PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS 
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 
830 AM EST THU NOV 19 2009 
 
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. 
IMPACTS OF THESE EVENTS ARE SUMMARIZED BY SEPARATING 3-MONTH OBSERVATIONS FROM 
3 OR MORE DECADES INTO EL NINO, NEUTRAL, AND LA NINA SETS, AVERAGING EACH 
SEPARATELY, AND THEN COMPUTING ANOMALIES.  THESE ARE CALLED "ENSO COMPOSITES", 
AND ARE USED TO SUBJECTIVELY MODIFY THE FORECAST. 
2) TRENDS - APPROXIMATED BY THE OCN TOOL AS 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). 
3) THE TROPICAL 30-60 DAY OSCILLATION - SOMETIMES CALLED MADDEN JULIAN 
OSCILLATION (MJO) - 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) THE PACIFIC DECADAL OSCILLATION (PDO) - AN ENSO-LIKE PATTERN OF CLIMATE 
VARIABILITY AFFECTING BOTH THE TROPICS AND THE NORTH PACIFIC AND NORTH AMERICAN 
REGIONS, BUT WHICH VARIES ON A MUCH LONGER TIME-SCALE THAN ENSO. 
6) 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. 
7) STATISTICAL FORECAST TOOLS - CANONICAL CORRELATION ANALYSIS (CCA), SCREENING 
MULTIPLE LINEAR REGRESSION (SMLR), CONSTRUCTED ANALOGUE (CA) AND ENSEMBLE CCA 
(ECCA). 
8) DYNAMICAL FORECAST MODELS - INCLUDING THE NCEP CLIMATE FORECAST SYSTEM (CFS). 
9) AN OBJECTIVE CONSOLIDATION (ABBREVIATED CON IN THE TEXT) OF THE OCN, CCA, 
SMLR, ECCA, 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. 
 
CURRENTLY MODERATE EL NINO CONDITIONS EXIST IN THE TROPICAL PACIFIC AND 
ARE EXPECTED TO PERSIST INTO THE 2009-10 NORTHERN HEMISPHERE WINTER.
THE LIKELIHOOD OF A CONTINUING EL NINO EVENT INFLUENCES THE TEMPERATURE 
AND PRECIPITATION OUTLOOKS FOR DJF 2009-10 THROUGH MAM 2010, MAINLY VIA EL NINO
COMPOSITES.  THE IMPACT OF EL NINO ON THE CLIMATE OVER NORTH AMERICA HAS HISTORICALLY
BEEN THE GREATEST DURING THE WINTER SEASONS. A STRONG EVENT IS LESS LIKELY, 
BUT STILL POSSIBLE. UNCERTAINTY IN THE FUTURE STRENGTH AND DURATION OF THIS EVENT 
IS CONSIDERED IN THE SEASONAL FORECASTS, ESPECIALLY AT LONGER LEAD TIMES. 
 
THE TEMPERATURE OUTLOOK FOR DJF 2009-10 INDICATES AN ENHANCED LIKELIHOOD OF 
ABOVE AVERAGE TEMPERATURES FOR MUCH OF THE WESTERN HALF OF THE CONUS AND 
ALASKA, AND ESPECIALLY SO IN THE NORTHERN ROCKIES ALONG THE CANADIAN BORDER. 
BELOW NORMAL TEMPERATURES ARE LIKELY FROM CENTRAL TEXAS ALONG THE GULF COAST TO 
THE MID-ATLANTIC. IN LOCATIONS WHERE THE CHANCE OF ABOVE OR BELOW AVERAGE 
SEASONAL MEAN TEMPERATURES ARE SIMILAR TO A RANDOM DRAW FROM THE HISTORICAL 
RECORD (CLIMATOLOGY), EQUAL CHANCES OF BELOW, NEAR, AND ABOVE AVERAGE ARE 
INDICATED. 
 
BELOW MEDIAN PRECIPITATION IS MOST LIKELY DURING DJF 2009-10 FOR PARTS OF THE 
PACIFIC NORTHWEST AND THE OHIO VALLEY. ABOVE MEDIAN PRECIPITATION AMOUNTS ARE 
MOST LIKELY IN TEXAS, FLORIDA, AND IN CALIFORNIA, AND NORTHERN SECTIONS OF 
ALASKA. IN LOCATIONS WHERE THE LIKELIHOOD OF ABOVE OR BELOW MEDIAN SEASONAL 
PRECIPITATION IS SIMILAR TO THE CLIMATOLOGICAL PROBABILITIES, EQUAL CHANCES OF 
BELOW, NEAR, AND ABOVE MEDIAN PRECIPITATION ARE INDICATED. 
 
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 
 
WEEKLY SEA SURFACE TEMPERATURE (SST) ANOMALIES HAVE RAPIDLY WARMED IN LATE 
OCTOBER AND EARLY NOVEMBER, AND EXCEED +1.5 CELSIUS ACROSS MUCH OF THE 
EQUATORIAL PACIFIC OCEAN AND ARE LOCALLY OVER +2C CELSIUS FROM THE DATE LINE 
EAST TO 130W. OUTGOING LONGWAVE RADIATION ANOMALIES ARE NOT YET IN SYNC WITH AN 
EL NINO EVENT. TRADE WINDS WERE VERY WEAK IN MID TO LATE OCTOBER BUT ARE CLOSE 
TO NORMAL AT PRESENT. SUBSURFACE HEAT CONTENT IS GENERALLY ABOVE NORMAL IN THE 
UPPER 200 METERS OF THE TROPICAL PACIFIC OCEAN WITH WATER TEMPERATURE ANOMALIES 
EXCEEDING +5 CELSIUS AT THERMOCLINE DEPTH NEAR 130W, MUCH MORE THAN A MONTH 
AGO. HISTORICALLY, POSITIVE TEMPERATURE ANOMALIES IN THE UPPER OCEAN PRECEDE 
THE ONSET AND FURTHER DEVELOPMENT OF EL NINO EVENTS. THUS TROPICAL PACIFIC 
TEMPERATURES ARE UNLIKELY TO RETURN TO AN ENSO NEUTRAL STATE PRIOR TO SPRING 
2010. 
 
 
 
PROGNOSTIC DISCUSSION OF SST FORECASTS 
 
THE CURRENT MEAN PDF CORRECTED ENSEMBLE CFS FORECAST INDICATES SST ANOMALIES IN 
THE NINO 3.4 REGION PRESENTLY AT PEAK NEAR +1.5 CELSIUS, THUS CALLING FOR 
MODERATE TO STRONG EL NINO CONDITIONS BUT NO FURTHER STRENGTHENING. THE CPC 
STATISTICAL MODELS ARE GENERALLY FORECASTING A MODERATE EL NINO EVENT PEAKING 
BETWEEN +1 TO +1.5 DEGREES CELSIUS DURING THE EARLY PART OF THE WINTER. THE CPC 
CONSOLIDATION OF NINO 3.4 SST TEMPERATURE ANOMALY FORECASTS INDICATES THAT THE 
CURRENT EL NINO WILL LIKELY WEAKEN AND END BY MAM OR AMJ 2010. THE CFS FORECAST 
IS NO LONGER AMONG THE WARMEST ONES IN THE IRI MULTI-MODEL ENSEMBLE PLUME AND 
CONSENSUS BY EYE OF THE IRI PLUME AGREES WELL WITH CPC'S CONSOLIDATION FORECAST. 
 
PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS 
 
THE TEMPERATURE AND PRECIPITATION OUTLOOKS ARE BASED ON THE CONSOLIDATION 
FORECAST, A SKILL-WEIGHTED AND CALIBRATED PROBABILISTIC FORECAST DERIVED FROM 
THE CFS, SMLR, OCN, CCA, AND ECCA FORECAST TOOLS. EL NINO COMPOSITES ARE THE 
MAJOR FORECAST TOOL FOR FORECASTS FROM DJF 2009-10 THROUGH MAM 2010. THE CFS 
WAS RELIED UPON TO A CONSIDERABLE DEGREE. ITS FORECASTS HAVE BEEN CONSISTENT 
WITH DEVELOPING EL NINO CONDITIONS, THOUGH POSSIBLY ON THE TOO-INTENSE SIDE 
EARLY ON. 
 
PROGNOSTIC DISCUSSION OF OUTLOOKS - DJF 2009 TO DJF 2010 
 
TEMPERATURE: 
 
THE TEMPERATURE OUTLOOKS FOR DJF 2009-10 THROUGH DJF 2010-11 INDICATE THAT 
THREE-MONTH MEAN TEMPERATURES ARE MOST LIKELY TO BE IN THE ABOVE NORMAL 
CATEGORY FOR MUCH OF THE WESTERN U.S. MAINLY DUE TO COMPOSITES, AND THE 
CONSOLIDATION. ALL OUTLOOKS USE THE CPC CONSOLIDATION FORECAST AS A STARTING 
POINT WITH MODIFICATIONS DUE TO THE INFLUENCE OF THE EXPECTED IMPACT OF EL NINO 
FROM DJF THROUGH MAM. SEASONAL MEAN TEMPERATURES ARE MOST LIKELY TO BE IN THE 
BELOW AVERAGE CATEGORY FOR THE SOUTHEAST, SECTIONS OF THE MID-ATLANTIC AND 
ALONG THE GULF COAST REGIONS FROM DJF 2009 TO FMA 2010 AS A RESULT OF EL NINO. 
 
THE LIKELIHOOD OF ABOVE AVERAGE TEMPERATURES IN THE NORTH-CENTRAL US PEAKS IN 
JFM. MUCH OF ALASKA IS INDICATED TO HAVE AN ENHANCED LIKELIHOOD OF ABOVE 
AVERAGE TEMPERATURES DUE TO THE LONG TERM CLIMATE TREND, CONSISTENT WITH THE 
CFS AND OCN FORECASTS. 
 
FORECAST LEADS FROM AMJ 2010 THROUGH DJF 2010 ARE BASED ON THE CONSOLIDATION 
FORECAST AND ATTRIBUTABLE TO TEMPERATURE TRENDS AND WEAK INTERANNUAL SIGNALS. 
 
PRECIPITATION: 
 
THE PRECIPITATION OUTLOOKS FOR DJF 2009-10 THROUGH MAM 2010 ARE MAINLY BASED ON 
THE EXPECTED IMPACTS OF AN EL NINO EVENT, INCLUDING THOSE DEPICTED BY EL NINO 
COMPOSITES, WHILE THE LONGER LEAD FORECASTS FROM AMJ TO DJF 2010-11 ARE MAINLY 
BASED ON THE CONSOLIDATION, WHICH USES ONLY STATISTICAL TOOLS AS INPUT AFTER 
MJJ 2010. 
 
THE AREA OF ENHANCED PROBABILITY OF BELOW MEDIAN PRECIPITATION FORECAST FOR THE 
PACIFIC NORTHWEST FROM DJF 2009 THROUGH MAM 2010 IS A RESULT OF COMPOSITES OF 
THE EXPECTED IMPACTS OF EL NINO. BELOW MEDIAN PRECIPITATION IS ALSO MOST LIKELY 
FOR PARTS OF THE MISSISSIPPI AND OHIO VALLEYS FROM DJF 2009-10 THROUGH MAM 2010 
LARGELY DUE TO EL NINO.  LIKELY ABOVE MEDIAN PRECIPITATION FOR THE GULF COAST 
AND FLORIDA INTO THE SPRING OF 2010 IS MAINLY A RESULT OF THE EXPECTED IMPACT 
OF EL NINO BEGINNING WITH DJF 2009, PEAKING IN JFM 2010 AND LIKELY EXTENDING 
INTO MAM. THE ENHANCED PROBABILITY OF ABOVE MEDIAN PRECIPITATION ACROSS THE 
ENTIRE SOUTHERN US DURING THE WINTER SEASONS WHICH EXTENDS INTO THE SOUTHERN 
PLAINS DURING JFM 2010 IS DUE TO EXPECTED EL NINO IMPACTS. DUE TO THE INHERENT 
NATURALY VARIABILITY AMONG DIFFERENT EL NINO EVENTS, THE SHIFTS IN THE 
PROBABILITY DISTRIBUTION ACROSS THE SOUTHWEST AND CALIFORNIA IS FAIRLY SMALL. 
 
USING THE CONSOLIDATION FORECASTS AS A GUIDE, SIGNALS PRIMARILY DUE TO 
PRECIPITATION TRENDS ARE INDICATED IN JJA 2010 TO SON 2010. PARTS OF THE 
PACIFIC NORTHWEST ARE MOST LIKELY TO RECEIVE BELOW MEDIAN PRECIPITATION DURING 
THE SUMMER OF 2010. A DECADAL PRECIPITATION TREND LEADS TO THE ENHANCED 
PROBABILITY OF ABOVE MEDIAN PRECIPITATION EAST OF THE CENTRAL ROCKIES. FLORIDA 
AND PARTS OF THE SOUTHERN ATLANTIC COAST ARE MOST LIKELY TO RECEIVE ABOVE 
MEDIAN PRECIPITATION FOR PARTICULAR SEASONS FROM JJA TO SON 2010 DUE TO DECADAL 
TRENDS. IN DJF 2010-11 BELOW MEDIAN PRECIPITATION DUE TO TRENDS RETURNS IN THE 
SOUTHEAST. 
 
NOTE - AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL 
PROBABILITIES) ARE NOW LABELED EC (EQUAL CHANCES). 
 
FORECASTER: HUUG VAN DEN DOOL 
 
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 DEC 17 2009 
 
1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17, 2001 
FORECAST RELEASE. 
 
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