No. 89: Sep-Oct 1993
March 17, 1992. Delta Flight 1083 en route from Pittsburgh to Atlanta. At approximately 8:30 PM, this flight was thought to be flying safely high above thundercloud tops, which were situated at 20,000-22,000 feet. The pilot, W.F. Blanchard describes what he observed:
"Then, from one of these clouds, a lightning bolt appeared that changed my mind instantly. This bolt came from the top of the buildup closest to our line of flight and formed an enormous loop in the sky. It started at the top of the cloud and went well above our altitude (to at least 40,00045,000 ft.) and then circled back down into the cloud. My impression is that it joined back into itself at the top of the cloud, but it may have returned to another of the peaks in the same cloud."
(Grynkewich, N.E., Jr.; "Lightning Loop," Weather, 47:493, 1992.)
Comment. There have been numerous recent reports of upwardly directed "rocket" lightning, but none in which the lightning returned back to the same cloud. Grynkewich may have seen some bizarre form of intercloud lightning.
Reference. Unusual and anomalous forms of lightning are cataloged in section GLL in our catalog: Lighting, Auroras. Details here.