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Griffith said a low-pressure storm system moved into Georgia during the middle of last week. When it arrived, it feathered up next to a high-pressure system that was hovering over the East Coast. The result: It got stuck, she said.
CNN meteorologist Jacqui Jeras said the atmosphere over north Georgia is completely saturated with water. A new storm system has moved into place now and, at any disturbance, is ready to drop more water on Atlanta. "It's just sitting there waiting for someone to ring the washcloth," she said. Jeras said the storm that remained stuck over Atlanta on Monday previously had brought needed rain to southern Texas. It sucked its moisture from the Gulf of Mexico, she said.
That system dissipated late Monday, but another has moved in to take its place, she said. Responding to the rain, creeks and rivers in metro Atlanta are overflowing in some places, setting new records. The Chattahoochee River in northeast Atlanta rose to a height not seen since 1919, Griffith said.
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http://www.cnn.com/2009/TECH/science/09/22/atlanta.weather.science/