The Eta-12 at 00 UTC 24 December 2001 forecasted a favorable synoptic-scale environment for heavy lake effect snow. Shown previously was the 24-hour Eta-12 forecast at 500, 700, and 850 hPa and for mean sea level pressure; it can be reviewed here.
Previous versions of the Eta, and other models at relatively coarse resolution compared to the Great Lakes and with simple microphysics, have been useful in predicting the necessary large-scale conditions favorable for the development of lake effect snow. But at coarse resolution relative to the lakes and with relatively simple precipitation microphysics, the models have not until now had the capability to explicitly predict actual lake effect snow events.
The new Eta-12 has some of the characteristics necessary to resolve some aspects of lake effect snows, including:
The next two sections will discuss the successes and shortcomings of the 00 UTC 24 December 2001 Eta-12 forecast in terms of mesoscale prediction of the lake effect snow event of 24-26 December. We will concentrate on both the resolution-dependent and precipitation scheme-dependent aspects of this particular case. The data will be on the Eta-12 native grid both horizontally and vertically, to allow the best assessment of model behavior with respect to the scale of the lake effect event possible. Unfortunately, we will be limited in time to 3-hourly intervals; this will limit us to either:
Note that the results we discuss here should only be generalized to other cases with care; this aspect of the case will be further discussed in the conclusions.