Generalizing the axisymmetric approach to hurricane intensity
John Persing, Colorado State Univ., Fort Collins, CO; and M. T. Montgomery
Efforts to describe the maximum intensity of a hurricane based only on parameters known outside of the hurricane or before formation, i.e. the a priori hurricane intensity or maximum potential intensity (MPI) problem, have shown some consistency with the observations, despite being constructed on purely axisymmetric principles. Real hurricanes, however, are only to some degree axisymmetric, with important asymmetric processes like environmental vertical wind shear, eyewall asymmetric features, wind-induced ocean cooling, to name a few. So while many assumptions are invoked to produce an MPI theory, we follow Emanuel's formulation and find an earlier stage in the derivation, a statement of combined balance of entropy and momentum in the boundary layer, is amenable to analysis of the effects of asymmetries on intensity. This statement of BL balance cannot serve as an a predictive theory for intensity, but it can serve as a descriptive theory. This is the starting point for evaluating the effect of inner-core asymmetries on intensity. We use a version of the RAMS modeling system that is idealized because it lacks ice physics, ocean interaction, and mean environemental shearing flows, but retains, of course, full three-dimensionality to test generalizations of the BL balance theory. .
Session 16B, Tropical Cyclone Intensity IV
Friday, 28 April 2006, 10:30 AM-12:30 PM, Regency Grand Ballroom
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