Accumulated cyclone energy
Encyclopedia
Accumulated cyclone energy (ACE) is a measure used by the National Oceanic and Atmospheric Administration
(NOAA) to express the activity of individual tropical cyclones and entire tropical cyclone seasons, particularly the North Atlantic hurricane season
. 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.
the squares of the estimated maximum sustained velocity of every active tropical storm (wind speed 35 knots (68.6 km/h) or higher), at six-hour intervals. If any storms of a season happen to cross years, the storm's ACE counts for the previous year. 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. Thus:
where vmax 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).
A related quantity is hurricane destruction potential (HDP), which is ACE but only calculated for the time where the system is a hurricane.
A season's ACE is used to categorize the hurricane season by its activity. Measured over the period 1951–2000 for the Atlantic basin, the median
annual index was 87.5 and the mean
annual index was 93.2. The NOAA categorisation system divides seasons into:
. 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, Hurricane Donna
in 1960
, with an ACE of 64.6, Hurricane Isabel
in 2003
with an ACE of 63.28, and the Great Charleston Hurricane of 1893 with an ACE of 63.5.
For definitions of the terms "above", "near", and "below" normal, see the Categories section above.
Mean 1950–2009: 101.2
Median 1950–2009: 88.0
. 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 2009 season
, and the most recent below normal season is the 2010 season
. 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).
The (unofficial) categorisation of seasons for this table is based mutatis mutandis on that used in the Atlantic basin:
Mean 1971-2009: 127.07
Median 1971-2009: 114
Calculations from Eastern North Pacific Tracks File at NHC
National Oceanic and Atmospheric Administration
The National Oceanic and Atmospheric Administration , pronounced , like "noah", is a scientific agency within the United States Department of Commerce focused on the conditions of the oceans and the atmosphere...
(NOAA) to express the activity of individual tropical cyclones and entire tropical cyclone seasons, particularly the North Atlantic hurricane season
Hurricane season
Hurricane season refers to a period in a year when hurricanes usually form. For more information see: Tropical cyclone#Times.* The Atlantic hurricane seasonFor a lists of past seasons, see:...
. 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
Tropical cyclone
A tropical cyclone is a storm system characterized by a large low-pressure center and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclones strengthen when water evaporated from the ocean is released as the saturated air rises, resulting in condensation of water vapor...
in the season.
Calculation
The ACE of a season is calculated by summingSummation
Summation is the operation of adding a sequence of numbers; the result is their sum or total. If numbers are added sequentially from left to right, any intermediate result is a partial sum, prefix sum, or running total of the summation. The numbers to be summed may be integers, rational numbers,...
the squares of the estimated maximum sustained velocity of every active tropical storm (wind speed 35 knots (68.6 km/h) or higher), at six-hour intervals. If any storms of a season happen to cross years, the storm's ACE counts for the previous year. 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. Thus:
where vmax is estimated sustained wind speed in knots.
Kinetic energy
Kinetic energy
The kinetic energy of an object is the energy which it possesses due to its motion.It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes...
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).
A related quantity is hurricane destruction potential (HDP), which is ACE but only calculated for the time where the system is a hurricane.
Categories
Median
In probability theory and statistics, a median is described as the numerical value separating the higher half of a sample, a population, or a probability distribution, from the lower half. The median of a finite list of numbers can be found by arranging all the observations from lowest value to...
annual index was 87.5 and the mean
Arithmetic mean
In mathematics and statistics, the arithmetic mean, often referred to as simply the mean or average when the context is clear, is a method to derive the central tendency of a sample space...
annual index was 93.2. The NOAA categorisation system divides seasons into:
- Above-normal season: An ACE value above 103 (117% of the 1951–2000 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 1951–2000 median)
Individual storms
The highest ever ACE estimated for a single storm in the Atlantic is 73.6, for Hurricane San Ciriaco in 18991899 Atlantic hurricane season
The 1899 Atlantic hurricane season ran through the summer and the first half of fall in 1899. The season was average, with 9 tropical storms, of which 5 became hurricanes and only two became major hurricanes....
. This single storm had an ACE higher than many whole Atlantic storm seasons. Other Atlantic storms with high ACEs include Hurricane Ivan
Hurricane Ivan
Hurricane Ivan was a large, long-lived, Cape Verde-type hurricane that caused widespread damage in the Caribbean and United States. The cyclone was the ninth named storm, the sixth hurricane and the fourth major hurricane of the active 2004 Atlantic hurricane season...
in 2004
2004 Atlantic hurricane season
The 2004 Atlantic hurricane season officially began on June 1, 2004, and lasted until November 30, 2004. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin...
, with an ACE of 70.4, Hurricane Donna
Hurricane Donna
Hurricane Donna in the 1960 Atlantic hurricane season was a Cape Verde-type hurricane which moved across the Leeward Islands, Puerto Rico, Hispanola, Cuba, The Bahamas, and every state on the East Coast of the United States...
in 1960
1960 Atlantic hurricane season
The 1960 Atlantic hurricane season was the least active Atlantic hurricane season since 1952. The season officially began on June 15, 1960, and lasted until November 15, 1960. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin...
, with an ACE of 64.6, Hurricane Isabel
Hurricane Isabel
Hurricane Isabel was the costliest and deadliest hurricane in the 2003 Atlantic hurricane season. The ninth named storm, fifth hurricane, and second major hurricane of the season, Isabel formed near the Cape Verde Islands from a tropical wave on September 6 in the tropical Atlantic Ocean...
in 2003
2003 Atlantic hurricane season
The 2003 Atlantic hurricane season was an active Atlantic hurricane season with tropical activity before and after the official bounds of the season – the first such occurrence in 50 years. The season produced 21 tropical cyclones, of which 16 developed into named storms; seven...
with an ACE of 63.28, and the Great Charleston Hurricane of 1893 with an ACE of 63.5.
Atlantic hurricane seasons by ACE index, 1950–2011
The term hyperactive is used by Goldenberg et al. (2001) 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). For the in progress season be advised that the ACE is preliminary based on NHC bulletins, which may later be revised.| Key | |
|---|---|
| • ACE | Accumulated cyclone energy |
| • TS | Number of tropical storms (including subtropicals) |
| • HR | Number of hurricanes (S-S Category Saffir-Simpson Hurricane Scale The Saffir–Simpson Hurricane Scale , or the Saffir–Simpson Hurricane Wind Scale , classifies hurricanes — Western Hemisphere tropical cyclones that exceed the intensities of tropical depressions and tropical storms — into five categories distinguished by the intensities of their sustained winds... 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 Categories section above.
| Season | ACE | TS | HR | MH | Classification |
|---|---|---|---|---|---|
| 2005 Atlantic hurricane season 2005 Atlantic hurricane season The 2005 Atlantic hurricane season was the most active Atlantic hurricane season in recorded history, repeatedly shattering numerous records. The impact of the season was widespread and ruinous with an estimated 3,913 deaths and record damage of about $159.2 billion... |
248 | 28 | 15 | 7 | Above normal (hyperactive) |
| 1950 Atlantic hurricane season 1950 Atlantic hurricane season The 1950 Atlantic hurricane season was the first year in which tropical cyclones were given official names in the Atlantic basin. Names were taken from the Joint Army/Navy Phonetic Alphabet, with the first named storm being designated "Able", the second "Baker", and so on. It was an active season... |
243 | 13 | 11 | 8 | Above normal (hyperactive) |
| 1995 Atlantic hurricane season 1995 Atlantic hurricane season The 1995 Atlantic hurricane season was the third most active Atlantic hurricane season on record. It officially began on June 1, 1995, and lasted until November 30, 1995. These dates conventionally delimit the period of each year when most tropical cyclones form in the north Atlantic ocean... |
228 | 19 | 11 | 5 | Above normal (hyperactive) |
| 2004 Atlantic hurricane season 2004 Atlantic hurricane season The 2004 Atlantic hurricane season officially began on June 1, 2004, and lasted until November 30, 2004. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin... |
225 | 15 | 9 | 6 | Above normal (hyperactive) |
| 1961 Atlantic hurricane season 1961 Atlantic hurricane season The 1961 Atlantic hurricane season officially began on June 15, 1961, and lasted until November 15, 1961. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin. The season had seven major hurricanes, the second highest number on... |
205 | 11 | 8 | 7 | Above normal (hyperactive) |
| 1955 Atlantic hurricane season 1955 Atlantic hurricane season The 1955 Atlantic hurricane season officially began on June 15, 1955, and lasted until November 15, 1955. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin. The 1955 season was active, with twelve tropical storms forming.Three... |
199 | 12 | 9 | 6 | Above normal (hyperactive) |
| 1998 Atlantic hurricane season 1998 Atlantic hurricane season The 1998 Atlantic hurricane season officially began on June 1, 1998, and lasted until November 30, 1998. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin; however, the season extended through December 1 as Hurricane Nicole remained... |
182 | 14 | 10 | 3 | Above normal (hyperactive) |
| 1999 Atlantic hurricane season 1999 Atlantic hurricane season The 1999 Atlantic hurricane season officially began on June 1, 1999, and lasted until November 30, 1999. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin.... |
177 | 12 | 8 | 5 | Above normal (hyperactive) |
| 2003 Atlantic hurricane season 2003 Atlantic hurricane season The 2003 Atlantic hurricane season was an active Atlantic hurricane season with tropical activity before and after the official bounds of the season – the first such occurrence in 50 years. The season produced 21 tropical cyclones, of which 16 developed into named storms; seven... |
175 | 16 | 7 | 3 | Above normal (hyperactive) |
| 1964 Atlantic hurricane season 1964 Atlantic hurricane season The 1964 Atlantic hurricane season officially began on June 15, 1964, and lasted until November 15, 1964. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin... |
170 | 12 | 6 | 6 | Above normal (hyperactive) |
| 1996 Atlantic hurricane season 1996 Atlantic hurricane season The 1996 Atlantic hurricane season was the first season since 1965 in which all tropical cyclones reached tropical storm status. It officially began on June 1, 1996, and lasted until November 30, 1996... |
166 | 13 | 9 | 6 | Above normal (hyperactive) |
| 2010 Atlantic hurricane season 2010 Atlantic hurricane season The 2010 Atlantic hurricane season was the third most active Atlantic hurricane season on record, tying with the 1887 Atlantic hurricane season, 1995 Atlantic hurricane season and the 2011 Atlantic hurricane season. It had the most number of named storms since the 2005 season and also ties with the... |
165 | 19 | 12 | 5 | Above normal (hyperactive) |
| 1969 Atlantic hurricane season 1969 Atlantic hurricane season The 1969 Atlantic hurricane season officially began on June 1, 1969, and lasted until November 30, 1969. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin. The season was among the most active on record, with 18 tropical cyclones, 12... |
158 | 18 | 12 | 5 | Above normal (hyperactive) |
| 1980 Atlantic hurricane season 1980 Atlantic hurricane season The 1980 Atlantic hurricane season officially began on June 1, 1980, and lasted until November 30, 1980. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin. The season was fairly active, with eleven storms forming, of which nine reached... |
147 | 11 | 9 | 2 | Above normal |
| 1966 Atlantic hurricane season 1966 Atlantic hurricane season The 1966 Atlantic hurricane season officially began on June 1, 1966, and lasted until November 30, 1966. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin. The 1966 season was near normal with eleven tropical storms... |
145 | 11 | 7 | 3 | Above normal |
| 2008 Atlantic hurricane season 2008 Atlantic hurricane season The 2008 Atlantic hurricane season was a very active hurricane season with sixteen named storms formed, including eight that became hurricanes and five that became major hurricanes. The season officially started on June 1 and ended on November 30. These dates conventionally delimit the period of... |
144 | 16 | 8 | 5 | Above normal |
| 1951 Atlantic hurricane season 1951 Atlantic hurricane season The 1951 Atlantic hurricane season was moderately active, starting with an pre-season hurricane and lasting until late October. The season officially started on June 15, when the United States Weather Bureau began its daily monitoring for tropical cyclone activity; the season officially ended... |
137 | 10 | 8 | 5 | Above normal |
| 1989 Atlantic hurricane season 1989 Atlantic hurricane season The 1989 Atlantic hurricane season was an active season that produced fifteen tropical cyclones, eleven named storms, seven hurricanes, and two major hurricanes. The season was officially designated from June 1, 1989, to November 30, 1989, dates which conventionally... |
135 | 11 | 7 | 2 | Above normal |
| 1967 Atlantic hurricane season 1967 Atlantic hurricane season The 1967 Atlantic hurricane season was the first year in which the National Hurricane Center was in operation. The season began on June 1, which was the date when the NHC activated radar stations across the Caribbean and Gulf of Mexico... |
122 | 8 | 6 | 1 | Near normal |
| 1958 Atlantic hurricane season 1958 Atlantic hurricane season The 1958 Atlantic hurricane season officially began on June 15, 1958, and lasted until November 15, 1958. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin... |
121 | 10 | 7 | 5 | Above normal |
| 2011 Atlantic hurricane season 2011 Atlantic hurricane season The 2011 Atlantic hurricane season is tied for the third most active season on record with 1887, 1995 and 2010. It began on June 1, 2011, and ended on November 30, 2011, however these dates conventionally delimit the period of each year when most tropical cyclones develop in the Atlantic basin... |
119 | 18 | 7 | 3 | Above normal |
| 1963 Atlantic hurricane season 1963 Atlantic hurricane season The 1963 Atlantic hurricane season was a below average Atlantic hurricane season, with nine named storms. Although the season officially began on June 1, the first storm did not form until nearly a month later. Hurricane Cindy made landfall in Texas before dissipating in the southern portion of the... |
118 | 9 | 7 | 2 | Near normal |
| 2000 Atlantic hurricane season 2000 Atlantic hurricane season The 2000 Atlantic hurricane season was the first season without a tropical cyclone in July since 1987. The season officially began on June 1, 2000, and lasted until November 30, 2000. The June through November dates conventionally delimit the period of each year when most tropical cyclones form in... |
116 | 15 | 8 | 3 | Above normal |
| 1954 Atlantic hurricane season 1954 Atlantic hurricane season The 1954 Atlantic hurricane season caused over $750 million in damage, the most of any season at the time. The season officially began on June 15, and nine days later the first named storm developed. Hurricane Alice developed in the Gulf of Mexico and moved inland along the Rio Grande,... |
113 | 11 | 8 | 2 | Above normal |
| 2001 Atlantic hurricane season 2001 Atlantic hurricane season The 2001 Atlantic hurricane season was a fairly active Atlantic hurricane season that produced 17 tropical cyclones, 15 named storms, nine hurricanes, and four major hurricanes. The season officially lasted from June 1, 2001, to November 30, 2001, dates which by convention limit the period of each... |
106 | 15 | 9 | 4 | Above normal |
| 1953 Atlantic hurricane season 1953 Atlantic hurricane season The 1953 Atlantic hurricane season was the first time an organized list of female names was used to name Atlantic storms. It officially began on June 15, and lasted until November 15, although activity occurred both before and after the season's limits... |
104 | 14 | 6 | 4 | Above normal |
| 1988 Atlantic hurricane season 1988 Atlantic hurricane season The 1988 Atlantic hurricane season was a moderately active season that proved costly and deadly, with 15 tropical cyclones directly affecting land. The season officially began on June 1, 1988, and lasted until November 30, 1988, although activity began on May 30 when a tropical... |
103 | 12 | 5 | 3 | Above normal |
| 1971 Atlantic hurricane season 1971 Atlantic hurricane season The 1971 Atlantic hurricane season was fairly active with several notable storms. Hurricane Edith, the strongest of the season, was a Category 5 on the Saffir-Simpson scale, the highest category on the scale. It struck Nicaragua at peak intensity, killing dozens, and later hit southern Louisiana... |
97 | 13 | 6 | 1 | Near normal |
| 1981 Atlantic hurricane season 1981 Atlantic hurricane season The 1981 Atlantic hurricane season officially began on June 1, 1981, and lasted until November 30, 1981. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin. The 1981 season was high in activity with 18 tropical depressions and... |
93 | 12 | 7 | 3 | Near normal |
| 1979 Atlantic hurricane season 1979 Atlantic hurricane season The 1979 Atlantic hurricane season was the first in which the Atlantic hurricane naming list included both male and female names. It officially began on June 1 and lasted until November 30, and there was tropical cyclone activity in every month. The dates conventionally delimit the period of each... |
91 | 9 | 5 | 2 | Near normal |
| 1990 Atlantic hurricane season 1990 Atlantic hurricane season The 1990 Atlantic hurricane season was the most active Atlantic hurricane season since 1969. It officially began on June 1, 1990, and lasted until November 30, 1990. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin... |
91 | 14 | 8 | 1 | Near normal |
| 1960 Atlantic hurricane season 1960 Atlantic hurricane season The 1960 Atlantic hurricane season was the least active Atlantic hurricane season since 1952. The season officially began on June 15, 1960, and lasted until November 15, 1960. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin... |
88 | 7 | 4 | 2 | Near normal |
| 1985 Atlantic hurricane season 1985 Atlantic hurricane season The 1985 Atlantic hurricane season had the most U.S. landfalling tropical cyclones since 1916. The season officially began on June 1, 1985, and lasted until November 30, 1985... |
88 | 11 | 7 | 3 | Near normal |
| 1952 Atlantic hurricane season 1952 Atlantic hurricane season The 1952 Atlantic hurricane season was the most recent season in which all named storms attained hurricane status, although it was the least active since 1946. The season officially started on June 15; however, a pre-season unnamed storm formed on Groundhog Day, becoming the only storm on... |
87 | 7 | 6 | 3 | Near normal |
| 1965 Atlantic hurricane season 1965 Atlantic hurricane season The 1965 Atlantic hurricane season officially began on June 1, 1965, and lasted until November 30, 1965. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin.... |
84 | 6 | 4 | 1 | Near normal |
| 1957 Atlantic hurricane season 1957 Atlantic hurricane season The 1957 Atlantic hurricane season officially began on June 15, 1957, and lasted until November 15, 1957. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin. The season was below average, with eight total storms and just three... |
84 | 8 | 3 | 2 | Near normal |
| 1976 Atlantic hurricane season 1976 Atlantic hurricane season The 1976 Atlantic hurricane season officially began on June 1, 1976, and lasted until November 30, 1976. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin... |
81 | 10 | 6 | 2 | Near normal |
| 2006 Atlantic hurricane season 2006 Atlantic hurricane season The 2006 Atlantic hurricane season was significantly less active than the record previous season. It marked the first since 2001 in which no hurricanes made landfall in the United States, and was the first since 1994 that no tropical cyclones formed during October. Following the intense activity of... |
79 | 10 | 5 | 2 | Near normal |
| 1959 Atlantic hurricane season 1959 Atlantic hurricane season The 1959 Atlantic hurricane season officially began on June 15, 1959, and lasted until November 15, 1959. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin... |
77 | 11 | 7 | 2 | Near normal |
| 1992 Atlantic hurricane season 1992 Atlantic hurricane season The 1992 Atlantic hurricane season had one of the latest dates on record for the first named storm. The season officially began on June 1, 1992, and lasted until November 30, 1992. It was the least active hurricane season in nine years due to a strong El Niño... |
75 | 7 | 4 | 1 | Near normal |
| 1975 Atlantic hurricane season 1975 Atlantic hurricane season The 1975 Atlantic hurricane season officially began on June 1, 1975, and lasted until November 30, 1975. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin... |
73 | 9 | 6 | 3 | Near normal |
| 2007 Atlantic hurricane season 2007 Atlantic hurricane season The 2007 Atlantic hurricane season was an active Atlantic hurricane season that produced 17 tropical cyclones, 15 tropical storms, six hurricanes, and two major hurricanes. It officially started on June 1 and ended on November 30, dates which conventionally delimit the... |
72 | 15 | 6 | 2 | Near normal |
| 1984 Atlantic hurricane season 1984 Atlantic hurricane season The 1984 Atlantic hurricane season officially began on June 1, 1984, and lasted until November 30, 1984. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin. The 1984 season was an active one in terms of named storms, but most of them... |
71 | 12 | 5 | 1 | Near normal |
| 2002 Atlantic hurricane season 2002 Atlantic hurricane season The 2002 Atlantic hurricane season was an average Atlantic hurricane season, officially starting on June 1, 2002 and ending on November 30, dates which conventionally limit the period of each year when tropical cyclones in the Atlantic Ocean tend to form... |
65 | 12 | 4 | 2 | Below normal |
| 1978 Atlantic hurricane season 1978 Atlantic hurricane season The 1978 Atlantic hurricane season officially began on June 1, 1978, and lasted until November 30, 1978. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin... |
62 | 12 | 5 | 2 | Below normal |
| 1974 Atlantic hurricane season 1974 Atlantic hurricane season The 1974 Atlantic hurricane season officially began on June 1, 1974, and lasted until November 30, 1974. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin... |
61 | 11 | 4 | 2 | Below normal |
| 1956 Atlantic hurricane season 1956 Atlantic hurricane season The 1956 Atlantic hurricane season officially began on June 15, 1956, and lasted until November 15, 1956. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin. The season was slightly below average, with only four hurricanes and eight... |
54 | 8 | 4 | 2 | Below normal |
| 2009 Atlantic hurricane season 2009 Atlantic hurricane season The 2009 Atlantic hurricane season was a below-average year, unlike the 2009 Pacific hurricane season, which was above average, both due to a moderate El Niño. During this year, nine tropical storms formed, the fewest since the 1997 season.An average season has ten tropical storms, six hurricanes... |
51 | 9 | 3 | 2 | Below normal |
| 1973 Atlantic hurricane season 1973 Atlantic hurricane season The 1973 Atlantic hurricane season was the first season to use the Saffir-Simpson Hurricane Scale, a scale developed in 1971 by Herbert Saffir and Robert Simpson used for rating the intensity of tropical cyclones. The season produced 24 tropical and subtropical cyclones, of which only 8 reached... |
43 | 8 | 4 | 1 | Below normal |
| 1997 Atlantic hurricane season 1997 Atlantic hurricane season The 1997 Atlantic hurricane season is the most recent Atlantic hurricane season to feature no tropical cyclones in August. The season officially began on June 1, 1997, and lasted until November 30, 1997... |
40 | 7 | 3 | 1 | Below normal |
| 1993 Atlantic hurricane season 1993 Atlantic hurricane season The 1993 Atlantic hurricane season was a period in the annual formation of tropical cyclones. It officially began on June 1, 1993, and lasted until November 30, 1993. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin... |
39 | 8 | 4 | 1 | Below normal |
| 1962 Atlantic hurricane season 1962 Atlantic hurricane season The 1962 Atlantic hurricane season was the least active since 1939, with only five named storms. Although the season officially began on June 15, the first storm did not form until August 26. Hurricane Alma brushed the outer banks before becoming extratropical southeast of New England,... |
36 | 5 | 3 | 1 | Below normal |
| 1986 Atlantic hurricane season 1986 Atlantic hurricane season The 1986 Atlantic hurricane season officially began on June 1, 1986, and lasted until November 30, 1986. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin... |
36 | 6 | 4 | 0 | Below normal |
| 1968 Atlantic hurricane season 1968 Atlantic hurricane season The 1968 Atlantic hurricane season officially began on June 1, 1968, and lasted until November 30, 1968. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin.... |
35 | 8 | 4 | 0 | Below normal |
| 1970 Atlantic hurricane season 1970 Atlantic hurricane season The 1970 Atlantic hurricane season officially began on June 1, 1970, and lasted until November 30, 1970. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin... |
34 | 10 | 5 | 2 | Below normal |
| 1987 Atlantic hurricane season 1987 Atlantic hurricane season The 1987 Atlantic hurricane season was a below-average hurricane season that was limited by an ongoing El Niño. The season officially began on June 1, 1987, and lasted until November 30, 1987, although activity began on May 25 when a tropical depression developed in the east central... |
34 | 7 | 3 | 1 | Below normal |
| 1991 Atlantic hurricane season 1991 Atlantic hurricane season The 1991 Atlantic hurricane season was the first season in over 24 years in which no hurricanes developed from tropical waves, which are the source for most North Atlantic tropical cyclones. The hurricane season officially began on June 1, and ended on November 30. It was the least... |
34 | 8 | 4 | 2 | Below normal |
| 1994 Atlantic hurricane season 1994 Atlantic hurricane season The 1994 Atlantic hurricane seasonofficially began June 1, 1994, and officially ended November 30, 1994. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin.... |
32 | 7 | 3 | 0 | Below normal |
| 1982 Atlantic hurricane season 1982 Atlantic hurricane season The 1982 Atlantic hurricane season officially began on June 1, 1982 and lasted until November 30, 1982, and was a below average season. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin... |
29 | 6 | 2 | 1 | Below normal |
| 1972 Atlantic hurricane season 1972 Atlantic hurricane season The 1972 Atlantic hurricane season officially began on June 1, 1972, and lasted until November 30, 1972. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin. A strong El Niño kept hurricane activity at a minimum, and in fact the season... |
28 | 7 | 3 | 0 | Below normal |
| 1977 Atlantic hurricane season 1977 Atlantic hurricane season The 1977 Atlantic hurricane season officially began on June 1, 1977, and lasted until November 30, 1977. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin.... |
25 | 6 | 5 | 1 | Below normal |
| 1983 Atlantic hurricane season 1983 Atlantic hurricane season The 1983 Atlantic hurricane season was the least active Atlantic hurricane season in 53 years, with only four tropical storms forming. The season officially began on June 1, 1983, and lasted until November 30, 1983. These dates conventionally delimit the period of each year when most storms... |
17 | 4 | 3 | 1 | Below normal |
Mean 1950–2009: 101.2
Median 1950–2009: 88.0
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 season1971 Pacific hurricane season
The 1971 Pacific hurricane season began on May 15, 1971 in the east Pacific, and on June 1, 1971 in the central Pacific. It ended on November 30, 1971. These dates conventionally delimit the period of time when tropical cyclones form in the east Pacific Ocean....
. The season with the highest ACE since 1971 is the 1992 season
1992 Pacific hurricane season
The 1992 Pacific hurricane season was the most active Pacific hurricane season on record. The most notable storm was Hurricane Iniki, which caused billions of dollars of damage to the Hawaiian Islands. Hurricanes Lester, Virgil, Winifred, and Orlene also made landfall and killed several people, but...
. The 1977 season
1977 Pacific hurricane season
The 1977 Pacific hurricane season was, at the time, the least active in recorded history. Only eight tropical storms formed, and four hurricanes; they would be tied and surpassed, respectively, by the 2010 Pacific hurricane season. There were no major hurricanes; the next time this happened would...
has the lowest ACE. The most recent above-normal season is the 2006 season
2006 Pacific hurricane season
The 2006 Pacific hurricane season was the most active Pacific hurricane season since 2000 producing 19 tropical storms or hurricanes. Eighteen developed within the National Hurricane Center area of warning responsibility, which is east of 140ºW, and one storm formed between 140ºW and the...
, the most recent near-normal season is the 2009 season
2009 Pacific hurricane season
The 2009 Pacific hurricane season was an active event in the annual cycle of tropical cyclone formation, due to a moderate El Niño, unlike the 2009 Atlantic hurricane season, which was relatively quiet. The season officially started on May 15 in the eastern Pacific, and on June 1 for the central...
, and the most recent below normal season is the 2010 season
2010 Pacific hurricane season
The 2010 Pacific hurricane season was the least active Pacific hurricane season, in terms of the number of named storms and hurricanes, on record, due to a moderate La Niña, unlike the 2010 Atlantic hurricane season, which was one of the most active on record...
. 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).
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)
| Season | ACE | TS | HR | MH | Classification |
|---|---|---|---|---|---|
| 1992 Pacific hurricane season 1992 Pacific hurricane season The 1992 Pacific hurricane season was the most active Pacific hurricane season on record. The most notable storm was Hurricane Iniki, which caused billions of dollars of damage to the Hawaiian Islands. Hurricanes Lester, Virgil, Winifred, and Orlene also made landfall and killed several people, but... |
290 | 28 | 16 | 10 | Above normal |
| 1990 Pacific hurricane season 1990 Pacific hurricane season The 1990 Pacific hurricane season is the fifth most active season on record. The 1990 season officially started on May 15 in the eastern Pacific, and on June 1 in the central Pacific, and lasted until November 30. These dates conventionally delimit the period of each year when most tropical... |
249 | 21 | 16 | 6 | Above normal |
| 1978 Pacific hurricane season 1978 Pacific hurricane season The 1978 Pacific hurricane season officially began May 15, 1978, in the eastern Pacific, June 1, 1978 in the central Pacific, and officially ended 30 November 1978. These dates conventionally delimit the period of time when tropical cyclones form in the eastern north Pacific Ocean.Activity this... |
207 | 19 | 14 | 7 | Above normal |
| 1983 Pacific hurricane season 1983 Pacific hurricane season 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. These dates conventionally delimit the period of each year when most tropical cyclones form in the northeastern Pacific Ocean.This... |
206 | 21 | 12 | 8 | Above normal |
| 1993 Pacific hurricane season 1993 Pacific hurricane season The 1993 Pacific hurricane season was a very active season that officially started May 15, 1993 in the eastern Pacific, and June 1, 1993 in the central Pacific, and lasted until November 30, 1993... |
201 | 15 | 11 | 9 | Above normal |
| 1984 Pacific hurricane season 1984 Pacific hurricane season 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. These dates conventionally delimit the period of each year when most tropical cyclones form in the northeastern Pacific... |
193 | 21 | 13 | 7 | Above normal |
| 1985 Pacific hurricane season 1985 Pacific hurricane season The 1985 Pacific hurricane season was an event in tropical cyclone meteorology. It officially started on May 15, 1985 in the eastern Pacific, and on June 1, 1985 in the central Pacific, and lasted until November 30, 1985... |
192 | 23 | 13 | 8 | Above normal |
| 1994 Pacific hurricane season 1994 Pacific hurricane season The 1994 Pacific hurricane season officially started on May 15, 1994 in the eastern Pacific, and on June 1, 1994 in the central Pacific, and lasted until November 30, 1994. These dates conventionally delimit the period of each year when most tropical cyclones form in the northeastern Pacific Ocean... |
185 | 20 | 10 | 5 | Above normal |
| 1991 Pacific hurricane season 1991 Pacific hurricane season The 1991 Pacific hurricane season was an event in tropical cyclone meteorology. The worst storm this year was Tropical Depression Five-E, which killed one person in Mexico. Elsewhere, Tropical Storm Ignacio injured forty people in Mexico, and Hurricane Fefa caused flooding in Hawaii... |
178 | 14 | 10 | 5 | Above normal |
| 1997 Pacific hurricane season 1997 Pacific hurricane season The 1997 Pacific hurricane season was a very active hurricane season. With hundreds of deaths and billions of dollars in damage, this season was the costliest and one of the deadliest Pacific hurricane seasons. This was due to a strong El Niño... |
167 | 19 | 9 | 7 | Above normal |
| 1982 Pacific hurricane season 1982 Pacific hurricane season 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. These dates conventionally delimit the period of each year when most tropical cyclones form in the northeastern Pacific Ocean.The... |
161 | 23 | 12 | 5 | Above normal |
| 2006 Pacific hurricane season 2006 Pacific hurricane season The 2006 Pacific hurricane season was the most active Pacific hurricane season since 2000 producing 19 tropical storms or hurricanes. Eighteen developed within the National Hurricane Center area of warning responsibility, which is east of 140ºW, and one storm formed between 140ºW and the... |
155 | 19 | 11 | 6 | Above normal |
| 1971 Pacific hurricane season 1971 Pacific hurricane season The 1971 Pacific hurricane season began on May 15, 1971 in the east Pacific, and on June 1, 1971 in the central Pacific. It ended on November 30, 1971. These dates conventionally delimit the period of time when tropical cyclones form in the east Pacific Ocean.... |
139 | 18 | 12 | 6 | Above normal |
| 1972 Pacific hurricane season 1972 Pacific hurricane season The 1972 Pacific hurricane season was an ongoing event in tropical cyclone meteorology. There were few notable storms this year. No one was killed and storm effects were generally not serious. The most notable systems were Hurricane Celeste and Joanne. Celeste was the strongest storm of the... |
136 | 14 | 8 | 4 | Near normal |
| 1998 Pacific hurricane season 1998 Pacific hurricane season The 1998 Pacific hurricane season was a moderately active Pacific hurricane season with seven tropical cyclones directly affecting land. The season officially started on May 15 in the eastern Pacific, and on June 1 in the central Pacific, and ended on November 30; these dates conventionally delimit... |
134 | 13 | 9 | 6 | Near normal |
| 1987 Pacific hurricane season 1987 Pacific hurricane season The 1987 Pacific hurricane season was the last year in which the Eastern Pacific Hurricane Center was the primary warning center for tropical cyclones in the eastern Pacific Ocean. The season officially started May 15, 1987 in the eastern Pacific, and June 1, 1987 in the central Pacific, and lasted... |
132 | 20 | 10 | 4 | Near normal |
| 1988 Pacific hurricane season 1988 Pacific hurricane season The 1988 Pacific hurricane season was a Pacific hurricane season that saw a below-average amount of tropical cyclones form, and that had only one landfalling storm. It officially began May 15, 1988 in the eastern Pacific, and June 1, 1988 in the central Pacific and lasted until November 30, 1988... |
127 | 15 | 7 | 3 | Near normal |
| 2009 Pacific hurricane season 2009 Pacific hurricane season The 2009 Pacific hurricane season was an active event in the annual cycle of tropical cyclone formation, due to a moderate El Niño, unlike the 2009 Atlantic hurricane season, which was relatively quiet. The season officially started on May 15 in the eastern Pacific, and on June 1 for the central... |
125 | 20 | 8 | 5 | Near normal |
| 2002 Pacific hurricane season 2002 Pacific hurricane season The 2002 Pacific hurricane season was an event in tropical cyclone meteorology. The most notable storm that year was Hurricane Kenna, which reached Category 5 on the Saffir-Simpson Hurricane Scale. It made landfall near Puerto Vallarta, in the Mexican state of Jalisco, on October 25... |
124 | 15 | 8 | 6 | Near normal |
| 1976 Pacific hurricane season 1976 Pacific hurricane season The 1976 Pacific hurricane season was a very deadly and costly one. Hurricanes Kathleen, Liza, and Madeline were the most notable storms this year. Hurricane Kathleen caused death and destruction in California and Arizona due to flooding. Hurricane Liza was the deadliest storm of the season when it... |
121 | 15 | 9 | 5 | Near normal |
| 1973 Pacific hurricane season 1973 Pacific hurricane season The 1973 Pacific hurricane season was an event in tropical cyclone meteorology. The most important system this year was Hurricane Ava, which was the most intense Pacific hurricane known at the time. Several other much weaker tropical cyclones came close to, or made landfall on, the Pacific coast of... |
114 | 12 | 7 | 3 | Near normal |
| 1975 Pacific hurricane season 1975 Pacific hurricane season The 1975 Pacific hurricane season officially started May 15, 1975 in the eastern Pacific, and June 1, 1975 in the central Pacific, and lasted until November 30, 1975. These dates conventionally delimit the period of each year when most tropical cyclones form in the northeast Pacific Ocean.The 1975... |
112 | 17 | 9 | 4 | Near normal |
| 1989 Pacific hurricane season 1989 Pacific hurricane season -Tropical Storm Adolph:The first storm of the season developed out of a weak area of low pressure situated about 570 mi south-southwest of Acapulco, Mexico. Tracking towards the west, the circluation briefly dissipated on May 30, before redeveloping the following day into Tropical... |
110 | 17 | 9 | 4 | Near normal |
| 2011 Pacific hurricane season 2011 Pacific hurricane season The 2011 Pacific hurricane season is an ongoing, annual cycle of tropical cyclone formation. The season officially started on May 15, 2011, for the eastern Pacific, and started on June 1, 2011, for the central Pacific, both of which ended on November 30, 2011. These dates conventionally... |
118 | 10 | 10 | 6 | Near normal |
| 1986 Pacific hurricane season 1986 Pacific hurricane season The 1986 Pacific hurricane season was less active than the 1985 Pacific hurricane season. It officially started May 15, 1986 in the eastern Pacific, and June 1, 1986 in the central Pacific, and lasted until November 30, 1986. These dates conventionally delimit the period of each year when almost... |
107 | 17 | 9 | 3 | Near normal |
| 1995 Pacific hurricane season 1995 Pacific hurricane season The 1995 Pacific hurricane season was the least active Pacific hurricane season since 1979. Of the eleven tropical cyclones that formed during the season, four affected land, with the most notable storm of the season being Hurricane Ismael, which killed at least 116 people in Mexico... |
100 | 10 | 7 | 3 | Near normal |
| 2005 Pacific hurricane season 2005 Pacific hurricane season The 2005 Pacific hurricane season officially began on May 15, 2005 in the eastern Pacific and on June 1, 2005 in the central Pacific, and lasted until November 30, 2005. These dates conventionally delimit the period of each year when most tropical cyclones form in the northeastern Pacific Ocean... |
96 | 15 | 7 | 2 | Near normal |
| 2000 Pacific hurricane season 2000 Pacific hurricane season The 2000 Pacific hurricane season was an event in tropical cyclone meteorology. There were few notable storms this year. Tropical Storms Miriam, Norman, and Rosa all made landfall in Mexico with minimal impact. Hurricane Daniel briefly threatened the U.S. state of Hawaii while weakening... |
95 | 19 | 6 | 2 | Near normal |
| 1974 Pacific hurricane season 1974 Pacific hurricane season 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. These dates conventionally delimit the period of each year when most tropical cyclones form in the northeast Pacific Ocean.With... |
90 | 18 | 11 | 3 | Near normal |
| 2001 Pacific hurricane season 2001 Pacific hurricane season The 2001 Pacific hurricane season was an event in tropical cyclone meteorology. The most notable storm that year was Hurricane Juliette, which caused devastating floods in Baja California, leading to 12 fatalities and $400 million worth of damage... |
90 | 15 | 8 | 2 | Near normal |
| 1999 Pacific hurricane season 1999 Pacific hurricane season The 1999 Pacific hurricane season officially started on May 15, 1999 in the eastern Pacific, and on June 1, 1999 in the central Pacific, and lasted until November 30, 1999. These dates conventionally delimit the period of each year when most tropical cyclones form in the northeastern Pacific... |
90 | 9 | 6 | 2 | Near normal |
| 2008 Pacific hurricane season 2008 Pacific hurricane season The 2008 Pacific hurricane season was an event in the annual cycle of tropical cyclone formation. It officially started May 15, 2008 in the eastern Pacific, started on June 1, 2008 in the central Pacific, and lasted until November 30, 2008.... |
83 | 15 | 7 | 2 | Below normal |
| 1980 Pacific hurricane season 1980 Pacific hurricane season The 1980 Pacific hurricane season was an ongoing event in tropical cyclone meteorology. This season may be described through a series of negatives: no one was killed; no damage was inflicted; and no tropical cyclones made landfall... |
77 | 14 | 7 | 3 | Below normal |
| 1981 Pacific hurricane season 1981 Pacific hurricane season The 1981 Pacific hurricane season was a moderately active Pacific hurricane season with six tropical cyclones directly affecting land. The season officially started on May 15 in the eastern Pacific, and on June 1 in the central Pacific, and ended on November 30; these dates conventionally delimit... |
72 | 15 | 8 | 1 | Below normal |
| 2004 Pacific hurricane season 2004 Pacific hurricane season 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... |
71 | 12 | 6 | 3 | Below normal |
| 1979 Pacific hurricane season 1979 Pacific hurricane season 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. These dates conventionally delimit the period of each year when most tropical cyclones form in the northeast Pacific Ocean.With ten... |
57 | 10 | 6 | 4 | Below normal |
| 2003 Pacific hurricane season 2003 Pacific hurricane season The 2003 Pacific hurricane season produced an unusually large number of tropical cyclones which affected Mexico. The most notable cyclones the year were Hurricanes Ignacio and Marty, which killed 2 and 12 people in Mexico, respectively, and were collectively responsible for about... |
56 | 16 | 7 | 0 | Below normal |
| 1996 Pacific hurricane season 1996 Pacific hurricane season The 1996 Pacific hurricane season was an event in tropical cyclone formation and the third least active Pacific hurricane season in recorded history, behind 1977 and 2010. It officially began May 15, 1996 in the eastern north Pacific and on June 1, 1996 in the central north Pacific. It ended on... |
53 | 9 | 5 | 2 | Below normal |
| 2007 Pacific hurricane season 2007 Pacific hurricane season The 2007 Pacific hurricane season was an event in the annual cycle of tropical cyclone formation. It officially started on May 15, 2007 in the eastern Pacific, designated as the area east of 140°W, and on June 1, 2007 in the central Pacific, which is between the International Date Line and 140°W,... |
53 | 11 | 4 | 1 | Below normal |
| 2010 Pacific hurricane season 2010 Pacific hurricane season The 2010 Pacific hurricane season was the least active Pacific hurricane season, in terms of the number of named storms and hurricanes, on record, due to a moderate La Niña, unlike the 2010 Atlantic hurricane season, which was one of the most active on record... |
49 | 7 | 3 | 2 | Below normal |
| 1977 Pacific hurricane season 1977 Pacific hurricane season The 1977 Pacific hurricane season was, at the time, the least active in recorded history. Only eight tropical storms formed, and four hurricanes; they would be tied and surpassed, respectively, by the 2010 Pacific hurricane season. There were no major hurricanes; the next time this happened would... |
22 | 8 | 4 | 0 | Below normal |
Mean 1971-2009: 127.07
Median 1971-2009: 114
Calculations from Eastern North Pacific Tracks File at NHC
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
- Global Tropical Cyclone Best Track Database
- Hurricane Metrics