A synoptic climatology of significant winter storms in the Twin Cities area

Although modern observing and modeling systems have resulted in improved forecasts of winter storms, there remains room for improvement. One factor which can have a significant influence on forecast accuracy is forecaster experience, particularly when that experience is acquired in the same area over many years. One benefit of such experience is increased skill in “pattern recognition”, which although intangible, can be of great importance when identifying potentially significant winter storms. Since it is desirable to maximize forecast skill in all situations, there is a need to provide forecasters with a means by which to increase their familiarity with atmospheric signals which are typically associated with significant winter storms in their forecast area. In an effort to achieve this, a climatology of significant winter storms in the Twin Cities area from 1950 through 2007 was constructed.

Events which produced six or more inches of snow were identified, resulting in a total of 109 events from 1950 through 2007. Basic meteorological charts from each event were reviewed, and events were categorized into five separate synoptic archetypes. Compositing was then performed for each archetype, and mean synoptic charts detailing conditions over the course of each type of event were produced. Compositing was performed utilizing the National Centers for Environmental Prediction (NCEP) / National Center for Atmospheric Research (NCAR) global reanalysis dataset.

Basic climatological information for each archetype is presented, providing general information on the snowfall which occurred, along with the seasonality of each type of event. Composite synoptic charts for each archetype are also presented, highlighting the surface and upper air patterns which are associated with the different event types. It is hoped that having a comprehensive yet concise summary of such events will provide forecasters with basic “pattern recognition” information, and help them anticipate the potential for significant Winter Storms in the Twin Cities area.