PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS 
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 
830 AM EDT THU AUG 21 2008 
 
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. 
 
THE EQUATORIAL PACIFIC RETURNED TO ENSO NEUTRAL CONDITIONS DURING JUNE 2008, 
AND STAYED THERE DURING JULY. AS WITH PREVIOUS TRANSITIONS FROM A LA NINA TO AN 
ENSO NEUTRAL STATE, A WEAK LA NINA ATMOSPHERIC CIRCULATION CONTINUES OVER THE 
TROPICS. ABOVE NORMAL SSTS EXTEND WESTWARD FROM NEAR THE SOUTH AMERICAN COAST 
TO CURRENTLY AROUND 140 W LONGITUDE. BELOW NORMAL SUBSURFACE WATER TEMPERATURES 
IN THE CENTRAL EQUATORIAL PACIFIC HAVE WAXED AND WANED IN AREA, DEPTH AND 
MAGNITUDE IN RESPONSE TO PERIODS OF STRONGER AND WEAKER TRADES. 
 
THERE IS GOOD AGREEMENT IN THE FORECAST FOR NINO 3.4 SST ANOMALIES IN THE NEXT 
FEW MONTHS. A CONSENSUS OF THE FORECASTS MAINTAINS ENSO NEUTRAL CONDITIONS, 
WITH NINO 3.4 SST ANOMALIES SLIGHTLY BELOW ZERO INTO THE BEGINNING OF NEXT 
YEAR. 
 
THE TEMPERATURE OUTLOOK FOR SON 2008 CALLS FOR ABOVE NORMAL TEMPERATURES ACROSS 
A BROAD SWATH OF THE U.S., FROM THE SOUTHWEST DESERT AND CENTRAL SOUTHERN 
STATES INTO THE NORTHEAST. THESE EXPECTED AREAS OF ABOVE ARE DUE PRIMARILY TO 
RECENT TEMPERATURE TRENDS AND FOLLOW CLOSELY THE RECENT OBJECTIVE CONSOLIDATION 
FORECAST, WHICH INCLUDES THE STATISTICAL FORECAST TOOLS AND THE CFS FORECAST. 
 
THERE IS AN ENHANCED LIKELIHOOD OF ABOVE MEDIAN PRECIPITATION FOR SON 2008 FOR 
THE NORTHEAST AND PARTS OF THE HIGH AND CENTRAL PLAINS AS INDICATED BY THE 
OBJECTIVE CONSOLIDATION DUE SOMEWHAT TO RECENT TRENDS. THE INCREASED LIKELIHOOD 
OF ABOVE MEDIAN RAINFALL FOR THE GULF AND SOUTHERN ATLANTIC COASTS IS DUE TO 
RECENT TRENDS RESULTING FROM GREATER THAN NORMAL CLIMATOLOGICAL TROPICAL 
ACTIVITY. 
 
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 
 
LA NINA CONDITIONS WERE REPLACED BY ENSO NEUTRAL CONDITIONS DURING JUNE 2008, 
AS INDICATED BY SEA SURFACE TEMPERATURES (SSTS) ACROSS THE EQUATORIAL PACIFIC 
OCEAN.  SSTS IN THE EAST-CENTRAL PACIFIC OCEAN ARE NOW LESS THAN ONE HALF OF 
ONE DEGREE CELSIUS BELOW ZERO. CONVECTION CONTINUES TO BE SLIGHTLY SUPPRESSED 
HOWEVER IN THE CENTRAL EQUATORIAL PACIFIC OCEAN, WHILE LOW LEVEL EASTERLY WINDS 
AND UPPER LEVEL WESTERLIES REMAIN ENHANCED OVER THE TROPICAL PACIFIC REGION, 
REFLECTING THE RESIDUAL INFLUENCE OF THE PAST LA NINA. SSTS ALONG THE EQUATOR 
ARE ABOVE NORMAL FROM ABOUT 140 W TO NEAR THE SOUTH AMERICAN COAST. SST 
ANOMALIES IN EARLY AUGUST WERE VERY NEAR ZERO IN THE NINO 3.4 REGION, FROM 170 
W TO 120 W LONGITUDE AND 5 S TO 5 N LATITUDE. WATER TEMPERATURES IN THE UPPER 
300 M OF THE EQUATORIAL PACIFIC HAVE INCREASED FROM FEBRUARY TO JUNE AND HAVE 
NOW STABILIZED SOMEWHAT ABOVE NORMAL FOR MUCH OF THE BASIN. BELOW NORMAL 
SUBSURFACE WATER TEMPERATURES AT GREATER DEPTH IN THE CENTRAL EQUATORIAL 
PACIFIC HAVE WAXED AND WANED IN AREA, DEPTH AND MAGNITUDE IN RESPONSE TO 
PERIODS OF STRONGER AND WEAKER TRADES. THE CURRENT STATE OF THE TROPICAL 
PACIFIC OCEAN AND ATMOSPHERE IS REPRESENTATIVE OF ENSO NEUTRAL CONDITIONS. 
 
 
PROGNOSTIC DISCUSSION OF SST FORECASTS 
 
MOST DYNAMICAL AND STATISTICAL SST FORECASTS FOR THE NINO 3.4 REGION PREDICT 
SSTS IN THE RANGE BETWEEN -0.5 AND +0.5 C, INDICATING ENSO-NEUTRAL CONDITIONS, 
THROUGH AUTUMN AND INTO NEXT YEAR. COMPARED TO LAST MONTHS FORECAST THE 
AGREEMENT AMONG TOOLS HAS MUCH INCREASED. ALL NCEP SST FORECASTS MAINTAIN 
SLIGHTLY NEGATIVE NINO 3.4 SST ANOMALIES THROUGH 2008 INTO 2009. A 
CONSOLIDATION OF NCEP FORECASTS SUGGESTS THAT NINO 3.4 SST ANOMALIES ARE MOST 
LIKELY TO REMAIN SLIGHTLY BELOW ZERO THROUGH THE SPRING OF 2009. CONSIDERING 
CURRENT OBSERVATIONS AND SST FORECASTS FROM STATISTICAL AND DYNAMICAL MODELS 
FROM NCEP AND FROM OTHER CENTERS NOT INCLUDED IN THE CONSOLIDATION FORECAST, 
ENSO NEUTRAL CONDITIONS ARE MOST LIKELY INTO EARLY NEXT YEAR WITH NINO 3.4 SST 
ANOMALIES EXPECTED TO BE WITHIN ONE HALF OF ONE DEGREE CELSIUS OF ZERO. 
 
ATMOSPHERIC CONDITIONS RELATED TO LA NINA OFTEN PERSIST FOR A FEW MONTHS AFTER 
SSTS RETURN TO ENSO NEUTRAL CONDITIONS - AND THIS YEAR IS NO EXCEPTION. 
RESIDUAL LA NINA ATMOSPHERIC CONDITIONS MAY SLIGHTLY ENHANCE TROPICAL ACTIVITY 
IN THE ATLANTIC AND SLIGHTLY SUPPRESS TROPICAL ACTIVITY IN THE EASTERN PACIFIC 
IN THE LATE SUMMER AND OR FALL.(SEE THE NOAA 2008 HURRICANE SEASON OUTLOOK 
DISCUSSION FOR MORE INFORMATION). 
 
 
PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS 
 
THE TEMPERATURE AND PRECIPITATION OUTLOOKS FOR ALL LEAD TIMES ARE BASED ON THE 
CONSOLIDATION (CON), A SKILL-WEIGHTED AND CALIBRATED OBJECTIVE BLEND OF THE 
CFS, CCA, SMLR, OCN, AND ECCA FORECAST TOOLS. OTHER TOOLS - IRI EPCP AND CAS 
-ARE CONSIDERED AND USED FOR EXPERT ADJUSTMENT OF THE FORECAST. THE CON 
FORECAST IS NOT AVAILABLE FOR ALASKA, SO THE FORECAST THERE IS BASED ON THE 
FORECASTERS COMBINING OCN, CCA, SMLR AND THE CFS FORECASTS. THE ENSO STATE IS 
NOT EXPECTED TO HAVE AN IMPACT ON THE COMING SEASONAL TEMPERATURE AND 
PRECIPITATION OUTLOOKS, WITH THE EXCEPTION OF RESIDUAL INDIRECT EFFECTS OF THIS 
PAST WINTERS LA NINA. THE TEMPERATURE AND PRECIPITATION OUTLOOKS FROM SON 2008 
TO SON 2009 CLOSELY FOLLOW THE CON FORECAST - THIS IS MORE OBVIOUS FOR 
TEMPERATURE THAN FOR PRECIPITATION BECAUSE THE LATTER HAS LITTLE SKILL. THE CFS 
FORECAST IS ONLY AVAILABLE AND PART OF THE CONSOLIDATION THROUGH FMA 2009. 
 
 
PROGNOSTIC DISCUSSION OF OUTLOOKS - SON 2008 TO SON 2009 
 
TEMPERATURE: 
 
THE OUTLOOK FOR SON 2008 INDICATES ENHANCED PROBABILITIES OF ABOVE NORMAL 
TEMPERATURES FOR A BROAD SWATH EXTENDING FROM THE DESERT SOUTHWEST EXTENDING 
EASTWARD ACROSS TEXAS TO THE NORTHEAST U.S. WITH CURRENT ENSO NEUTRAL 
CONDITIONS EXPECTED ABOVE NORMAL TEMPERATURES IN THE SON 2008 SEASON ARE 
LARGELY DUE TO RECENT TEMPERATURE TRENDS. ABOVE NORMAL TEMPERATURES IN THE 
NORTHEASTERN U.S. ARE BASED ON THE CONSOLIDATION FORECAST. 
 
TEMPERATURE FORECASTS AFTER SON 2008 CLOSELY FOLLOW THE CONSOLIDATION FORECAST 
DERIVED FROM THE CFS, OCN, CCA, ECCA AND SMLR. CURRENT ENSO NEUTRAL CONDITIONS 
AND UNCERTAINTY IN THE FUTURE ENSO STATE MEAN THAT ALL SEASONAL TEMPERATURE 
FORECASTS ARE LARGELY IMPACTED BY TEMPERATURE TRENDS. THE AREA OF ENHANCED 
CHANCES OF ABOVE NORMAL TEMPERATURES EXPANDS TO INCLUDE MOST OF THE U.S. EXCEPT 
FOR THE AREA WEST OF THE ROCKY MOUNTAINS FOR THE NDJ 2008-2009 THROUGH JFM 2009 
SEASONS. THE AREAS OF GREATER THAN CLIMATOLOGICAL PROBABILITIES OF ABOVE NORMAL 
TEMPERATURES DECREASE SUBSTANTIALLY THROUGH THE NEXT FEW THREE-MONTH PERIODS 
BEFORE EXPANDING TO COVER MOST OF THE WESTERN U.S. IN NEXT SUMMERS JAS 2009 
OUTLOOK. THE OUTLOOK FOR SON 2009 LOOKS SOMEWHAT SIMILAR TO THE FIRST SEASONAL 
OUTLOOK FOR SON 2008, DUE TO THE IMPORTANT INFLUENCE OF THE TEMPERATURE TRENDS 
BUT DIFFERENCES MAY BE NOTED DUE TO SMLR AND ECCA THE OUTLOOKS FOR ALASKA ARE 
DERIVED MAINLY FROM THE RECENT TEMPERATURE TRENDS WITH SECONDARY SUPPORT FROM 
OTHER TOOLS. 
 
 
PRECIPITATION: 
 
ELEVATED PROBABILITIES FOR ABOVE MEDIAN PRECIPITATION IN THE SON 2008 OUTLOOKS 
FOR FLORIDA AND PARTS OF THE GULF AND ATLANTIC COASTS, THE NORTHEAST, AND PARTS 
OF THE CENTRAL PLAINS ARE DERIVED FROM THE CONSOLIDATION FORECAST. MOST OF THE 
PRECIPITATION FORECASTS FOR SON 2008 ARE SUPPORTED BY RECENT PRECIPITATION 
TRENDS. THE ABOVE MEDIAN PRECIPITATION FORECAST FOR COASTAL AREAS IN THE 
SOUTHEAST IN SON 2008 ARE RELATED TO INCREASED TROPICAL ACTIVITY DURING RECENT 
YEARS AND ARE AGAIN INCLUDED IN THE JAS AND ASO 2009 OUTLOOKS. AREAS OF BELOW 
MEDIAN PRECIPITATION ARE FORECAST FOR PARTS OF THE DESERT SOUTHWEST FROM OND 
2008 TO DJF 2008-2009 AND FOR MUCH OF THE SOUTHEAST FROM NDJ 2008-2009 TO MAM 
2009 RESULTING FROM RECENT PREDICTABLE PRECIPITATION TRENDS AS INDICATED BY THE 
CONSOLIDATION. AREAS OF INCREASED PROBABILITY FOR ABOVE MEDIAN PRECIPITATION 
CENTERED AROUND THE TEXAS PANHANDLE FROM DJF 2008-2009 TO FMA 2009 ALSO 
REPRESENT RECENT TRENDS AS INDICATED BY THE CONSOLIDATION. 
 
 
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 SEP 18 2008 
 
1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17, 2001 
FORECAST RELEASE. 
 
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