PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS 
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 
830 AM EDT THU APR 16 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. 
 
ATMOSPHERIC AND OCEANIC CONDITIONS DURING THE PAST MONTH CONTINUED TO REFLECT 
WEAK LA NINA CONDITIONS. THE MONTHLY SEA SURFACE TEMPERATURES (SST) REMAIN 
BELOW AVERAGE ACROSS PARTS OF THE EAST-CENTRAL AND EASTERN PACIFIC OCEAN. WATER 
TEMPERATURES BELOW THE SURFACE REMAIN BELOW AVERAGE BUT DEPARTURES FROM NORMAL 
HAVE CONTINUED TO DECREASE. A TRANSITION TO ENSO-NEUTRAL CONDITIONS IS EXPECTED 
DURING APRIL 2009. 
 
THE TEMPERATURE OUTLOOK FOR MJJ 2009 CALLS FOR AN ENHANCED LIKELIHOOD OF 
BELOW-AVERAGE TEMPERATURES FOR SOUTHERN ALASKA, THE PACIFIC NORTHWEST COAST, 
AND THE UPPER MIDWEST. ABOVE-AVERAGE TEMPERATURES ARE EXPECTED FOR PORTIONS OF 
THE INTERIOR PACIFIC NORTHWEST, THE SOUTHWEST, MOST OF THE ROCKIES AND MUCH OF 
THE CENTRAL AND SOUTHERN GREAT PLAINS. THE TEMPERATURE OUTLOOK IS BASED ON 
STATISTICAL TOOLS, NUMERICAL CLIMATE MODEL OUTPUT, THE INFLUENCE OF SOIL 
MOISTURE, AND SSTS ALONG SOME COASTAL AREAS. ELSEWHERE, EQUAL CHANCES OF 
BELOW-, NEAR-, AND ABOVE-AVERAGE TEMPERATURES ARE PREDICTED. 
 
BELOW-MEDIAN PRECIPITATION IS ANTICIPATED FOR MJJ 2009 FOR A LARGE PORTION OF 
THE INTERIOR WEST, AND FOR EXTREME SOUTHWESTERN ALASKA. ABOVE-MEDIAN 
PRECIPITATION AMOUNTS ARE FORECAST FOR SOUTHEAST ALASKA, THE ALASKA PANHANDLE, 
THE UPPER MIDWEST, AND SOUTHERN SECTIONS OF BOTH ARIZONA AND NEW MEXICO.  THE 
PRIMARY INPUTS FOR THE PRECIPITATION OUTLOOK ARE NUMERICAL CLIMATE MODEL 
OUTPUT, CURRENT SOIL MOISTURE CONDITIONS AND LONG-TERM TRENDS. ELSEWHERE, EQUAL 
CHANCES OF BELOW-, NEAR-, AND ABOVE-MEDIAN PRECIPITATION IS PREDICTED. 
 
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 
 
OCEANIC CONDITIONS CURRENTLY REFLECT WEAK LA NINA CONDITIONS. THE PACIFIC 
DECADAL OSCILLATION (PDO) CONTINUES TO BE IN ITS NEGATIVE PHASE.  NEGATIVE SST 
ANOMALIES EXTEND FROM THE BERING SEA AND ALEUTIAN ISLANDS ALONG THE WESTERN 
COAST OF NORTH AMERICA AS FAR SOUTH AS CENTRAL CALIFORNIA, AND THEN 
SOUTHWESTWARD TO AND BEYOND THE HAWAIIAN ISLANDS. THESE COLD ANOMALIES TAKE THE 
FORM OF AN ARC, WHICH PARTIALLY ENCIRCLES A REGION OF POSITIVE SST ANOMALIES 
JUST NORTH OF THE HAWAIIAN ISLANDS. THESE WARM ANOMALIES EXTEND WESTWARD ACROSS 
THE NORTH PACIFIC OCEAN, PAST THE DATE LINE, TO APPROXIMATELY 170E LONGITUDE. 
THE SEA SURFACE TEMPERATURES (SSTS) REMAIN NEAR- TO BELOW-AVERAGE ACROSS MUCH 
OF THE EQUATORIAL CENTRAL AND EASTERN PACIFIC OCEAN, ACCORDING TO THE LATEST 
WEEKLY ANALYSIS. THE NINO 3.4 SST INDEX VALUE HAS NOW DIMINISHED TO NEAR ZERO 
DEG C. THE SUBSURFACE OCEANIC HEAT CONTENT ANOMALIES IN THE CENTRAL PACIFIC 
OCEAN (THE AVERAGE WATER TEMPERATURES IN THE UPPER 300 M) WEAKENED FURTHER 
DURING THE LAST MONTH TO ABOUT -0.1 DEG C, AS POSITIVE SUBSURFACE TEMPERATURE 
ANOMALIES FROM THE WESTERN PACIFIC EXPANDED EASTWARD INTO THE CENTRAL PACIFIC. 
 
ATMOSPHERIC TROPICAL CONVECTION REMAINED SUPPRESSED NEAR THE DATE LINE, AND 
ENHANCED ACROSS INDONESIA, BUT WEAKENED DURING THE SECOND HALF OF MARCH DUE TO 
MADDEN-JULIAN OSCILLATION (MJO) ACTIVITY. ENHANCED LOW-LEVEL EASTERLY WINDS AND 
UPPER-LEVEL WESTERLY WINDS ALSO DECREASED ACROSS THE EQUATORIAL PACIFIC. 
COLLECTIVELY, THE ATMOSPHERIC AND OCEANIC ANOMALIES ARE CONSISTENT WITH A 
WEAKENING LA NINA. 
 
PROGNOSTIC DISCUSSION OF SST FORECASTS 
 
FORECASTS OF NINO 3.4 SST FROM THE CPC CONSOLIDATION SST FORECAST INDICATE THE 
TRANSITION FROM WEAK LA NINA TO ENSO-NEUTRAL CONDITIONS AS SPRING 2009 
PROGRESSES. THE CPC CONSOLIDATION SST FORECAST - AN OBJECTIVE COMBINATION OF 
SEVERAL STATISTICAL TOOLS AND THE CLIMATE FORECAST SYSTEM (CFS) MODEL - ALSO 
PREDICTS THAT ENSO-NEUTRAL CONDITIONS COULD PERSIST THROUGHOUT THE REMAINDER OF 
2009. THE ENSEMBLE MEAN FORECAST FROM THE CLIMATE FORECAST SYSTEM MODEL SHOWS A 
MORE RAPID WARMUP, WITH A TRANSITION TO SLIGHTLY POSITIVE VALUES DURING MJJ 
2009, AND BORDERLINE WARM EVENT CONDITIONS BY LATE SUMMER. HOWEVER, THE GENERAL 
CONSENSUS OF ABOUT A DOZEN OTHER STATISTICAL AND DYNAMICAL SST FORECASTS FROM 
OTHER CENTERS LENDS MORE CREDENCE TO THE CPC CONSOLIDATION FORECAST. 
 
PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS 
 
THE TEMPERATURE AND PRECIPITATION OUTLOOKS FOR ALL LEAD TIMES ARE BASED HEAVILY 
ON THE CONSOLIDATION FORECAST (CON), A SKILL-WEIGHTED AND CALIBRATED OBJECTIVE 
BLEND OF THE CFS, SMLR, OCN, CCA, AND ECCA FORECAST TOOLS. THE IRI MULTI-MODEL 
ENSEMBLE FORECASTS BASED ON SEVERAL DYNAMIC CLIMATE MODELS, THE ECPC CLIMATE 
FORECAST, AND THE CAS TOOL WERE ALSO CONSIDERED AND USED TO ADJUST THE FORECAST. 
THE CONSOLIDATION FORECAST IS NOT AVAILABLE FOR ALASKA, SO THE FORECAST THERE 
IS BASED ON A SUBJECTIVE COMBINATION OF DYNAMICAL MODEL (CFS, IRI, ECPC) 
FORECASTS, AND THE CCA, OCN, AND SMLR STATISTICAL FORECASTS. NEAR THE WEST 
COAST, SSTS WERE UTILIZED AT TIMES FOR THE TEMPERATURE OUTLOOKS WHILE RECENT 
SOIL MOISTURE CONDITIONS CONTRIBUTED TO BOTH TEMPERATURE AND PRECIPITATION 
OUTLOOKS AT EARLY LEADS. 
 
PROGNOSTIC DISCUSSION OF OUTLOOKS - MJJ 2009 TO MJJ 2010 
 
TEMPERATURE: 
 
THE TEMPERATURE OUTLOOK FOR MJJ 2009 INDICATES GREATER THAN CLIMATOLOGICAL 
PROBABILITIES FOR ABOVE-AVERAGE TEMPERATURES FOR MOST OF THE INTERIOR WEST, AS 
WELL AS FOR MOST OF THE ROCKIES, THE CENTRAL HIGH PLAINS AND NEARLY ALL OF THE 
SOUTHERN PLAINS. GREATER THAN CLIMATOLOGICAL PROBABILITIES FOR BELOW-AVERAGE 
TEMPERATURES ARE INDICATED FOR SOUTHERN ALASKA, THE ALASKA PANHANDLE, COASTAL 
AREAS OF THE PACIFIC NORTHWEST, AND THE UPPER MIDWEST. 
 
MOST OF THE FORECAST TOOLS - STATISTICAL AND DYNAMICAL, INCLUDING THE 
CONSOLIDATED CONSENSUS FORECAST - SUGGEST AN INCREASED LIKELIHOOD FOR RELATIVE 
WARMTH ACROSS THE SOUTHWEST DURING MJJ 2009, EXTENDING EASTWARD INTO THE 
CENTRAL AND SOUTHERN PLAINS, AND NORTHWARD INTO OREGON AND IDAHO. THE LONG, 
NEAR-COASTAL ARC OF BELOW-AVERAGE TEMPERATURES DEPICTED ON THE OFFICIAL MJJ 
2009 MAP IS SUPPORTED BY THE ECPC, IRI, THE PERSISTENCE OF COLD WATER ALONG THE 
WESTERN COAST OF NORTH AMERICA, AND TO A MODEST DEGREE THE CFS AND CON TOOLS. 
THE AREA OF ANOMALOUSLY COOL TEMPERATURES ANTICIPATED OVER THE UPPER MIDWEST IS 
GENERALLY SUPPORTED BY THE CPC CONSOLIDATION (CON), THE ECPC, THE CFS, AND TO A 
LESSER DEGREE THE SMLR AND CCA TOOLS. THIS AREA OF ANOMALOUS COLD ACROSS THE 
UPPER MIDWEST DURING MJJ 2009 IS ALSO FORECAST BECAUSE OF EXPECTED SOIL 
MOISTURE CIRCULATION FEEDBACK MECHANISMS WITHIN THE BOUNDARY LAYER. 
 
THE SATURATED SOILS ACROSS THE UPPER MIDWEST COULD ALSO HAVE AN EFFECT ON THE 
TEMPERATURE FORECAST FOR JJA 2009. THE CFS AND ECPC DYNAMICAL MODELS, AND TO A 
LESSER DEGREE THE CON, LEND STRONG SUPPORT FOR THE BELOW-AVERAGE TEMPERATURES 
PREDICTED IN THAT REGION. WITH THE LARGE EXTENT OF ANOMALOUS COLD PREDICTED BY 
THE CFS AND ECPC ACROSS THE CENTRAL CONUS DURING JJA, AND THE CON NOT SHOWING 
SIGNIFICANT TILTS IN THE ODDS FOR EITHER COLD OR WARM ACROSS MUCH OF THIS 
REGION, IT WAS DECIDED THAT EQUAL CHANCES (EC) IS PROBABLY THE BEST FORECAST. 
 
REMAINING FORECAST LEADS FROM JAS 2009 THROUGH MJJ 2010 ARE MAINLY BASED ON THE 
CONSOLIDATED CONSENSUS FORECAST AND LONG TERM TRENDS ADJUSTED TO SOME EXTENT BY 
WEAK SIGNALS FROM THE VARIOUS OTHER TOOLS. 
 
PRECIPITATION: 
 
THE PRECIPITATION OUTLOOK FOR MJJ 2009 INDICATES GREATER THAN CLIMATOLOGICAL 
PROBABILITIES FOR PRECIPITATION AMOUNTS FALLING WITHIN THE UPPERMOST TERCILE 
OVER THE UPPER MIDWEST, SOUTHERN PORTIONS OF BOTH ARIZONA AND NEW MEXICO, 
SOUTHEAST ALASKA AND THE ALASKA PANHANDLE. GREATER THAN CLIMATOLOGICAL 
PROBABILITIES FOR PRECIPITATION AMOUNTS FALLING WITHIN THE LOWEST TERCILE ARE 
INDICATED OVER THE NORTHERN AND CENTRAL PORTIONS OF BOTH THE INTERMOUNTAIN WEST 
AND THE ROCKIES, AS WELL AS OVER SOUTHWESTERN PARTS OF ALASKA. 
 
THE LARGE AREA OF BELOW-AVERAGE PRECIPITATION PREDICTED OVER THE NORTHWEST IN 
MJJ 2009 IS BASED ON THE CON, ECPC, ECCA, IRI, CFS AND CCA TOOLS. THE AREA OF 
RELATIVE DRYNESS ANTICIPATED OVER SOUTHWESTERN ALASKA IS DUE TO THE CFS AND 
ECPC FORECASTS. THE ABOVE-AVERAGE PRECIPITATION AMOUNTS DEPICTED OVER 
SOUTHEASTERN ALASKA AND THE ADJOINING PANHANDLE ARE ATTRIBUTED TO THE CFS AND 
ECPC FORECASTS. ELEVATED CHANCES FOR ABOVE-AVERAGE RAINFALL ALONG PORTIONS OF 
THE US-MEXICAN BORDER IS SUGGESTIVE OF WHAT COULD BE AN ENHANCED MONSOON SEASON 
FOR THE SOUTHWEST. THIS AREA HAS SUBSTANTIAL SUPPORT FROM BOTH THE CFS AND ECPC 
TOOLS, WITH SOMEWHAT LESS SUPPORT INDICATED BY THE ENSEMBLE CCA (ECCA). 
ALTHOUGH THE PREDICTION OF THE MAGNITUDE AND TIMING OF THE MONSOON IS VERY 
DIFFICULT AT BEST, THERE ARE SOME OBJECTIVE INDICATIONS THAT TILT THE 
PROBABILITIES TOWARD THE WETTEST TERCILE OF THE PRECIPITATION DISTRIBUTION. 
 
MOVING INTO THE JJA AND JAS 2009 SEASONS, THE CFS, ECPC AND ECCA CONTINUE TO GO 
WITH WETTER THAN AVERAGE CONDITIONS ACROSS THE MONSOON REGION OF THE SOUTHWEST. 
THE CON, ECCA, CCA AND OCN CONTINUE TO SHOW GOOD SUPPORT FOR THE RELATIVE 
DRYNESS PREDICTED OVER THE NORTHWEST. THE JAS, ASO, AND SON SEASONS FAVOR ABOVE 
AVERAGE PRECIPITATION AMOUNTS OVER PORTIONS OF FLORIDA, BASED LARGELY ON 
RAINFALL TRENDS ASSOCIATED WITH INCREASED TROPICAL ACTIVITY DURING RECENT 
YEARS. IN THE NORTHEAST U.S. FOR JAS AND ASO 2009, WETTER THAN AVERAGE 
CONDITIONS ARE FAVORED BY THE CON, WHICH IS CONSISTENT WITH A RECENT TREND FOR 
WETNESS ACROSS THIS AREA. FOR SEASONS OND 2009 TO MJJ 2010, THE PRECIPITATION 
FORECASTS ARE BASED HEAVILY ON THE OBJECTIVE CONSOLIDATION AND RECENT TRENDS. 
IN REGIONS WHERE PRECIPITATION SIGNALS WERE WEAK, OR IN CONFLICT, EQUAL CHANCES 
(EC) OF BELOW-, NEAR-, AND ABOVE-AVERAGE PRECIPITATION IS PREDICTED. 
 
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 MAY 21 2009 
 
1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17, 2001 
FORECAST RELEASE. 
 
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