A cooler, drier continental airmass was moving into the Tennessee Valley on the evening of Sunday, September 21st. Showers and a few thunderstorms developed along the associated frontal boundary as it crossed into the Huntsville County Warning and Forecast Area late in the afternoon and through much of the evening. One thunderstorm began to strengthen as it crossed from the Lynchburg, TN area into northwestern portions of Franklin County, TN (Image 1). The total lightning data, in fact, provided the first indication that this cell was undergoing strengthening. Notice the “spike” in data, particularly beginning at 2153Z, when values jumped from a moving average of around 50-100 to over 200.
Severe weather was not expected this evening, with somewhat unfavorable environmental conditions. Nevertheless, cells during the late afternoon were being watched for incidences of strong winds (up to about 40 mph), small hail and frequent lightning. The “spike” in the lightning data was the first indicator that this cell was undergoing strengthening and prompted heightened situational awareness and thus closer inspection of radar data. A special weather statement was issued for this cell at 2204Z. Had it not been for the total lightning data running and viewable in the AWIPS II window, a closer inspection of this cell may not have been prompted until later. These data have proven beneficial to operations for over a decade now at the Huntsville NWS office, and will continue to be a integral part of operations here for some time to come.