Accumulated_Cyclone_Energy Accumulated_Cyclone_Energy

Accumulated Cyclone Energy - Definition and Overview

Accumulated Cyclone Energy or ACE is a measure used by NOAA to express the activity of Atlantic hurricane seasons.

The ACE is calculated by summing the squares of the estimated sustained velocity of every active tropical storm (wind speed 35 knots or higher), at six hourly intervals. For use as an index a unit of 104 kt2 is assumed.

Measured over the period 1951-2000 NOAA have calculated:

  • Median annual index: 87.5
  • Mean annual index: 93.2

Atlantic hurricane seasons are categorised as:

  • Above-normal season: An ACE value above 103 (117% of the median), provided at least two of the following three parameters exceed the long-term average: number of tropical storms (10), hurricanes (6), and major hurricanes (2).
  • Near-normal season: neither above-normal nor below normal
  • Below-normal season: An ACE value below 66 (75% of the median)

Hurricane seasons 1950-2004 by ACE index

SeasconACETSHRMHClassification
1950 Atlantic hurricane season24313118Above average
1995 Atlantic hurricane season22819115Above average
2004 Atlantic hurricane season2221496Above average
1961 Atlantic hurricane season2051187Above average
1955 Atlantic hurricane season1991296Above average
1998 Atlantic hurricane season18214103Above average
1999 Atlantic hurricane season1771285Above average
2003 Atlantic hurricane season1751673Above average
1964 Atlantic hurricane season1701266Above average
1996 Atlantic hurricane season1661396Above average
1969 Atlantic hurricane season15817125Above average
1980 Atlantic hurricane season1471192Above average
1966 Atlantic hurricane season1451173Above average
1951 Atlantic hurricane season1371085Above average
1989 Atlantic hurricane season1351172Above average
1967 Atlantic hurricane season122861Near average
1958 Atlantic hurricane season1211075Above average
1963 Atlantic hurricane season118972Near average
2000 Atlantic hurricane season1161483Above average
1954 Atlantic hurricane season1131182Above average
2001 Atlantic hurricane season1061594Above average
1953 Atlantic hurricane season1041464Near/Above average
1988 Atlantic hurricane season1031253Above average
1971 Atlantic hurricane season971361Near average
1981 Atlantic hurricane season931173Near average
1979 Atlantic hurricane season91852Near average
1990 Atlantic hurricane season911481Near average
1960 Atlantic hurricane season88742Near average
1985 Atlantic hurricane season881173Near average
--- (Median = 87.5) ---
1952 Atlantic hurricane season87763Near average
1965 Atlantic hurricane season85641Near average
1957 Atlantic hurricane season84832Near average
1976 Atlantic hurricane season81862Near average
1959 Atlantic hurricane season781172Near average
1992 Atlantic hurricane season75641Near average
1975 Atlantic hurricane season73863Near average
1984 Atlantic hurricane season711251Near average
2002 Atlantic hurricane season661242Below average
1978 Atlantic hurricane season621152Below average
1974 Atlantic hurricane season61742Below average
1956 Atlantic hurricane season54842Below average
1973 Atlantic hurricane season43741Below average
1997 Atlantic hurricane season40731Below average
1993 Atlantic hurricane season39841Below average
1962 Atlantic hurricane season36531Below average
1986 Atlantic hurricane season36640Below average
1968 Atlantic hurricane season35740Below average
1970 Atlantic hurricane season341052Below average
1987 Atlantic hurricane season34731Below average
1991 Atlantic hurricane season34842Below average
1994 Atlantic hurricane season32730Below average
1982 Atlantic hurricane season29521Below average
1972 Atlantic hurricane season28430Below average
1977 Atlantic hurricane season25651Below average
1983 Atlantic hurricane season17431Below average
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