14 NC counties and 2 VA counties are under alert, including Johnston, Nash, Halifax, Edgecombe, and Mecklenburg, VA counties. Details
Published: 2007-07-18 07:09:46
Updated: 2007-07-18 07:09:46
Posted July 18, 2007
By Kelly Snyder
MIKE MOSS SAYS: Kelly, I'm posting this months after you sent in the question, I'm afraid. Unfortunately, we receive so many questions that not only are we unable to answer every one, but occasionally a few slip through unread until sometime down the road. This one was an especially entertaining mystery at first, but with the help of a couple of folks from the Morehead Planetarium and Science Center who were visiting and looking over my shoulder when I read it, I think we have an answer. Of course, you may have figured this out yourself by now as well.
We think what produced the phenomenon was some kind of big sale or grand opening, etc, in which part of the festivities and promotion involved the use of a cluster of multiple (in this case four) searchlights swinging around the sky in a choreographed manner. Sometimes this is visually obvious, but there are some reasons it may not have been in this case. I checked weather observations across the area for the time frame you mentioned, and found that there was a broken to overcast, and probably smooth and stratified, layer of clouds at about 6000 feet above the ground during the afternoon and evening in question, with the surface dewpoint at the time a low 15 degrees. This indicates a very dry sub-cloud layer, and likely very little or nothing in the way of haze or fog, etc. Because of that, the "spots" from the lights would have been quite visible dancing across the base of the clouds, but there would have been little in the way of scattering particles between the ground and the cloud that would have made the "beams" themselves visible.
A good analogy would be to imagine sitting in a large room with a white ceiling while someone points a couple of hidden flashlights upwards and swings them around. In a very clean room, you would see only the light on the ceiling, but in a smoky or foggy room scattering along the path would allow you to trace the beam back down to the flashlights.