Extended Abstract (228K)P4.6
Upper Air Constant-Pressure Composites of Midwestern Thundersnow Events
Patrick S. Market, University of Missouri, Columbia, MO; and A. M. Oravetz, D. Gaede, E. Bookbinder, R. Ebert, and C. Melick
Thundersnow events from 1961 through 1990 were examined. Chosen events occurred in the Midwest on synoptic hours and featured thunder and snow only, a stratification that lead to 97 cases of thundersnow. The thundersnow events were classified into categories based upon the setting in which each event occurred; examples include: with a cyclone, with a front, in a lake effect situation, etc. Events that occurred with a cyclone (N=80) were the focus of this study, and further classified based upon where the thundersnow occurred in relation to the cyclone (northwest of it, northeast, etc.) in keeping with previous work. Mean fields of standard atmospheric variables at several levels (900 mb, 850 mb, 700 mb, 500 mb, and 300 mb) were then generated with compositing software at the time of initiation as well as 12, 24, 36, and 48 hour prior to thundersnow initiation. Such convective snow events associated with cyclones will of course occur in a dynamic environment, with ample moisture and lift. However, the composite thundersnow event occurring northwest of a cyclone center (N=33) tends to occur with deeper, better-developed, negatively-tilted cyclones as a result of upright convection. Conversely, the composite thundersnow occurring to the northeast of a cyclone (N=19) tends to be associated with weaker, less-developed, neutrally-tilted systems and more likely the result of a slantwise parcel displacement.
Poster Session 4, Thursday Posters
Thursday, 15 January 2004, 9:45 AM-11:00 AM, Room 4AB
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