Camp Creak Area
May Be Subject To
Some Of Strongest
BY BILL JONES
David Gaffin, a National Weather Service researcher who is studying a weather phenomenon called "mountain waves," says the Camp Creek area of southern Greene County may be subject to some of the strongest wind gusts of any location along the southern Appalachian Mountains.
A "wind tower" installed at Camp Creek Elementary School by the National Weather Service in the fall of 2008 is being used to study "mountain waves" of air that researchers believe may be responsible for high winter and spring winds in the Camp Creek area.
"Mountain waves are observed near large mountain ranges around the world whenever the large-scale winds are perpendicular to the mountain ranges," said Gaffin, a Morristown-based National Weather Service senior forecaster and principal researcher on mountain waves.
He added, "These waves can produce very strong wind gusts in the foothills, and can also create strong turbulence which adversely affects aviation.
"The formation of mountain waves is similar to (what happens) when fast-moving water flows over a large boulder in a river," Gaffin said.
"As the river current flows over the stationary boulder, waves are formed downstream of the boulder," he noted.
AIR TURBULENCE DESCRIBED
The atmosphere, Gaffin said, behaves in a similar fashion when the wind flow encounters a large mountain range (a stationary object) with a stable air mass in place.
"In a stable air mass, air wants to either remain at its same altitude or descend, Gaffin said, much like water wants to flow downward.
He said, "So, when a strong southeast wind flow is perpendicular to the southwest-to-northeast oriented southern Appalachians, it will be forced to rise over the mountains. With a stable air mass also in place, this air will immediately descend on the other side of the mountains in the form of wave."
Gaffin noted that the strong wind gusts from these waves generally only affect the foothills where the bottom of the wave intersects the ground.
"During a mountain wave event, many people outside of the foothills will not experience much wind and may wonder what all the fuss is about," he said. "However, those people who live in the narrow corridor along the foothills where these waves intersect the ground (such as the Camp Creek, Greystone, and Horse Creek areas of Greene County) can sometimes experience hurricane force wind gusts."
GUSTS UP TO 81 MPH
Gaffin noted that wind gusts up to 81 miles per hour were measured Wednesday, Dec. 2, at the Camp Creek wind tower during a strong mountain wave event when strong winds from the southeast developed in a stable air mass.
"Mountain waves generally occur 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," Gaffin said.
"The peak month for mountain wave activity in the western foothills of the southern Appalachians is December."
Overall, mountain waves will mainly occur along a narrow corridor of the foothills that is parallel to the mountain range, Gaffin said.
"Camp Creek was chosen to have a NOAA wind tower constructed because it is located in an area that has a terrain profile that is very conducive to mountain wave formation," he added. "A favorable terrain profile for mountain waves is one where steep slopes are found on the leeward side (side facing opposite of the direction the wind comes from) with more gently-rising slopes on the windward side (side facing the direction the wind comes from)."
The Camp Creek area, Gaffin noted, has steep slopes that descend quickly into the valley, while more gently-rising slopes are located on the eastern side of the mountains.
"Also, Camp Creek's location on the other side of the mountains from the French Broad River Valley may contribute to the high winds observed there," Gaffin said. "When southeast winds flow up this valley, they are likely accelerated as the valley constricts the flow (much the same way that constricting a water hose will cause the water to spray faster and farther).
SOME OF STRONGEST WINDS
"It's likely that Camp Creek has some of the strongest wind gusts of anywhere along the foothills of the southern Appalachian Mountains. But because of the lack of observations near the mountains, this claim can not be fully verified."
However, Gaffin said some of his initial research studies into mountain waves suggest that this may be the case.
In an article posted recently on the Web site of the National Weather Service's Morristown office, Gaffin said, "It was found that the Cove Mountain (in the Great Smoky Mountains National Park) and Camp Creek (in southern Greene County) observation sites reported the fastest winds of all the available data."
It is possible, he said in the article, that the Camp Creek site may have experienced even higher winds than those reported, since a visit to this site found that there was some potential blockage (in the form of a higher gymnasium roof) to the southeast of the anemometer (a wind-speed measuring device).
"The fact that Cove Mountain had the highest wind speeds of any reporting site along the western foothills was likely the result of its location near the highest ridges of the western side of the southern Appalachian Mountains," he added. "This conclusion was made because the wind speeds at Cove Mountain were found to be even stronger than those observed at Clingmans Dome (which was 2,519 feet higher than Cove Mountain) during the five available wind events."
Because mountain waves normally produce high winds in a narrow area along the foothills, it is still possible that some of the sites examined in this study were not at the proper location to directly measure mountain-wave-induced high winds in their immediate vicinities, Gaffin noted.
"Thus, high winds due to mountain waves may be more extensive (and of stronger intensities) along the western foothills of the southern Appalachian Mountains than can be determined in this study," he added.
"However, this study should be considered a first step in confirming that the Cove Mountain and Camp Creek areas are not just reliable damage-reporting sites, but also experience some of the strongest winds during mountain-wave events along the western foothills of the southern Appalachian Mountains."