August 2004: Accumulated Cyclone Energy (ACE) Index*

Ocean Basin Tropical Cyclone Cyclogenesis Date Cyclolysis Date Saffir-Simpson Category Maximum 6-hr Sustained Wind (kt) Maximum 6-hr Wind Gust (kt) Accumulated Cyclone Energy (ACE) Index (kt2)*
Northwest Pacific
 Aere-04 8/19/04 8/26/04 Cat 2 85 105 10.3 x 104
Northwest Pacific
 Chaba-04 8/18/04 8/31/04 Cat 5 155 190 57.83 x 104
Northwest Pacific
 Malakas-04 8/10/04 8/12/04 TS 35 45 0.74 x 104
Northwest Pacific
 Megi-04 8/14/04 8/19/04 Cat 1 65 80 3.73 x 104
Northwest Pacific
 Meranti-04 8/3/04 8/8/04 Cat 2 90 110 5.59 x 104
Northwest Pacific
 Namtheun-04 7/25/04 8/1/04 Cat 4 115 140 0.1225 x 104 (Aug)
16.45 x 104 (Total)
Northwest Pacific
 Rananim-04 8/7/04 8/13/04 Cat 2 90 110 8.84 x 104
Northwest Pacific
 Songda-04 8/27/04 9/8/04 Cat 4 130 160 11.68 x 104 (Aug)
43.34 x 104 (Total)
Northeast Pacific
 Estelle-04 8/19/04 8/26/04 TS 60 75 2.68 x 104
Northeast Pacific
 Frank-04 8/23/04 8/26/04 Cat 1 75 90 3.67 x 104
Northeast Pacific
 Georgette-04 8/26/04 8/30/04 TS 50 65 2.91 x 104
Northeast Pacific
 Howard-04 8/30/04 9/5/04 Cat 4 120 145 0.59 x 104 (Aug)
12.75 x 104 (Total)
Atlantic
 Alex-04 7/31/04 8/5/04 Cat 3 105 130 11.17 x 104
Atlantic
 Bonnie-04 8/9/04 8/12/04 TS 55 65 2.5 x 104
Atlantic
 Charley-04 8/9/04 8/15/04 Cat 4 125 150 10.44 x 104
Atlantic
 Danielle-04 8/13/04 8/21/04 Cat 2 90 110 11.95 x 104
Atlantic
 Earl-04 8/13/04 8/16/04 TS 40 50 1.05 x 104
Atlantic
 Frances-04 8/25/04 9/7/04 Cat 4 125 155 23.88 x 104 (Aug)
47.13 x 104 (Total)
Atlantic
 Gaston-04 8/27/04 9/1/04 TS 60 75 1.85 x 104 (Aug)
2.18 x 104 (Total)
Atlantic
 Hermine-04 8/29/04 8/31/04 TS 45 55 1.01 x 104


*The Accumulated Cyclone Energy (ACE) Index is calculated by summing the squares of the estimated 6-hourly maximum sustained wind speed in knots (Vmax2) for all periods in which the tropical cyclone is a tropical storm or greater intensity. For a complete description of the ACE Index see Bell et al. (2000), Bulletin of the American Meteorological Society (81) S1-S50.


The Saffir-Simpson Scale for Tropical Cyclones

Category Miles Per Hour (mph) Knots (kt) Kilometers Per Hour (km hr-1)
Tropical Storm
 39-73 34-63 63-118
Cat 1
 74-95 64-82 119-153
Cat 2
 96-110 83-95 154-177
Cat 3
 111-130 96-113 178-209
Cat 4
 131-155 114-135 210-249
Cat 5
 155 135 249