Department of Environmental Sciences

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Seminar Abstracts
Environmental Sciences Seminar Abstract            

  Evolution and Dynamical Processes of Solitary Precipitation Bands Within the Comma-Head Region of Northeast U.S. Cyclones
Brian Colle
Stony Brook University

Intense solitary precipitation bands are frequently observed in the comma-head sector of extratropical cyclones. This research utilizes unique Dual-Doppler radar observations, high-resolution analyses, model simulations, and potential vorticity (PV) inversions to explore the evolution and dynamical processes of these solitary precipitation bands. Analysis of 36 banded events using case study and composite approaches reveals a common cyclone evolution and associated band life cycle. A majority of banded events develop in the left exit region of an upper jet, in a region of concentrated upper-PV advection along the poleward edge of an upper PV "hook." Band formation occurs as midlevel frontogenesis rapidly increases along a mesoscale trough that extends poleward of the 700-hPa low. At the same time, conditional stability is reduced near 500 hPa due to differential horizontal temperature advection in moist southwest flow ahead of the approaching upper trough. Band maturity is marked by increasing conditional stability, but a compensating increase in frontogenetical forcing. PV inversions and model simulations with varying degrees of latent heating reveal that latent heating associated with the band itself is critical to the development and maintenance of the frontogenetical forcing for the band. Band dissipation occurs as the frontogenesis weakens and the conditional stability is restored. PV inversions show that the band is susceptible to changes in the meso-alpha scale flow associated with the formation of diabatic PV anomalies east of the band, which contribute to frontolysis and band dissipation.

Last updated: 04/21/2009