High Resolution Measurements of Cyclone Structure: the Profiling of Winter Storms Project (PLOWS)

A two year field campaign, Profiling of Winter Storms (PLOWS), was completed during the 2008-09 and 2009-10 winters to study the dynamic and microphysical processes that govern the spatial and temporal variability of precipitation in the warm frontal and “wrap-around” deformation zone of continental extratropical cyclones over the central United States. Here the preliminary findings of PLOWS are reviewed focusing on exceptionally high, ~15 meter horizontal resolution measurements of precipitation band structure. The banded structure is examined by combining high-resolution, vertical-plane observations of radar reflectivity and Doppler velocity from the Wyoming Cloud Radar and in situ microphysics measurements made onboard the NCAR/NSF C130 with ground-based observations from a vertically-pointing X-band Doppler radar and wind profiler. These measurements are related to the larger scale cyclone structure in order to provide an interpretation of the dynamics of these bands consistent with the thermodynamic and kinematic measurements.

Several outstanding features of the data will be emphasized including the common overrunning of upper tropospheric dry air over the warm front, the prevalence of elevated, upright, deep convection on the warm side of wrap-around region, the near-omnipresence of cloud-top convection, turbulence and supercooled water at very cold temperatures, the surprising lack of banded features on the cold side of the wrap around, and the complete misinterpretation of all of these features that one obtains from analysis of WSR-88D reflectivity measurements due to their poor resolution.