclone Activity (NTC) (100%)
229
2004 ATLANTIC BASIN TROPICAL CYCLONE ACTIVITY
Atlantic Basin NTC Activity by Ten Day Periods
0
10
20
30
40
50
60
NT
C V
alu
e
June July August September October November
2004 Season
Climatology
2005 Season
2004 United States Hurricane Landfalls
Name Date Landfall
Location
Landfall Intensity (kts)
Insured Damage
(Millions)
Charley – Landfall 1
8/13 Cayo Costa, FL
130 $7000
Charley – Landfall 2
8/14 Cape Romain, SC
70 $50
Frances 9/5 Hutchinson Island, FL
90 $4500
Gaston 8/29 Awendaw, SC
65 $65
Ivan 9/16 Gulf Shores, AL
105 $7000
Jeanne 9/26 HutchinsonIsland, FL
105 $3500
Outline
2004 Atlantic Basin Statistics
Activity-Enhancing Features
Westward Track-Enhancing Features
Conclusions
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 Values (in Standard Deviations)
Period ΔV U850mb SST Genesis Parameter
Aug-Sep Named Storm Formations South of 25°N
1950-1969 -0.1 0.8 0.0 0.3 4.7
1970-1994 -0.4 -0.8 -0.4 -0.7 3.3
1995-2003 1.2 0.4 0.9 1.2 5.4
2004 2.3 (2) 0.5 (17) 1.8 (3) 2.2 (2) 9 (T-1)
Atlantic Basin Genesis Parameter Ratios
Ratio Named Storm Formations south of 25°N Ratio
Highest 5 / Lowest 5 33 / 14 (2.4:1)
Highest 10 / Lowest 10 58 / 21 (2.8:1)
Highest 25 / Lowest 25 132 / 77 (1.7:1)
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 Values (in Standard Deviations)
Period UP
1950-1969 0.5
1970-1994 -0.3
1995-2003 -0.3
2004 -0.2
Outline
2004 Atlantic Basin Statistics
Activity-Enhancing Features
Westward Track-Enhancing Features
Conclusions
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)
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)
Period GP
(Genesis)
UP
(Upper-Level Winds)
WP
(Track)
LP
(Landfall)
Aug-Sep US Hurricane Landfalls
1950-1969 0.3 0.5 0.0 0.5 1.4
1970-1994 -0.7 -0.3 0.0 -0.7 1.0
1995-2003 1.2 -0.3 -0.1 0.5 1.0
2004 2.2 (2) -0.2 (31) 1.1 (5) 2.0 (2) 6 (1)
United States Landfall Parameter Ratios
Ratio Named Storm Ratio
Hurricane Ratio
Intense Hurricane Ratio
Highest 5 /
Lowest 5
21 / 7
(3:1)
13 / 3
(4.3:1)
7 / 2
(3.5:1)
Highest 10 /
Lowest 10
32 / 12
(2.7:1)
19 / 4
(4.8:1)
11 / 2
(5.5:1)
Highest 25 /
Lowest 25
64 / 43
(1.5:1)
37 / 23
(1.6:1)
22 / 9
(2.4:1)
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