9.5 Probabilistic forecasting from a mesoscale ensemble at Dugway Proving Ground

Thursday, 10 January 2013: 9:30 AM
Room 17A (Austin Convention Center)
Jason C. Knievel, NCAR, Boulder, CO; and Y. Liu, G. Roux, W. Wu, T. M. Hopson, S. F. Halvorson, F. W. Gallagher III, J. C. Pace, and S. P. Swerdlin

Since 2007, weather forecasters and test directors at Dugway Proving Ground (DPG), UT have relied upon a mesoscale ensemble prediction system (EPS) known as the Ensemble Four-Dimensional Weather System (E-4DWX). This presentation will describe E-4DWX, why it was developed, and how forecasters use it.

At DPG, military materiel is tested outdoors. Accurate forecasts promote accurate tests and minimize costly cancellations, delays, and last-minute modifications to procedures and equipment. At DPG and many other test ranges, weather is shaped by myriad elements, including interactions among synoptic and mesoscale circulations, regional and local terrain, heterogeneity in land cover and substrate, radiative transfer, clouds and precipitation, and mixing in the boundary layer. E-4DWX was developed in an effort to account for the uncertainty in these elements.

E-4DWX has 30 members, each producing 36–48-h forecasts 4 times per day from continuous FDDA (four-dimensional data assimilation) analyses on a 272-processor high performance computer (HPC). Members differ from one another in model core; in initial-, lateral-, and lower-boundary conditions; and in physical parameterizations. Forecasts of the most useful near-surface variables are dynamically calibrated via quantile regression, generating true probabilistic depictions of the atmosphere's future state. Forecasters view E-4DWX's output via customized figures including means, standard deviations, fraction of the ensemble exceeding a threshold, spaghetti diagrams of time series, and model soundings. Forecasters at DPG have come to appreciate the invaluable utility of probabilistic guidance in supporting the range's test missions.

The technologies that underpin E-4DWX have been applied in multiple locations around the world for multiple purposes. Although this presentation features the role of E-4DWX at DPG, it is broadly relevant to any decision-maker concerned about local and rapidly changing weather.

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