Hurricane and Tropical Cyclones

Accumulated Cyclone Energy (ACE)

East Pacific
West Pacific
Indian Ocean
Southern Hemisphere

Updated: September 02, 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
BERTHA August 01, 2014 70 5.2325
CRISTOBAL August 24, 2014 75 7.6975
FIVE August 24, 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 100 3.4025
HERNAN July 26, 2014 65 2.98
ISELLE July 31, 2014 120 23.1
JULIO August 04, 2014 105 21.95
KARINA August 13, 2014 70 12.6775
LOWELL August 19, 2014 65 5.0175
MARIE August 22, 2014 140 20.52

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

Invest 99L Organizing Over Gulf of Mexico

By Dr. Jeff Masters

The center of a broad area of low pressure associated with tropical wave 99L is now over the warm waters of the Gulf of Mexico's Bay of Campeche, and the disturbance is growing more organized as it heads west-northwest at about 10 mph. Sea Surface Temperatures (SSTs) were very warm, near 30°C (86°F), the atmosphere was moist, and wind shear was moderate, 15 - 20 knots. These conditions are favorable for development.

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