The Union County Landspout
9 June 2001
Bryan P. McAvoy
NOAA/National Weather Service
A weak tornado touched down near Carlisle, South Carolina, on 9 June 2001. Image taken by Tony Henderson.
Author's Note: The following report has not been subjected to the scientific peer review process.
During the afternoon of June 9, 2001, a weak tornado occurred in southern Union County, South Carolina. The tornado touched down around 330 pm EDT (1930 UTC), about 3 miles west southwest of Carlisle, in the heart of the Sumter National Forest, and dissipated a few minutes after 4 pm. The damage path was never surveyed, but local fire and rescue reported some minor tree damage where the tornado went into the woods.
When we say "tornado", we do not mean the classic supercell tornado, which forms over a depth of thousands of feet and can produce catastrophic damage. In this case, the tornado was one that is usually classified as a "landspout". The phrase is derived from the more common "waterspout" which is a weak tornado that forms over water, and is seldom if ever associated with a parent mesocyclone.
In the case of the Union County tornado, it occurred in a fairly typical landspout environment. The associated convection was very weak, not more than a moderate shower. The radar four panels (Fig. 1) show the reflectivity pattern from 0.5, 1.5, 2.4 and 3.4 degree elevation scans. In other words, these images were taken at the same time, but at different elevations in the storm. Notice how small and weak the cell is. The storm top, in the fourth panel (lower right), does not even extend to 20,000 feet, and these images represent the storm at its strongest. The storm relative velocity data from the same time (Fig. 2) show no organized areas of rotation, nor any strong storm top divergence.
Figure 1. KGSP radar reflectivity at 1948 UTC 9 June 2001 at 0.5 degrees (upper left), 1.5 degrees (upper right), 2.4 degrees (lower left), and 3.4 degrees (lower right).
Figure 2. As in Fig. 1, except for Storm Relative Motion.
This is typical of a landspout as all the dynamics for the tornado occur very low in the atmosphere, below the cloud base. As a result, the Weather Surveillance Radar (WSR-88D) at the National Weather Service office at the GSP airport could not effectively scan these features, as they occur too low in the atmosphere and on too small a scale for the beam to detect them at long range.
But, there most definitely was a tornado. Witnesses watched the landspout for nearly 30 minutes. In fact one witness, Tony Henderson, even took pictures (Fig. 3).
Figure 3. Image of weak tornado over Union County, South Carolina, near Carlisle. Image taken by Tony Henderson.
During its life, the landspout was nearly stationary, drifting only slowly to the southeast. This is a typical characteristic of landspouts. Landspouts are usually stationary as they form in a weakly sheared environment, which is anathema to other types of tornado production. Witnesses said there was very little rain and no lightning and thunder, another landspout characteristic. The evening sounding from nearby Greensboro, North Carolina, had weak lower tropospheric shear, though winds increased aloft.
Essentially, a landspout forms when a broad, weak area of cyclonic or anticyclonic rotation in the low levels of the atmosphere is caught up in the updraft of a developing cumulus cloud. The effect is similar to that of a figure-skater pulling in her arms to spin faster. As the area of rotation is stretched and constricts, it rotates faster, until condensation occurs and the funnel become visible. In this case, the landspout was frequently in contact with the ground. Thus, by definition, it was a tornado.