2005 Atlantic Hurricane Season Statistics - Accumulated Cyclone Energy (ACE)

Accumulated Cyclone Energy (ACE)

The table to the right shows the tropical storms of the 2005 season ranked from highest to lowest Accumulated Cyclone Energy (ACE), given to three significant figures. The total for the season was 248 x 104 kt2 which is the highest seasonal ACE value recorded. It is slightly higher than that for 1950 season which had an ACE of 243 x 104 kt2. ( the final storm of the season, Zeta, lasted into 2006. In calculating the seasonal ACE, the whole ACE of Zeta, including the contribution made in 2006, was used.)

ACE measures a combination of both the strength and duration of a tropical cyclone, so longer-lasting storms may accumulate more ACE than stronger storms with shorter durations. This discrepancy is most obvious in the comparatively high ACE value of Hurricane Emily to Hurricanes Katrina and Rita: Emily was not as strong as either storm, but formed out in the Atlantic and made a long track across the Caribbean Sea before making landfall. Katrina and Rita, however, both developed in the Bahamas, close to the U.S. mainland, and lasted for much shorter periods of time. In addition, Ophelia and Epsilon are high for their intensity because they maintained themselves for a long period of time and were slow to build and dissipate, as neither was ever more intense than a Category 1 storm.

The average ACE per storm in 2005 was actually close to the seasonal average. In comparison with previous seasons with high seasonal ACE values, relatively few strong, long-lasting storms, such as Cape Verde-type hurricanes, formed. Thus, although the number of named storms in 2005 was about 40% greater than that in any season since 1950, the seasonal ACE was only marginally greater than the previous record, set in 1950 itself, when the average ACE per storm was approximately double that of 2005.

Source: Best Track data from the Tropical Cyclone Reports.