Are there regimes in Tropical Cyclone Activity in the North Atlantic?
S. D. Aberson, Hurricane Research Division, AOML, Miami, FL The recent surge in tropical cyclone activity in the North Atlantic Ocean has led to a flurry of papers concerning its cause, whether anthropogenic global warming, natural variability, or a combination. Holland and Webster (2007), has a good background and reference list on this topic. In that particular study, the authors found that North Atlantic Ocean tropical storm, hurricane, and major hurricane numbers during the last century exhibited three stable and distinct regimes separated by sharp transitions. Each regime has about 50% more tropical storms and hurricanes annually than the previous one and is associated with a distinct sea surface temperature (SST) range in the eastern Atlantic Ocean, defined as the region 5-25oN, 55-20oW. Notwithstanding the question of how accurate the data are, an issue well addressed by Holland and Webster (2007), these conclusions are based upon an incorrect interpretation of the data due to a