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]

^ ^a ^b "Measuring overall activity: The Accumulated Cyclone Energy (ACE) index". National Weather Service Climate Prediction Center. NOAA. Retrieved 30 January 2024.
^ "Climate Change Indicators: Tropical Cyclone Activity". United States Environmental Protection Agency. EPA. Retrieved 30 January 2024.
^ ^a ^b ^c "Glossary of NHC Terms". National Oceanic and Atmospheric Administration, National Hurricane Center and Central Pacific Hurricane Center. Retrieved 31 January 2024.
^ Gray, William Mason (26 May 1988). Forecast of Atlantic Seasonal Hurricane Activity for 1988 (PDF) (Report). Colorado State University. p. 13-14.
^ 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.
^ "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.

[NWS_CPC-1] "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.

[NHC_Glossary-3] "Glossary of NHC Terms". National Oceanic and Atmospheric Administration, National Hurricane Center and Central Pacific Hurricane Center. Retrieved 31 January 2024.

[1988_AHS-4] Gray, William Mason (26 May 1988). Forecast of Atlantic Seasonal Hurricane Activity for 1988 (PDF) (Report). Colorado State University. p. 13-14.

[SOC_1999-5] 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.

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