Physical Processes Governing the Rapid Deepening Tail of Maritime Cyclogenesis

The positively skewed distribution of maritime cyclone maximum deepening rates is investigated for cyclones as a class rather than through individual case study, using a series of experiments employing perpetual January simulations from the global version of the fifth-generation Pennsylvania State University NCAR Mesoscale Model (MM5). The relative roles of latent heat release, baroclinic instability, and boundary layer friction in producing this tail behavior are elucidated. The experiments reveal that the strongest maritime storms are the result of the baroclinic dynamics of the relative few being preferentially enhanced through feedback with the available moisture. Strong baroclinic forcing, in the absence of this moisture availability and resultant latent heating, does not produce the skewed rapid deepening tail behavior. An increase in surface roughness and accompanying friction in the maritime region provides only a slight brake on cyclone development. The results support previous research that argued that the rapid deepening tail is evidence of a fundamentally distinct pattern of behavior characteristic of maritime cyclones compared to continental systems, and that this behavior is the result of process interactions (baroclinic dynamics and latent heat release) rather than the nature of the data.