SATELLITE-DERIVED LATENT HEATING DISTRIBUTION AND ENVIRONMENTAL-INFLUENCES IN HURRICANE-OPAL (1995)

The total (i.e., convective and stratiform) latent hear release (LHR) cycle in the eyewall region of Hurricane Opal (October 1995) has been estimated using observations from the F-10, F-11, and F-13 Defense Met eorological Satellite Program Special Sensor Micromave/Imagers (SSM/Is ). This LHR cycle occurred during the hurricane's rapid intensificatio n and decay stages (3-5 October 1995). The satellite observations reve aled that there were at least two major episodes in which a period of elevated total LHR (i.e., convective burst) occurred in the eyewall re gion. During these convective bursts, Opal's minimum pressure decrease d by 50 mb and the LHR generated by convective processes increased, as greater amounts of latent heating occurred at middle and upper levels . It is hypothesized that the abundant release of latent heat in Opal' s middle- and upper-tropospheric region during these convective burst episodes allowed Opal's eyewall to become more buoyant, enhanced the g eneration of kinetic energy and, thereby, rapidly intensified the syst em. The observations also suggest that Opal's intensity became more re sponsive to the convective burst episodes (i.e., shorter time lag betw een LHR and intensity and greater maximum wind increase) as Opal becam e more Intense. Analyses of SSM/I-retrieved parameters, sea surface te mperature observations, and the European Centre for Medium-Range Weath er Forecasts (ECMWF) data reveal that the connective rainband (CRB) cy cles and sea surface and tropopause temperatures, in addition to large -scale environmental forcing, had a profound influence on Opal's episo des of convective burst and its subsequent intensity. High sea surface (29.7 degrees C) and low tropopause (192 K) temperatures apparently c reated a greater potential for Opal's maximum intensity. Strong horizo ntal moisture flux convergence within Opal's outer-core regions (i.e., outside 333-km radius from the center) appeared to help initiate and maintain Opal's CRBs. These CRBs, in turn, propagated inward to help g enerate and dissipate the eyewall convective bursts. The first CRB tha t propagated into Opal's eyewall region appeared to initiate the first eyewall convective burst. The second CRB propagated to within ill km of Opal's center and appeared to dissipate the first CRB, subjecting i t to subsidence and the loss of water vapor flux. The ECMWF upper-trop ospheric height and wind analyses suggest that Opal interacted with a diffluent trough that initated an outflow channel, and generated high values of upper-tropospheric eddy relative angular momentum flux conve rgence. The gradient wind adjustment processes associated with Opal's outflow channel, in turn, may have helped to initiate and maintain the eyewall convective bursts. The ECMWF analyses also suggest that a dry air intrusion within the southwestern quadrant of Opal's outer-core r egion, together with strong vertical wind shear, subsequently terminat ed Opal's CRB cycle and caused Opal to weaken prior to landfall.