The OWLeS Orographic (O2) Field Campaign: Adventures in Intense Snowstorms on the Tug Hill Plateau

Rising a modest 500 m above the eastern shore of Lake Ontario, the Tug Hill Plateau of northern New York averages up to 750 cm of snow annually and likely experiences the most intense snowstorms in the world. These storms are generated by long-lake-axis-parallel (LLAP) snowbands that develop over Lake Ontario and intersect the plateau's gentle western slope. World-record snowfalls recorded on the plateau include 30 cm in 1 h (Copenhagen, NY, 2 Dec 1966) and 130 cm in 16 h (Bennetts Bridge, NY, 17–18 Jan, 1959). In addition, a remarkable 24-h accumulation of 195 cm was recorded in Montague, NY from 11–12 Jan 1997, but is unofficial because five measurements were made during the period rather than four.

During December 2013 and January 2014, the National Science Foundation sponsored Ontario Winter Lake-effect Storms (OWLeS) project examined lake-effect storms in the vicinity of Lake Ontario. Research platforms included the University of Wyoming King Air Research Aircraft, three Center for Severe Weather Research (CSWR) mobile Doppler on Wheels radars, the University of Alabama at Huntsville Mobile Integrating Profiling Systems, and five mobile sounding systems. Scientists from the University of Utah and State University of New York at Albany operated a transect of profiling radars from the eastern shore of Lake Ontario to upper elevations on the Tug Hill Plateau, as well as lowland (145 m MSL) and upland (385 m MSL) snow-study stations, providing an unprecedented look at orographic enhancement during lake-effect snowstorms.

During intensive observing periods (IOPs), snowfall rates at the upland site reached 13.9 cm/h, 36.5 cm/(6 h), and 98 cm/(24 h). During the 12-day period encompassing IOPs 1–5, the upland site received 252 cm of snow with a mean water content of only 5.9%. Despite an elevation difference of only 240 m, the mean orographic ratio (i.e., upland/lowland liquid equivalent precipitation) for 6-h periods during which manual cores of fresh snow were collected at both sites was a remarkable 2.06, representing an enhancement factor of 8.6/(1000 m). Analysis of the data collected by OWLeS observing platforms combined with snow and precipitation measurements from the upland and lowland sites provides new insights into the mechanisms contributing to intense snowfall rates during lake-effect storms and a unique perspective on orographic precipitation enhancement over modest topography.