J1.4 Severe Winds due to Mountain Waves along the Western Foothills of the Southern Appalachian Mountains

Wednesday, 26 June 2013: 9:45 AM
Tulip Grove BR (Sheraton Music City Hotel)
Matt Hinkin, TV Broadcast & NWS MRX, Knoxville, TN; and D. M. Gaffin

Handout (4.7 MB)

Mountain waves are frequently observed near large mountain ranges around the world, when the large-scale winds are perpendicular to the mountain ranges. These mountain waves can produce very strong wind gusts in a narrow area along the foothills, and can also create strong turbulence above the mountains which adversely affects aviation. Strong wind gusts generated by mountain waves generally affect only a narrow zone in the foothills of the mountains where the bottom of the wave intersects the ground. Wind gusts around 100 mph have been routinely measured on the Tennessee side of the Great Smoky Mountains National Park (GSMNP) during strong mountain wave events when strong southeasterly winds occurred within a stable air mass. Wind gusts in excess of 80 mph have also been routinely measured at the Camp Creek community of east Tennessee during mountain wave events.

Mountain waves can also occur along the eastern foothills of the southern Appalachian Mountains when the large-scale wind flow is from the northwest. While mountain wave events occur more frequently on the eastern side of the mountains (due to the more frequent occurrence of northwest winds versus southeast winds), it's likely that high winds due to mountain waves are stronger on the western side because of the steeper slopes that descend quickly into the Great Tennessee Valley.

Mountain wave events along the western foothills of the southern Appalachians occur mostly during the cooler months of the year from late fall through early spring (mid October to mid April), when large low pressure systems and stable air masses are more common. The peak month for mountain wave activity along the western foothills of the southern Appalachians is December. Some specific examples of strong mountain wave events in east Tennessee that will be examined in this presentation include: the 17 October 2006 event (which closed many roads in the GSMNP during one of their busiest times of the year), the 9 March 2011 event (which damaged the roof of the Camp Creek Elementary School), the 24 December 2009 event (which destroyed a historic barn in Cades Cove of GSMNP), and the recent 20 December 2012 event (which created extensive damage in the Camp Creek community of east Tennessee).

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