Analysis and Predictability of the Wasatch Windstorm of 1 December 2011
Weather Research and Forecasting (WRF) model simulations, initialized with North American Mesoscale analyses, were completed to assess: (1) the fidelity of high-resolution models (1.3-km horizontal grid spacing) to resolve the dynamics of this downslope windstorm, and (2) why there was apparent enhanced predictability in high-resolution model guidance, compared to other windstorm locations. The model simulation captured core features of the downslope wind event, including the spatial extent and timing of the strongest surface winds. However, the model developed stronger mountain-wave breaking in the lee of the Wasatch, a broader hydraulic jump, and a downstream rotor located farther west than observed. To investigate the predictability of this windstorm, an 11-member ensemble of 72-h WRF high-resolution forecasts was initialized from 0000 UTC 29 November 2011 reforecasts from the Global Ensemble Forecast System. Eight of the eleven members generated a strong, localized windstorm with the outliers arising from reduced cross-barrier synoptic-scale flow.