A Preliminary Climatology of Thunderstorm Penetrations of the Tropopause in the United States

Abstract

This paper presents a four year climatology of penetrations of the tropopause (of more than 5000 ft) by thunderstorms at ten locations in the United States. WSR-57 radar data for 1961 through 1964 were used to determine the vertical extent of the penetrations. Most penetrations occurred during the spring and summer months with only the central part of the United States showing penetrations in both February and October. Maximum penetrations occurred during the afternoon and evening hours with several mountain and coastal stations reporting only one or two total penetrations for a few of the night hours for the four year period. The largest number of penetrations occurred from the coast of the Gulf of Mexico northward into the center of the country, with only one-tenth as many penetrations reported at some of the coastal stations. The highest penetrations also occurred near the center of the country. Cloud tops equal to or greater than 60,000 ft MSL were found in large numbers (more than 50) from the Gulf coast northward, near the area of maximum severe thunderstorm activity, with other stations reporting less than 12 such clouds for the four years. The same area of maximum penetrations reported more than 20 time periods of more than four consecutive hours of penetrations while most of the coastal stations had only one such occurrence during the four years.