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MMM SEMINAR NCAR

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An Examination of the Long-lived MCV of 10-13 June 2003

Tom Galarneau

Department of Earth and Atmospheric Sciences

University at Albany/SUNY

A noteworthy aspect of the period 5-14 June 2003 during BAMEX was the occurrence of episodic severe weather over the Plains that was triggered by disturbances embedded in an anomalously strong subtropical jet (STJ). The STJ began south of Hawaii, stretched eastward to New Mexico and Texas, then northeastward to the Canadian Maritime Provinces. Over the eastern Pacific, periodic disturbances moved along the STJ in an area where the criterion for barotropic instability was satisfied. These disturbances triggered and enhanced convective development as they crossed the Rockies and encountered moist unstable air.

At 0000 UTC 10 June (00Z/10), the leading upper-level STJ disturbance crossed the Rockies and helped organize diurnally forced convection over the higher terrain into a Mesoscale Convective System (MCS) over western New Mexico and eastern Texas. As the MCS moved southeast toward the Gulf of Mexico, mid-level vorticity associated with the MCS moved northeast toward Oklahoma. This mid-level vorticity triggered a second MCS over central Oklahoma by 00Z/11,which developed into a mature MCV by 18Z/11 over southern Missouri and northern Arkansas. This MCV could be tracked northeast to northern New York and southern Canada by 00Z/14. Noteworthy aspects of this MCV were: 1) its longevity, 2) its growth as a mid-level disturbance toward the surface, 3) its upshear tilt in lowest 6 km as evident from profiler observations, 4) its ability to reorganize convection, and 5) its interaction with an existing baroclinic zone over the Great Lakes. The purpose of this talk is to present the structural evolution of this long-lived MCV from its incipient phase to its transition into a frontal cyclone.

Tuesday, 21 June 2005, 3:30 PM

Refreshments 3:15 PM

NCAR-Foothills Laboratory

3450 Mitchell Lane

Bldg 2 Auditorium (Rm1022)