PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS 
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 
830 AM EDT THU AUG 20 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. 
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. 
THE MAIN FORECAST TOOLS ARE AS FOLLOWS: 
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. 
 
CURRENT EL NINO CONDITIONS ARE EXPECTED TO STRENGTHEN AND PERSIST INTO THE 
BOREAL WINTER AND 2010. THE INCREASING LIKELIHOOD OF A CONTINUING EL NINO EVENT 
INFLUENCES THE TEMPERATURE AND PRECIPITATION OUTLOOKS FOR OND 2009 THROUGH MAM 
2010. THE IMPACT OF EL NINO ON THE CLIMATE OVER NORTH AMERICA IS EXPECTED TO 
INCREASE FROM HAVING LITTLE OR NO IMPACT FOR SON 2009 TO THE GREATEST IMPACT 
DURING THE WINTER SEASONS. A WEAK TO MODERATE EL NINO EVENT IS EXPECTED DURING 
WINTER, THOUGH A STRONGER EVENT IS 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 SON 2009 INDICATES AN ENHANCED LIKELIHOOD OF ABOVE 
NORMAL TEMPERATURES FOR THE NORTHEAST US, THE WEST COAST, THE SOUTHWEST US, AND 
ALASKA. WHERE THE LIKELIHOOD OF ABOVE OR BELOW NORMAL SEASONAL MEAN 
TEMPERATURES ARE SIMILAR TO THE CLIMATOLOGY, EQUAL CHANCES OF BELOW, NEAR, AND 
ABOVE NORMAL ARE INDICATED. 
 
BELOW MEDIAN ACCUMULATED PRECIPITATION IS MOST LIKELY DURING SON 2009 FOR PARTS 
OF THE PACIFIC NORTHWEST AND THE NORTHERN ROCKY MOUNTAINS. ABOVE MEDIAN 
PRECIPITATION AMOUNTS ARE MORE LIKELY OVER THE GULF COAST AND FLORIDA, AND FOR 
PARTS OF THE CENTRAL PLAINS. WHERE THE LIKELIHOOD OF ABOVE OR BELOW MEDIAN 
SEASONAL PRECIPITATION IS SIMILAR TO THE CLIMATOLOGY, 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 
 
MONTHLY SEA SURFACE TEMPERATURE (SST) ANOMALIES EXCEED +0.5 CELSIUS ACROSS MOST 
OF THE EQUATORIAL PACIFIC OCEAN AND ARE FROM +1 TO +1.5 CELSIUS IN THE EASTERN 
HALF OF THE BASIN. SUBSURFACE HEAT CONTENT IS GENERALLY ABOVE NORMAL IN THE 
UPPER 200 METERS OF THE TROPICAL PACIFIC OCEAN WITH TEMPERATURE ANOMALIES 
EXCEEDING +2 CELSIUS IN THE REGION BELOW 100 METERS DEPTH WEST OF ABOUT 160 W 
AND JUST BELOW THE SURFACE IN THE EASTERN PACIFIC. HISTORICALLY, POSITIVE 
TEMPERATURE ANOMALIES IN THE UPPER OCEAN PRECEDE THE ONSET AND FURTHER 
DEVELOPMENT OF EL NINO EVENTS, AND TROPICAL PACIFIC TEMPERATURES ARE UNLIKELY 
TO RETURN TO AN ENSO NEUTRAL STATE PRIOR TO JANUARY AFTER MAINTAINING AN EL 
NINO STATE INTO AUGUST. THE TEMPERATURE STATE OF THE TROPICAL PACIFIC IS 
UNUSUAL WITH POSITIVE ANOMALIES ACROSS THE ENTIRE BASIN AT AND BELOW THE 
SURFACE. 
 
THE MOST RECENT 30-DAY OUTGOING LONGWAVE RADIATION ANOMALIES INDICATE THAT 
CONVECTION IS SUPPRESSED OVER THE MARITIME CONTINENT AND ENHANCED ACROSS THE 
WESTERN PACIFIC TO THE INTERNATIONAL DATE LINE, AS WELL AS NORTH OF THE EQUATOR 
TO THE EAST. WESTERLY WIND BURSTS OFTEN OCCUR OVER THE WESTERN EQUATORIAL 
PACIFIC AS AN EL NINO EVENT DEVELOPS AS OCCURRED AT THE END OF JULY. TROPICAL 
OCEANIC AND ATMOSPHERIC ANOMALIES REFLECT THE CURRENT EL NINO STATE. 
 
PROGNOSTIC DISCUSSION OF SST FORECASTS 
 
THE CURRENT MEAN ENSEMBLE CFS FORECAST INDICATES SST ANOMALIES EXCEEDING +1.5 
CELSIUS BEFORE THE END OF 2009, WITH THE ENSEMBLE SPREAD RANGING FROM +1 TO 
ABOUT +2 CELSIUS, THUS CALLING FOR MODERATE TO STRONG EL NINO CONDITIONS BY THE 
BOREAL WINTER SEASON. THIS FORECAST IS NEAR THE TOP OF THE IRI MULTI-MODEL 
ENSEMBLE PLUME. THE CPC STATISTICAL MODELS ARE GENERALLY FORECASTING A WEAK TO 
MODERATE EL NINO EVENT PEAKING AROUND +1 TO +1.5 CELSIUS AROUND THE END OF 
2009, WHERE THE CONSTRUCTED ANALOG METHOD PREDICTS THE GREATEST POSITIVE 
ANOMALY. THE STATISTICAL MODEL FORECASTS ARE NOW CONSIDERABLY WARMER THAN THEY 
WERE IN THEIR FORECASTS IN PREVIOUS MONTHS, AND REMAIN COOLER THAN THE 
DYNAMICAL MODEL ENSO FORECASTS. THE CPC CONSOLIDATION OF NINO 3.4 SST 
TEMPERATURE ANOMALY FORECASTS INDICATES THAT POSITIVE TROPICAL PACIFIC SST 
ANOMALIES ARE MOST LIKELY TO CONTINUE INTO MAM 2010. 
 
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 GIVEN 
INCREASING WEIGHTS IN THE OUTLOOKS WITH THE CONTINUATION OF THE CURRENT WARM 
PACIFIC STATE INTO AUGUST. OUTLOOKS FOR MAM 2010 AND LATER ARE BASED ON THE 
CONSOLIDATION FORECASTS AND LARGELY ATTRIBUTABLE TO DECADAL CLIMATE TRENDS. 
 
PROGNOSTIC DISCUSSION OF OUTLOOKS - SON 2009 TO SON 2010 
 
TEMPERATURE: 
 
THE TEMPERATURE OUTLOOKS FOR SON 2009 THROUGH SON 2010 INDICATE THAT 
THREE-MONTH MEAN TEMPERATURES ARE MOST LIKELY TO BE IN THE ABOVE NORMAL 
CATEGORY FOR MUCH OF THE US WITH A SIGNIFICANT CLIMATE SIGNAL. ALL OUTLOOKS TO 
SOME EXTENT FOLLOW THE CPC CONSOLIDATION FORECAST WITH MODIFICATIONS DUE TO THE 
INFLUENCE OF THE EXPECTED IMPACT OF AN EL NINO STATE. THE STATISTICAL 
CONSOLIDATION DOES NOT ACCOUNT FOR INCREASES IN THE SKILL OF FORECASTS THAT 
INCLUDE A CLEAR ENSO SIGNAL. AREAS OF LIKELY WARMER THAN NORMAL MEAN 
TEMPERATURES ARE AN INDICATION OF THE CURRENT CLIMATE STATE, PARTLY 
ATTRIBUTABLE TO DECADAL CLIMATE TRENDS, BUT ALSO DUE TO INTERANNUAL VARIABILITY 
ATTRIBUTABLE TO THE ENSO STATE. BEGINNING IN SON 2009 AND CONTINUING TO SOME 
DEGREE THROUGHOUT THE NEXT 12 MONTHS, ABOVE NORMAL MEAN TEMPERATURES ARE MOST 
LIKELY IN THE US SOUTHWEST, PRIMARILY AS A RESULT OF THE LOCAL TEMPERATURE 
TREND. THE PROBABILITY OF WARMER THAN NORMAL TEMPERATURES ARE DECREASED 
SIGNIFICANTLY FROM DJF TO FMA 2010 BY THE EXPECTED IMPACT OF EL NINO. SEASONAL 
MEAN TEMPERATURES ARE MOST LIKELY TO BE IN THE BELOW NORMAL CATEGORY FOR THE 
SOUTHEAST AND ALONG THE GULF COAST FROM NDJ 2009 TO FMA 2010 AS A RESULT OF EL 
NINO IMPACTS. BEGINNING IN THE NORTHEAST FOR SON 2009 AND BECOMING MORE LIKELY 
OVER THE NORTHERN CENTRAL US DURING THE WINTER SEASONS, MEAN TEMPERATURES ARE 
MOST LIKELY TO BE IN THE ABOVE NORMAL CATEGORY. THOUGH MEAN WINTER TEMPERATURES 
IN THE NORTHERN PLAINS HAVE MOST OFTEN BEEN ABOVE NORMAL IN THE LAST DECADE, 
THIS DECADAL TEMPERATURE SIGNAL SHOULD BE ENHANCED DUE TO THE DEVELOPING EL 
NINO WHICH IS INDICATED BY SIGNIFICANTLY GREATER PROBABILITIES FOR BOTH THE 
NORTHERN PLAINS AND PACIFIC NORTHWEST. MUCH OF ALASKA IS INDICATED TO HAVE AN 
ENHANCED LIKELIHOOD OF ABOVE NORMAL TEMPERATURES DUE TO THE CLIMATE TREND AND 
FOLLOWING THE CFS AND OCN FORECASTS. 
 
THE CFS FORECASTS FOR OND 2009 THROUGH MAM 2010 INDICATE A STRONG EL NINO AND 
IMPACTS RESULTING FROM AN EL NINO CLIMATE STATE. THE CFS OUTLOOKS HAVE 
INFLUENCED THE FORECAST ALONG WITH ENSO COMPOSITES, THROUGH THE CON AND AS A 
REPRESENTATION OF POSSIBLE EL NINO IMPACTS. THE FORECASTS ARE SOMEWHAT 
CONSERVATIVE COMPARED TO THE CFS, BECAUSE THE STRENGTH OF THE DEVELOPING EL 
NINO IS STILL UNCERTAIN. 
 
FORECAST LEADS FROM AMJ 2010 THROUGH SON 2010 ARE BASED ON THE CONSOLIDATION 
FORECAST AND ATTRIBUTABLE TO TEMPERATURE TRENDS AND WEAK INTERANNUAL SIGNALS. 
 
PRECIPITATION: 
 
THE PRECIPITATION OUTLOOK FOR SON 2009 IS BASED PRIMARILY ON THE CONSOLIDATION 
FORECAST, AS ARE THE LATER LEADS FROM AMJ TO SON 2010. FOR THE FORECASTS FROM 
OND 2009 THROUGH MAM 2010 SIGNIFICANT WEIGHT HAS BEEN GIVEN TO THE EXPECTED 
IMPACTS OF A PROBABLE EL NINO EVENT. THE CFS PRECIPITATION FORECAST AND ENSO 
COMPOSITES HAVE BEEN USED AS A GUIDE TO PREDICTABLE IMPACTS. CONFIDENCE IN THE 
IMPACTS OF A PREDICTED EL NINO EVENT HAS INCREASED SINCE LAST MONTH. 
 
THE AREA OF ENHANCED PROBABILITY OF BELOW MEDIAN PRECIPITATION FORECAST FOR THE 
PACIFIC NORTHWEST FROM SON 2009 THROUGH FMA 2010 IS A RESULT OF BOTH THE 
DECADAL CLIMATE TREND AND THE IMPACT OF AN EL NINO. BELOW MEDIAN PRECIPITATION 
IS ALSO MOST LIKELY FOR PARTS OF THE MISSISSIPPI AND OHIO VALLEYS FROM DJF 
THROUGH MAM 2010 LARGELY DUE TO EL NINO. LIKELY ABOVE MEDIAN PRECIPITATION FOR 
THE GULF COAST AND FLORIDA INTO THE SPRING OF 2010 IS ALMOST ENTIRELY DUE TO 
THE CLIMATE TREND IN THE FIRST SON 2009 SEASON AND MAINLY A RESULT OF THE 
LIKELY IMPACT OF EL NINO BEGINNING WITH OND 2009, PEAKING IN JFM 2010. THE 
ENHANCED PROBABILITY OF ABOVE MEDIAN PRECIPITATION DUE TO EL NINO EXTENDS INTO 
THE SOUTHERN PLAINS IN OND 2010 AND ACROSS THE ENTIRE SOUTHERN US DURING THE 
WINTER SEASONS. 
 
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 FROM JJA TO SON 2010 DUE TO A DECADAL TREND IN TROPICAL 
PRECIPITATION. 
 
NOTE - AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL 
PROBABILITIES) ARE NOW LABELED EC (EQUAL CHANCES). 
 
FORECASTER: DAN COLLINS 
 
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 SEP 17 2009 
 
1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17, 2001 
FORECAST RELEASE. 
 
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