26th Conference on Hurricanes and Tropical Meteorology


Subtropical jet disturbances as initiators of convection during BAMEX

Lance F. Bosart, University at Albany/SUNY, Albany, NY; and T. J. Galarneau

The Bow Echo and Mesoscale Convective Vortex Experiment (BAMEX) was conducted from 18 May to 7 July 2003. The 5-14 June 2003 period during BAMEX featured an anomalously strong STJ across the southern US from California to the lower Mississippi Valley. Multiple convective disturbances originated over the BAMEX domain in conjunction with transient disturbances embedded in the STJ. The regularity of these embedded transient disturbances over the eastern Pacific suggests that barotropic instability may have played a role in their origin. Once these transient disturbances were inland and east of the Rockies, they acted to trigger organized convective systems, probably in response to an increase in the Rossby penetration depth in response to decreasing stability and increasing moisture.

A particularly long-lived MCV formed over Oklahoma near 0600 UTC 11 June at the northern end of a squall line that was triggered by a transient disturbance embedded in the STJ. This MCV could be tracked northeastwards to Ohio. It was noteworthy for its upshear tilt, for growing upscale, and for strengthening as it attached itself to a surface baroclinic zone situated just to the south of the Great Lakes. As the MCV attached itself to the surface baroclinic zone it also acquired frontal structure. The surface potential temperature gradient was locally enhanced in the warm frontogenesis region and where northerly flow off the cold waters of lake Michigan surged southward.

The purpose of this poster will be to present the results of the 11-12 June 2003 MCV case study and to show the evolution and structure of the transient disturbances embedded in the subtropical jet.

extended abstract  Extended Abstract (1.7M)

Poster Session 1, Posters
Wednesday, 5 May 2004, 1:30 PM-1:30 PM, Richelieu Room

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