Hurricane and Tropical Cyclones

Accumulated Cyclone Energy (ACE)

Atlantic
East Pacific
West Pacific
Indian Ocean
Southern Hemisphere
Global

Updated: April 24, 2014

Atlantic Tropical Cyclones of 2014

Tropical Cyclone Name Start Date Max Wind Speed (kt) ACE (104 kt2)

East Pacific Tropical Cyclones of 2014

Tropical Cyclone Name Start Date Max Wind Speed (kt) ACE (104 kt2)

10 Things We Know About Accumulated Cyclone Energy

1. There is no evidence of a systematic increasing or decreasing trend in ACE for the years 1970-2012.

2. There is a cyclical variation in the ACE of 6 and 12 months' length.

3. The contribution of ACE from the Eastern and Western Pacific is approximately 56% of the total ACE.

4. The contribution of ACE from the Atlantic Ocean is approximately 13% of the total ACE.

5. The minimum and maximum values of ACE per month are respectively 1.8 and 266.4.

6. The average value of ACE per month is 61.2.

7. The minimum and maximum values of ACE per year are respectively 416.2 and 1145.0.

8. The average value of the ACE per year is 730.5.

9. The total of ACE for 2012 through September is 540.8.

10. There is a correlation of ACE between some oceans.

What is Accumulated Cyclone Energy?

Accumulated cyclone energy, or "ACE," is used to express the activity and destructive potential of individual tropical cyclones and entire tropical cyclone seasons. ACE is calculated as the square of the wind speed every 6 hours, and is then scaled by a factor of 10,000 for usability. The ACE of a season is the sum of the ACE for each storm and takes into account the number, strength, and duration of all the tropical storms in the season. The caveat to using ACE as a measure of the activity of a season is that it does not take the size of the hurricane or tropical storm into account. The damage potential of a hurricane is proportional to the square or cube of the maximum wind speed, and thus ACE is not only a measure of tropical cyclone activity, but a measure of the damage potential of an individual cyclone or a season.

Jeff Masters' Blog

Category 4 Tropical Cyclone Ita Hits Queensland, Australia

By Dr. Jeff Masters

Category 4 Tropical Cyclone Ita powered ashore along Australia’s Queensland coast near 9 pm local time (10 UTC) on Friday with sustained winds rated at 145 mph by the Joint Typhoon Warning Center. Fortunately, Ita appeared to be undergoing an eyewall replacement cycle at landfall, and was probably weaker than a Category 4 storm when it came ashore. Ita hit a portion of the coast that is relatively lightly populated, and damage should be nowhere near the $3.6 billion price tag of Tropical Cyclone Yasi of February 2, 2011.

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