The three-dimensional patterns of the large-scale divergence and vertical motion over North America are derived at twelve-hour intervals for a one-week period beginning May 21, 1962. The distribution of severe storms in the central and eastern United States during that period is examined and related to the patterns of vertical motion.nThe mean profile of large-scale vertical motion near early-morning storms is compared with that near late-afternoon storms;the two profiles are found to be quite different. The morning storms correlate highly with the pat-terns of upward motion;the afternoon storms do not, presumably because other factors such as local heating are of comparable importance.
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