PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS 
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD 
830AM EDT THURSDAY APR 18 2013 
 
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 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. 
 
ATMOSPHERIC AND OCEANIC OBSERVATIONS OVER THE LAST FEW MONTHS INDICATE 
ENSO-NEUTRAL CONDITIONS. PREDICTIONS OF SEA SURFACE TEMPERATURE (SST) IN THE 
NINO 3.4 REGION OF THE PACIFIC OCEAN FROM DYNAMICAL AND STATISTICAL MODELS 
INDICATE THAT SST WILL BE CLOSE TO THE CLIMATOLOGICAL MEAN THROUGH BOREAL 
SUMMER. THE OFFICIAL ENSO OUTLOOK IS FOR A CONTINUATION OF ENSO-NEUTRAL 
CONDITIONS AT LEAST THROUGH THE NORTHERN HEMISPHERE SUMMER 2013. CONFIDENCE IN 
PREDICTIONS FOR THE STATE OF ENSO IN LATE SUMMER 2013 AND BEYOND IS LOW AT THIS 
TIME. 
 
THE SEASONAL TEMPERATURE OUTLOOK FOR MJJ 2013 INDICATES ENHANCED PROBABILITIES 
FOR ABOVE NORMAL TEMPERATURES FOR THE NORTHERN SECTIONS OF ALASKA, THE 
SOUTHWEST CONUS, THE CENTRAL AND SOUTHERN ROCKIES, THE CENTRAL AND SOUTHERN 
PLAINS, AND MOST AREAS EAST OF THE MISSISSIPPI RIVER. TEMPERATURES IN HAWAII 
HAVE ENHANCED CHANCES TO BE IN THE BELOW NORMAL CATEGORY. 
 
THE MJJ 2013 PRECIPITATION OUTLOOK INDICATES THAT PROBABILITIES OF BELOW MEDIAN 
PRECIPITATION ARE ENHANCED FOR SECTIONS OF THE WESTERN CONUS FROM NW TEXAS TO 
WASHINGTON STATE. THE CHANCES FOR BELOW MEDIAN RAINFALL ARE ENHANCED FOR 
HAWAII, BUT STARTING ONLY IN JJA. 
 
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 
 
EQUATORIAL SSTS ARE CLOSE TO LONG TERM AVERAGES THROUGHOUT THE PACIFIC. MOST OF 
THE SST ANOMALIES ARE WITHIN ONE-HALF DEGREE CELSIUS OF THE CLIMATOLOGICAL 
NORMALS. THE CURRENT WEEKLY NINO 3.4 INDEX IS -0.0 C, LESS NEGATIVE THAN IT WAS 
A MONTH AGO. HEAT CONTENT IN THE UPPER 300 METERS OF THE EQUATORIAL PACIFIC 
OCEAN HAS INCREASED AND IS NOW CLOSE TO LONG-TERM AVERAGE VALUES. LOW LEVEL 
EASTERLY WINDS AT 850 HPA WERE SLIGHTLY ENHANCED OVER THE CENTRAL TROPICAL 
PACIFIC OVER THE LAST FEW WEEKS. POSITIVE ANOMALIES IN OUTGOING LONG-WAVE 
RADIATION (OLR) NEAR AND TO EITHER SIDE OF THE DATE LINE INDICATE SUPPRESSED 
CONVECTION, AND NEGATIVE ANOMALIES IN OLR FARTHER WEST AND NEAR INDONESIA 
INDICATE ENHANCED CONVECTION FOR THE LAST 30 DAYS.  EARLIER MJO ACTIVITY, FOR 
NOW MUCH WEAKENED, LIKELY CONTRIBUTED TO THESE ANOMALIES. 
 
PROGNOSTIC DISCUSSION OF SST FORECASTS 
 
ENSO-NEUTRAL CONDITIONS ARE LIKELY TO CONTINUE THROUGH THE NORTHERN HEMISPHERE 
SUMMER 2013. THE NINO 3.4 SST ANOMALY FORECAST FROM THE CFSV2, CA, MARKOV AND 
CCA ALL SHOW SLIGHT COOLING TO -0.5 BY EARLY FALL. MOST OTHER DYNAMICAL AND 
STATISTICAL MODELS PREDICT THE NINO 3.4 SST ANOMALY TO REMAIN BETWEEN -0.5 C 
AND +0.5 C THROUGH LATE 2013. SST FORECASTS SUPPORT ENSO NEUTRAL CONDITIONS 
THROUGH THE SPRING AND SUMMER WITH GREATER UNCERTAINTY FOLLOWING THE SPRING 
BARRIER. ENSO IS THUS NOT A FACTOR IN THE U.S. FORECAST FOR 2013. 
 
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 NORTHERN HEMISPHERE SUMMER 2013. THE 
FORECASTS WERE BASED PRIMARILY ON DYNAMICAL MODEL OUTPUT FROM THE NMME AND IMME 
FOR MJJ THROUGH SON 2013, WITH SOME ADDITIONAL CONSIDERATION FROM STATISTICAL 
FORECAST TOOLS, SOIL MOISTURE CONDITIONS, DECADAL TRENDS AND THE CONSOLIDATION 
(CON) FORECAST. OUTLOOKS FOR OND 2013 ONWARD WERE BASED MOSTLY ON THE 
CONSOLIDATION, WHICH LARGELY REFLECTS TRENDS. 
 
PROGNOSTIC DISCUSSION OF OUTLOOKS - MJJ 2013 TO MJJ 2014 
 
TEMPERATURE 
 
THE TEMPERATURE OUTLOOKS FOR MJJ THROUGH ASO 2013 INDICATE ENHANCED CHANCES FOR 
ABOVE NORMAL TEMPERATURES FOR NORTHERN ALASKA, THE SOUTHWEST, THE SOUTHERN AND 
CENTRAL PLAINS, AND THE EASTERN HALF OF THE CONUS.  ENHANCED PROBABILITIES OF 
BELOW NORMAL TEMPERATURES ARE NOT INDICATED ANYWHERE AT ANY TIME. THESE 
FORECASTS ARE SUPPORTED BY THE MODELS OF THE NMME AND IMME, AND ALSO LARGELY 
CONSISTENT WITH DECADAL TRENDS. SUBSTANTIAL SOIL MOISTURE DEFICITS OVER MUCH OF 
THE WEST AND CENTRAL CONUS ARE ALSO CONSISTENT WITH AN INCREASED LIKELIHOOD OF 
ABOVE NORMAL TEMPERATURES DURING THE WARM SEASON. NORTHERN ALASKA IS MORE 
LIKELY TO EXPERIENCE ABOVE NORMAL TEMPERATURES FOR MJJ THROUGH OND 2013 AS 
INDICATED BY THE DECADAL TEMPERATURE TRENDS. THESE TEMPERATURE TRENDS ARE DUE 
IN PART TO REDUCED ARCTIC OCEAN SEA ICE COVER IN THIS REGION DURING RECENT 
YEARS FOR THE SPRING THROUGH AUTUMN SEASONS. 
 
INCREASED CHANCES OF ABOVE NORMAL TEMPERATURES CONTINUE ACROSS MOST OF THE 
CONUS INTO SON 2013. FOR SON 2013 AND BEYOND, TEMPERATURE OUTLOOKS ARE 
PRIMARILY A RESULT OF SIGNALS RELATED TO DECADAL VARIABILITY AS DETERMINED BY 
THE CONSOLIDATION FORECAST. ENHANCED PROBABILITIES OF ABOVE NORMAL TEMPERATURES 
CONTINUE FOR PORTIONS OF THE GREAT LAKES REGION, THE NORTHEAST, THE SOUTH AND 
THE SOUTHWEST THROUGHOUT THE YEAR INTO AMJ 2014. ENHANCED CHANCES FOR ABOVE 
NORMAL TEMPERATURES FOR NORTHERN ALASKA REAPPEAR FROM FMA 2014 FORWARD. 
 
IN AREAS WITHOUT SUBSTANTIAL AND RELIABLE CLIMATE SIGNALS, EQUAL CHANCES OF 
BELOW, NEAR AND ABOVE NORMAL SEASONAL MEAN TEMPERATURES IS INDICATED. 
 
PRECIPITATION 
 
THE PRECIPITATION OUTLOOK FOR MJJ 2013 INDICATES ELEVATED CHANCES FOR BELOW 
MEDIAN ACCUMULATED PRECIPITATION FOR SECTIONS OF THE WESTERN CONUS FROM NW 
TEXAS TO WASHINGTON STATE. THIS IS INDICATED BY A CONSENSUS OF STATISTICAL 
TOOLS AND DYNAMICAL MODEL FORECASTS FROM THE NMME AND IMME.  ENHANCED CHANCES 
OF ABOVE MEDIAN PRECIPITATION ARE NOT INDICATED ANYWHERE AT ANY TIME. DURING 
JJA THROUGH SON, THERE ARE ENHANCED ODDS FOR BELOW-MEDIAN PRECIPITATION AT 
LOCATIONS WEST OF THE ROCKIES. DYNAMICAL MODELS INDICATE A CONTINUATION OF THE 
TENDENCY FOR BELOW MEDIAN PRECIPITATION IN PARTS OF THE SOUTHWEST MONSOON 
REGION THROUGH EARLY 2013. DECADAL TRENDS FOR BELOW MEDIAN PRECIPITATION ALSO 
EMERGE IN THE SOUTHEAST FOR NDJ 2013 THROUGH FMA 2014. 
 
IN AREAS WITHOUT SUBSTANTIAL AND RELIABLE CLIMATE SIGNALS, EQUAL CHANCES OF 
BELOW, NEAR AND ABOVE MEDIAN SEASONAL PRECIPITATION AMOUNTS IS 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 MAY 16 2013 
 
 
1981-2010 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 19, 2011 
FORECAST RELEASE. 
$$