Large-Scale Characteristics of Tropical Cyclones

William M. Frank Department of Environmental Sciences, University of Virginia, Charlottesville 22903

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Abstract

Rawinsonde composites from the west Pacific and West Indies are used to analyze some of the properties of tropical cyclones and their influences upon larger scale circulations. Composites of storms with different intensities are compared to determine the scales of different circulation features. The radial wind and vertical motion anomalies which occur during the transition from pre-storm convective system to mature tropical cyclone are found to be confined to the inner 6° and 2°, respectively, while the tangential circulation increases at least to the edge of the 15° grid.

Tropical cyclones are found to be net sources of kinetic energy and sinks of relative angular momentum. Of the storms studied, only typhoons made significant contributions to large-scale meridional fluxes of westerly momentum and kinetic energy through a plane 10° north of the storm centers. Fluxes of other quantities were negligible. All of the tropical weather systems were found to be largely thermodynamically self-contained when viewed on a scale of 12° radius.

The wake regions of westerly-moving tropical cyclones are favorable locations for subsequent tropical cyclogenesis while the path areas ahead of the cyclone are generally suppressed for storms exhibiting significant upper level outflow to the southwest.

Abstract

Rawinsonde composites from the west Pacific and West Indies are used to analyze some of the properties of tropical cyclones and their influences upon larger scale circulations. Composites of storms with different intensities are compared to determine the scales of different circulation features. The radial wind and vertical motion anomalies which occur during the transition from pre-storm convective system to mature tropical cyclone are found to be confined to the inner 6° and 2°, respectively, while the tangential circulation increases at least to the edge of the 15° grid.

Tropical cyclones are found to be net sources of kinetic energy and sinks of relative angular momentum. Of the storms studied, only typhoons made significant contributions to large-scale meridional fluxes of westerly momentum and kinetic energy through a plane 10° north of the storm centers. Fluxes of other quantities were negligible. All of the tropical weather systems were found to be largely thermodynamically self-contained when viewed on a scale of 12° radius.

The wake regions of westerly-moving tropical cyclones are favorable locations for subsequent tropical cyclogenesis while the path areas ahead of the cyclone are generally suppressed for storms exhibiting significant upper level outflow to the southwest.

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