A Composite Analysis of the Core of a Mature Hurricane

William M. Frank Department of Meteorology, The Pennsylvania State University, University Park, PA 16802

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Abstract

An unusually large quantity of aircraft data was obtained within the core of Hurricane Frederic (1979). These data are combined with Powell's surface observations of the same storm and composited. The data are sufficiently abundant to allow three-dimensional kinematic analyses of poorly documented parameters such as divergence and vertical velocity. Patterns of related but independently determined parameters such as radar reflectivities, cloud water concentrations and kinematically-derived vertical velocities agree well. Diagnostic budget analyses of sensible heat and angular momentum are computed for the storm inflow layer.The analysis provides a unique quantitative picture of the inflow layer of a mature, asymmetric hurricane.

The depth of the inflow layer decreases with decreasing radius. As a result, surface drag coefficients derived from angular momentum budgets do not appear to increase with increasing wind speed. The sensible heat budget shows downward subgrid-scale heat fluxes near cloud base and indicates that the net flux of sensible heat from the sea to the air in the core region is probably on the order of 50 W m2, which is much smaller than most previous estimates.

Abstract

An unusually large quantity of aircraft data was obtained within the core of Hurricane Frederic (1979). These data are combined with Powell's surface observations of the same storm and composited. The data are sufficiently abundant to allow three-dimensional kinematic analyses of poorly documented parameters such as divergence and vertical velocity. Patterns of related but independently determined parameters such as radar reflectivities, cloud water concentrations and kinematically-derived vertical velocities agree well. Diagnostic budget analyses of sensible heat and angular momentum are computed for the storm inflow layer.The analysis provides a unique quantitative picture of the inflow layer of a mature, asymmetric hurricane.

The depth of the inflow layer decreases with decreasing radius. As a result, surface drag coefficients derived from angular momentum budgets do not appear to increase with increasing wind speed. The sensible heat budget shows downward subgrid-scale heat fluxes near cloud base and indicates that the net flux of sensible heat from the sea to the air in the core region is probably on the order of 50 W m2, which is much smaller than most previous estimates.

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