| As part of a National Science Foundation and NOAA sponsored research project, coupled ocean and atmosphere measurements were acquired during the passage of Tropical Cyclones (TC) Isidore (18-25 Sept 2002) and Lili (28 Sept- 4 Oct) from the NOAA WP-3Ds in the Caribbean Sea and Gulf of Mexico. For both TCs, the aircraft-based strategy sampled pre-storm, storm and post-storm current, temperature and salinity conditions in the Caribbean Sea and the Gulf of Mexico in and north of the Yucatan straits using airborne expendable ocean profilers. Profiles of temperature, wind and humidity were acquired simultaneously during the storm flights to examine the atmospheric boundary layer structure as well as remotely sensed surface conditions of waves and winds.As Isidore moved along the periphery of pre-storm ocean grids across the Yucatan Straits, he intensified to a Category 3 storm. Preliminary results suggest that upwelling and vertical mixing processes were balanced by the horizontal advection of thermal gradients by the Loop Current. Thus, no significant cooling was observed in the straits. By contrast, the water over the Yucatan shelf significantly cooled as the storm made landfall on the Yucatan Peninsula as the TC was downgraded to a tropical storm. The storm subsequently moved northward and created an area of broad cooling with ~28oC SSTs prior to landfall in Louisiana on 25 Sept. Lili (28 Sept) formed in the northwest Caribbean Sea and followed Isidore's track. Due to deep, warm layers in this oceanic regime, no significant SST cooling was observed from the ocean profilers. Lili then moved over the western tip of Cuba and into the Gulf of Mexico directly over the pre- and post-Isidore ocean grids. During this period, she intensified to a Category 4 hurricane just north of the Loop Current boundary. As in the Isidore case, no significant cooling was observed in the Loop Current, however, north of this boundary, SSTs decreased by an additional ~2oC due to shear-induced ocean mixing processes. As Lili interacted with the cooler wake induced by Isidore a few days prior in the northern Gulf of Mexico, she suddenly weakened in strength prior to landfall on 4 Oct. In this context, the 3-dimensional upper ocean heat budgets were important in documenting processes that affected air-sea fluxes and hence TC intensity changes in these two storms. |
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