Fewer storms, but the storms we do get will be on average larger.
http://www.agu.org/pubs/crossref/2010/2010GL042518.shtml
Projection of changes in tropical cyclone activity and cloud height due to greenhouse warming: Global cloud-system-resolving approach
Abstract: Tropical cyclone (TC) activity change due to global warming (GW) has been investigated using general circulation models. However, they involve uncertainty in treating the ensemble effects of deep convections. Here we sidestep such uncertainty by using a global cloud-system-resolving model (GCRM) and assess TC changes with a time-slice experiment for the present-day and future GW experiments spanning 5 months each. The results support the Intergovernmental Panel on Climate Change Fourth Assessment Report; reduction in global frequency but increase in more intense TCs. Consistent with recent studies, frequency is reduced over the North Atlantic due to intensified vertical wind shear. Over the Pacific, frequency is almost unchanged and the genesis location shifts eastward under the prescribed El-Niño like sea surface temperature change. With the GCRM's advantage of representing mesoscale properties, we find that the cloud height becomes taller for more intense TCs and that this relationship is strengthened with GW.
