Connections between atmospheric outflow and the upper ocean thermal structure in Hurricane Irene (2011)

The ocean has long been recognized as the heat source fueling the Carnot engine that is a tropical cyclone (TC). While the magnitude of the contribution remains an area of active research, coupled numerical forecast models have begun to incorporate ocean observations collected during aircraft weather reconnaissance missions to enhance the accuracy of TC track and intensity forecasts. The ocean impacts the TC intensity through surface heat fluxes, which increase the buoyancy of near-surface air and enhance vertical motion and the development of the secondary circulation.

Here, links between the heat supplied by the upper ocean, the magnitude and prevalence of deep convection in the TC inner core, and the magnitude and orientation of the TC outflow are explored in a combined model and observational study of Hurricane Irene (2011). Hurricane Irene was selected due to the ready availability of observational data collected and the COAMPS-TC model run in real time during the Training and Research in Oceanic and atmospheric Processes In tropical Cyclones (TROPIC) 2011 field program.

In the ocean, changes in ocean heat content (OHC) are compared to surface fluxes from the COAMPS-TC analyses. These changes are compared to the development of tropopause penetrating convection, as well as changes in the upper-level outflow. Also, the evolution of the secondary circulation will be compared to the evolution of the primary circulation. Lead and lag relationships will be investigated both within the secondary circulation and between the primary and secondary circulations. Results of this research will be presented and will serve as a baseline for further study during the Office of Naval Research Tropical Cyclone Intensity field program in 2015.