13.5 Predictability and morphology of Great Salt Lake-Effect precipitation

Thursday, 2 September 2010: 2:30 PM
Alpine Ballroom A (Resort at Squaw Creek)
Trevor I. Alcott, University of Utah, Salt Lake City, UT; and W. J. Steenburgh and N. F. Laird

Great Salt Lake-Effect (GSLE) precipitation is an important piece of the hydroclimate of Utah's Salt Lake Valley and Northern Wasatch Front, and remains a forecasting challenge. This study constructs a 1997-2009 event climatology and combines radar, reanalysis data and mesonet observations to 1) provide general statistics regarding event occurrence, 2) identify synoptic and mesoscale conditions characteristic of GSLE events, 3) determine factors that control the intensity, location and morphology of GSLE precipitation structures, and 4) evaluate the ability of an ingredients-based forecasting methodology to predict the onset and morphology of GSLE events. The study period contains over 150 events where precipitation is deemed partly or entirely driven by lake-effect processes, with events occurring most often in late fall and early spring. Conditions shown to be characteristic of GSLE events in past studies translate well to the new longer climatology. Low-level thermodynamic and dynamic profiles are shown to provide some discrimination between banded and non-banded structures, and a new ingredients-based forecast technique utilizing several derived variables shows some improvement in skill over the use of existing empirical methodologies.
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