The Weather Channel Approach to the Naming of High-Impact Winter Storms in the Continental U.S
Thomas Niziol, Bruce Rose, Stu Ostro, Bryan Norcross and Peter Neilley
The Weather Company
Winter storms produce significant societal impacts across the U.S. each year. In many cases, weather systems that are responsible for these major storms maintain an identity as they traverse the nation. By tagging these systems with a name identity, communications of the risks, threats and impacts of the storms to the public greatly simplified by the short, simple storm identity. This is especially true in digital and mobile products where “hash-tagged” reference to the storm is essential to clearly identify the storm in length-restricted messages such as Twitter and text messages. Further, the act of naming a storm indicates a degree of significance to the event leading to greater awareness and preparation.
After a successful internal dry run during the winter of 2011-2012, The Weather Channel debuted its winter storm naming program this past winter. Since winter storms are complex with a wide variety of weather conditions and precipitation types, the criteria to name a storm is less straightforward than naming tropical storms or hurricanes. Moreover, in order to ensure that storm names can be used to facilitate communication in advance of its threats, naming must be based upon predicted storm intensity rather than an observed intensity as with tropical storms.
The Weather Channel experimented with a combination of objective forecast parameters and algorithms, as well as subjective and objective assessments by a team of three senior meteorologists. We settled on an approach whereby societal threats and impacts were estimated and compared to predetermined thresholds. Both forecasted meteorological elements of the storm (e.g. snow and ice accumulation, temperature, wind) and non-meteorological factors such as population and time of day were part of this impact assessment. This included the computation of a specific winter storm index using a technique described in Cerruti and Decker (2011). This Local Winter Storm Scale (LWSS) was extended to all major cities in the continental U.S. and was valid for the upcoming 48 hours, to help support the overall storm-naming decision process.
For the winter of 2013-2014, The Weather Channel will extend its use of objective, quantitative metrics to guide the naming decisions. In particular, a new nationally-calibrated version of the Regional Snowfall Index based on The National Climatic Data Center's Regional Snowfall Index RSI (Squires et al., 2011) will be used in addition to the LWSS. The NCDC RSI index, is a post-analysis tool to assess storm impact based on snowfall, population and areal coverage, normalized to snowfall standards in six of the nine climatic zones across the CONUS. A forecast, national version of the RSI will be the primary basis for naming decisions in the upcoming winter. Thresholds for the “Name/Don't Name” decision will be established based on hindcasts of prior winter naming decisions. The combined use of the RSI and LWSS indices are expected to account for a broader set of winter weather factors such as ice, wind and temperature, and will be used to arbitrate cases between the thresholds.
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.
Squires, Michael F. , Jay H. Lawrimore, Richard R. Heim Jr. David A. Robinson, Mathieu R. Gerbush, and Thomas W. Estilow, Leejah Ross, 2011: Regional Snowfall Impact Scale. 27th IIPS, Seattle, WA.