Tuesday, September 22, 2009

A Perfect Deluge

After enduring more than a year of severe drought, the residents of northern Georgia and bordering States had been hoping for a tropical storm that might restore the vegetation, recharge the streams and fill their reservoirs. Alas, in the middle of a lackluster hurricane season, relief came not in the form of a powerful storm but as the effects of a plodding cold front. Unfortunately, it was a gift that kept on giving, drenching the region with 10-20 inches of rain and producing catastrophic floods throughout the area.

The cold front, curving from the eastern Great Lakes to central Texas, established a clash zone, with warm, humid air to its southeast and cool, dry air to its northwest. As the front inched to the east, a southerly flow of Gulf air invaded the Southeastern States, priming the region for thunderstorms. The front and its low pressure center provided lift, pulling the soupy air up and over the invading wedge of cool air; the terrain of northern Georgia and its border areas, higher than the Gulf Plain to the south and east, augmented this lift as the warm, moist air streamed up from the south. All of these factors ignited thunderstorms along the edge of the front, which, lacking a potent shove from the jet stream, lounged over these uplands, dropping heavy rain before redeveloping and training over the same areas.

In effect, a Perfect Deluge was established and continued to intensify until the front moved further to the east. Despite a respite today, more precipitation is expected throughout the week as another cold front drops from the Midwest. Hopefully, that rainmaker won't linger over this flood zone which has no capacity to absorb additional moisture; any rain that falls will quickly move to the swollen streams and rivers.