Minutes of the January 28, 2008 Meeting
Smoky Mountain AMS Chapter


A few people met first for dinner at Calhoun's on the River in Knoxville, and then moved to our usual meeting place on the University of Tennessee Agricultural campus. Around twenty people attended to hear David Gaffin (Senior Forecaster with the National Weather Service in Morristown) speak about "On Severe Winds and Foehn Warming associated with Mountain-Wave Events in the Western Foothills of the Southern Appalachian Mountains". The abstract of his talk was: "Widespread reports of wind damage (large trees and power lines down) occurred in the southern Appalachian region on 23 December 2004, 17 October 2006, 25 February 2007, and 1 March 2007. Especially hard hit were the western foothills of the Great Smoky Mountains National Park and the Camp Creek area in the foothills of southeast Greene County, where numerous trees were reported down which closed almost all roads in these areas. In addition, several homes were damaged and a few barns were destroyed in the Camp Creek area. The magnitude of these winds in the foothills (measured at over 100 mph) was surprising, since they far exceeded the wind speeds forecasted by the operational computer models. Another surprising finding was that most of the severe damage was confined to a narrow area along the foothills of the mountains, rather than in the higher elevations where stronger winds are normally expected. It was ultimately determined that these high winds were caused by mountain waves. Besides the high winds in the foothills, mountain-wave events also create a significant aviation hazard due to extreme turbulence and a temperature forecast challenge in the central and northern Great Tennessee Valley due to foehn warming. Foehn winds are more commonly known as the "Chinook winds" near the Rockies and the "Santa Ana winds" of southern California (where wildfires normally erupt during their occurrences). The purpose of this talk is to (1) examine the similar characteristics of the four mountain-wave events with extreme winds of 23 December 2004, 17 October 2006, 25 February 2007, and 1 March 2007, and (2) examine their associated foehn warming in the Great Tennessee Valley."




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