Interaction of a Jetstream with a Squall Line Originating Along an Upper Level Cold Frontal Boundary as Determined from a Comparison of Model and Quad-Doppler Analyses

On 8 June 2003, an expansive line of convection along an upper level cold front was sampled during the Bow Echo and Mesoscale Convective Vortex Experiment (BAMEX). The National Oceanic and Atmospheric Administration (NOAA) P-3 aircraft and the National Research Lab (NRL) P-3 aircraft simultaneously sampled the trailing and leading edge of this MCS, respectively with X-band Doppler radars. Data from these two airborne radars have been synthesized to produce a quad-Doppler analysis of the developing 8 June MCS, yielding detailed three-dimensional wind profiles of the system.

A simulation of this MCS was conducted using the Weather Research and Forecasting (WRF) model utilizing a 1 km nested grid centered over the quad-Doppler domain, along with 3 km and 9 km outer nests to capture progressively larger synoptic scale patterns.

The quad-Doppler analysis reveals that the convective line was oriented parallel to, and embedded within, the upper level jetstream. To assess the interaction between the MCS and jetstream, vertical cross sections orthogonal to the simulated convective line were analyzed, which indicate strong transport of low momentum air upward into the jetstream via the convective updraft. Such an interaction is clearly evident in the quad-Doppler analysis, as small scale deviations and eddies within the upper level jetstream are observed. An analysis of this complex interaction will be presented, complete with a discussion of possible feedbacks induced within the MCS and jetstream.