The role of warm sector convection in the development of mesoscale banded snowfall.

摘要

Anecdotal evidence from National Weather Service area forecast discussions suggests that, in some instances, warm sector convection may inhibit moisture transport to areas of snowfall further north. This study investigates the validity of this hypothesis using a three domain MM5 simulation, with grids of 36, 12, and 4 km. Two cases are simulated. First, physical processes involved in the production of mesoscale banded snowfall and the initiation and maintenance of convection will be discussed. Second, diabatic heating output from MM5 is used to compute a potential vorticity (PV) budget to investigate the diabatically generated low-level PV produced by convection. Third, the diabatically produced PV is isolated and inverted using a piecewise technique to analyze the effects of this PV anomaly on the large scale flow. Lastly, a Lagrangian moisture budget is calculated along trajectories emanating from the convection to determine the impact of convection on northward moisture transport.; In each case, convection does little to inhibit the production of banded snowfall. Convection actually serves to enhance some physical processes that lead to banded snow. Investigation of the two cases suggests that there is a large amount of variability in the impacts convection can have on both mesoscale and large-scale processes that result in banded snowfall. This work provides examples of the processes that must be analyzed in a situation with banded snowfall and convection, as well as methodologies for appropriately analyzing these processes.