Abstract
We present an observational study of the possible effects of sea surface fluxes of latent and sensible heat on rapidly deepening cyclones over the western Atlantic Ocean. Based on the recognition that conventional operational models (specifically the LFM), until very recently, routinely underpredicted the intensity of such cyclogenesis events, we form the hypothesis that this failure may be systematically related to the amount of warming that can occur from the ocean, through sensible heating and the condensation of evaporated sea water aloft. We test this idea for a sample of 29 explosive cases occurring between 1981 and 1985. Results indicate a strong correlation between the underestimate of 24 hour central pressure fall by the model and the increase in 1000–500 mb thickness that would occur if that layer were to become neutrally stable to surface parcels saturated at sea surface temperature. We find the correlation particularly robust for the more rapid deepeners of the sample.
In the second portion of this study, the climatology of the difference between this “potential saturation thickness” and the actual 1000–500 mb thickness is calculated. From twice daily data extending over 15 years (1963–77), the mean is computed for positive values of thickness difference only. Regions of large mean values correspond quite well with regions of frequent explosive cyclogenesis.
