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Univ. of Missouri/Columbia: "Investigation of significant thundersnow events in the Midwestern United States"

Final Report


Our work is now complete on the development composites of the various types of thundersnow event (Task D). Those events associated with a cyclone were chosen first for examination, and stratified according to a number of factors, including

* the location of the snowfall with respect to the cyclone center, and
* the intensity of snowfall.

Composites now exist which depict the typical state of the atmosphere during, and up to 48 hr prior to, thundersnow occurrence in the Midwest.
In brief, our composite fields reveal what at first appear to be those of a typical synoptic-scale snowstorm. However, examination of the location of the thundersnow with respect to the cyclone center revealed some unique results. In particular, those thundersnow events that occur northwest of a cyclone center are associated with stronger, deeper systems possessing a negativly-tilted trough aloft. Thundersnow occurrences northeast of a cyclone center occur with a weaker, younger cyclone, as evidenced by higher heights before and during the event, and neutrally-tilited trough in the height pattern aloft. These fields will be a necessary foundation for the thundersnow forecasting approach that is now being developed.

Yet, these findings fail to distinguish our composited cases from other cyclones that did not feature thundersnow. Consequently, we turned to soundings and vertcial profiles of derived variables in order to determine why our test subjects became electrified. The underlying assumption here is that charge is induced via convection and the charge separation it is to achieve in stronger, warm-season convection. Thundersnow events northwest of a cyclone center were more likely to occur in the presence of potential instability (and the trowal, perhaps), while thundersnow northeast of a cyclone was more prone to a potentially neutral environment, negative equivalent potential vorticity, and overlaying a region of frontogenesis. In the former case, there is forcing for ascent with potential instability, while in the latter case, there is forcing for ascent in a atmosphere featuring conditional symmetric instability.

Mrs. Angela Oehl-Oravetz, the graduate student working on this project, completed these tasks in early May, 2003, and graduated with her Master’s degree on 18 May 2003.


Ms. Rebecca Ebert graduated in December 2002 and has continued at the University of Missouri-Columbia to pursue her Master’s degree.
Mr. Brian Pettegrew, a Master’s degree student assisted the project at no cost by helping to draft an article for the Bulletin of the American Meteorological Society on a recent severe thundersnow event.

Mr. Evan Bookbinder, journeyman forecaster, assisted the research team in his first collaborative research project with the National Weather Service.



As before, our collaborative effort has been excellent for the Department of Atmospheric Science at the University of Missouri-Columbia. We maintain strong ties with the National Weather Service Office in Springfield, MO, which continues to be a crucial partner in our scientific pursuits. We have retained one of our undergraduate students, Ms. Rebecca Ebert, as a graduate student in the Program, and she will perform her master’s work on thundersnow. We have also begun stirring greater interest in prospective graduate students as a result of our thundersnow work. Lastly, these research results have been incorporated into Dr. Market's course offerings on Synoptic Meteorology II, Mesoscale Meteorology and Dynamics, and the graduate-level Advanced Synoptic Meteorology.


Through this collaborative research effort, the National Weather Service has been able to continue its partnership with the University of Missouri-Columbia. The program has also raised interest in the office for other research efforts among the meteorologists. Several proposals for other collaborative research efforts are currently being developed.

The results of this study will be used to train the other meteorologists in the forecasting of thundersnow during the upcoming winter weather season.


Oravetz, A., 2003: Composite Analysis of Thundersnow Events in the Central United States. M.S. Thesis, University of Missouri-Columbia, 120 pp.

Market, P.S., R.L. Ebert, and A.M. Oravetz, 2003: Composite Meteorological Fields on Isentropic Surfaces. 3rd Conf. on Isentropic Meteorology, Millersville University of Pennsylvania, (April 2003).

Oravetz, A., P. Market, D. Gaede, E. Bookbinder, and A. Lupo, 2002: Composite Analyses Of Midwestern Convective Snow Events. Annual Meeting of the National Weather Association, Ft. Worth, TX. (October 2002).

Market, P., 2002: A Thundersnow Climatology. Presented to the St. Louis (Weldon Spring) WFO Winter Weather Workshop (November 2002).

Market, P., 2002: Thundersnow: What It Is And Is Not. Presented to the St. Louis (Weldon Spring) WFO Winter Weather Workshop (November 2002).



Scientific problems have been non-existent. However, the compositing work has been quite a task, and with the new accounting procedures at UMC mentioned in our previous report, the suspected need for a 6-month no-cost extension soon has arisen. We made our request earlier this fall, and that extension was granted.


Once the staffing problems mentioned in the previous reports were remedied, no other problems were encountered.