Post on 19-Dec-2015
Outline
• Current Conditions
• Primary Factors– 2nd Year La Nina– Drought Region / Feedback– Role of AO/NAO
• Streamflow Outlook– Historical– SERFC Ensemble Streamflow Prediction
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
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.