Wednesday, 8 November 2006: 10:45 AM
St. Louis AB (Adam's Mark Hotel)
Proximity sounding studies have played an important role in our understanding of severe thunderstorm environments for a long time. For the most part, these studies have been limited to the United States, primarily because of the existence of databases of events. The recent development of an extensive European Severe Weather Database (ESWD, www.eswd.eu) has allowed us the opportunity to create proximity soundings for events in Europe. We have chosen to create those soundings using NCAR/NCEP reanalysis data as part of a larger effort to model the distribution of severe thunderstorm environments around the world. The dataset consists of 138 proximity soundings associated with significant (F2 or stronger) tornadoes and 55 significant non-tornadic soundings (wind gusts of hurricane strength and/or hail at least 5 cm in diameter) from the period 1958-1999, as well as the soundings taken at the same locations, at the same time on the same day of the year for the other years, producing a null-case set. These soundings can be compared to a similar dataset previously created for the United States. In general, CAPE values are much lower and deep tropospheric shear slightly lower in Europe than in the United States. As a first result, we have looked at the probability that a particular combination of CAPE and deep tropospheric shear will be associated with significant severe or tornadic events. The peak probabilities are higher for the European soundings. The overall frequency of significant events is lower in Europe because the atmosphere is much less likely to produce combinations of high CAPE and shear in Europe than in the United States. We are currently looking at a broader range of parameters in an effort to develop relationships between the environmental conditions and events that can produce realistic modelled distributions of events in both regions. In particular, the stronger role of orographic boundary layer forcing (shear, heat, moisture) in Europe compared to the US Mid-West may present a challenge for the reanalysis proximity sounding approach.
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