6a.4 Impact of a Warm Ocean Eddy’s Circulation on Hurricane-induced Sea Surface Cooling with Implications for Hurricane Intensity

Evaporation from the sea surface, primarily within a hurricane’s core, provides the heat energy required to intensify and maintain the storm (e.g. Cione and Uhlhorn 2003, Emanuel 2003, and references therein). If the sea surface temperature (SST) decreases within the storm core, so does the heat energy available to the storm. Generally, in the deep ocean, SST cooling within the storm core occurs primarily because the storm’s surface winds impose a wind stress on the upper ocean, and the resulting ocean current shear generates turbulent mixing and entrainment of cooler water into the upper oceanic mixed layer from below (e.g. Ginis 1995, 2002, and references therein). In addition, for slowmoving hurricanes especially, the storm’s cyclonic wind stress generates upper-ocean current divergence and upwelling, which in turn may contribute significantly to storm-core SST cooling (Price 1981; Yablonsky and Ginis 2009, hereafter YG09). Evaporative heat flux to the atmosphere, while vital to the hurricane, contributes far less than mixing/entrainment to storm-core SST cooling in the deep ocean (Price 1981; Shen and Ginis 2003; D’Asaro et al. 2007). Since the SST in advance of a hurricane cannot account for the storm-induced SST cooling, upper oceanic heat content (OHC, also known as tropical cyclone or hurricane heat potential) ahead of the storm has become more widely accepted than pre-storm SST as a measure of the ocean energy available to the hurricane for future storm intensification and/or maintenance (e.g. Mainelli et al. 2008; Shay et al. 2000). l Leipper and Volgenau ws: OHC, original y defined by (1972), can be calculated as follo