Danger Degree Project

Assessing the Threat of Winter Events

The Danger Degree Project was developed as a method of classifying past winter snowfall events. This was an effort to create a historical reference, or climatology, for use in assessing the threat of snowfall cases that may or may not fall into the National Weather Service (NWS) defined criteria for winter weather advisories or warnings.

The danger degree rating of a winter snowfall event is derived by using a checklist of weather and societal factors including wind strength, temperature, other observed weather elements, time of day, and seasonality. The end value represents the threat, or danger degree, of the event. For this study, meteorologists at the Duluth Weather Forecast Office (WFO) worked to compile over 250 checklists for snowfall cases at the Duluth and International Falls airports, dating back to 1997.

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Motivation:
The motivation behind the Danger Degree Project comes from situations where the physical science can be perfect, but its utility is greatly reduced where there is not adequate attention to the societal aspects. Understanding how a winter weather event impacts the community will be increasingly valuable to the National Weather Service and its Meteorologists.

Theory:
The greater the Danger Degree of an event, the greater the potential impact that event has on the community.

Ultimatly determine what the impact on the community was for these events and if there is a correlation between the Danger Degree and true impact.

Process:
In order to classify winter events we
developed a "checklist" of meteorological and societal factors that are given values. These values are added to result in a quantitative "score" or Danger Degree for each event. For this project, meteorologists at the Duluth Weather Forecast Office (WFO) worked to compile over 250 checklists for snowfall cases dating from 1997 to 2009.

Preliminary Findings:
Several events with Winter Storm Warnings fell into category with Low Danger Degree Values (Less than 5), suggesting Low Potential Impact.

Several events not associated with a winter weather advisory or warning had High Danger Degree (greater than 14), suggesting a High Potential Impact.

The Danger Degree Checklist

For additional information on how the NWS is involved with this project how the data will be used to improve NWS products and services, please contact Amanda.