PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD
830 AM EST THU DEC 20 2007 

SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS

THE MAIN FACTORS WHICH USUALLY INFLUENCE THE SEASONAL CLIMATE OUTLOOK INCLUDE:
1) EL NINO AND LA NINA - WHICH COMPRISE EL NINO/SOUTHERN OSCILLATION OR ENSO.
2) TRENDS - APPROXIMATED BY THE DIFFERENCE BETWEEN THE MOST RECENT 10-YEAR MEAN 
OF TEMPERATURE OR 15-YEAR MEAN OF PRECIPITATION FOR A GIVEN LOCATION AND TIME 
OF YEAR AND THE 30-YEAR CLIMATOLOGY PERIOD (CURRENTLY 1971-2000). THE OCN TOOL 
REPRESENTS THE TREND.
3) THE TROPICAL 30-60 DAY OSCILLATION - AFFECTS CLIMATE VARIABILITY WITHIN 
SEASONS.
4) THE NORTH ATLANTIC OSCILLATION (NAO) AND THE PACIFIC NORTH AMERICAN (PNA) 
PATTERNS - WHICH AFFECT THE TEMPERATURE ANOMALY PATTERN ESPECIALLY DURING THE 
COLD SEASONS. THESE PHENOMENA ARE CURRENTLY KNOWN TO BE PREDICTABLE ONLY OVER A 
WEEK OR SO.
5) PERSISTENTLY DRY OR WET SOILS IN THE SUMMER AND SNOW AND ICE COVER ANOMALIES 
IN THE WINTER. THESE FACTORS TEND TO PERSIST FOR LONG PERIODS AND ACT AS A KIND 
OF MEMORY IN THE CLIMATE SYSTEM.
6) STATISTICAL FORECAST TOOLS - CANONICAL CORRELATION ANALYSIS (CCA)... AND 
SCREENING MULTIPLE LINEAR REGRESSION (SMLR).
7) DYNAMICAL FORECAST MODELS... INCLUDING THE NCEP CLIMATE FORECAST SYSTEM 
(CFS).
8) AN OBJECTIVE CONSOLIDATION (ABBREVIATED CON IN THE TEXT) OF THE OCN... 
CCA... SMLR AND CFS FORECASTS IS USED AS A FIRST GUESS IN PREPARING THE 
FORECAST MAPS. THIS TECHNIQUE MAKES OPTIMUM USE OF THE KNOWN SKILL OF OUR 
FORECAST TOOLS.

A MODERATELY STRONG COLD EVENT (LA NINA) CONTINUES ACROSS THE PACIFIC BASIN.  
SEA SURFACE TEMPERATURES (SSTS) ARE BELOW AVERAGE THROUGHOUT THE CENTRAL AND 
EASTERN EQUATORIAL PACIFIC OCEAN, WITH ANOMALOUSLY COLD SSTS EXTENDING FROM THE 
SOUTH AMERICAN COAST WESTWARD BEYOND THE DATE LINE TO 160E LONGITUDE.  SSTS IN 
THE NINO 3.4 REGION (FROM 5N TO 5S AND 170W TO 120W) ARE A GOOD INDICATOR OF 
THE STRENGTH OF A LA NINA.  SSTS IN THE NINO 3.4 REGION AVERAGED 1.5 DEGREES C 
BELOW NORMAL DURING NOVEMBER, WHERE A VALUE OF 1.0 TO 1.5 DEGREES BELOW NORMAL 
INDICATES THE EXISTENCE OF MODERATE LA NINA CONDITIONS. 

THESE OBSERVATIONS AGREE WITH WHAT MOST DYNAMICAL AND STATISTICAL MODELS HAVE, 
FOR SOME TIME, BEEN PREDICTING FOR THIS FALL AND WINTER.  THESE FORECASTS AND 
OBSERVATIONS SUPPORT A PREDICTION OF MODERATE LA NINA CONDITIONS FOR THE 
JANUARY-FEBRUARY-MARCH (JFM) 2008 SEASON AND POSSIBLY FMA 2008 AS WELL, 
FOLLOWED BY WEAK LA NINA CONDITIONS FOR MAM.  THE CONSENSUS OF MODEL FORECASTS 
FOR NINO 3.4 SSTS INDICATE THAT THE CURRENT SST ANOMALIES OF BETWEEN 1 AND 2 
DEGREES C BELOW NORMAL ARE LIKELY TO PERSIST THROUGH JFM 2008 ... AND THEN 
GRADUALLY DIMINISH DURING FMA AND MAM (SPRING) 2008. 
 
THE TEMPERATURE AND PRECIPITATION OUTLOOKS FOR JANUARY-FEBRUARY-MARCH (JFM) 
2008 REFLECT LA NINA IMPACTS IN COMBINATION WITH RECENT TRENDS.  TEMPERATURES 
FROM THE PACIFIC NORTHWEST EASTWARD ACROSS THE NORTHERN TIER OF STATES TO 
NORTHERN MICHIGAN ARE EXPECTED TO BE COOLER THAN THE AVERAGE OF RECENT YEARS 
AND SEASONAL MEANS SHOULD BE MORE IN LINE WITH THOSE EXPECTED IN THE 1971-2000 
CLIMATE BASE PERIOD.  MOST OF THE REMAINDER OF THE NATION, INCLUDING NORTHWEST 
ALASKA, IS LIKELY TO EXPERIENCE ABOVE AVERAGE TEMPERATURES, BASED ON A 
COMBINATION OF TREND AND LA NINA INFLUENCES.   ELSEWHERE... THE FORECAST CALLS 
FOR EQUAL CHANCES (EC) OF ABOVE-, NEAR-, AND BELOW AVERAGE TEMPERATURES.

THE PRECIPITATION OUTLOOK FOR JFM 2008 FAVORS ABOVE AVERAGE PRECIPITATION 
AMOUNTS IN THE PACIFIC NORTHWEST AND NORTHERN ROCKIES, AND FROM THE CENTRAL 
MISSISSIPPI VALLEY NORTHEASTWARD TO THE CENTRAL GREAT LAKES.  BELOW AVERAGE 
PRECIPITATION AMOUNTS ARE EXPECTED IN THE SOUTHWEST... THE SOUTHERN AND CENTRAL 
PLAINS... ALONG THE GULF COAST AND THROUGHOUT MUCH OF THE SOUTHEASTERN U.S. 
INCLUDING FLORIDA, THE MIDDLE ATLANTIC COAST STATES AND COASTAL SECTIONS FROM 
THE DELMARVA PENINSULA TO FAR EASTERN SECTIONS OF MASSACHUSETTS.  ELSEWHERE... 
THE FORECAST CALLS FOR EQUAL CHANCES (EC) OF ABOVE-, NEAR-, AND BELOW AVERAGE 
PRECIPITATION.  THESE PRECIPITATION SIGNALS ARE THE EXPECTED RESPONSE TO A 
MODERATE LA NINA, ALONG WITH A RELATIVELY SMALL INFLUENCE FROM TRENDS.

BASIS AND SUMMARY OF THE CURRENT LONG-LEAD OUTLOOKS
NOTE: FOR GRAPHICAL DISPLAYS OF THE FORECAST TOOLS DISCUSSED BELOW SEE:
HTTP://WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/PREDICTIONS/90DAY/TOOLS/BRIEFING

CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS

SEA SURFACE TEMPERATURES (SSTS) ARE SUBSTANTIALLY BELOW AVERAGE IN THE 
EQUATORIAL PACIFIC FROM THE SOUTH AMERICAN COAST TO JUST WEST OF THE DATE LINE. 
 SST ANOMALIES ARE BETWEEN -2 AND -3 C FROM 120W EASTWARD... WHILE TEMPERATURES 
IN THE CENTRAL EQUATORIAL PACIFIC ARE MOSTLY BETWEEN 1 AND 2 DEGREES C BELOW 
NORMAL.  AVERAGE SSTS IN THE NINO 3.4 AND NINO 4 REGIONS IN NOVEMBER WERE -1.5 
C AND -1.1 C IN THOSE REGIONS RESPECTIVELY.  NINO 3 TEMPERATURE DEPARTURE IS 
NEAR -1.7 C, WHILE NINO 1+2 TEMPERATURE HAS AVERAGED ABOUT -2.2 C DEGREES BELOW 
AVERAGE IN NOVEMBER.  OCEAN TEMPERATURES IN THE UPPERMOST 200 METERS IN THE 
EAST PACIFIC HAVE REMAINED WELL BELOW NORMAL, WITH LARGEST DEPARTURES OF -4 TO 
-6 C BETWEEN 130W AND 140W, AND ALSO BETWEEN 90W AND 110W.  ANOMALIES IN 
OUTGOING LONGWAVE RADIATION SHOW SUPRESSED CONVECTION (POSITIVE ANOMALIES) OVER 
MUCH OF THE EQUATORIAL PACIFIC... ESPECIALLY NEAR AND JUST WEST OF THE DATE 
LINE. LOW LEVEL EASTERLY WINDS ARE STRONGER THAN NORMAL OVER THE CENTRAL 
TROPICAL PACIFIC. THESE ATMOSPHERIC CIRCULATION ANOMALIES ARE CONSISTENT WITH 
LA NINA CONDITIONS.  

PROGNOSTIC DISCUSSION OF SST FORECASTS

THERE IS CONSENSUS AMONG SST PREDICTION METHODS THAT NINO 3.4 SSTS WILL REMAIN 
AT AROUND 1 DEGREE C OR MORE BELOW NORMAL THROUGH JFM 2008.  THE LATEST CFS 
FORECAST INDICATES JFM SST ANOMALIES IN THE NINO 3.4 REGION OF AROUND -1.8 C, 
REACHING A MINIMUM OF ABOUT -1.9 C DURING FMA 2008.  THE STATISTICAL TOOLS... 
THE MARKOV MODEL... CCA... AND CONSTRUCTED ANALOG PREDICT SST ANOMALIES OF 
BETWEEN -0.9 AND -1.6 C FOR JFM.  A CONSOLIDATION FORECAST BASED ON CCA, 
CONSTRUCTED  ANALOG (CA), MARKOV AND CFS MODELS PREDICTS GREATEST ANOMALIES OF 
ABOUT -1.4 C IN DJF 2007-08, -1.1 C IN JFM 2008, AND CONTINUES TO STEADILY RISE 
TO NEAR -0.5 C BY MAM 2008.  BEYOND THIS TIME, ENSO NEUTRAL CONDITIONS ARE 
PREDICTED BY THE CONSOLIDATION TOOL AT LEAST THROUGH SON 2008.  THE 
CONSOLIDATION METHOD GIVES A 98% CONFIDENCE THAT THE NINO 3.4 SSTS WILL REMAIN 
BELOW THE -0.5 C THRESHOLD ASSOCIATED WITH LA NINA CONDITIONS THROUGH JFM 2008, 
AND 86% THROUGH FMA 2008 AND A 54% CHANCE BY MAM.  

PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS

THE TEMPERATURE OUTLOOKS FOR ALL LEAD TIMES ARE BASED ON THE CONSOLIDATION 
(CON) TOOL... WHICH IS A SKILL-AND SPREAD-WEIGHTED OBJECTIVE BLEND OF THE 
CFS... CCA... SMLR AND OCN FORECAST TOOLS.  IN ADDITION, COMPOSITES OF MODERATE 
(WEAK) LA NINA EVENTS FROM 1950-2006 WERE USED FOR JFM 2008 (FMA AND MAM 2008). 
 PRECIPITATION OUTLOOKS FOR JFM 2008 THROUGH MAM 2008 ARE DERIVED ALMOST 
ENTIRELY FROM COMPOSITES OF LA NINAS... WITH PROBABILITIES ADJUSTED TO REFLECT 
THE EXPECTED INTENSITY OF THE CURRENT LA NINA CONDITIONS.  THE CON IS NOT 
AVAILABLE FOR ALASKA... SO THE FORECAST THERE IS BASED LARGELY ON ANALYSIS OF 
THE CFS WITH CONSIDERATION OF THE OCN... CCA AND SMLR.   PRECIPITATION OUTLOOKS 
FOR AMJ 2008 AND BEYOND REFLECT WEAK SIGNALS FROM LONG TERM TRENDS.

PROGNOSTIC DISCUSSION OF OUTLOOKS - JFM 2008 TO JFM 2009

TEMPERATURE:

THE TEMPERATURE OUTLOOK FOR JFM 2008 CALLS FOR ENHANCED CHANCES OF ABOVE 
AVERAGE TEMPERATURES FOR MOST OF THE SOUTHERN AND CENTRAL CONUS AS WELL AS 
NORTHWEST ALASKA, WITH NEAR AVERAGE TEMPERATURES FORECAST FROM THE PACIFIC 
NORTHWEST EASTWARD ACROSS THE NORTHERN TIER OF STATES TO NORTHERN MICHIGAN.  
EQUAL CHANCES (EC) OF ABOVE-, NEAR- AND BELOW AVERAGE TEMPERATURES ARE EXPECTED 
ELSEWHERE.  THE JFM 2008 TEMPERATURE FORECAST IS BASED LARGELY ON 
TREND-ADJUSTED LA NINA COMPOSITES (FOR MODERATE EVENTS), AND CONSIDERATION OF 
THE CONSOLIDATION TOOL, THE CFS AND IRI TOOLS, AND CURRENT AND ANTICIPATED 
LOCATIONS OF SIGNIFICANT SNOW/ICE COVER.  THE SEASONAL OUTLOOKS FOR FMA AND MAM 
2008 LARGELY REFLECT THESE SAME TOOLS THOUGH THE TREND-ADJUSTED LA NINA 
COMPOSITES THAT WERE USED WERE FOR WEAK COLD EVENTS.  THE TREND DOMINATES THE 
TEMPERATURE CONSOLIDATION FORECAST OUTLOOKS BEYOND MAM.

PRECIPITATION:

THE PRECIPITATION OUTLOOK FOR JFM 2008 CALLS FOR ELEVATED CHANCES OF ABOVE 
AVERAGE PRECIPITATION AMOUNTS IN THE PACIFIC NORTHWEST AND FROM THE CENTRAL 
MISSISSIPPI VALLEY, THROUGH SECTIONS OF THE OHIO VALLEY AND TENNESSEE, TO THE 
CENTRAL GREAT LAKES.  ELEVATED CHANCES FOR BELOW AVERAGE PRECIPITATION ARE 
FORECAST FOR THE SOUTHWEST, THE SOUTHERN ROCKIES, THE SOUTHERN AND CENTRAL 
PLAINS, THE SOUTHEAST, AND FROM VIRGINIA AND DELAWARE UP THE IMMEDIATE EAST 
COAST TO FAR EASTERN MASSACHUSETTS.   FOR FMA AND MAM 2008... THE PREDICTED 
ANOMALY PATTERNS ARE FAIRLY SIMILAR TO THAT FOR JFM, THOUGH LA NINA BASED 
SUPPORT FOR THE ABOVE AVERAGE PRECIPITATION AREAS DISAPPEARS BY MAM 2008.  
THESE FORECASTS ARE BASED PRIMARILY ON TREND-ADJUSTED LA NINA COMPOSITES 
(MODERATE EVENTS FOR JFM, WEAK EVENTS FOR FMA AND MAM 2008), AND TO A LESSER 
EXTENT ON THE CONSOLIDATION TOOL.  FORECASTS FOR AMJ 2008 AND BEYOND ARE BASED 
ON LONG-TERM TRENDS AND THE CONSOLIDATION TOOL.  THE LIKELIHOOD OF ABOVE 
AVERAGE PRECIPITATION IS INCREASED ACROSS FLORIDA FROM JAS-SON 2008, WHICH 
COINCIDES WITH THE EXPECTED BULK OF SEASONAL TROPICAL CYCLONE ACTIVITY.  BELOW 
AVERAGE PRECIPITATION AMOUNTS ARE EXPECTED FOR SECTIONS OF THE PACIFIC 
NORTHWEST FROM MJJ THROUGH ASO 2008, AND FOR SECTIONS OF THE SOUTHEAST IN DJF 
2008-09 AND JFM 2009. 

NOTE - AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL 
PROBABILITIES) ARE NOW LABELED EC (EQUAL CHANCES).

FORECASTER: ANTHONY ARTUSA

FOR A DESCRIPTION OF OF THE STANDARD FORECAST TOOLS - THEIR SKILL- AND THE
FORECAST FORMAT PLEASE SEE OUR WEB PAGE AT
HTTP:/WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/PREDICTIONS/90DAY/DISC.HTML
(USE LOWER CASE LETTERS)

INFORMATION ON THE FORMATION OF SKILL OF THE CAS FORECASTS MAY BE FOUND AT:
HTTP://WWW.CPC.NCEP.NOAA.GOV/SOILMST/FORECASTS.HTML (USE LOWERCASE LETTERS)

NOTES - THESE CLIMATE OUTLOOKS ARE INTENDED FOR USE PRIOR TO THE START OF THEIR 
VALID PERIOD.  WITHIN ANY GIVEN VALID PERIOD OBSERVATIONS AND SHORT AND MEDIUM 
RANGE FORECASTS SHOULD BE CONSULTED.

THIS SET OF OUTLOOKS WILL BE SUPERSEDED BY THE ISSUANCE OF THE NEW SET NEXT 
MONTH ON THU JAN 17 2008

1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17, 2001 
FORECAST RELEASE.

$$
