# Accumulated cyclone energy

Accumulated cyclone energy (ACE) is a metric used to compare overall activity of tropical cyclones, utilizing the available records of windspeeds at six-hour intervals to synthesize storm duration and strength into a single index value.[1] The ACE index may refer to a single storm or to groups of storms such as those within a particular month, a full season or combined seasons.[2] It is calculated by summing the square of tropical cyclones' maximum sustained winds, as recorded every six hours, but only for windspeeds of at least tropical storm strength (≥ 34 kn; 63 km/h; 39 mph);[3] the resulting figure is divided by 10,000 to place it on a more manageable scale.[1]

The calculation originated as the Hurricane Destruction Potential (HDP) index, which sums the squares of tropical cyclones' maximum sustained winds while at hurricane strength, at least 64 knots (≥ 119 km/h; 74 mph)[3] at six-hour recorded intervals across an entire season.[4] The HDP index was later modified to further include tropical storms, that is, all wind speeds of at least 34 knots (≥ 63 km/h; 39 mph),[3] to become the accumulated cyclone energy index.[5]

The highest ACE calculated for a single tropical cyclone on record worldwide is 87.01, set by Cyclone Freddy in 2023.[6]

## History

The accumulated cyclone energy index is an offshoot of Hurricane Destruction Potential (HDP), an index created in 1988 by William Gray and his associates at Colorado State University[4] who argued the destructiveness of a hurricane's wind and storm surge is better related to the square of the maximum wind speed (${\displaystyle v_{\max }^{2}}$) than simply to the maximum wind speed (${\displaystyle v_{\max }}$).[4] The HDP index is calculated by squaring the estimated maximum sustained wind speeds for tropical cyclones while at hurricane strength, that is, wind speeds of at least 64 knots (≥ 119 km/h; 74 mph).[3] The squared windspeeds from six-hourly recorded intervals are then summed across an entire season.[5][4] This scale was subsequently modified in 1999 by the United States National Oceanic and Atmospheric Administration (NOAA) to include not only hurricanes but also tropical storms, that is, all cyclones while windspeeds are at least 34 knots (≥ 63 km/h; 39 mph).[3] NOAA named the newly modified index accumulated cyclone energy.[5] Since the calculation was more broadly adjusted by NOAA, the index has been used in a number of different ways such as to compare individual storms, and by various agencies and researchers including the Australian Bureau of Meteorology and the India Meteorological Department.[7][8] The purposes of the ACE index include to categorize how active tropical cyclone seasons were as well as to identify possible long-term trends in a certain area such as the Lesser Antilles.[9]

## Calculation

Accumulated cyclone energy is calculated by summing the squares of the estimated maximum sustained velocity of tropical cyclones when wind speeds are at least tropical storm strength (≥ 34 kn; 63 km/h; 39 mph)[3] at recorded six-hour intervals. The sums are usually divided by 10,000 to make them more manageable. One unit of ACE equals 10−4 kn2, and for use as an index the unit is assumed. Thus:

${\displaystyle {\text{ACE}}=10^{-4}\sum v_{\max }^{2}}$ (for ${\displaystyle v_{\max }}$ ≥ 34 kn),

where ${\displaystyle v_{\max }}$ is estimated sustained wind speed in knots at six-hour intervals.[5]

Kinetic energy is proportional to the square of velocity. However, unlike the measure defined above, kinetic energy is also proportional to the mass ${\displaystyle m}$(corresponding to the size of the storm) and represents an integral of force equal to mass times acceleration, ${\displaystyle F=m\times a}$, where acceleration is the antiderivative of velocity, or ${\displaystyle v_{\max }}$. The integral is a difference at the limits of the square antiderivative, rather than a sum of squares at regular intervals. Thus, the term applied to the index, accumulated cyclone energy, is a misnomer since the index is neither a measure of kinetic energy nor "accumulated energy."

## Atlantic Ocean

Within the Atlantic Ocean, the United States National Oceanic and Atmospheric Administration and others use the ACE index of a season to classify the season into one of four categories.[9] These four categories are extremely active, above-normal, near-normal, and below-normal, and are worked out using an approximate quartile partitioning of seasons based on the ACE index over the 70 years between 1951 and 2020.[9] The median value of the ACE index from 1951 to 2020 is 96.7 x 104 kt2.[9]

Classification criteria
Category ACE Index % of 1951–2020
median
Extremely active > 159.6 > 165%
Above-normal > 126.1 > 130%
Near-normal 73–126.1 75–130%
Below-normal < 73 < 75%
Reference:[9]
Top 10 Atlantic hurricane seasons
Season TS HU MH ACE
1933 20 11 6 258.57
2005 28 15 7 245.3
1893 12 10 5 231.15
1926 11 8 6 229.56
1995 19 11 5 227.10
2004 15 9 6 226.88
2017 17 10 6 224.88
1950 16 11 6 211.28
1961 12 8 5 188.9
1998 14 10 3 181.76

### Individual storms in the Atlantic

The highest ever ACE estimated for a single storm in the Atlantic is 73.6, for the San Ciriaco hurricane in 1899. A Category 4 hurricane which lasted for four weeks, 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 Irma in 2017, with an ACE of 64.9, the Great Charleston Hurricane in 1893, with an ACE of 63.5, Hurricane Isabel in 2003, with an ACE of 63.3, and the 1932 Cuba hurricane, with an ACE of 59.8.[11]

Since 1950, the highest ACE of a tropical storm was Tropical Storm Philippe in 2023, which attained an ACE of 9.4.[12] The highest ACE of a Category 1 hurricane was Hurricane Nadine in 2012, which attained an ACE of 26.3. The record for lowest ACE of a tropical storm is jointly held by Tropical Storm Chris in 2000 and Tropical Storm Philippe in 2017, both of which were tropical storms for only six hours and had an ACE of just 0.1. The lowest ACE of any hurricane was 2005's Hurricane Cindy, which was only a hurricane for six hours, and 2007's Hurricane Lorenzo, which was a hurricane for twelve hours; Cindy had an ACE of just 1.5175 and Lorenzo had a lower ACE of only 1.475. The lowest ACE of a major hurricane (Category 3 or higher), was Hurricane Gerda in 1969, with an ACE of 5.3.[13] The following table shows those storms in the Atlantic basin from 1851–2021 that have attained over 50 points of ACE.[13]

Storm Year Peak classification ACE Duration
Hurricane Three 1899
Category 4 hurricane
73.6 28 days
Hurricane Ivan 2004
Category 5 hurricane
70.4 23 days
Hurricane Irma 2017
Category 5 hurricane
64.9 13 days
Hurricane Nine 1893
Category 3 hurricane
63.5 20 days
Hurricane Isabel 2003
Category 5 hurricane
63.3 14 days
Hurricane Fourteen 1932
Category 5 hurricane
59.8 15 days
Hurricane Donna 1960
Category 4 hurricane
57.6 16 days
Hurricane Carrie 1957
Category 4 hurricane
55.8 21 days
Hurricane Inez 1966
Category 5 hurricane
54.6 21 days
Hurricane Sam 2021
Category 4 hurricane
53.8 14 days
Hurricane Luis 1995
Category 4 hurricane
53.7 15 days
Hurricane Allen 1980
Category 5 hurricane
52.3 12 days
Hurricane Esther 1961
Category 5 hurricane
52.2 18 days
Hurricane Matthew 2016
Category 5 hurricane
50.9 12 days

### Historical ACE in recorded Atlantic hurricane history

50
100
150
200
250
300
1950
1960
1970
1980
1990
2000
2010
2020

There is an undercount bias of tropical storms, hurricanes, and major hurricanes before the satellite era (prior to the mid–1960s), due to the difficulty in identifying storms.

Classification criteria

Extremely active
Above-normal
Near-normal
Below-normal
Accumulated Cyclone Energy - Atlantic
Season ACE TS HU MH Classification
1851 36.24 6 3 1 Below normal
1852 73.28 5 5 1 Near normal
1853 76.49 8 4 2 Near normal
1854 31.00 5 3 1 Below normal
1855 18.12 5 4 1 Below normal
1856 48.94 6 4 2 Below normal
1857 46.84 4 3 0 Below normal
1858 44.79 6 6 0 Below normal
1859 55.73 8 7 1 Below normal
1860 62.06 7 6 1 Below normal
1861 49.71 8 6 0 Below normal
1862 46.03 6 3 0 Below normal
1863 50.35 9 5 0 Below normal
1864 26.55 5 3 0 Below normal
1865 49.13 7 3 0 Below normal
1866 83.65 7 6 1 Near normal
1867 59.97 9 7 1 Below normal
1868 34.65 4 3 0 Below normal
1869 51.02 10 7 1 Below normal
1870 87.8 11 10 2 Near normal
1871 88.39 8 6 2 Near normal
1872 65.38 5 4 0 Below normal
1873 69.47 5 3 2 Below normal
1874 47.05 7 4 0 Below normal
1875 72.48 6 5 1 Below normal
1876 56.05 5 4 2 Below normal
1877 73.36 8 3 1 Near normal
1878 180.85 12 10 2 Extremely active
1879 63.63 8 6 2 Below normal
1880 131.08 11 9 2 Above normal
1881 59.25 7 4 0 Below normal
1882 59.4675 6 4 2 Below normal
1883 66.7 4 3 2 Below normal
1884 72.06 4 4 1 Below normal
1885 58.3 8 6 0 Below normal
1886 166.165 12 10 4 Extremely active
1887 181.26 19 11 2 Extremely active
1888 84.945 9 6 2 Near normal
1889 104.0425 9 6 0 Near normal
1890 33.345 4 2 1 Below normal
1891 116.105 10 7 1 Near normal
1892 115.8375 9 5 0 Near normal
1893 231.1475 12 10 5 Extremely active
1894 135.42 7 5 4 Above normal
1895 68.765 6 2 0 Below normal
1896 136.0825 7 6 2 Above normal
1897 54.54 6 3 0 Below normal
1898 113.2375 11 5 1 Near normal
1899 151.025 10 5 2 Above normal
1900 83.345 7 3 2 Near normal
1901 98.975 13 6 0 Near normal
1902 32.65 5 3 0 Below normal
1903 102.07 10 7 1 Near normal
1904 30.345 6 4 0 Below normal
1905 28.3775 5 1 1 Below normal
1906 162.88 11 6 3 Extremely active
1907 13.06 5 0 0 Below normal
1908 95.11 10 6 1 Near normal
1909 93.34 12 6 4 Near normal
1910 63.9 5 3 1 Below normal
1911 34.2875 6 3 0 Below normal
1912 57.2625 7 4 1 Below normal
1913 35.595 6 4 0 Below normal
1914 2.53 1 0 0 Below normal
1915 130.095 6 5 3 Above normal
1916 144.0125 15 10 5 Above normal
1917 60.6675 4 2 2 Below normal
1918 39.8725 6 4 1 Below normal
1919 55.04 5 2 1 Below normal
1920 29.81 5 4 0 Below normal
1921 86.53 7 5 2 Near normal
1922 54.515 5 3 1 Below normal
1923 49.31 9 4 1 Below normal
1924 100.1875 11 5 2 Near normal
1925 7.2525 4 1 0 Below normal
1926 229.5575 11 8 6 Extremely active
1927 56.4775 8 4 1 Below normal
1928 83.475 6 4 1 Near normal
1929 48.0675 5 3 1 Below normal
1930 49.7725 3 2 2 Below normal
1931 47.835 13 3 1 Below normal
1932 169.6625 15 6 4 Extremely active
1933 258.57 20 11 6 Extremely active
1934 79.0675 13 7 1 Near normal
1935 106.2125 8 5 3 Near normal
1936 99.775 17 7 1 Near normal
1937 65.85 11 4 1 Below normal
1938 77.575 9 4 2 Near normal
1939 43.6825 6 3 1 Below normal
1940 67.79 9 6 0 Below normal
1941 51.765 6 4 3 Below normal
1942 62.485 11 4 1 Below normal
1943 94.01 10 5 2 Near normal
1944 104.4525 14 8 3 Near normal
1945 63.415 11 5 2 Below normal
1946 19.6125 7 3 0 Below normal
1947 88.49 10 5 2 Near normal
1948 94.9775 10 6 4 Near normal
1949 96.4475 16 7 2 Near normal
1950 211.2825 16 11 6 Extremely active
1951 126.325 12 8 3 Above normal
1952 69.08 11 5 2 Below normal
1953 98.5075 14 7 3 Near normal
1954 110.88 16 7 3 Near normal
1955 158.17 13 9 4 Above normal
1956 56.6725 12 4 1 Below normal
1957 78.6625 8 3 2 Near normal
1958 109.6925 12 7 3 Near normal
1959 77.1075 14 7 2 Near normal
1960 72.9 8 4 2 Below normal
1961 188.9 12 8 5 Extremely active
1962 35.5675 7 4 0 Below normal
1963 117.9325 10 7 3 Near normal
1964 153 13 7 5 Above normal
1965 84.33 10 4 1 Near normal
1966 145.2175 15 7 3 Above normal
1967 121.705 13 6 1 Near normal
1968 45.0725 9 5 0 Below normal
1969 165.7375 18 12 3 Extremely active
1970 40.18 14 7 2 Below normal
1971 96.5275 13 6 1 Near normal
1972 35.605 7 3 0 Below normal
1973 47.85 8 4 1 Below normal
1974 68.125 11 4 2 Below normal
1975 76.0625 9 6 3 Near normal
1976 84.1725 10 6 2 Near normal
1977 25.3175 6 5 1 Below normal
1978 63.2175 12 5 2 Below normal
1979 92.9175 9 6 2 Near normal
1980 148.9375 11 9 2 Above normal
1981 100.3275 12 7 3 Near normal
1982 31.5025 6 2 1 Below normal
1983 17.4025 4 3 1 Below normal
1984 84.295 13 5 1 Near normal
1985 87.9825 11 7 3 Near normal
1986 35.7925 6 4 0 Below normal
1987 34.36 7 3 1 Below normal
1988 102.9925 12 5 3 Near normal
1989 135.125 11 7 2 Above normal
1990 96.8025 14 8 1 Near normal
1991 35.5375 8 4 2 Below normal
1992 76.2225 7 4 1 Near normal
1993 38.665 8 4 1 Below normal
1994 32.02 7 3 0 Below normal
1995 227.1025 19 11 5 Extremely active
1996 166.1825 13 9 6 Extremely active
1997 40.9275 8 3 1 Below normal
1998 181.7675 14 10 3 Extremely active
1999 176.5275 12 8 5 Extremely active
2000 119.1425 15 8 3 Near normal
2001 110.32 15 9 4 Near normal
2002 67.9925 12 4 2 Below normal
2003 176.84 16 7 3 Extremely active
2004 226.88 15 9 6 Extremely active
2005 245.3 28 15 7 Extremely active
2006 78.535 10 5 2 Near normal
2007 73.885 15 6 2 Near normal
2008 145.7175 16 8 5 Above normal
2009 52.58 9 3 2 Below normal
2010 165.4825 19 12 5 Extremely active
2011 126.3025 19 7 4 Above normal
2012 132.6325 19 10 2 Above normal
2013 36.12 14 2 0 Below normal
2014 66.725 8 6 2 Below normal
2015 62.685 11 4 2 Below normal
2016 141.2525 15 7 4 Above normal
2017 224.8775 17 10 6 Extremely active
2018 132.5825 15 8 2 Above normal
2019 132.2025 18 6 3 Above normal
2020 180.3725 30 14 7 Extremely active
2021 145.5575 21 7 4 Above normal
2022 94.4225 14 8 2 Near normal
2023 145.5565 20 7 3 Above normal
2024 TBD TBD TBD TBD Upcoming season

## Eastern Pacific

Most intense Pacific
hurricane seasons[14]
Rank Season ACE value
1 2018 318.1
2 1992 294.3
3 2015 290.2
4 1990 249.5
5 1978 207.7
6 1983 206.2
7 2014 202.4
8 1993 201.8
9 1984 193.7
10 1985 193.1

Within the Eastern Pacific Ocean, the United States National Oceanic and Atmospheric Administration and others use the ACE index of a season to classify the season into one of three categories.[15] These three categories are above-, near-, and below-normal and are worked out using an approximate tercile partitioning of seasons based on the ACE index and the number of tropical storms, hurricanes, and major hurricanes over the 30 years between 1991 and 2020.[15]

For a season to be defined as above-normal, the ACE index criterion and two or more of the other criteria given in the table below must be satisfied.[15]

The mean value of the ACE index from 1991 to 2020 is 108.7 x 104 kt2, while the median value is 97.2 x 104 kt2.[15]

Classification criteria
Category ACE Index % of 1991–2020
median
Tropical
storms
Hurricanes Major
hurricanes
Above-normal > 115 > 120% 17 or more 9 or more 5 or more
Near normal 80–115 80–120% 16 or fewer 8 or fewer 4 or fewer
Below-normal < 80 < 80%
Reference:[15]

### Individual storms in the Pacific

The highest ever ACE estimated for a single storm in the Eastern or Central Pacific, while located east of the International Date Line is 62.8, for Hurricane Fico of 1978. Other Eastern Pacific storms with high ACEs include Hurricane John in 1994, with an ACE of 54.0, Hurricane Kevin in 1991, with an ACE of 52.1, and Hurricane Hector of 2018, with an ACE of 50.5.[16]

The following table shows those storms in the Eastern and Central Pacific basins from 1971 through 2023 that have attained over 30 points of ACE.[17]

Storm Year Peak classification ACE Duration
Hurricane Fico 1978
Category 4 hurricane
62.8 20 days
Hurricane John 1994
Category 5 hurricane
54.0 19 days
Hurricane Kevin 1991
Category 4 hurricane
52.1 17 days
Hurricane Hector 2018
Category 4 hurricane
50.5 13 days
Hurricane Dora 2023
Category 4 hurricane
48.4 12 days
Hurricane Tina 1992
Category 4 hurricane
47.7 22 days
Hurricane Trudy 1990
Category 4 hurricane
45.8 16 days
Hurricane Lane 2018
Category 5 hurricane
44.2 13 days
Hurricane Dora 1999
Category 4 hurricane
41.4 13 days
Hurricane Jimena 2015
Category 4 hurricane
40.0 15 days
Hurricane Guillermo 1997
Category 5 hurricane
40.0 16 days
Hurricane Norbert 1984
Category 4 hurricane
39.6 12 days
Hurricane Norman 2018
Category 4 hurricane
36.6 12 days
Hurricane Celeste 1972
Category 4 hurricane
36.3 16 days
Hurricane Sergio 2018
Category 4 hurricane
35.5 13 days
Hurricane Lester 2016
Category 4 hurricane
35.4 14 days
Hurricane Olaf 2015
Category 4 hurricane
34.6 12 days
Hurricane Jimena 1991
Category 4 hurricane
34.5 12 days
Hurricane Doreen 1973
Category 4 hurricane
34.3 16 days
Hurricane Ioke 2006
Category 5 hurricane
34.2 7 days
Hurricane Marie 1990
Category 4 hurricane
33.1 14 days
Hurricane Orlene 1992
Category 4 hurricane
32.4 12 days
Hurricane Greg 1993
Category 4 hurricane
32.3 13 days
Hurricane Hilary 2011
Category 4 hurricane
31.2 9 days

† – Indicates that the storm formed in the Eastern/Central Pacific, but crossed 180°W at least once; therefore, only the ACE and number of days spent in the Eastern/Central Pacific are included.

### Historical ACE in recorded Pacific hurricane history

100
200
300
400
1971
1980
1990
2000
2010
2020
Observed monthly values for the PDO index, 1900–present.
Historical East Pacific Seasonal Activity, 1981–2015.

Data on ACE is considered reliable starting with the 1971 season.

Classification criteria

Above-normal
Near-normal
Below-normal
Accumulated Cyclone Energy - Pacific
Season ACE TS HU MH Classification
1971 139 18 12 6 Above normal
1972 136 14 8 4 Near normal
1973 114 12 7 3 Near normal
1974 90 18 11 3 Near normal
1975 112 17 9 4 Near normal
1976 121 15 9 5 Above normal
1977 22 8 4 0 Below normal
1978 207 19 14 7 Above normal
1979 57 10 6 4 Below normal
1980 77 14 7 3 Below normal
1981 72 15 8 1 Below normal
1982 161 23 12 5 Above normal
1983 206 21 12 8 Above normal
1984 193 21 13 7 Above normal
1985 192 24 13 8 Above normal
1986 107 17 9 3 Near normal
1987 132 20 10 4 Above normal
1988 127 15 7 3 Near normal
1989 110 17 9 4 Near normal
1990 245 21 16 6 Above normal
1991 178 14 10 5 Above normal
1992 295 27 16 10 Above normal
1993 201 15 11 9 Above normal
1994 185 20 10 5 Above normal
1995 100 10 7 3 Near normal
1996 53 9 5 2 Below normal
1997 167 19 9 7 Above normal
1998 134 13 9 6 Above normal
1999 90 9 6 2 Near normal
2000 95 19 6 2 Near normal
2001 90 15 8 2 Near normal
2002 125 16 8 6 Near normal
2003 56 16 7 0 Below normal
2004 71 12 6 3 Below normal
2005 96 15 7 2 Near normal
2006 155 19 11 6 Above normal
2007 52 11 4 1 Below normal
2008 83 17 7 2 Near normal
2009 127 20 8 5 Above normal
2010 52 8 3 2 Below normal
2011 121 11 10 6 Above normal
2012 98 17 10 5 Near normal
2013 76 20 9 1 Below normal
2014 201 22 16 9 Above normal
2015 290 26 16 11 Above normal
2016 184 22 13 6 Above normal
2017 100 18 9 4 Near normal
2018 318 23 13 10 Above normal
2019 97 19 7 4 Near normal
2020 73 17 4 3 Below normal
2021 93 19 8 2 Near normal
2022 116 19 10 4 Above normal
2023 164 17 10 8 Above normal
2024 TBD TBD TBD TBD Upcoming season

## Western Pacific

Most intense Pacific typhoon seasons
Rank Seasons ACE value
1 1997 570.4
2 2004 480.6
3 1992 470.1
4 2015 462.9
5 1994 454.6
6 1958 445.8
7 1957 440.2
8 1965 436.2
9 1962 423
10 1996 416.5
Source:[18]

### Historical ACE in recorded Western Pacific typhoon history

There is an undercount bias of tropical storms, typhoons, and super typhoon before the satellite era (prior to the mid–1950s), due to the difficulty in identifying storms.

Classification criteria

Extremely active
Above-normal
Near-normal
Below-normal
Accumulated cyclone energy - Pacific typhoon
Season ACE TS TY STY Classification
1950 160.2 18 12 1 Below normal
1951 283.4 25 16 1 Above normal
1952 338 29 20 6 Above normal
1953 362.6 24 17 5 Extremely active
1954 305.5 19 15 5 Above normal
1955 249.8 31 20 4 Near normal
1956 305.6 26 18 5 Above normal
1957 440.2 22 18 8 Extremely active
1958 445.8 23 21 9 Extremely active
1959 397.6 25 18 8 Extremely active
1960 326.7 30 19 2 Above normal
1961 365.6 27 20 9 Extremely active
1962 423 30 23 12 Extremely active
1963 386 25 19 14 Extremely active
1964 403.1 38 26 13 Extremely active
1965 436.3 34 21 15 Extremely active
1966 302.2 30 20 8 Above normal
1967 398.1 34 19 11 Extremely active
1968 356.8 27 20 13 Extremely active
1969 203.7 19 13 7 Near normal
1970 287.5 24 12 11 Above normal
1971 380.2 35 25 11 Extremely active
1972 413 29 22 14 Extremely active
1973 148.1 21 12 3 Below normal
1974 205.3 32 16 0 Near normal

## North Indian

There are various agencies over the North Indian Ocean that monitor and forecast tropical cyclones, including the United States Joint Typhoon Warning Center, as well as the Bangladesh, Pakistan and India Meteorological Department.[7] As a result, the track and intensity of tropical cyclones differ from each other, and as a result, the accumulated cyclone energy also varies over the region.[7] However, the India Meteorological Department has been designated as the official Regional Specialised Meteorological Centre by the WMO for the region and has worked out the ACE for all cyclonic systems above 17 knots (31 km/h; 20 mph) based on their best track analysis which goes back to 1982.[7][19]

Top 5 North Indian Ocean cyclone seasons
Season D DD CS SCS VSCS ESCS SUCS ACE
2019 12 11 8 6 6 3 1 93
2023 9 7 6 5 4 3 0 55
2007 11 8 4 2 2 2 1 46.1
2013 10 6 5 4 3 1 0 45.6
1999 10 8 5 3 3 2 1 44.3
References:[7][19]

## References

1. ^ a b "Measuring overall activity: The Accumulated Cyclone Energy (ACE) index". National Weather Service Climate Prediction Center. NOAA. Retrieved 30 January 2024.
2. ^ "Climate Change Indicators: Tropical Cyclone Activity". United States Environmental Protection Agency. EPA. Retrieved 30 January 2024.
3. "Glossary of NHC Terms". National Oceanic and Atmospheric Administration, National Hurricane Center and Central Pacific Hurricane Center. Retrieved 31 January 2024.
4. ^ a b c d Gray, William Mason (26 May 1988). Forecast of Atlantic Seasonal Hurricane Activity for 1988 (PDF) (Report). Colorado State University. p. 13-14.
5. ^ a b c d Bell, Gerald D; Halpert, Michael S; Schnell, Russell C; Higgins, R. Wayne; Lawrimore, Jay; Kousky, Vernon E; Tinker, Richard; Thiaw, Wasila; Chelliah,Muthuvel; Artusa, Anthony (June 2000). "Climate Assessment for 1999". Bulletin of the American Meteorological Society. 81 (6): S19. doi:10.1175/1520-0477(2000)81[s1:CAF]2.0.CO;2.
6. ^ "Real-Time Southern Hemisphere Statistics by Storm for 2022/2023". Colorado State University. Archived from the original on 11 March 2023. Retrieved 11 March 2023.
7. Mohapatra M; Vijay Kumar, V (March 2017). "Interannual variation of tropical cyclone energy metrics over North Indian Ocean". Climate Dynamics. 48 (5–6): 1431–1445. Bibcode:2017ClDy...48.1431M. doi:10.1007/s00382-016-3150-3. S2CID 130486452.
8. ^ Weekly Tropical Climate Note July 14, 2020 (Report). Australian Bureau of Meteorology. 14 July 2020. Archived from the original on 4 September 2020. Retrieved 4 September 2020.
9. "Background information: North Atlantic Hurricane Season". United States Climate Prediction Center. 22 May 2019. Archived from the original on 24 July 2020. Retrieved 22 August 2020.
10. ^ "Accumulated Cyclone Energy of North Atlantic hurricanes". Our World in Data. Retrieved 15 February 2020.
11. ^ "Atlantic hurricane best track (HURDAT version 2)" (Database). United States National Hurricane Center. 5 April 2023. Retrieved 12 February 2024. This article incorporates text from this source, which is in the public domain.
12. ^ "Real-Time North Atlantic Ocean Statistics compared with climatology". tropical.atmos.colostate.edu. Retrieved 5 October 2023.
13. ^ a b "Atlantic hurricanes by ACE - 1950-2012". Policlimate. Archived from the original on 10 August 2017. Retrieved 7 August 2017.
14. ^ "Basin Archives: Northeast Pacific Ocean Historical Tropical Cyclone Statistics". Fort Collins, Colorado: Colorado State University. Retrieved 8 July 2022.
15. "Background information: Eastern Pacific Hurricane Season". United States Climate Prediction Center. 22 May 2019. Archived from the original on 24 July 2020. Retrieved 22 August 2020.
16. ^ "Eastern Pacific Best Track Data - (1949 - present)". National Hurricane Center. Retrieved 12 August 2018.
17. ^ Webb, Eric. "Hurricane Hector 2018 - Discussion". Twitter. Retrieved 12 August 2018.
18. ^ http://tropical.atmos.colostate.edu/Realtime/index.php?arch&loc=northwestpacific
19. ^ a b Tropical Cyclone Energy Matrix over North Indian Ocean (PDF) (Report). India Meteorological Department. 2020. Archived (PDF) from the original on 18 July 2020. Retrieved 3 September 2020.