An important measure of the total seasonal activity is NOAA’s Accumulated Cyclone Energy (ACE) index, which accounts for the collective intensity and duration of Atlantic tropical storms and hurricanes during a given hurricane season. The ACE index is also used to define above-, near-, and below-normal hurricane seasons. A value of 117% of the median (Median value is 87.5) corresponds to the lower boundary for an above-normal season.
For the 2005 Atlantic hurricane season the outlook calls for an extremely active season, with the seasonal ACE index forecasted to range from 180%-270% of the median. This range is above the 175% baseline that Goldenberg et al. (Science, 2001) use to define a hyperactive season. The outlook also calls for a seasonal total of 18-21 tropical storms, with 9-11 becoming hurricanes, and 5-7 of these becoming major hurricanes [categories 3-4-5 on the Saffir-Simpson scale]. Because the ACE index does not directly account for the numbers of tropical storms, hurricanes, and major hurricanes, the predicted ACE range can verify even if these numbers fall outside their predicted ranges.
