Isn't the primary suppressing factor this year be the weak El Nino? The climate models must not yet model the triggering mechanisms for El Nino or they would have predicted them. My second point is that the distribution of water vapor particularly in the upper troposphere is the major projected global warming feedback. Modeling of tropical convection including tropical storms will be essential to determining the extent of warming above the 1C warming anticipated from man-made CO2.
That's been mentioned in what I read for suppressing late season hurricanes, but the main reason for the early season suppression was a high shear environment. The storms were getting ripped apart before circulation could get established.