Future Changes in the Atlantic Warm Pool: An Implication for the Occurrence of Intense Hurricanes

The recent increase in the number of tropical cyclones (TCs) in the Atlantic basin has prompted the need for a better understanding of the factors controlling the increase. The Atlantic Warm Pool (AWP) is known to impact hurricane trajectories by shifting the origin of the storms eastward, and thus reducing the probability of landfall in the United States. However, it is still unclear if and how the AWP might affect hurricane intensifications. Therefore, in this research, the potential role of the AWP on hurricane intensification is investigated. This study goes beyond surface temperature profiles, and focuses on the potential significance of the depth and heat content of the AWP on the intensification of TCs. Using the Simple Ocean Data Assimilation reanalysis, and the HURDAT data set, a minimum ocean heat content (OHC) threshold is established for the intensification of TCs into category five hurricanes. The projected changes in the established minimum threshold under the IPCC RCP 4.5 and 8.5 scenarios are further analyzed using the ensemble OHC mean from 15 CMIP5 models. Results suggest that OHC will continue to rise in accordance with the net gain in incoming radiation attributed to greenhouse gas emissions (GHG). Speculations of the possible expansion of a well-developed AWP region capable of sustaining category 5 hurricanes are given. Results are also indicative of a higher probability of major hurricane occurrence and land-falling due to the changes in the geographical extent of the AWP. Although other atmospheric variables have to be taken into account, these preliminary results primarily suggest that a high OHC in the AWP area may be a necessary condition for a TC to develop into a category five hurricane, indicating that subsurface temperature profiles may be useful as predictors when forecasting the intensity of a TC.