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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. [2] 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. [3] 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); [4] the resulting figure is divided by 10,000 to place it on a more manageable scale. [2]
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) [4] at six-hour recorded intervals across an entire season. [5] 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), [4] to become the accumulated cyclone energy index. [6]
The highest ACE calculated for a single tropical cyclone on record worldwide is 87.01, set by Cyclone Freddy in 2023. [7]
The ACE index is an offshoot of Hurricane Destruction Potential (HDP), an index created in 1988 by William Gray and his associates at Colorado State University [5] who argued the destructiveness of a hurricane's wind and storm surge is better related to the square of the maximum wind speed () than simply to the maximum wind speed (). [5] 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). [4] The squared windspeeds from six-hourly recorded intervals are then summed across an entire season. [6] [5] 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). [4] 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. [8] [9] 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. [10]
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) [4] 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 kn 2, and for use as an index the unit is assumed. Thus:
where is estimated sustained wind speed in knots at six-hour intervals. [6]
Kinetic energy is proportional to the square of velocity. However, unlike the measure defined above, kinetic energy is also proportional to the mass (corresponding to the size of the storm) and represents an integral of force equal to mass times acceleration, , where acceleration is the antiderivative of velocity, or . 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."
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. [12] 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. [13] The median value of the ACE index from 1951 to 2020 is 96.7 x 104 kt2 [14]
Category | ACE Index [kt2] | % of 1951–2020 median | |||
---|---|---|---|---|---|
Extremely active | > 159.6 | > 165% | |||
Above-normal | 126.1–159.6 | 130%–165% | |||
Near-normal | 73.0–126.1 | 75%–130% | |||
Below-normal | < 73.0 | < 75% | |||
Reference: [15] |
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 |
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. [16]
Since 1950, the highest ACE of a tropical storm was Tropical Storm Philippe in 2023, which attained an ACE of 9.4. [17] 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 0.1225. 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. [18] The following table shows those storms in the Atlantic basin from 1851–2021 that have attained over 50 points of ACE. [18]
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 |
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
Season | ACE | TS | HU | MH | Classification |
---|---|---|---|---|---|
1851 | 36.24 | 6 | 3 | 1 | Below normal |
1852 | 73.28 | 5 | 5 | 1 | Below normal |
1853 | 76.49 | 8 | 4 | 2 | Below 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 | Below 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 | Above normal |
1892 | 115.8375 | 9 | 5 | 0 | Above 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 | Above 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 | Below 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 | Above 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 | Below 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 | Above 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 | Above normal |
1968 | 45.0725 | 9 | 5 | 0 | Below normal |
1969 | 149 | 18 | 12 | 3 | Above normal |
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 | Below 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 | Below 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 | Above normal |
2001 | 110.32 | 15 | 9 | 4 | Above 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 | Below 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 | 161.63 | 18 | 11 | 5 | Extremely active |
Most intense Pacific hurricane seasons [20] | ||
---|---|---|
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. [21] These four categories are extremely active, 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. [21]
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. [21]
The mean value of the ACE index from 1991 to 2020 is 108.7 × 104 kt2, while the median value is 97.2 × 104 kt2. [21]
Category | ACE Index | % of 1991–2020 median | Tropical storms | Hurricanes | Major hurricanes |
---|---|---|---|---|---|
Extremely active | > 170 | > 180% | 22 or more | 10-16 or more | 9-11 or more |
Above-normal | 110-169 | 110%–175% | 15-19 or more | 8 or more | 6 or more |
Near normal | 80–110 | 80–112% | 10-19 or fewer | 9 or fewer | 2-5 or fewer |
Below-normal | < 22-80 | < 75% | — | ||
Reference: [21] |
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. [22]
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. [23]
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.
Data on ACE is considered reliable starting with the 1971 season.
Classification criteria
Season | ACE | TS | HU | MH | Classification |
---|---|---|---|---|---|
1971 | 139 | 18 | 12 | 6 | Above normal |
1972 | 136 | 14 | 8 | 4 | Above normal |
1973 | 114 | 12 | 7 | 3 | Above normal |
1974 | 90 | 18 | 11 | 3 | Near normal |
1975 | 112 | 17 | 9 | 4 | Above normal |
1976 | 121 | 15 | 9 | 5 | Above normal |
1977 | 22 | 8 | 4 | 0 | Below normal |
1978 | 207 | 19 | 14 | 7 | Extremely active |
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 | Extremely active |
1984 | 193 | 21 | 13 | 7 | Extremely active |
1985 | 192 | 24 | 13 | 8 | Extremely active |
1986 | 107 | 17 | 9 | 3 | Near normal |
1987 | 132 | 20 | 10 | 4 | Above normal |
1988 | 127 | 15 | 7 | 3 | Above normal |
1989 | 110 | 17 | 9 | 4 | Above normal |
1990 | 245 | 21 | 16 | 6 | Extremely active |
1991 | 178 | 14 | 10 | 5 | Extremely active |
1992 | 295 | 27 | 16 | 10 | Extremely active |
1993 | 201 | 15 | 11 | 9 | Extremely active |
1994 | 185 | 20 | 10 | 5 | Extremely active |
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 | Above 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 | Extremely active |
2015 | 290 | 26 | 16 | 11 | Extremely active |
2016 | 184 | 22 | 13 | 6 | Extremely active |
2017 | 100 | 18 | 9 | 4 | Near normal |
2018 | 318 | 23 | 13 | 10 | Extremely active |
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 | 82 | 13 | 5 | 3 | Near normal |
This section needs expansion. You can help by adding to it. (July 2023) |
TSR forecasts Date | Tropical storms | Total Typhoons | Intense TCs | ACE | Ref. |
---|---|---|---|---|---|
Average (1991–2020) | 25.5 | 16.0 | 9.3 | 301 | [24] |
Category | 1990 –2020 ACE Index [kt2] | |||
---|---|---|---|---|
Extremely active | > 328 | |||
Near-normal | 259 - 328 | |||
Below-normal | < 259 | |||
Reference: [10] |
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: [25] |
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[ clarification needed ]
Season | ACE | TS | TY | STY | Classification |
---|---|---|---|---|---|
1950 | 160.2 | 18 | 12 | 1 | Below normal |
1951 | 283.4 | 25 | 16 | 1 | Near normal |
1952 | 338 | 29 | 20 | 6 | Extremely active |
1953 | 362.6 | 24 | 17 | 5 | Extremely active |
1954 | 305.5 | 19 | 15 | 5 | Near normal |
1955 | 249.8 | 31 | 20 | 4 | Below normal |
1956 | 305.6 | 26 | 18 | 5 | Near 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 | Near normal |
1961 | 365.6 | 27 | 20 | 8 | Extremely active |
1962 | 423 | 30 | 23 | 6 | Extremely active |
1963 | 386 | 25 | 19 | 8 | Extremely active |
1964 | 403.1 | 38 | 26 | 7 | Extremely active |
1965 | 436.3 | 34 | 21 | 11 | Extremely active |
1966 | 302.2 | 30 | 20 | 3 | Near normal |
1967 | 398.1 | 34 | 19 | 5 | Extremely active |
1968 | 356.8 | 27 | 20 | 4 | Extremely active |
1969 | 203.7 | 19 | 13 | 2 | Below normal |
1970 | 287.5 | 24 | 12 | 7 | Near normal |
1971 | 380.2 | 35 | 25 | 6 | Extremely active |
1972 | 413 | 29 | 22 | 2 | Extremely active |
1973 | 148.1 | 21 | 12 | 3 | Below normal |
1974 | 205.3 | 32 | 16 | 0 | Below normal |
1975 | 171 | 20 | 14 | 3 | Below normal |
1976 | 301.3 | 25 | 14 | 4 | Near normal |
1977 | 164.1 | 19 | 11 | 3 | Below normal |
1978 | 236.8 | 28 | 15 | 1 | Below normal |
1979 | 278.4 | 23 | 14 | 4 | Near normal |
1980 | 237.8 | 23 | 15 | 2 | Below normal |
1981 | 227 | 28 | 16 | 2 | Below normal |
1982 | 356.1 | 25 | 19 | 2 | Extremely active |
1983 | 219.7 | 23 | 12 | 4 | Below normal |
1984 | 274 | 27 | 16 | 2 | Near normal |
1985 | 231.2 | 25 | 17 | 1 | Below normal |
1986 | 334.2 | 26 | 19 | 3 | Extremely active |
1987 | 356.5 | 23 | 17 | 6 | Extremely active |
1988 | 227.9 | 25 | 13 | 1 | Below normal |
1989 | 305 | 30 | 21 | 5 | Near normal |
1990 | 377.8 | 30 | 21 | 4 | Extremely active |
1991 | 414.3 | 29 | 20 | 5 | Extremely active |
1992 | 470.1 | 31 | 21 | 4 | Extremely active |
1993 | 267.1 | 29 | 20 | 3 | Near normal |
1994 | 454.6 | 34 | 20 | 6 | Extremely active |
1995 | 255.1 | 26 | 15 | 5 | Below normal |
1996 | 416.5 | 33 | 21 | 6 | Extremely active |
1997 | 570.4 | 29 | 23 | 11 | Extremely active |
1998 | 152.9 | 18 | 9 | 3 | Below normal |
1999 | 109.9 | 23 | 11 | 1 | Below normal |
2000 | 252.9 | 25 | 14 | 4 | Below normal |
2001 | 307.3 | 29 | 21 | 3 | Near normal |
2002 | 390.6 | 24 | 16 | 8 | Extremely active |
2003 | 337.4 | 22 | 17 | 5 | Extremely active |
2004 | 480.6 | 31 | 20 | 6 | Extremely active |
2005 | 309.9 | 24 | 18 | 3 | Near normal |
2006 | 321.3 | 21 | 13 | 6 | Near normal |
2007 | 219.5 | 22 | 16 | 5 | Below normal |
2008 | 178.4 | 27 | 12 | 2 | Below normal |
2009 | 278.1 | 23 | 15 | 5 | Near normal |
2010 | 121.4 | 14 | 9 | 1 | Below normal |
2011 | 189.7 | 18 | 10 | 4 | Below normal |
2012 | 302.3 | 25 | 15 | 4 | Near normal |
2013 | 276.3 | 27 | 16 | 5 | Near normal |
2014 | 277.8 | 20 | 12 | 8 | Near normal |
2015 | 462.9 | 26 | 20 | 9 | Extremely active |
2016 | 261.9 | 26 | 17 | 6 | Near normal |
2017 | 169.4 | 26 | 13 | 2 | Below normal |
2018 | 361.6 | 31 | 16 | 7 | Extremely active |
2019 | 276.8 | 30 | 18 | 5 | Near normal |
2020 | 152.8 | 23 | 12 | 2 | Below normal |
2021 | 209.6 | 23 | 10 | 5 | Below normal |
2022 | 163.2 | 22 | 12 | 3 | Below normal |
2023 | 268.5 | 16 | 11 | 4 | Near normal |
2024 | 210.1 | 25 | 14 | 6 | Current season |
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. [8] 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. [8] 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. [8] [26]
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: [8] [26] |
This section needs expansion. You can help by adding to it. (October 2023) |
The 1983 Atlantic hurricane season was the least active Atlantic hurricane season in the satellite era and the least active overall since 1930. 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 form in the Atlantic basin. The season had very little activity, with only seven tropical depressions, four of which reached tropical storm strength or higher. This led to the lowest accumulated cyclone energy count since 1977.
Tropical cyclones are ranked on one of five tropical cyclone intensity scales, according to their maximum sustained winds and which tropical cyclone basins they are located in. Only a few classifications are used officially by the meteorological agencies monitoring the tropical cyclones, but other scales also exist, such as accumulated cyclone energy, the Power Dissipation Index, the Integrated Kinetic Energy Index, and the Hurricane Severity Index.
2010, with only 64 named systems, was considered as one of the least active years for tropical cyclones on record. During the year, tropical cyclones formed within seven different tropical cyclone basins, located within various parts of the Atlantic, Pacific and Indian Oceans. During the year, a total of 111 tropical cyclones developed, with 64 of them being named by either a Regional Specialized Meteorological Center (RSMC) or a Tropical Cyclone Warning Center (TCWC). The most active basin was the North Atlantic, which documented 19 named systems, while the North Indian Ocean, despite only amounting to five named systems, was its basin's most active since 1998. Conversely, both the West Pacific typhoon and East Pacific hurricane seasons experienced the fewest cyclones reaching tropical storm intensity in recorded history, numbering 14 and 8, respectively. Activity across the southern hemisphere's three basins—South-West Indian, Australian, and South Pacific—was spread evenly, with each region recording 7 named storms apiece. The southern hemisphere's strongest tropical cyclone was Cyclone Edzani, which bottomed out with a barometric pressure of 910 mbar in the South-West Indian Ocean. Nineteen Category 3 tropical cyclones formed, including four Category 5 tropical cyclones in the year. The accumulated cyclone energy (ACE) index for the 2010, as calculated by Colorado State University was 573.8 units.
During 2005, tropical cyclones formed within seven different tropical cyclone basins, located within various parts of the Atlantic, Pacific and Indian Oceans. During the year, a total of 141 systems formed with 94 of these developing further and were named by the responsible warning centre. The strongest tropical cyclone of the year was Hurricane Wilma, which was estimated to have a minimum barometric pressure of 882 hPa (26.05 inHg). 2005 was above-average in terms of the number of storms. The most active basin in the year was the North Atlantic, which documented 28 named systems. The Western Pacific had an near-average season with 23 named storms. The Eastern Pacific hurricane season experienced an above-average number of tropical storm intensity systems, numbering 15. Activity across the southern hemisphere's three basins – South-West Indian, Australian, and South Pacific – was fairly significant, with the regions recording 23 named storms altogether, with the most intense Southern Hemisphere cyclone of the year, Cyclone Percy from the South Pacific Ocean basin peaking at 145 mph (235 km/h) and 900 millibars. Throughout the year, 28 Category 3 tropical cyclones formed, including eight Category 5 tropical cyclones in the year. The accumulated cyclone energy (ACE) index for the 2005, as calculated by Colorado State University was 899.6 units.
Throughout 2006, 133 tropical cyclones formed in seven bodies of water known as tropical cyclone basins. Of these, 80 have been named, including two tropical cyclones in the South Atlantic Ocean, and a tropical cyclone in the Mediterranean Sea, by various weather agencies when they attained maximum sustained winds of 65 km/h (40 mph). The strongest storms of the year were Typhoon Yagi in the Western Pacific, and Cyclone Glenda of the Australian region. The deadliest and costliest storms of the year were a series of five typhoons that struck the Philippines and China; Chanchu, Bilis, Saomai, Xangsane, and Durian, with most of the damage being caused by Durian of November. So far, 27 Category 3 tropical cyclones formed, including five Category 5 tropical cyclones in the year. The accumulated cyclone energy (ACE) index for the 2006, as calculated by Colorado State University was 761 units.
The following is a glossary of tropical cyclone terms.
During 2017 tropical cyclones formed within seven different tropical cyclone basins, located within various parts of the Atlantic, Pacific and Indian Oceans. During the year, a total of 146 tropical cyclones had formed. 88 tropical cyclones had been named by either a Regional Specialized Meteorological Center (RSMC) or a Tropical Cyclone Warning Center (TCWC). The strongest and deadliest tropical cyclone was Hurricane Maria with a minimum barometric pressure of 908 mbar and killing 3,000 people in Puerto Rico and Dominica. The costliest tropical cyclone of the year was Hurricane Harvey in the Atlantic, which struck Houston metropolitan area in August causing US$125 billion in damage, tying with Hurricane Katrina as the costliest tropical cyclone worldwide.
During 2019, tropical cyclones formed within seven different tropical cyclone basins, located within various parts of the Atlantic, Pacific and Indian Oceans. During the year,a total of 142 systems formed, with 100 of these developing further and being named by the responsible warning centre. The strongest tropical cyclone of the year was Typhoon Halong, with a minimum barometric pressure of 905 hPa (26.72 inHg). Cyclone Idai became the deadliest tropical cyclone of the year, after killing at least 1,303 people in Mozambique, Malawi, Zimbabwe, and Madagascar. The costliest tropical cyclone of the year was Typhoon Hagibis, which caused more than $15 billion in damage after striking Japan.
2020 was regarded as the most active tropical cyclone year on record, documenting 104 named tropical systems. During the year, 142 tropical cyclones formed in bodies of water known as tropical cyclone basins. Of these, a record-high of 104, including three subtropical cyclones in the South Atlantic Ocean and three tropical-like cyclones in the Mediterranean, were named by various weather agencies when they attained maximum sustained winds of 35 knots. The strongest storm of the year was Typhoon Goni, peaking with a pressure of 905 hPa (26.72 inHg). The deadliest storm of the year was Hurricane Eta which caused 175 fatalities and another 100+ to be missing in Central America and the US, while the costliest storm of the year was Hurricane Laura, with a damage cost around $19.1 billion in the Greater Antilles, The Bahamas, and the Gulf Coast of the United States.
During 2004, tropical cyclones formed within seven different tropical cyclone basins, located within various parts of the Atlantic, Pacific and Indian Oceans. During the year, a total of 132 systems formed with 82 of these developing further and were named by the responsible warning centre. The strongest tropical cyclone of the year was Cyclone Gafilo, which was estimated to have a minimum barometric pressure of 895 hPa (26.43 inHg). The most active basin in the year was the Western Pacific, which documented 29 named systems, while the North Atlantic 15 named systems formed. Conversely, both the Eastern Pacific hurricane and North Indian Ocean cyclone seasons experienced a below average number of named systems, numbering 12 and 4, respectively. Activity across the southern hemisphere's three basins—South-West Indian, Australian, and South Pacific—was spread evenly, with each region recording seven named storms apiece. Throughout the year, 28 Category 3 tropical cyclones formed, including seven Category 5 tropical cyclones formed in the year. The accumulated cyclone energy (ACE) index for the 2004, as calculated by Colorado State University was 1024.4 units.
Throughout 2013, 139 tropical cyclones formed in seven different areas called basins. Of these, 67 have been named by various weather agencies when they attained maximum sustained winds of 35 knots. The strongest and deadliest tropical cyclone of the year was Typhoon Haiyan, which was estimated to have a minimum barometric pressure of 895 hPa (26.43 inHg) and caused at least 6,300 deaths in the Philippines. The costliest tropical cyclone of the year was Hurricane Manuel, which was responsible for at least $4.2 billion worth of damages in Mexico. 21 major tropical cyclones formed in 2013, including five Category 5 tropical cyclones. The accumulated cyclone energy (ACE) index for the 2013, as calculated by Colorado State University was 618.5 units.
Throughout 2009, 130 tropical cyclones formed in bodies of water known as tropical cyclone basins. Of these, 81 were named, including a subtropical cyclone in the South Atlantic Ocean, by various weather agencies when they attained maximum sustained winds of 35 knots. The strongest storm of the year was Typhoon Nida in the Western Pacific Ocean. The deadliest and costliest storm of the year was Typhoon Morakot (Kiko), causing 789 fatalities and $6.2 billion worth of damages through its track in the Philippines, Japan, Taiwan, China, and the Korean Peninsula. Throughout the year, twenty-one Category 3 tropical cyclones formed, including five Category 5 tropical cyclones in the year. The accumulated cyclone energy (ACE) index for the 2009, as calculated by Colorado State University was 609.6 units.
The 2025 Atlantic hurricane season is the future event for the annual Atlantic hurricane season in the Northern Hemisphere. The season officially begins on June 1, 2025, and will end on November 30, 2025. These dates, adopted by convention, historically describe the period in each year when most subtropical or tropical cyclogenesis occurs in the Atlantic Ocean. The National Hurricane Center (NHC) will begin issuing regular Tropical Weather Outlooks on May 15, 2025, about two weeks prior to the start of the season.
During 2001, tropical cyclones formed in seven different areas called basins, located within various parts of the Atlantic, Pacific and Indian Oceans. A total of 128 tropical cyclones formed within bodies of water known as tropical cyclone basins, with 83 of them were further named by the responsible weather agencies when they attained maximum sustained winds of 35 knots. Typhoon Faxai is the strongest tropical cyclone throughout the year, peaking with a pressure of 915 hPa (27.02 inHg) and attaining 10-minute sustained winds of 195 km/h (120 mph). The deadliest tropical cyclone of the year was Lingling in the West Pacific which caused 379 fatalities in total as it struck the Philippines and Vietnam, while the costliest storm of the year was Michelle, with a damage cost of around $2.43 billion as it catastrophically affected the Greater Antilles and the Bahamas in late October. So far, 23 Category 3 tropical cyclones formed, including two Category 5 tropical cyclones formed in the year. The accumulated cyclone energy (ACE) index for the 2001, as calculated by Colorado State University was 672.4 units.
During 2000, tropical cyclones formed in seven different areas called basins, located within various parts of the Atlantic, Pacific, and Indian Oceans. A total of 140 tropical cyclones formed within bodies of water known as tropical cyclone basins, with 81 of them being further named by their responsible weather agencies when they attained maximum sustained winds of 35 knots. The strongest storm of the year was Cyclone Hudah, peaking with a minimum pressure of 905 hPa (26.72 inHg), and with 10-minute sustained winds of 220 km/h (135 mph). The highest confirmed number of deaths from a storm was from Typhoon Kai-tak, which killed 188 people, however, Leon–Eline may have killed up to 722 people. The costliest storm was Saomai, which caused $6.3 billion in damage. The accumulated cyclone energy (ACE) index for the year 2000, as calculated by Colorado State University was 677.3 units.
The year 1997 was regarded as one of the most intense tropical cyclone years on record, featuring a record 12 category 5-equivalent tropical cyclones, according to the Saffir–Simpson hurricane wind scale. The year also featured the second-highest amount of accumulated cyclone energy (ACE) on record, just behind 1992 and 2018. Throughout the year, 108 tropical cyclones have developed in bodies of water, commonly known as tropical cyclone basins. However, only 89 tropical cyclones were of those attaining 39 mph or greater, falling just below the long term average of 102 named systems. The most active basin was the Western Pacific, attaining an ACE amount of 571, the highest ever recorded in any season in any basin on record. The deadliest tropical cyclone was Severe Tropical Storm Linda (Openg). The costliest tropical cyclone was Super Typhoon Winnie (Ibiang), which set a record for having the largest eye on record. The most intense tropical cyclone was Hurricane Linda, peaking at 902 hPa/mbar. Typhoon Paka (Rubing), the longest-lived system, produced the fourth-highest ACE for a single tropical cyclone, just behind Typhoon Nancy (1961), Hurricane/Typhoon Ioke (2006), and Cyclone Freddy (2023). The accumulated cyclone energy (ACE) index for the 1997, as calculated by Colorado State University was 1,099.2 units.
During 1999, tropical cyclones formed within seven different bodies of water called basins. To date, 142 tropical cyclones formed in bodies of water known as tropical cyclone basins, of which 72 were given names by various weather agencies. The strongest tropical cyclone of the year was Gwenda, attaining maximum sustained winds of 120 knots and a pressure of 900 hPa (26.58 inHg), later tied with Inigo in 2003. Floyd was the costliest tropical cyclone of the year, with around $6.5 billion worth of damages as it affected the Bahamas, the East Coast of the United States, and the Atlantic Canada. The deadliest cyclone of this year was the 1999 Odisha cyclone, which was blamed for over 9,667 deaths as it devastated India. It was also the strongest Northern Hemisphere cyclone of the year with the pressure of 912 hPa (26.93 inHg) and third most intense tropical cyclone worldwide next to Cyclone Gwenda and Cyclone Vance. Three Category 5 tropical cyclones were formed in 1999. The accumulated cyclone energy (ACE) index for the 1999, as calculated by Colorado State University was 606.4 units.
During 1996, tropical cyclones formed within seven different tropical cyclone basins, located within various parts of the Atlantic, Pacific, and Indian Oceans. During the year, a total of 139 tropical cyclones formed in bodies of water known as tropical cyclone basins. 90 of them were named by various weather agencies when they attained maximum sustained winds of 35 knots. The strongest tropical cyclone of the year was Cyclone Daniella, peaking with a pressure of 915 hPa (27.02 inHg) in the open waters of the Indian Ocean. Hurricane Fran and Typhoon Herb tie for the costliest storm of the year, both with a damage cost of $5 billion. The deadliest tropical cyclone of the year was the 1996 Andhra Pradesh cyclone, which was blamed for over 1,000 fatalities as it directly affected the state of Andhra Pradesh in India. Five Category 5 tropical cyclones were formed in 1996. The accumulated cyclone energy (ACE) index for the 1996, as calculated by Colorado State University was 960 units.
During 1995, tropical cyclones formed within seven different bodies of water called basins. To date, 110 tropical cyclones formed, of which 74 were given names by various weather agencies. The strongest storm and the deadliest storm of the year was Typhoon Angela, which reached a minimum central pressure of 910 hPa (26.87 inHg) and caused a total of 936 deaths throughout the Philippines. The costliest storm of the year was Hurricane Opal, which caused $4.7 billion in damage throughout Central America and the Gulf Coast of the United States. The accumulated cyclone energy (ACE) index for the 1995, as calculated by Colorado State University was 779.3 units.
During 1993, tropical cyclones formed within seven different bodies of water called basins. To date, 110 tropical cyclones formed, of which 78 were given names by various weather agencies. Only one Category 5 tropical cyclone was formed in 1993. The accumulated cyclone energy (ACE) index for the 1993, as calculated by Colorado State University was 710.4 units.
Data: Colorado State University
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