Dr. Jeff Masters' WunderBlog

Top U.S. weather story of 2007: the Southeast U.S. drought

Posted by: Dr. Jeff Masters, 3:29 PM GMT en Enero 01, 2008

The year 2007 is in the record books as the driest or second driest year on record for much of the Southeastern U.S. A mere 31.85 inches of rain fell in Atlanta, Georgia, during the year, 62% of the average of 48 inches. This year's rainfall total just missed breaking the record of 31.80 inches set in 1954. Rainfall records in Atlanta go back to 1930. The drought was worse in Alabama, where Birmingham had its driest year on record--just 28.86", a full 25 inches below average, smashing the record low of 36.14" set in 1931. Huntsville was even drier--a mere 28.65"--29 inches below average. Surrounding areas of Tennessee, North Carolina, South Carolina, Kentucky and Virginia also experienced extraordinarily dry years (Figure 1).

Figure 1. Drought conditions in the Southeastern U.S. were at the highest level possible--exceptional drought--at the end of 2007. Image credit: NOAA.

Although the current drought is exceptional, Atlanta has had much drier 2-year periods. During the drought of 1954-1955, Atlanta received 68.23 inches of precipitation--a 28 inch deficit from the normal 2-year rainfall. The deficit for the past two years is only 16 inches, since an average amount of rain fell in 2006 (48.46 inches). Based on the climatological record, Georgia can expect a two-year drought about once in 25 years, and a drought lasting three or more years about once every 40 years. Drought is part of the natural cycle in Georgia, and it would not be a surprise to see the drought of 2007 continue until the winter of 2008. Although December 2007 saw Atlanta's first above average month of rainfall since November 2006, the coming two weeks look very dry, and the current La Nina atmospheric pattern usually brings below average rainfall.

What is causing the Georgia drought?
Two main factors are responsible for the Southeast U.S. drought. Most importantly, a persistent jet stream pattern has set up that steers storms away from the region, and into Texas instead. Texas, which suffered extreme drought in 2006, found itself awash in floods in 2007, as the jet stream pattern brought storm after storm to the state. Another contributing factor to the current Southeast drought is the absence of tropical storms and hurricanes during 2006 and 2007. These storms are an important part of the annual rainfall budget for the Southeast. For example, in 2005, 29% of Atlanta's yearly rainfall came from five tropical storms:

1.36" Arlene June 11-12, 2005
1.40" Katrina, August 29-30, 2005
5.48" Cindy, July 6-8, 2005
5.41" Dennis, July 9-12, 2005
2.94" Tammy, October 6-8, 2005

Figure 2. Over ten inches of rain fell on Atlanta in 2005 from two tropical cyclones, Dennis and Cindy. Tropical cyclones accounted for 29% of Atlanta's rainfall that year. Image credit: NOAA/HPC.

There is little evidence that global warming contributed to this drought. The Southeastern U.S. has cooled by about 0.1° F over the past 100 years, even as the rest of the globe has warmed 1° F. The reasons for this lack of warming in the Southeast are not fully understood. One theory is that the cooling is due to air pollution blocking sunlight. Another theory, proposed by Georgia State Climatologist David Stooksbury, attributes the cooling to the shift from 80 percent row crops (like corn and cotton) to 60 percent forest. Land use changes like this can have a significant impact on how solar energy heats the air once it is absorbed by the soil.

Why Atlanta is vulnerable to drought
Atlanta, unlike most major cities, grew up around rail lines rather than a major body of water. Although the Chattahoochee River runs through Atlanta, the city lies on top of a watershed, with no large bodies of water upstream. The rivers and streams in the region are small, and the bedrock limits how much ground water is available. The Lake Lanier reservoir that supplies Atlanta with most of its water was constructed in the 1950s. Since that time, the population of Atlanta has quadrupled, increasing the pressure on the reservoir's limited water. Lake Lanier is at its record lowest level--more than 19 feet below average. If the drought continues into the summer of 2008, and no tropical storms arrive to break the drought, Atlanta may run out of water.

By 2030, the population of the Atlanta metropolitan area is expected to increase from 5 million to 9 million. Current water resources in the regions will be unable to support this population increase, unless planners make a concerted and expensive effort to plan ahead. The expected increase in temperatures over the coming decades due to global warming will make future droughts in the region even more severe, so Atlanta has a very tough road ahead of it.

Jeff Masters

Georgia Drought Series 2 (HurricaneIan)

Like my last series, this Series of photos concern the drought in North Georgia. These were taken at Lake Chatuge, Georgia. This is near the North Carolina Line and near a town called Hiawassee. North Georgia is experiencing a major drought. These docks are designed to float and adjust to water depth, however, now they are high and dry. The depth of these lakes varies from season to season, however, this is by far the lowest I have ever seen it. This water is not only used for drinking, this is also the primary supply of hydro-electric power for the region. The drought is causing other problems as well, the leaves are not changing properly, some look burnt and others fall off before turning. North Georgia and surrounding areas need rain in the worst way. The good news is it is raining

Scenes from Lake Lanier, GA (DadandMarcher)

Here are a few scenes from Lake Lanier in Buford, GA. We are going through a record setting drought this year. Everyday now we set a new record for the Lake level since the inception of the lake in the 1950's

Categories: Drought

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552. Sfloridacat5 6:59 PM GMT en Enero 03, 2008
It was cold this morning. We hit 30 degrees at 5:30am at my house (Ft. Myers area). That easily beat the old record of 34 degrees. But temps are expected back in the low 70s by tomorrow and low 80s by Sunday. Member Since: Septiembre 16, 2007 Posts: 0 Comments: 2027

553. ShenValleyFlyFish 7:01 PM GMT en Enero 03, 2008
vort Isn't everyone in Florida a Yankee deserter or escaped from Cuba? Member Since: Septiembre 9, 2007 Posts: 36 Comments: 4684

554. sporteguy03 7:03 PM GMT en Enero 03, 2008
Thanks for the update weather456 Member Since: Julio 7, 2005 Posts: 0 Comments: 4824

555. weatherboyfsu 7:06 PM GMT en Enero 03, 2008
Good morning, We definitely are experiencing Global Warming!!!! I live about 25 miles west of Orlando Florida and we got down to 24 degrees this morning. Some records set.........Yep.....we definitely are causing global warming........Yeah right!!!!!! I believe along with many prominent scientist that we humans have little or no affect on long term changes to our earths atmosphere. This earth will be here long after we are gone. Come on people, we do not know everything and we surely cant analyze our earth on such a short resume.(How long have we been keeping records?) LOL>>>>>>> Before we could do enough damage to cause an effect, we would be extinct ourselves from the damage we caused. So, basically, we couldnt if we wanted to. One more thing.....There are more species that are extinct then are living......Go figure! Have a great day and go out and make this world a better place because its the right thing to do not because we have to save our behinds........... Member Since: Julio 17, 2005 Posts: 0 Comments: 1025

556. weatherboyfsu 7:08 PM GMT en Enero 03, 2008
Hello and Good Afternoon,,,,,,,, Member Since: Julio 17, 2005 Posts: 0 Comments: 1025

557. NEwxguy 7:20 PM GMT en Enero 03, 2008
from outside boston Fair 11°F (-12°C) Humidity: 46 % Wind Speed: NW 14 G 23 MPH Barometer: 30.49" (1034.5 mb) Dewpoint: -6°F (-21°C) Wind Chill: -5°F (-21°C) Visibility: 10.00 mi Member Since: Septiembre 6, 2007 Posts: 816 Comments: 13132

560. Cavin Rawlins 7:29 PM GMT en Enero 03, 2008
sporteguy03, ur welcome Member Since: Julio 24, 2005 Posts: 407 Comments: 19076

561. hurricane24 7:31 PM GMT en Enero 03, 2008
soz but we have td10s in the south pacfic!

562. hurricane23 8:01 PM GMT en Enero 03, 2008
The begining of the parade! Member Since: Mayo 14, 2006 Posts: 8 Comments: 13277

563. Cavin Rawlins 8:04 PM GMT en Enero 03, 2008
Dvorak readings will begin shortly Member Since: Julio 24, 2005 Posts: 407 Comments: 19076

564. WeatherChickSTL 8:06 PM GMT en Enero 03, 2008
New blog up . . .

566. biff4ugo 8:26 PM GMT en Enero 28, 2008
I keep hearing about the melting of the Antarctic Ice sheet, but the temperatures look well within the average temperatures. What is up with that??? Member Since: Diciembre 28, 2006 Posts: 107 Comments: 1188

567. biff4ugo 1:45 PM GMT en Febrero 18, 2008
I'm very happy to see the south getting rain again. Tornadoes are not so welcome but we take the good with the bad. January's record snow coverage is a very good thing to help cool the hemisphere down. Go La Nina Go! Member Since: Diciembre 28, 2006 Posts: 107 Comments: 1188

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