Tuesday, 5 October 2004
Post mesoscale convective system convection
A single line of intense convective precipitation followed or preceded by a longer period of lighter rainfall typifies a normal precipitation structure of a Mesoscale Convective System (MCS) passage. However, some sequences of events involve the onset of secondary deep convection in the same geographical area soon after the passage of many MCSs. On occasion, this post MCS convection can result in an equivalent severe weather potential as with the main convective line of the parent MCS. Given the challenge of forecasting the occurrence of post MCS convection provides a motivation for a study to determine if there is a precursor signature for this type of convection based on operational datasets. All MCSs during the year 2003 are being investigated to develop a synoptic climatology of all events that do and do not develop post MCS convection. Given that one of the processes of an (MCS) is to remove gravitational instability over the region in which it passes, special attention is being paid in how the MCS environment acts to distribute the stabilized air in its wake. Initial results suggest that the strength of the ground-relative low-level flow along the trailing outflow boundary appear stronger for the post MCS convection events. The type of low-level forcing and the location of best instability relative to the parent MCS forms also provide some relation to the existence of post MCS convection. Signals conducive to the formation of post-MCS convection will be presented in terms how they modulate the wake of the stabilized post-MCS air.