Outlook for Precipitation in Georgia
Plummer, Gayther L.
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Outlooks for climate changes in the next few decades must take into account all historic evidence for climatic changes in the past. Wet-dry periods are historic facts and evidence of cyclic periods is abundant. Thus, a century or more of historic patterns become precursors for patterns that project trends for several decades -- not precisely but generally. Weather and climate in Georgia are governed primarily by two airmass systems: 1) the semi-permanent, Azores, high-pressure system affects Georgia's Coastal Plain area most directly, and 2) the continental polar airmasses affect the Southern Appalachian mountains. These airmasses cause droughts; they sometimes confront each other over Georgia as stationary frontal systems that cause much wet weather. Dry weather statewide occurred periodically at intervals of 7-yr, 9-yr, 11-yr, and others. Each cyclic pattern overlays the others. Possible outlooks for rainfall from the comparatively dry decade of the 1980's are: 1) an up-trend that brings more precipitation, 2) a down-trend into yet drier weather, and 3) an extension, or continuation, of the relatively dry weather of the 1980s. History indicates that an up-trend in precipitation from 1986 until 1990 to 1993 is a reasonable expectation; but that trend was modified in June 1988, perhaps temporarily. Another series of dry weather periodically is expected from about 1994 through 1999. Two major dry-weather periods, similar to the decades of the 193Os, '50s and '80s, are expected about 2010-2015 throughout southeastern U.S. The outlook is bleak for the kind of wet-weather periods that occurred in the 1940's, '60s, and early '70s.