https://www.cpc.ncep.noaa.gov/products/outlooks/hurricane2003/August/background_information.html
Accumulated Cyclone Energy Index
by the way on a related topic, mets in the west pac have been talking about modifying the SS scale to add a Cat 6 for super typhoons of 192 mph or higher.
that reminds me of way back when in the original tornado Fujita scale there was an F6 category for tornadoes from 320 mph to the speed of sound (640 mph).
it was dropped because no tornado ever reached F6, but for super typhoons in the west pac, there are a few that have reached 192 mph or higher (and in the east pac too.)