Hurricane and Tropical Cyclones

Accumulated Cyclone Energy (ACE)

East Pacific
West Pacific
Indian Ocean
Southern Hemisphere

Updated: July 25, 2014

Average year:
2014 year-to-date:

Atlantic Tropical Cyclones of 2014

Tropical Cyclone Name Start Date Max Wind Speed (kt) ACE (104 kt2)
ARTHUR July 01, 2014 85 6.785
TWO July 01, 2014 0 0

East Pacific Tropical Cyclones of 2014

Tropical Cyclone Name Start Date Max Wind Speed (kt) ACE (104 kt2)
AMANDA May 23, 2014 135 18.065
BORIS June 03, 2014 35 0.3675
CRISTINA June 10, 2014 130 12.9025
DOUGLAS June 30, 2014 40 2.7975
ELIDA June 30, 2014 45 0.89
FAUSTO July 07, 2014 40 0.8475
GENEVIEVE July 25, 2014 40 0.2825

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 3 Typhoon Rammasun hits the Philippines

By Dr. Jeff Masters

Category 3 Typhoon Rammasun powered ashore in the Philippines in the Bicol Region of Luzon Island near 5 am EDT on Tuesday, bringing sustained winds near 125 mph and torrential rains. Rammasun was the first typhoon to strike the Philippines since devastating Category 5 Super Typhoon Haiyan in November 2013. Rammasun's eye passed just north of Samar Island where Haiyan initially made landfall, and passed just north of Legaspi on Luzon, dropping the pressure to 966 mb near 10 UTC.

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