PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS 
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD 
830AM EDT THURSDAY SEP 19 2013 
 
SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS 
 
THE MAIN FACTORS THAT USUALLY INFLUENCE THE SEASONAL CLIMATE OUTLOOK INCLUDE: 
1) EL NINO AND LA NINA - WHICH TOGETHER 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", WHICH ARE USED AT TIMES 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 
1981-2010). 
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 CONSIDERED LESS PREDICTABLE ON A SEASONAL 
TIMESCALE THAN ENSO. 
5) THE PACIFIC DECADAL OSCILLATION (PDO) - AN ENSO-LIKE PATTERN OF CLIMATE 
VARIABILITY AFFECTING 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 SPRING AND 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). AN EXPERIMENTAL MODEL FORECAST SYSTEM, THE NATIONAL MULTI-MODEL 
ENSEMBLE, COMPRISED OF SEVERAL MODELS AND DESIGNATED NMME, MAY ALSO BE USED 
EXPERIMENTALLY AND SUBJECTIVELY UNTIL IT IS INCLUDED INTO THE CONSOLIDATION. AN 
INTERNATIONAL MODEL ENSEMBLE DESIGNATED IMME IS ALSO AVAILABLE. 
9) CONSOLIDATION (CON) - AN OBJECTIVE, SKILL WEIGHTED COMBINATION 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. 
 
RECENT ATMOSPHERIC AND OCEANIC OBSERVATIONS CONTINUE TO INDICATE ENSO NEUTRAL 
CONDITIONS. THE OFFICIAL ENSO OUTLOOK CALLS FOR A CONTINUATION OF THE ENSO 
NEUTRAL STATE INTO BOREAL WINTER 2013/2014. 
 
THE OCTOBER-NOVEMBER-DECEMBER (OND) 2013 TEMPERATURE OUTLOOK INDICATES ELEVATED 
CHANCES FOR ABOVE-NORMAL TEMPERATURES IN MUCH OF THE WEST, THE ALASKA 
PANHANDLE, NEW ENGLAND, AND FOR THE NORTH SLOPE OF ALASKA. THE CONFIDENCE FOR 
ABOVE-NORMAL TEMPERATURES IS HIGHEST OVER PORTIONS OF ARIZONA, NEW MEXICO, AND 
MAINE. THE OND 2013 PRECIPITATION OUTLOOK CALLS FOR ELEVATED CHANCES OF 
ABOVE-MEDIAN PRECIPITATION IN NORTHERN PORTIONS OF BOTH THE ROCKIES AND HIGH 
PLAINS. 
IN AREAS WHERE THE LIKELIHOODS OF SEASONAL MEAN TEMPERATURES AND SEASONAL 
ACCUMULATED PRECIPITATION AMOUNTS ARE SIMILAR TO CLIMATOLOGICAL PROBABILITIES, 
EQUAL CHANCES (EC) IS SHOWN. 
 
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 
 
NEAR-EQUATORIAL SEA-SURFACE TEMPERATURES (SST) ARE NEAR-AVERAGE AS OF EARLY MID 
SEPTEMBER 2013 ACROSS THE CENTRAL AND EAST-CENTRAL PACIFIC, AND BELOW-AVERAGE 
IN THE EASTERN PACIFIC. IN THE MOST RECENT WEEK, SST ANOMALIES IN THE NINO 3.4 
REGION ARE ZERO DEGREES CELSIUS. BUOY MEASUREMENTS INDICATE A LARGE VOLUME OF 
ANOMALOUSLY WARM SUB-SURFACE WATER, ABOUT +1C ANOMALY TYPICALLY, BETWEEN 50-200 
METERS DEEP OVER THE WESTERN, CENTRAL AND EAST-CENTRAL EQUATORIAL PACIFIC, AND 
NEARER TO THE SURFACE IN THE EASTERN PACIFIC TO ABOUT 100W. 
 
LOW-LEVEL (850-HPA) TRADE WINDS REMAINED NEAR AVERAGE ACROSS THE EQUATORIAL 
PACIFIC, BUT THERE HAVE BEEN OCCASIONAL SHORT PERIODS OF ANOMALOUS EASTERLIES 
IN THE WEST PACIFIC. TROPICAL CONVECTION CONTINUES TO BE ENHANCED OVER 
INDONESIA AND SUPPRESSED ALONG THE EQUATOR OVER THE CENTRAL PACIFIC AND 
EASTWARD. COLLECTIVELY, THESE OCEANIC AND ATMOSPHERIC CONDITIONS REFLECT THE 
ENSO NEUTRAL STATE. 
 
PROGNOSTIC DISCUSSION OF SST FORECASTS 
 
ENSO NEUTRAL CONDITIONS ARE EXPECTED TO CONTINUE THROUGH THE NORTHERN 
HEMISPHERE WINTER OF 2013/14. THE CPC CONSOLIDATION OF NINO 3.4 SST FORECASTS 
PREDICTS ANOMALIES LIKELY RANGING FROM 0.0 TO -0.3 DEGREES C THROUGH THE 
REMAINDER OF 2013 AND INTO 2014. THE RANGE OF MOST DYNAMICAL AND STATISTICAL 
MODEL FORECASTS INCLUDED IN THE IRI PLUME, NMME AND IMME REMAINS FROM -0.3 TO 
+0.6 DEGREES C THROUGH EARLY 2014. A PECULIAR DICHOTOMY PERSISTS WITH MANY 
STATISTICAL MODELS NEUTRAL BUT A FEW TENTHS NEGATIVE, AND A LARGE MAJORITY OF 
DYNAMICAL MODELS NEUTRAL BUT A FEW TENTH POSITIVE. OVERALL,FORECASTS THUS FAVOR 
A CONTINUATION OF THE ENSO NEUTRAL STATE THROUGH AUTUMN AND WINTER. COMPARED TO 
LAST MONTH THE PLUME OF FORECASTS HAS NUDGED UPWARD BY 0.2 DEGREES C. 
 
PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS 
 
THE TEMPERATURE AND PRECIPITATION OUTLOOKS WERE MADE CONSIDERING ENSO NEUTRAL 
CONDITIONS TO BE MOST LIKELY THROUGH EARLY SPRING 2014. THE FORECASTS FROM OND 
2013 THROUGH FMA 2014 WERE BASED ON A COMBINATION OF STATISTICAL TOOLS AND 
DYNAMICAL MODEL GUIDANCE INCLUDING THE CFS, THE NMME AND THE IMME. THE 
CONSOLIDATION AND DECADAL TRENDS FROM THE OCN WERE CONSIDERED FOR ALL LEADS. 
DECADAL CLIMATE TRENDS WERE THE PRIMARY SOURCE OF PREDICTABILITY FOR THE 
FORECASTS AFTER FMA 2014. 
 
 
 
PROGNOSTIC DISCUSSION OF OUTLOOKS - OND 2013 TO OND 2014 
 
TEMPERATURE 
 
COMPARED TO LAST MONTH'S RELEASE WE REMOVED SOME SIGNALS, PARTICULARLY FOR THE 
EXTENT OF FAVORED ABOVE AVERAGE TEMPERATURE IN THE NORTHEASTERN QUADRANT OF THE 
CONUS IN THE FIRST SIX LEADS. ON THE OTHER HAND ELEVATED ODDS OF ABOVE AVERAGE 
TEMPERATURES IN THE WEST WERE EXTENDED NORTHWESTWARD TO INCLUDE THE PACIFIC 
NORTHWEST AND THE ALASKA PANHANDLE. 
 
THE SEASONAL TEMPERATURE OUTLOOK FOR OND 2013 INDICATES ELEVATED CHANCES OF 
ABOVE-NORMAL TEMPERATURES FOR MUCH OF THE WEST, NEW ENGLAND, AND FOR BOTH THE 
PANHANDLE AND NORTH SLOPE OF ALASKA. FOR THE REGIONS NOTED, THE OUTLOOK IS 
PRIMARILY BASED ON DYNAMICAL MODEL GUIDANCE FROM THE CFS, NMME AND IMME, IN 
ADDITION TO THE CONSOLIDATION (CON) TOOL. FOR THE NORTH SLOPE OF ALASKA, THE 
TEMPERATURE OUTLOOK IS MAINLY FROM SIGNIFICANT POSITIVE DECADAL TRENDS, 
PRESUMABLY RELATED TO A REDUCTION IN ARCTIC OCEAN SEA ICE COVER DURING RECENT 
YEARS FOR THIS SEASON. 
 
THE NEXT FOUR OUTLOOKS (NDJ 2013 THROUGH FMA 2014) ARE HEAVILY BASED ON 
DYNAMICAL MODEL GUIDANCE, AND THE CON TOOL. ENHANCED CHANCES FOR ABOVE-NORMAL 
TEMPERATURES IS CONCENTRATED IN THE WEST THROUGH JFM2014. FROM FMA 2014 ONWARD, 
THE TEMPERATURE OUTLOOKS ARE PRIMARILY BASED ON THE CON TOOL, WHICH TAKES 
LONG-TERM TRENDS INTO ACCOUNT. THERE ARE ELEVATED ODDS OF BELOW-NORMAL 
TEMPERATURES OVER PORTIONS OF THE PACIFIC NORTHWEST FROM MAM THROUGH AMJ 2014. 
THIS APPEARS TO BE DUE TO DECADAL TEMPERATURE TRENDS. 
 
FROM FMA TO JJA 2014, THERE ARE ENHANCED CHANCES FOR ABOVE-NORMAL TEMPERATURES 
ACROSS MUCH OF THE SOUTHERN AND PARTS OF THE EASTERN CONUS, WITH THE HIGHEST 
PROBABILITIES INDICATED OVER THE SOUTHWEST. FROM JAS TO SON 2014, THERE ARE 
ELEVATED ODDS OF ABOVE-NORMAL TEMPERATURES ACROSS MUCH OF THE SOUTHERN CONUS, 
THE NORTHEAST, AND FLORIDA. THIS IS BASED MOSTLY ON THE CON, AND IS ATTRIBUTED 
TO LONGER-TERM TEMPERATURE TRENDS. POSITIVE DECADAL TEMPERATURE TRENDS ARE 
SIGNIFICANT FROM AMJ - OND 2014 ACROSS FAR NORTHERN ALASKA. 
 
IN AREAS WITHOUT SUBSTANTIAL AND RELIABLE CLIMATE SIGNALS, EQUAL CHANCES OF 
BELOW, NEAR AND ABOVE NORMAL SEASONAL MEAN TEMPERATURES ARE INDICATED. 
 
PRECIPITATION 
 
COMPARED TO LAST MONTH'S RELEASE WE REMOVED SOME SIGNALS, PARTICULARLY FOR 
ENHANCED ODDS FOR ABOVE MEDIAN PRECIPITATION IN THE OHIO VALLEY IN OND. ON THE 
OTHER HAND ELEVATED ODDS FOR BELOW MEDIAN PRECIPITATION WERE ADDED IN THE 
INTERIOR SOUTHWEST FROM NDJ - MAM. 
 
THE OND 2013 PRECIPITATION OUTLOOK INDICATES AN ENHANCED LIKELIHOOD OF 
ABOVE-MEDIAN PRECIPITATION OVER MONTANA AND NORTHERN IDAHO. THIS FORECAST IS 
PRIMARILY BASED ON DYNAMICAL MODEL GUIDANCE FROM THE CFS, NMME AND IMME. THESE 
SAME TOOLS SUPPORT A SIMILAR PRECIPITATION FORECAST FOR MONTANA AND IDAHO FOR 
NDJ2013-14, BUT IN ADDITION, THERE ARE ENHANCED CHANCES OF BELOW-MEDIAN 
PRECIPITATION FOR THE SOUTHERN ATLANTIC COAST STATES, AND THE INTERIOR 
SOUTHWEST, BASED ON THE CON TOOL, WHERE DECADAL PRECIPITATION TRENDS TILT THE 
ODDS TOWARDS BELOW-MEDIAN IN THIS REGION THROUGH THE JFM 2014 SEASON FOR THE 
SOUTHEAST AND THROUGH MAM2014 FOR THE SOUTHWEST. 
 
SEASONAL PRECIPITATION SIGNALS ARE WEAK AND UNRELIABLE FOR MOST OF THE 
REMAINING SEASONS, EXCEPT FOR THE PACIFIC NORTHWEST IN JJA AND JAS 2014, WHERE 
HISTORICAL TRENDS FAVOR BELOW-MEDIAN PRECIPITATION. 
 
IN AREAS WITHOUT SUBSTANTIAL AND RELIABLE CLIMATE SIGNALS, EQUAL CHANCES OF 
BELOW, NEAR AND ABOVE MEDIAN SEASONAL TOTAL PRECIPITATION AMOUNTS ARE INDICATED. 
 
FORECASTER: HUUG VAN DEN DOOL 
 
THE CLIMATIC NORMALS ARE BASED ON CONDITIONS BETWEEN 1981 AND 2010, FOLLOWING 
THE WORLD METEROLOGICAL ORGANIZATION CONVENTION OF USING THE MOST RECENT 3 
COMPLETE DECADES AS THE CLIMATIC REFERENCE PERIOD.  THE PROBABILITY ANOMALIES 
FOR TEMPERATURE AND PRECIPITATION BASED ON THESE NEW NORMALS BETTER REPRESENT 
SHORTER TERM CLIMATIC ANOMALIES THAN THE FORECASTS BASED ON OLDER NORMALS. 
 
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 OCT 17 2013 
 
 
1981-2010 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 19, 2011 
FORECAST RELEASE. 
$$