13.2 Ontario Winter Lake-effect Systems (OWLeS): Fine-scale dual-Doppler and microphysical radar observations of small-scale circulations in intense lake-effect snow bands

Wednesday, 5 August 2015: 4:15 PM
Republic Ballroom AB (Sheraton Boston )
Joshua Wurman, Center for Severe Weather Research, Boulder, CO; and K. A. Kosiba

The OWLeS (Ontario Winter Lake-effect Systems) field project was conducted December 2013 and January 2014 in the United States and Canada along the shores of Lake Ontario to better understand the underlying kinematic and microphysical processes of lake-effect snow. OWLeS utilized 3 mobile X-Band radar systems (Doppler on Wheels; DOWs), instrumented aircraft (University of Wyoming King Air), sounding systems, and other surface instrumentation to document the structure and evolution of approximately 24 lake-effect systems.

This study focuses on the intense convective bands that form parallel to the long-axis of the lake, which often contain small-scale rotations (~100s meters in diameter) that are associated with increased surface winds and may impact hydrometeor transport within these bands. Dual-Doppler radar analyses and evolution of the dual-polarization signatures characteristic in two (15 December 2013 and 20 January 2014) of these intense snow bands will be presented. In particular, the evolution of the fields before, during and after the development of small-scale vortices and their effects on the band structure will be discussed. Vorticity and trajectory analyses suggest that the misovortices form as a result of vortex sheet instability and subsequent stretching. Similar dual-polarization signatures were observed in both events, but the 20 January event, which was associated with the passage of an Arctic front, exhibited a narrow region of relatively larger ZDR along the leading edge of the band, indicating a change in hydrometeor type.

In 2015, additional fine-scale DOW data were collected in two Northeast coast blizzards (26 January and 14 February). Boundary layer streaks, similar in appearance to features observed in the hurricane boundary layer, were present in both storms. Dual-polarization signatures differed between the two storms, with the storm on 14 February exhibiting mixed phase precipitation through much of the observation duration. Preliminary results will be presented from these two events.

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