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No. 20: Mar-Apr 1982

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A Most Peculiar Cloud Arch

July 12, 1980. Strait of Gibraltar.

"At 1825 GMT whilst the vessel was transiting the Strait of Gibraltar, a line of low cloud was observed in an otherwise cloudless sky, see sketch. The cloud was in the form of an arc in an east-west line, reaching the surface approximately 2 n. mile ahead and astern of the vessel. Visibility under the cloud was about 10 n. mile in the north-south direction and 2 n. mile to the east and west. Once the vessel reached the point where the cloud touched the surface, the visibility was reduced to approximately 1.5 n. mile. Whilst the vessel was passing the cloud, the barograph trace fell almost vertically and both the air and sea temperatures dropped several degrees."

(Shepherd, F.; "Cloud," Marine Observer, 51:107, 1981.)

Comment. This is just one more mysterious cloud arch, but on a very small scale. What bizarre meteorological conditions create such strange structures?

Reference. Other unusual cloud phenomena may be found in Section GWC in our Catalog: Tornados, Dark Days. For more information on this book, visit: here.

Curious cloud arch in the Strait of Gibralta
A curious cloud arch in the Strait of Gibralta. The ends terminated in the ocean at points 4 miles apart.

From Science Frontiers #20, MAR-APR 1982. 1982-2000 William R. Corliss