Systematic Biases in NCEP Model Guidance for 2017-2018 East Coast Winter Storms

A review of systematic biases in model guidance for 2017 and 2018 East Coast winter storms will be presented. This presentation is born out of storm reviews, conducted by the Model Evaluation Group at the Environmental Modeling Center, wherein problems with model guidance have been documented in a case-by-case basis. We will expound upon these individual case studies by summarizing the systematic biases that limit forecaster confidence and predictability across temporal and spatial scales.

Model performance related to cyclone formation, track, and intensity will be presented. Additionally, aspects of precipitation forecasting, including quantitative precipitation forecasts, precipitation type, and snowfall totals, will be discussed. Global ensemble systems from NCEP and ECMWF will be examined with an interest in medium-to-long range confidence in coastal cyclogenesis and subsequent storm track and deepening. This will be further evaluated using deterministic runs of global and mesoscale models. In shorter ranges, precipitation forecasts from global, mesoscale, and convection-allowing models and ensembles will be compared to assess characteristics, such as precipitation extent and type, that are critical for rainfall and snowfall forecasting.

Although a number of cases will be examined, this presentation will place a particular focus on the winter storms that occurred along the East Coast of the United States on 13-14 March 2017 and 3-5 January 2018.