An Examination of the Areal Extent of High Winds due to Mountain Waves along the Western Foothills of the Southern Appalachian Mountains

High winds due to mountain waves have been found to occur frequently along the western foothills of the southern Appalachian Mountains from November through March. When these high wind events occurred, reports of significant wind damage were normally received from two main areas in east Tennessee: the Great Smoky Mountains National Park (GSMNP) and the Camp Creek community of southeast Greene County. It was not known whether the GSMNP and the Camp Creek areas are just more reliable at reporting wind damage or actually have stronger winds compared to other areas along the western foothills. Thus, a study was conducted to examine the available observations along the western foothills of the southern Appalachian Mountains to determine the areal extent of these high winds during mountain-wave events. Due to the lack of ASOS and AWOS stations in the western foothills, eighteen WeatherBug and three RAWS stations were examined on the 52 dates between 1999 and 2007 when mountain-wave-induced warning-level winds were reported at Cove Mountain in the GSMNP. Although the Cove Mountain site was at a higher elevation than most of the other sites in the western foothills, it was concluded that the higher wind speeds at Cove Mountain were mainly due to its location in the foothills of the highest ridges on the western side of the southern Appalachian Mountains. This conclusion was made because the wind speeds at Cove Mountain were found to be even stronger than those observed at the highest elevation site at Clingmans Dome. On the dates that Cove Mountain reported warning-level winds, it was found that only the Camp Creek site also reported at least advisory-level winds on nearly every date (87%). In addition, it was found that only the Camp Creek, Coker Creek, Shady Valley, and Erwin sites reported warning-level winds on a few of the Cove Mountain dates. The Camp Creek and Coker Creek sites reported warning-level winds on roughly a third of the dates that they were available, while the Shady Valley site reported warning-level winds on roughly a tenth of the dates that it was available. Composite maps of surface isobars, surface isotherms, and 850-hPa isotachs from the warning-level wind dates revealed that the warning-level winds at Camp Creek, Coker Creek and Shady Valley resulted from a stronger low pressure system (with stronger 850-hPa winds) compared to that which produced warning-level winds at Cove Mountain. Also, weaker cold-air damming on the eastern side of the southern Appalachian Mountains appeared to allow warning-level winds at the Coker Creek and Shady Valley sites, with the weakest cold-air damming observed during the warning-level wind dates at Shady Valley.