Intense lake-effect snowstorms regularly develop over the eastern Great Lakes, resulting in extreme winter weather conditions with snowfalls sometimes exceeding 1 m. The Ontario Winter Lake-effect Systems (OWLeS) field campaign sought to obtain unprecedented observations of these highly complex winter storms. OWLeS employed an extensive and diverse array of instrumentation, including the University of Wyoming King Air research aircraft, five university-owned upper-air sounding systems, three Center for Severe Weather Research Doppler on Wheels radars, a wind profiler, profiling cloud and precipitation radars, an airborne lidar, mobile mesonets, deployable weather Pods, and snowfall and particle measuring systems. Close collaborations with National Weather Service Forecast Offices during and following OWLeS have provided a direct pathway for results of observational and numerical modeling analyses to improve the prediction of severe lake-effect snowstorm evolution. The roles of atmospheric boundary layer processes over heterogeneous surfaces (water, ice, and land), mixed-phase microphysics within shallow convection, topography, and mesoscale convective structures are being explored. More than 75 students representing nine institutions participated in a wide variety of data collection efforts, including the operation of radars, radiosonde systems, mobile mesonets, and snow observation equipment in challenging and severe winter weather environments.

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This paper presents an 8-yr (1999-2006) climatology of the frequency of open-cell convection over the northeastern Pacific Ocean and the thermodynamic and kinematic environment associated with its development. The climatology is based on synthetic aperture radar-derived wind speed images and reanalysis data. The climatology shows that open-cell convection was a cold-season phenomenon, having occurred in environments in which the difference in temperature between the near-surface air and the sea surface is negative and in environments with positive surface sensible and latent heat fluxes. Within the region between the surface and 500 hPa, the 700-850-hPa layer median static stability was near moist adiabatic while that for the remainder was conditionally unstable. The median magnitude of the vertical wind shear was largest in the 925-hPa-nearsurface and 500-700-hPa layers while that at midlevels was relatively weak. Similarities are highlighted between the organization of open-cell convection over the northeastern Pacific Ocean and tropical deep moist maritime convection in terms of cold-pool dynamics. Avenues for future work are discussed.

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