Dual-polarimetric Doppler on Wheels observations of long lake-axis-parallel lake-effect snow storms over Lake Ontario

Oswego, NY is well known for its legendary snow storms (e.g., 102 inches over a 5 day span in January 1966). Because of this, many meteorology students from across the country are attracted to SUNY Oswego's campus, including the lead author in the 1990s. These legendary snows are the result of lake-effect snow storms forming along the greatest fetch of Lake Ontario, termed long lake-axis-parallel (LLAP) bands by Oswego meteorologists. The lake-effect snows of the western Great Lakes have been well-studied compared to the monster storms of the eastern Great Lakes (Erie and Ontario). Hence, SUNY Oswego proposed a study on these storms and was awarded an NSF EAGER (EArly concept Grants for Exploratory Research) grant to use the Center for Severe Weather Research (CSWR) Doppler on Wheels (DOW), mobile probe truck, three tornado pods, a mobile rawinsonde system, and detailed surface observations by ten undergraduate students (e.g., standard meteorological observations and precipitation type on Formvar slides) to improve our understanding of LLAP storms during the 2010-11 winter season.

The DOW collected unprecedented high resolution data of the reflectivity and velocity structures of these Lake Ontario storms, including vortices on the miso- and mesoscale, vertical cross sections across the band showing two layer flow fields with greatest low-level convergence occurring on the south side of a west-east oriented band (not in the core), elevated reflectivity (similar to a bounded weak echo region), and over-shooting tops. The frequency of the circulations observed in these bands was surprising, with some of them lasting for over an hour and having shear values (delta-Vs) between 10 and 35 ms-1. The diameters of these circulations were between 1 and 20 km. The DOW is also dual-polarimetric so for the first time we will study the processes controlling hydrometeor type in LLAP bands. For example, signatures supportive of dendritic snow growth in the core of the band and more pellets on the edges of the band have been noted on the DOW fields and confirmed by surface observations taken by the students.