The chart at right shows the Accumulated Cyclone Energy (ACE) for every tropical cyclone formed during the season. The ACE is, broadly speaking, a measure of the energy of the hurricane multiplied by the length of time that existed, and of particularly intense hurricanes. The longer lasting and more intense the hurricane it meant a higher RCTs. The value of ACE is only calculated for tropical systems of 34 knots (39 mph, 63 km / h) or more tropical storms and strong.