NOAA's National Weather Service Weather Forecast Office

Since 1994, the COMET Cooperative Project between WFO St. Louis and Saint Louis University has allowed us to investigate the spectrum of storm evolutions associated with bow echoes and squall lines which produced damaging straight-line winds, and non-supercell tornadoes across the Mid-Mississippi Valley Region.  In many of our cases, wind damage stretched over 150 to 200 miles in length.  Over one third of our cases occurred during the late night or early morning hours while the remaining MCS events formed either during mid day or the late afternoon.   In many of our cases,  the presence of an external  boundary caused by earlier convection or a quasi-stationary frontal boundary was documented. Such boundaries played a role in either intensifying a pre-existing vortex or caused a vortex to rapidly form and intensify. We will further expand upon this issue with the cases shown below.

The information presented is a sample of the MCS bowing events we studied over the past several years.   Each case will begin with a brief overview of the storm's pre-convective environment.  This part will be followed by specific segments of the storm's evolution. In many cases, we will present interesting aspects of the storm reflectivity and Doppler velocity structures, and vortex evolutions which may form along the leading edge or northern side of the bowing segment.  Rotational velocity (Vr) and Mid-Altitude Radial Convergence (MARC) time-height traces will be shown to view the evolution of tornado(non-tornadic) vortices and the MARC velocity signature.  Some of the cases presented here might be good candidates for instructional use. If you have questions about the content in each case, please feel free to contact Gary Schmocker or Ron Przybylinski.

Thanks

Severe Case #1: 25 May 1996
     Preconvective Environment
     Radar Analysis

Severe Case #2: 14 June 1998
    Preconvective Environment
     Radar Analysis

Severe Case #3: 18 June 1998

More cases will be forth-coming.