Transcript December Briefing Outline • Current Conditions • Primary Factors – 2nd Year La Nina – Drought Region / Feedback – Role of AO/NAO • Streamflow Outlook –

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
20
15
2
El Niño
1.5
El Niño
10
1
5
0.5
0
0
-5
ENSO MEI
-0.5
-10
La Niña
-15
-20
-25
-1
La Niña
-1.5
La Niña
-2.5
Jan-04
Apr-04
Jul-04
Oct-04
Jan-05
Apr-05
Jul-05
Oct-05
Jan-06
Apr-06
Jul-06
Oct-06
Jan-07
Apr-07
Jul-07
Oct-07
Jan-08
Apr-08
Jul-08
Oct-08
Jan-09
Apr-09
Jul-09
Oct-09
Jan-10
Apr-10
Jul-10
Oct-10
Jan-11
Apr-11
Jul-11
Oct-11
-30
-2
Take Away:
Correlation between ENSO & SE US
Rainfall never fully made up deficits from past drought?
Running Rainfall (in)
Jan-04
Apr-04
Jul-04
Oct-04
Jan-05
Apr-05
Jul-05
Oct-05
Jan-06
Apr-06
Jul-06
Oct-06
Jan-07
Apr-07
Jul-07
Oct-07
Jan-08
Apr-08
Jul-08
Oct-08
Jan-09
Apr-09
Jul-09
Oct-09
Jan-10
Apr-10
Jul-10
Oct-10
Jan-11
Apr-11
Jul-11
Oct-11
Lanier Pool (ft)
1075
20
Lanier Pools recover
In 2009
1060
Rainfall Deficits Increase
from Winter 2007 to Spring
2008
1045
15
1070
10
1065
5
0
-5
-10
1055
-15
1050
-20
-25
-30
Running Rainfall
Lanier Pool (ft)
1st vs 2nd Year La Niña Composites
Year 1
Year 2
Year 1 - worked out fairly well
Year 2 - generally drier
‘Double-Dip’ Las Niñas
Data courtesy of Melissa
Griffin (Florida Asst. SC)
Weather Can Override Climate
40%
18%
43%
35%
35%
30%
38%
35%
28%
43%
23%
35%
27%
63%
10%
9%
22%
69%
25%
18%
57%
16%
23%
12%
23%
65%
61%
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.
weather.gov/serfc
SERFC Journal 2-3 times a week
Water Resources Outlook – bi-weekly