Using the WRF Model to Identify Genesis Mechanisms for Bow Echo Mesoscale Vortices
Michael St.Laurent Jr., Lyndon State College, Littleton, NH; and N. T. Atkins
The Weather Research and Forecasting Model (WRF) was used to simulate the June 10, 2003 Saint Louis bow echo during the Bow Echo and MCV Experiment (BAMEX) to gain a better understanding of mesovortex genesis. Two distinct vortex generation processes were found from the simulations. The first process tilts streamwise vorticity from downdraft outflow to create an individual vortex with positive vertical vorticity. A second process forms vortex couplets by tilting vortex lines oriented north to south along the gust front by a local maximum in updraft. The couplet will have a cyclonic vortex to the north, with an anticyclonic vortex to the south. All vortices were found to strengthen after their formation by updraft stretching. Vortex generation methods were found to relate to bow echo stage. Single, positive only vortices were most prevalent during the cellular and mature bow echo stages. Vortex couplets were only found to be most prevalent during the early stages of bow echo development.
To confirm the model results, the simulations were compared to four observational studies of bow echoes referenced in the literature. Radar data showed cyclonic only vortices throughout the life cycle of the bow echo, with the strongest forming during the mature stage. During the early bow echo stage, radar observations showed suggestion of possible vortex couplets.
Poster Session 1, Student Conference General Poster Session
Sunday, 20 January 2008, 5:30 PM-7:00 PM, Exhibit Hall B
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