Thunderstorms, some severe, with very heavy rain have moved into the Mid South and Tennessee Valley today. Flash flooding and severe thunderstorms will be possible from the central Gulf Coast to the Upper Great Lakes. The greatest threat of excessive rains will be in portions of the Lower and Middle Mississippi Valleys. This storm system has a history of producing life threatening flash floods. Read More >
The 15-16 April 2007 High Wind Event
Author's Note: The following report has not been subjected to the scientific peer review process
On 15-16 April 2007, a significant high wind event occurred across the western Carolinas including much of the North Carolina Mountains and Foothills. The event resulted in widespread reports of downed trees, property damage, power outages, as well as injuries and fatalities. From an operational standpoint, the event was well anticipated as a High Wind Watch was issued on the afternoon of the 14th for the Mountains and Foothills. This Watch was then upgraded to a High Wind Warning in the early morning hours of the 15th. The synoptic evolution of the event will be discussed in section 2 with the impacts focused on in section 3.
2. Synoptic Overview
The high wind event occurred after a low pressure system and associated cold front moved eastward across the western Carolinas the morning of the 15th (Fig. 1). A few hours later this low pressure system redeveloped and deepened along the Mid-Atlantic coastline with a minimum pressure of 972 hPa (Fig. 2). By the morning of the 16th, the pressure continued to fall to 968 hPa (Fig. 3). With the deepening low pressure to the northeast and an area of high pressure to the west, the western Carolinas region was under the influence of a strong pressure gradient.
Aloft, at 500 hPa, the event was marked by a sharp upper level trough axis that moved across the region on the 15th (Fig. 4a), before developing into a closed upper level low over the northeastern United States on the 16th (Fig. 4b). Just above the surface, at 850 hPa, strong winds of 40 kts or greater were present along the spine of the Appalachians at both 0000 UTC (Fig. 5a) and 1200 UTC (Fig. 5b) on the 16th. These strong low level winds at the 850 hPa level, as well as the cold frontal passage and deepening surface low located to the northeast created a synoptic situation conducive to a high wind event.
Figure 1. Hydrometeorological Prediction Center (HPC) surface fronts and pressure analysis at 1200 UTC 15 April 2007. Click on image to enlarge.
Figure 2. Hydrometeorological Prediction Center (HPC) surface fronts and pressure analysis at 0600 UTC 16 April 2007. Click on image to enlarge.
Figure 3. Hydrometeorological Prediction Center (HPC) surface fronts and pressure analysis at 1200 UTC 16 April 2007. Click on image to enlarge.
Figure 4. Storm Prediction Center (SPC) objective analysis of 500 mb geopotential height, temperature, and wind at 1200 UTC 15 April 2007 (left) and 1200 UTC 16 April 2007 (right). Click on images to enlarge.
Figure 5. Storm Prediction Center (SPC) objective analysis of 500 mb geopotential height, temperature, and wind at 0000 UTC 16 April 2007 (left) and 1200 UTC 16 April 2007 (right). Click on images to enlarge.
3. Societal Impacts
As a result of the event, thousands of trees were blown down across the western Carolinas, as well as widespread damage to homes and businesses across the region. Also, at least three deaths and seven injuries were directly attributable to the strong winds.
Overall, the damaging winds took place in two distinct "bursts." The first occurred during the evening of the 15th along and near the Blue Ridge. A 66 mph wind gust was recorded at the Asheville Regional Airport during the evening, as well as an 83 mph gust recorded by an observer on Flat Top Mountain at an elevation of 4,320 ft. Widespread trees and powerlines were reported blown down throughout the evening, which also resulted in damage to a few homes. The second segment of this event occurred during the day on the 16th and affected locations across much of the Piedmont of the Carolinas, in addition to the Mountains and Foothills. During this period, much like the evening before, numerous trees and powerlines were blown down, with some structures sustaining damage due to falling trees. Power outages were also widespread, affecting hundreds of thousands of customers. At the peak of the event, around 30,000 people were without power in Henderson County alone. Many remained without power until the 19th. Also of note is the fact that approximately 5% of the apple trees in Henderson County were uprooted, furthering the economic impact of the event.
During 15-16 April 2007, a high wind event occurred, causing considerable damage to trees, structures, and widespread power outages across the western Carolinas. The event occurred in two primary "bursts" as a strong low pressure system deepened over the Mid-Atlantic and along the East Coast. Wind gusts of up to 80 mph were recorded across the North Carolina Mountains, with numerous places experiencing winds in excess of 60 mph during the course of the event. Overall the event was well anticipated, with a High Wind Watch being issued on the afternoon of the 14th, a little more than 24 hours before the first round of damaging winds took place.
The upper air analysis and sounding graphics were obtained from the Storm Prediction Center and surface analyses were obtained from the Hydrometeorological Prediction Center. Also, thanks to Justin Lane for access to the storm data for the event.