 The season 's activity was reflected with an accumulated cyclone energy ( ACE ) rating of 77 , which is slightly below the 1950 – 2000 average of 94 @.@ 7 . ACE is , broadly speaking , a measure of the power of the hurricane multiplied by the length of time it existed , so storms that last a long time , as well as particularly strong hurricanes , have high ACEs . It is only calculated for full advisories on tropical systems at or exceeding 34 knots ( 39 mph , 63 km / h ) or tropical storm strength . 
