Adapting existing Winter Storm Indices to Predictions of High-Impact Winter Weather

The Weather Channel (now formally known as The Weather Company or TWC) operates a human-in-the-loop forecast system that produces about 11,000 point forecasts in the CONUS. The Global Forecast Center (GFC) produces hourly forecasts of temperature, wind, precipitation type and amount through 60 hours, and daily forecasts of these and other quantities through 10 days. During this upcoming 2013-2014 winter season, there is a desire to combine these 11,000 objective GFC snowfall forecasts with information of areal extent and population of each forecast point – and in so doing produce nationwide predictions of Regional Snowfall Impact as described in Squires et. al. (2011), and a Local Winter Storm Scale (LWSS) as described in Cerruti and Byers (2011).

The RSI is a regional winter storm severity scale developed by the National Climatic Data Center (NCDC) and is a regional extension of the Northeast Snowfall Index Scale or NESIS (Kocin and Uccellini, 2004). The scale is based upon all notable CONUS snowstorms since 1900, thus RSI is carefully calibrated against historical snowstorms, their periodicity, and average intensity in terms of areal extent and the proportion of the regional population that is affected. In the case of LWSS, there is no historical calibration, but the index takes into account additional winter elements such as ice, wind chill, and blowing and drifting snow. Moreover, TWC used nationwide LWSS indices as internal guidance with good success in the winter of 2012-2013.

The GFC forecasts of RSI and LWSS will be valid for periods up to four days in advance and will be used for weather content and weather products available on TWC's cable channel telecast, their website weather.com, and Mobile devices such as smartphones and notepad computers. Notably, the predicted RSI and LWSS indices will be used in decision support of the naming of winter storms process taking place at TWC (Niziol et. al., 2013). This presentation will describe the adaptation of the existing NCDC RSI and LWSS indices into predictive quantities built from the CONUS forecasts of the GFC. In addition, a few case studies from the winter-in-progress will be shown to highlight known strengths and shortcomings of these new forecast elements.

References:

Cerruti, Brian J., Steven G. Decker, 2011: The Local Winter Storm Scale: A Measure of the Intrinsic Ability of Winter Storms to Disrupt Society. Bull. Amer. Meteor. Soc., 92, 721–737.

Kocin, Paul, and L. Uccellini, 2004: A snowfall impact scale derived from Northeast Storm snowfall distributions. Bull. Amer. Meteor. Soc., 85, 177-194.

Squires, Michael F., Jay H. Lawrimore, Richard R. Heim Jr. David A. Robinson, Mathieu R. Gerbush, Thomas W. Estilow, and Leejah Ross, 2011: Regional Snowfall Impact Scale. 27th IIPS, Seattle, WA.