September 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)*
South Indian
Phoebe-04 9/2/04 9/4/04 TS 55 70 0.87 x 104
Northwest Pacific
Songda-04 8/27/04 9/7/04 Cat 4 130 160 31.66 x 104 (Sep)
43.34 x 104 (Total)
Northwest Pacific
Sarika-04 9/4/04 9/7/04 TS 60 75 3.13 x 104
Northwest Pacific
Meari-04 9/20/04 9/29/04 Cat 4 120 145 26.53 x 104
Northeast Pacific
Howard-04 8/31/04 9/5/04 Cat 4 120 145 12.16 x 104 (Sep)
12.75 x 104 (Total)
Northeast Pacific
Isis-04 9/8/04 9/16/04 Cat 1 65 80 5.75 x 104
Northeast Pacific
Javier-04 9/11/04 9/19/04 Cat 4 130 160 26.69 x 104
Atlantic
Frances-04 8/25/04 9/7/04 Cat 4 125 155 22.92 x 104 (Sep)
46.80 x 104 (Total)
Atlantic
Gaston-04 8/27/04 9/1/04 TS 60 75 0.33 x 104 (Sep)
2.18 x 104 (Total)
Atlantic
Ivan-04 9/3/04
9/22/04
9/17/04
9/24/04
Cat 5 145 175 69.86 x 104
Atlantic
Jeanne-04 9/14/04 9/27/04 Cat 3 100 120 24.80 x 104
Atlantic
Karl-04 9/17/04 9/24/04 Cat 4 120 145 27.99 x 104
Atlantic
Lisa-04 9/20/04 10/3/04 Cat 1 65 80 9.27 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



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