Forecasters in the Great Lakes region have for several decades recognized a general relationship of wind speed and over-lake fetch to lake-effect snowstorm morphology. A recent study using idealized mesoscale model simulations of lake-effect conditions over circular and elliptical lakes showed the ratio of wind speed to maximum fetch distance (U/L) may be used to effectively predict lake-effect snowstorm morphology. The current investigation provides an assessment of the U/L criteria using observational data sets. Previously published Great Lakes lake-effect snowstorm observational studies were used to identify events of known mesoscale morphology. Hindcasts of nearly 640 lake-effect events were performed using historical observations and U/L as the predictor.

Results show that the quantity U/L contains important information on the different mesoscale lake-effect morphologies, however it provides only a limited benefit when being used to predict mesoscale morphology in real lake-effect situations. The U/L criteria exhibited the greatest probability of detecting lake-effect shoreline band events, often the most intense, but also experienced a relatively large number of false hindcasts.

In addition, the Great Lakes Environmental Research Laboratory ice cover digital data set was used in combination with observations from past lake-effect events to account for regions of significant ice cover and assess the impact of ice cover on the use of U/L as a predictor. Results show that hindcasts of lake-effect morphology using the U/L criteria were slightly improved when the reduction of open-water areas due to lake ice cover was taken into account.