December Briefing

Outline

• Current Conditions

• Primary Factors– 2nd Year La Nina– Drought Region / Feedback– Role of AO/NAO

• Streamflow Outlook– Historical– SERFC Ensemble Streamflow Prediction

Past 30 Day (% of Normal) Rainfall

Past 60 Day (% of Normal) Rainfall

YTD (% of Normal) Rainfall

Drought Monitor

Recent enhanced inflows have stabilized but not increased pool elevation

Typical US Temperature, Precipitation and Jet Stream Patterns during La

Niña Winters

Jet Stream / Active Weather Generally North of ACF

Jan-

04Ap

r-04

Jul-0

4O

ct-0

4Ja

n-05

Apr-

05Ju

l-05

Oct

-05

Jan-

06Ap

r-06

Jul-0

6O

ct-0

6Ja

n-07

Apr-

07Ju

l-07

Oct

-07

Jan-

08Ap

r-08

Jul-0

8O

ct-0

8Ja

n-09

Apr-

09Ju

l-09

Oct

-09

Jan-

10Ap

r-10

Jul-1

0O

ct-1

0Ja

n-11

Apr-

11Ju

l-11

Oct

-11

-30

-25

-20

-15

-10

-5

0

5

10

15

20

-2.5

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

ENSO MEIRunning Rainfall (in)

El NiñoEl Niño

La Niña

La Niña

La Niña

ENSO vs Rainfall Surplus/Deficits (Climate Division 2 and 3)

Take Away: Correlation between ENSO & SE US Rainfall never fully made up deficits from past drought?

Lani

er P

ool (

ft)

Lake Lanier Pool vs Rainfall Surplus/Deficits (Climate Division 2 and 3)

Jan-

04Ap

r-04

Jul-0

4O

ct-0

4Ja

n-05

Apr-

05Ju

l-05

Oct

-05

Jan-

06Ap

r-06

Jul-0

6O

ct-0

6Ja

n-07

Apr-

07Ju

l-07

Oct

-07

Jan-

08Ap

r-08

Jul-0

8O

ct-0

8Ja

n-09

Apr-

09Ju

l-09

Oct

-09

Jan-

10Ap

r-10

Jul-1

0O

ct-1

0Ja

n-11

Apr-

11Ju

l-11

Oct

-11

1045

1050

1055

1060

1065

1070

1075

-30

-25

-20

-15

-10

-5

0

5

10

15

20

Running RainfallLanier Pool (ft)

Rainfall Deficits Increase from Winter 2007 to Spring

2008

Lanier Pools recoverIn 2009

1st vs 2nd Year La Niña Composites

Year 1 Year 2Year 1 - worked out fairly wellYear 2 - generally drier

‘Double-Dip’ Las Niñas

Data courtesy of Melissa Griffin (Florida Asst. SC)

Weather Can Override Climate

Historical Data – Second Year La NiñaDecember – April Period

18%

43%

40%

35%

30%

35%

35%

28%

38%

23%

35%

43%

Lake Lanier Inflows

Upper Flint

Lower Chattahoochee

Apalachicola Watershed

Ensemble Streamflow PredictionFor Jan 1 - March 31

63%10%

27%

69%22%

9%

57%18%

25%

61%23%

16%

65%

23%

12%

Lake Lanier Inflows

Lovejoy

Whitesburg

Blountstown

Albany

Summary

• La Niña will dominate this winter. Generally, this will continue to reinforce reduced rainfall and overall drought across the Southeast U.S.

• AO/NAO can tend to either enhance or override the ENSO signal.

• Extremely low stream flow and soil moisture will reduce inflows.

• Very tight rainfall gradient over basin north of Lake Lanier.

• A switch to El Niño by next fall, the record of the last decade would favor an end of the 2010-12 drought.

SERFC Journal 2-3 times a week

Water Resources Outlook – bi-weekly

weather.gov/serfc

QUESTIONS