Despite threats of 4-5 inches of rain along the I-85 corridor due to the remnants of Hurricane Ida, it appears that most of the Atlanta area only received in the neighborhood of 2-3 inches of precipitation. Here in Lawrenceville, I’ve recorded 1.87 inches since the rain started early this morning. In Alpharetta, they recorded 3.11 inches, and in Johns Creek, the Atlanta Athletic Club measured 2.98 inches.

Other Georgia locations received much more rain. Pine Mountain was reporting 5.48 inches of rainfall today, while Columbus recorded 5.01 inches. These two areas seem to be the hardest hit, and from glancing at the radar this afternoon, it seems that Alabama got the most rain. Gainesville recorded 2.44 inches, while Marietta saw 2.77 inches. The official Atlanta rain gauge at Hartsfield Airport recorded 2.71 inches.

The rain did cause some area rivers to reach flood stage. Big Creek in Alpharetta is flooding, as is Pew Creek in Gwinnett County, Peachtree Creek in Atlanta, and the Nickajack Creek in Cobb county. Suwanee Creek is expected to experience minor flooding tomorrow morning.

There’s still more rain to come before Ida bids Georgia farewell (and her remnants cause problems in the Delmarva peninsula). But, looking at the radar now, it seems like the forecasters should have picked I-59 in Alabama as the worst hit area, rather then the I-85 corridor.

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I hope you enjoyed the beautiful weather today, with highs eight degrees above normal. In fact, the last week is the first time we’ve gone seven days without any rain since the middle of August. That’s about to change.

The map to the right tells the story. A combination of a cold front, a low pressure system now over Texas, and Hurricane Ida will bring as much as four inches of rain to north Georgia beginning Monday night through Wednesday morning.

Much will depend on Ida’s exact path. While the official forecast from the Hurricane Center takes her path over extreme south Georgia, the GFS and Canadian models are much further north, passing over the Atlanta area. Over the past few forecast updates, the Hurricane Center has brought Ida’s path further north.

The Weather Service has issued a flash flood watch for much of North Georgia from Tuesday morning through Wednesday morning. Despite the lack of rain over the last week, the ground is still extremely wet, and any rain over two inches or so could trigger yet more flooding.

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Now that September is over, we can look back at a month that will be remembered for plenty of rain. Of course, it all depended on where you were: Gwinnett, Cobb and Douglas counties received far more precipitation than did the official measuring station at Hartsfield Airport. Still, it was the fifth wettest September on record in Atlanta, with 8.94 inches, or 219% of normal. It was the third wettest September in Macon with 10.68 inches, or 328% of normal, and the fourth wettest in Athens, with 9.86 inches, or 279% of normal rainfall.

At my house in Lawrenceville, I recorded 16.28 inches of rain, or 427% of normal rain. Gainesville reported 12.10 inches of rain, or 275% of normal, and Peachtree DeKalb airport had 15.74 inches of precipitation, or 420% of normal. The image above graphically displays the month’s rainfall. Click on it to enlarge.

Cooler than normal temperatures early in the month were balanced out with warmer than normal temperatures later on, ending up with a more or less normal average temperature for September. Atlanta’s mean temperature was 73.4 degrees, two tenths of a degree above normal. In Gainesville, the average of 71.0 degrees was 0.7 degrees cooler than normal, and in Athens, temperatures were half a degree above normal, with 73.1.

By now, even the most cynical will have to admit that the drought that plagued Georgia from 2006-2008 is finally over. A recent study by Columbia University indicated the drought wasn’t caused by global warming, and in fact wasn’t that unusual. The study says that the drought appeared more serious this time because of the Atlanta region’s growing population. While there was enough water for the region during similar droughts in the 1950s, not enough additional water storage was available to meet needs this time.

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Weather-wise, the rainfall that caused the record-breaking flooding in metro Atlanta is now over. Of course, it’s going to take a while for roads to be rebuilt, and damage to homes to be repaired, but the last few days of dry weather has allowed river levels to recede and land to dry out.

The US Geological Survey declared the flooding a 500 year flood, according to an article in the AJC. Basing their data on river flow gauges, the USGS said there is only a 1/2 of one percent chance of a flood of the magnitude we saw this week. That doesn’t mean it will be another 500 years before we see this much rain, it’s just that the odds are very slim.

The weather service reports nine record river flows in the area, including Suwanee Creek cresting at 14.3 feet, more than two feet above the previous record. Additionally there were five top 5 record flows at other river gauges. Lake Lanier rose by about three feet due to all the rain.

Here are some rainfall totals from Monday, September 14th at 8 AM through Tuesday, September 22nd at 8 AM:

Kennesaw: 20.37 inches
Lawrenceville: 19.32 inches
Marietta: 18.91 inches
Douglasville: 18.18 inches
Tucker: 18.08 inches
Kennesaw: 17.6 inches
Canton: 17.14 inches
Snellville: 17.13 inches
Roswell: 15.49 inches
Doraville: 13.88 inches
Chamblee: 13.19 inches
Johns Creek: 13.16 inches
Dunwoody: 12.37 inches
Atlanta Hartsfield: 11.23 in.
Gainesville: 10.27 inches
Athens: 8.72 inches

You can see the full list as reported by the weather service and cooperative stations here.

One of the major causes of all the rain was a low pressure system west of Georgia being blocked by a high pressure system to our north. Even after the storms passed, the blocking pattern remained, which caused the continuing high humidity and 10 degree above average low temperatures over the past few days. This weekend, a cold front will finally push the whole system away, and give us cooler temperatures with low humidity, and a chance to dry out wet crawl spaces.

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The weather service has reported 24 hour rainfall totals for North Georgia ending at 8 AM on Monday, September 21st. Here are some highlights:

Athens: .65 inches
Atlanta: .87 inches
Canton: 3.95 inches
Carrollton: 7.66 inches
Cartersville: 1.68 inches
Cleveland: 3.68 inches
Chamblee: 4.28 inches
Cumming: 1.80 inches
Doraville: 5.37 inches
Gainesville: .82 inches
Lafayette: 7.20 inches
Marietta: 3.54 inches
Rome: 2.61 inches
Sautee: 5.18 inches
West Point: 4.33 inches

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