Conclusions and Summary from the Dynamic/Synoptic Analysis
November 9-14, 1996 in the Great Lakes

4. Summary and conclusions The following summary and questions can be gleaned form this study of the Veteran's day snowstorm of 1996:

  • The severe snowfall in NE Ohio on the evening of 11/9/96 was underpredicted by all NWP models, but shows up well in the diagnostic analysis of the storm. In retrospect, the slowing down and tilt of the upper longwave feature may have helped this system strengthen and hit the brakes as it rotated into the eastern lakes. Q-vector analysis from the QG model equations shows strong Q-vector forcing in the same vicinity as the heaviest snowfall. This forcing indicates a frontolytic transverse frontal circulation and may have given clues to both problems in the predictive models. it is unclear from our analyses whether the snowfall was lake-enhanced, but the high tallies of observed snow in the Cleveland high-elevation snowbelts support this idea.

  • The vertical structure of temperature within the quasistationary longwave trough is highly anomalous. Very cold upper air temperatures for early November combine with a strong shear zone well to the south and west of the lakes to keep any NVA and sinking processes away from the region. This results in three days of nearly pseudo-adiabatic environments from the surface to 500 Mb in many locations. This is an excellent case study for determining the interaction between synoptic dynamic processes and warm lake mesoscale circulation's, since any forcing of the system will be efficiently communicated in the vertical due to very low static stability's.

  • The quiescent trough axis near the vortex center appears an ideal breeding zone for lake effect snow storms in that nearly steady state and weakly cyclonic flow can remain in place for long duration's.

  • The QG model is not much aware of the lakes but some potentially interesting omega and divergence patterns were found when looking in cross-section along a predetermined trajectory from southern L. Michigan through L. Erie. There were clear, but weak, ascent regions over and downwind of these two lakes and there were weak convergence bands coincident with the lakes.

  • In terms of sensible weather, the diurnal production of widespread cell convection and possible interference with the lake bands' intensity and coverage is a baffling problem. This would likely only occur early in the season since the Benard convection requires reasonable surface radiative heating; moreover, the cellular convection should not be produced over the lake surface (at least with any diurnal signal). A possible scenario might be the advection of small cells into lake convergence and bandedness regions that upsets the mesoscale circulation within these snow bands.

In conclusion, the fine scale dynamic features induced by the lakes and the interaction between the lakes and the large scale dynamics should be more closely studied. This is potentially a fertile area of research, since the theoretical framework of interaction between the large-scale and lake effect circulations is quite incomplete; however, different tools for deducing these relationships would be needed since the QG theory is not well suited for diagnosing near surface processes and dynamics. Secondly, for a lake effect researcher, the diurnal variation of this storm is provocative. Links between overland cellular convection and weakening or disorganized band convection have not been explained previous to this case, and the author has no knowledge of the phenomenon being observed prior to this case.

Q Vectors
Terms for using data resources. CD-ROM available.
Credits and Acknowledgments for WW2010.
Department of Atmospheric Sciences (DAS) at
the University of Illinois at Urbana-Champaign.

Hurricane Andrew