Organization and Structure of Clouds and Precipitation on the Mid-Atlantic Coast of the United States. Part VI: The Synoptic Evolution of a Deep Tropospheric Frontal Circulation and Attendant Cyclogenesis

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  • 1 Atmospheric Sciences Department, University of Washington, Seattle, Washington
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Abstract

Interactions between an upper-level frontal system and an initially weak surface cold front resulted in the production of a deep, precipitating frontal structure over the south Atlantic states on 26–27 January 1986. Attendant with the intensification of the frontal circulation was the development of an intense marine cyclone off the Delmarva peninsula. The increase in frontal-circulation strength is attributed to a favorable vertical superposition of the surface frontal trough and the upper-level frontogenetic horizontal deformation field that resulted in a deep column of divergence over the surface frontal trough. The surface cyclone developed partly, and indirectly, in response to the increase in warm-air advection in the lower stratosphere, which was directly related to an increase in the slope of the dynamic tropopause. The increase in the slope of the tropopause is hypothesized to have been the result of the combined effect of adiabatic advection of low tropopause height in the cold air of the upper trough and the latent heating associated with the onset of deep convection during the frontal development.

Abstract

Interactions between an upper-level frontal system and an initially weak surface cold front resulted in the production of a deep, precipitating frontal structure over the south Atlantic states on 26–27 January 1986. Attendant with the intensification of the frontal circulation was the development of an intense marine cyclone off the Delmarva peninsula. The increase in frontal-circulation strength is attributed to a favorable vertical superposition of the surface frontal trough and the upper-level frontogenetic horizontal deformation field that resulted in a deep column of divergence over the surface frontal trough. The surface cyclone developed partly, and indirectly, in response to the increase in warm-air advection in the lower stratosphere, which was directly related to an increase in the slope of the dynamic tropopause. The increase in the slope of the tropopause is hypothesized to have been the result of the combined effect of adiabatic advection of low tropopause height in the cold air of the upper trough and the latent heating associated with the onset of deep convection during the frontal development.

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