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)

ObservedActivity

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

NTC

Val

ue

June July August September October November

2004 Season

Climatology

2005 Season

Figure taken from http://www.nhc.noaa.gov/tracks/2004atl.gif

Figure taken from http://www.wunderground.com/hurricane/at2005.asp

9 Landfalls

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

August-September 2004 SST Anomalies

1860 1900 1940 1980 2020

Adapted from Goldenberg et al. 2001

August-September 2004 850 MB U Anomaly

August-September 2004 V Anomalies

200 mb

850 mb

Anomalous Northerlies

Anomalous Southerlies

August-September 2004 OLR Anomaly

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)

SSTA + U

V

1.5 km

1.5 km12 km

Genesis Parameter (GP) Component Locations

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)

August-September SST (1995-2004) – (1950-1969)

August-September 200 mb U (1995-2004) – (1950-1969)

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)

- ZWA

12 km

Upper-Level Wind Parameter (UP) Location

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

1995-2003 Intense Hurricane Tracks (32 tracks)

FRANOPAL

BRET

August-September 500 mb Ht. (2004) – (1995-2003)

August-September 500 mb Ht. (2004) – (1995-2003)

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)

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