Accumulated cyclone energy (ACE) is a measure used by the National Oceanic and Atmospheric Administration (NOAA) to express the activity of Atlantic hurricane seasons. It uses an approximation of the energy used by a tropical system over its lifetime and is calculated every six-hour period. The ACE of a season is the sum of the ACEs for each storm and takes into account the number, strength, and duration of all the tropical storms in the season. ^[1] The National Oceanic and Atmospheric Administration (NOAA) is a scientific agency of the United States Department of Commerce focused on the conditions of the oceans and the atmosphere. ... The Atlantic Ocean is Earths second-largest ocean, covering approximately one_fifth of its surface. ... Hurricane seaons can refer to : The Atlantic hurricane season The Pacific hurricane season This is a disambiguation page — a navigational aid which lists pages that might otherwise share the same title. ... Cyclone Catarina, a rare South Atlantic tropical cyclone viewed from the International Space Station on March 26, 2004 Hurricane and Typhoon redirect here. ...

Calculation

The ACE is calculated by summing the squares of the estimated maximum sustained velocity of every active tropical storm (wind speed 35 knots or higher), at six-hour intervals. The numbers are usually divided by 10,000 to make them more manageable. The unit of ACE is 10⁴ kt², and for use as an index the unit is assumed. If any storms of a season happen to cross years, the storm's ACE counts for the previous year. ^[2] For evaluation of sums in closed form see evaluating sums. ... A knot is a unit of speed abbreviated kt or kn. ...

where v_max is estimated sustained wind speed in knots.

Kinetic energy is proportional to the square of velocity, and by adding together the energy per some interval of time, the accumulated energy is found. As the duration of a storm increases, more values are summed and the ACE also increases such that longer-duration storms may accumulate a larger ACE than more-powerful storms of lesser duration. Although ACE is a value proportional to the energy of the system, it is not a direct calculation of energy (the mass of the moved air and therefore the size of the storm would show up in a real energy calculation) because of the the NHC estimates ACE is anywhere from 2.2 Terawatts - 1.6 Exawatts. The kinetic energy of an object is the extra energy which it possesses due to its motion. ...

A related quantity is hurricane destruction potential (HDP), which is ACE but only calculated for the time where the system is a hurricane. ^[1]

Climatology

Measured over the period 1951-2005 for the Atlantic basin:

• Median annual index: 89.5
• Mean annual index: 102.3

A season's ACE is used to categorize the hurricane season by its activity. NOAA categorisation system^[3] divides them into: In probability theory and statistics, a median is a type of average that is described as the number dividing the higher half of a sample, a population, or a probability distribution, from the lower half. ... In mathematics and statistics, the arithmetic mean (or simply the mean) of a list of numbers is the sum of all the members of the list divided by the number of items in the list. ...

• Above-normal season: An ACE value above 103 (115% of the current 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 (74% of the current median)

Individual storms

The highest ever ACE estimated for a single storm in the Atlantic is 73.6, for Hurricane San Ciriaco in 1899. This single storm had an ACE higher than many whole Atlantic storm seasons. Other Atlantic storms with high ACEs include Hurricane Ivan in 2004, with an ACE of 70.4, and Hurricane Donna in 1960, with an ACE of 64.6. Hurricane San Ciriaco was an Atlantic tropical cyclone which crossed Puerto Rico over the two day period August 8 to August 9, 1899, in an east-southeast to west-northwest direction. ... The 1899 Atlantic hurricane season was an ongoing event in the annual cycle of tropical cyclone formation. ... Lowest pressure 910 mbar (hPa) Damage $19. ... The 2004 Atlantic hurricane season officially began on June 1, 2004, and lasted until November 30, 2004. ... Lowest pressure ≤930 mbar (hPa) Damage $3. ... First storm formed: June 22, 1960 Last storm dissipated: Sept. ...

ACE index for hurricane seasons 1950-2006

Image File history File links No higher resolution available. ...

The scale on the left represents the total Accumulated Cyclone Energy Index for the Atlantic Season, and the scale on the right the ACE/Storm average for that season.

Atlantic hurricane seasons 1950-2007 by ACE index

The term hyperactive is used by Goldenberg et al. (2001) ^[4][5] based on a different weighting algorithm which places more weight on major hurricanes, but typically equating to an ACE of about 153 (171% of the current median).

Key
• ACE	Accumulated cyclone energy
• TS	Number of tropical storms
• HR	Number of hurricanes (S-S Category 1–5)
• MH	Number of major hurricanes (Category 3–5)
(Fields with record values are in bold)

For definitions of the terms "above", "near", and "below" normal, see the Climatology section above. The Saffir-Simpson Hurricane Scale is a scale classifying most Western Hemisphere tropical cyclones that exceed the intensities of tropical depressions and tropical storms, and thereby become hurricanes. ...

The 2005 Atlantic hurricane season was the most active Atlantic hurricane season in recorded history, shattering previous records on repeated occasions. ... The 1950 Atlantic hurricane season was an on going event in the annual cycle of tropical cyclone formation. ... The 1995 Atlantic hurricane season officially began on June 1, 1995, and lasted until November 30, 1995. ... The 2004 Atlantic hurricane season officially began on June 1, 2004, and lasted until November 30, 2004. ... The 1961 Atlantic hurricane season officially began on June 1, 1961, and lasted until November 30, 1961. ... The 1955 Atlantic hurricane season officially began on June 1, 1955, and lasted until November 30, 1955. ... The 1998 Atlantic hurricane season officially began on June 1, 1998, and lasted until November 30, 1998. ... The 1999 Atlantic hurricane season officially began on June 1, 1999, and lasted until November 30, 1999. ... First storm formed: April 20, 2003 Last storm dissipated: Dec. ... First storm formed: June 2, 1964 Last storm dissipated: Nov. ... The 1996 Atlantic hurricane season officially began on June 1, 1996, and lasted until November 30, 1996. ... First storm formed: July 25, 1969 Last storm dissipated: Nov. ... First storm formed: July 31, 1980 Last storm dissipated: Nov. ... The 1966 Atlantic hurricane season was an ongoing event in the annual cycle of tropical cyclone formation. ... The 1951 Atlantic hurricane season was an ongoing event in the annual cycle of tropical cyclone formation. ... B C D E F G H I J K Categories: | ... ... The 1958 Atlantic hurricane season was an ongoing event in the annual cycle of tropical cyclone formation. ... ... The 2000 Atlantic hurricane season officially began on June 1, 2000, and lasted until November 30, 2000. ... The 1954 Atlantic hurricane season was an on-going event in the cycle of tropical cyclone formation. ... The 2001 Atlantic hurricane season officially began on June 1, 2001, and lasted until November 30, 2001. ... The 1953 Atlantic hurricane season was an ongoing event in the annual cycle of tropical cyclone formation. ... The 1988 Atlantic hurricane season officially began on June 1, 1988, and lasted until November 30, 1988. ... The 1971 Atlantic hurricane season officially began on June 1, 1971, and lasted until November 30, 1971. ... First storm formed: May 6, 1981 Last storm dissipated: November 17, 1981 Strongest storm: Harvey - 946 mbar (27. ... First storm formed: June 19, 1979 Last storm dissipated: Oct. ... ... First storm formed: June 22, 1960 Last storm dissipated: Sept. ... First storm formed: July 15, 1985 Last storm dissipated: Nov. ... The 1952 Atlantic hurricane season was an event in the annual cycle of tropical cyclone formation. ... The 1965 Atlantic hurricane season was an ongoing event in the annual cycle of tropical cyclone formation. ... ... The 1976 Atlantic hurricane season was an ongoing event in the annual cycle of tropical cyclone formation. ... The 2006 Atlantic hurricane season was an event in the annual cycle of tropical cyclone formation. ... The 1959 Atlantic hurricane season was an ongoing event in the annual cycle of tropical cyclone formation. ... The 1992 Atlantic hurricane season officially began on June 1, 1992, and lasted until November 30, 1992. ... The 1975 Atlantic hurricane season officially began on June 1, 1975, and lasted until November 30, 1975. ... First storm formed: Aug. ... The 2007 Atlantic hurricane season is an ongoing event in the annual cycle of tropical cyclone formation. ... The 2002 Atlantic hurricane season officially began on June 1, 2002, and lasted until November 30, 2002. ... The 1974 Atlantic hurricane season officially began on June 1, 1974, and lasted until November 30, 1974. ... The 1978 Atlantic hurricane season was an ongoing event in the annual cycle of tropical cyclone formation. ... The 1956 Atlantic hurricane season was an ongoing event in the annual cycle of tropical cyclone formation. ... The 1973 Atlantic hurricane season was an ongoing event in the annual cycle of tropical cyclone formation. ... The 1997 Atlantic hurricane season officially began on June 1, 1997, and lasted until November 30, 1997. ... First storm formed: Jun. ... The 1962 Atlantic hurricane season was an ongoing event in the annual cycle of tropical cyclone formation. ... The 1986 Atlantic hurricane season officially began on June 1, 1986, and lasted until November 30, 1986. ... The 1968 Atlantic hurricane season officially began on June 1, 1968, and lasted until November 30, 1968. ... The 1970 Atlantic hurricane season officially began on June 1, 1970, and lasted until November 30, 1970. ... The 1987 Atlantic hurricane season officially began on June 1, 1987, and lasted until November 30, 1987. ... The 1991 Atlantic hurricane season officially began on June 1, 1991, and lasted until November 30, 1991. ... The 1994 Atlantic hurricane season officially began on June 1, 1994, and lasted until November 30, 1994. ... First storm formed: June 2, 1982 Last storm dissipated: Oct. ... First storm formed: May 23, 1972 Last storm dissipated: Nov. ... ... The 1983 Atlantic hurricane season was an ongoing event in the annual cycle of tropical cyclone formation. ...

East Pacific ACE

Accumulated Cyclone Energy is also used in the eastern and central Pacific Ocean. Data on ACE is considered reliable starting with the 1971 season. The season with the highest ACE since 1971 is the 1992 season. The 1977 season has the lowest ACE. The most recent above-normal season is the 2006 season, the most recent near-normal season is the 2002 season, and the most recent below normal season is the 2005 season. ^[6] The 35 year median 1971-2005 is 115 x 10⁴kt² (100 in the EPAC zone east of 140°W, 13 in the CPAC zone); the mean is 130 (112 + 18). First storm formed: May 21, 1971 Last storm dissipated: Nov. ... The 1992 Pacific hurricane season was an ongoing event in tropical cyclone formation. ... The 1977 Pacific hurricane season officially started May 15, 1977 in the eastern Pacific, and June 1, 1977 in the central Pacific, and lasted until November 30, 1977. ... The 2006 Pacific hurricane season was an event in the annual cycle of tropical cyclone formation. ... First storm formed: May 24, 2002 Last storm dissipated: Oct. ... This unusual mosiac of storms shows, from left to right, Hurricane Jova, Hurricane Kenneth, and Tropical Storm Max. ...

The (unofficial) categorisation of seasons for this table is based mutatis mutandis on that used in the Atlantic basin:

• Above-normal season: An ACE value above 135 (117% of the median), provided at least two of the following three parameters exceed the long-term average: number of tropical storms (16), hurricanes (9), and major hurricanes (4).
• Near-normal season: neither above-normal nor below normal
• Below-normal season: An ACE value below 86 (75% of the median)

Calculations from Eastern North Pacific Tracks File at NHC[1] The 1992 Pacific hurricane season was an ongoing event in tropical cyclone formation. ... The 1990 Pacific hurricane season officially started on May 15, 1990 in the eastern Pacific, and on June 1, 1990 in the central Pacific, and lasted until November 30, 1990. ... First storm formed: May 30, 1978 Last storm dissipated: Oct. ... Pacific Hurricane Seasons 1981 1982 1983 1984 1985 The 1983 Pacific hurricane season officially started May 15, 1983 in the eastern Pacific, and June 1, 1983 in the central Pacific, and lasted until November 30, 1983. ... The 1993 Pacific hurricane season officially started May 15, 1993 in the eastern Pacific, and June 1, 1993 in the central Pacific, and lasted until November 30, 1993. ... Pacific Hurricane Seasons 1982 1983 1984 1985 1986 The 1984 Pacific hurricane season officially started May 15, 1984 in the eastern Pacific, and June 1, 1984 in the central Pacific, and lasted until November 30, 1984. ... Pacific Hurricane Seasons 1983 1984 1985 1986 1987 The 1985 Pacific hurricane season officially started May 15, 1985 in the eastern Pacific, and June 1, 1985 in the central Pacific, and lasted until November 30, 1985. ... Pacific Hurricane Seasons 1992 1993 1994 1995 1996 The 1994 Pacific hurricane season officially started May 15, 1994 in the eastern Pacific, and June 1, 1994 in the central Pacific, and lasted until November 30, 1994. ... Pacific Hurricane Seasons 1989 1990 1991 1992 1993 The 1991 Pacific hurricane season officially started May 15, 1991 in the eastern Pacific, and June 1, 1991 in the central Pacific, and lasted until November 30, 1991. ... Pacific Hurricane Seasons 1995 1996 1997 1998 1999 The 1997 Pacific hurricane season officially started May 15, 1997 in the eastern Pacific, and June 1, 1997 in the central Pacific, and lasted until November 30, 1997. ... Pacific Hurricane Seasons 1980 1981 1982 1983 1984 The 1982 Pacific hurricane season officially started May 15, 1982 in the eastern Pacific, and June 1, 1982 in the central Pacific, and lasted until November 30, 1982. ... The 2006 Pacific hurricane season was an event in the annual cycle of tropical cyclone formation. ... First storm formed: May 21, 1971 Last storm dissipated: Nov. ... ... Pacific Hurricane Seasons 1996 1997 1998 1999 2000 The 1998 Pacific hurricane season officially started May 15, 1998 in the eastern Pacific, and June 1, 1998 in the central Pacific, and lasted until November 30, 1998. ... ... First storm formed: May 24, 2002 Last storm dissipated: Oct. ... The 1976 Pacific hurricane season officially started May 15, 1976 in the eastern Pacific, and June 1, 1976 in the central Pacific, and lasted until November 30, 1976. ... Hurricane Ava formed on the 2nd of June 1973 south of Mexico and moved out towards sea. ... ... First storm formed: June 2, 1975 Last storm dissipated: Nov. ... The 1989 Pacific hurricane season officially started May 15, 1989 in the Eastern Pacific, and June 1, 1989 in the Central Pacific, and lasted until November 30, 1989. ... First storm formed: May 22, 1986 Last storm dissipated: Oct 22, 1986 Strongest storm: Roslyn - 125 kts Total storms: 17 Major storms (Cat. ... ... This unusual mosiac of storms shows, from left to right, Hurricane Jova, Hurricane Kenneth, and Tropical Storm Max. ... The 2000 Pacific hurricane season was an ongoing event in tropical cyclone meteorology. ... Pacific Hurricane Seasons 1972 1973 1974 1975 1976 The 1974 Pacific hurricane season officially started May 15, 1974 in the eastern Pacific, and June 1, 1974 in the central Pacific, and lasted until November 30, 1974. ... Pacific Hurricane Seasons 1997 1998 1999 2000 2001 The 1999 Pacific hurricane season officially started May 15, 1999 in the eastern Pacific, and June 1, 1999 in the central Pacific, and lasted until November 30, 1999. ... The 2001 Pacific hurricane season officially started on May 15, 2001 in the eastern Pacific, and on June 1, 2001 in the central Pacific, and lasted until November 30, 2001. ... Pacific Hurricane Seasons 1978 1979 1980 1981 1982 The 1980 Pacific hurricane season officially started May 15, 1980 in the eastern Pacific, and June 1, 1980 in the central Pacific, and lasted until November 30, 1980. ... Pacific Hurricane Seasons 1979 1980 1981 1982 1983 The 1981 Pacific hurricane season officially started May 15, 1981 in the eastern Pacific, and June 1, 1981 in the central Pacific, and lasted until November 30, 1981. ... The 2004 Pacific hurricane season officially started on May 15, 2004 in the eastern Pacific, and on June 1, 2004 in the central Pacific, and lasted until November 30, 2004. ... Pacific Hurricane Seasons 1977 1978 1979 1980 1981 The 1979 Pacific hurricane season officially started May 15, 1979 in the eastern Pacific, and June 1, 1979 in the central Pacific, and lasted until November 30, 1979. ... The 2003 Pacific hurricane season officially started May 15, 2003 in the eastern Pacific, and June 1, 2003 in the central Pacific, and lasted until November 30, 2003. ... The 1996 Pacific hurricane season officially started May 15, 1996 in the eastern Pacific, and June 1, 1996 in the central Pacific, and lasted until November 30, 1996. ... The 1977 Pacific hurricane season officially started May 15, 1977 in the eastern Pacific, and June 1, 1977 in the central Pacific, and lasted until November 30, 1977. ...

West Pacific ACE

ACE is also used in the western Pacific. 2004 had an ACE of 464 10⁴ kt² for the NW Pacific. This was the third highest since 1965, after 1992 and 1997. The 40 year norm (1965-2004) is 305 +/-99 10⁴ kt².

See also

Tropical cyclones Portal

• List of Atlantic hurricane seasons

Image File history File links Download high resolution version (1000x662, 320 KB) http://eol. ... ...

References

External links

• NOAA ACE by year from 1851
• National Climatic Data Center - Atlantic Basin 2004 Accumulated Cyclone Energy (ACE) Index
• National Climatic Data Center - Atlantic Basin 2005 Accumulated Cyclone Energy (ACE) Index
• 2004 Pacific NW Typhoon Season ACE pdf