PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD
830 AM EDT THU APR 17 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) 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.
6) STATISTICAL FORECAST TOOLS - CANONICAL CORRELATION ANALYSIS (CCA) AND 
SCREENING MULTIPLE LINEAR REGRESSION (SMLR).
7) DYNAMICAL FORECAST MODELS - INCLUDING THE NCEP CLIMATE FORECAST SYSTEM (CFS).
8) AN OBJECTIVE CONSOLIDATION (ABBREVIATED CON IN THE TEXT) OF THE OCN, CCA, 
SMLR 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.

COLD EPISODE (LA NINA) CONDITIONS CONTINUE ACROSS THE TROPICAL PACIFIC, THOUGH 
THE EPISODE HAS WEAKENED OVER THE PAST FEW WEEKS.  SEA SURFACE TEMPERATURES 
(SSTS) ARE BELOW AVERAGE THROUGHOUT THE EQUATORIAL PACIFIC BETWEEN 150E AND 
110W. SSTS IN THE NINO 3.4 REGION (FROM 5N TO 5S AND 170W TO 120W) ARE A GOOD 
INDICATOR OF THE STRENGTH OF A LA NINA.  THE WEEKLY NINO 3.4 INDEX VALUE PEAKED 
IN MID-FEBRUARY NEAR -2.1 DEG C, AND HAS SINCE DECREASED TO NEAR -0.9 BY THE 
START OF APRIL.  THIS DECREASE IN THE NINO 3.4 INDEX IS CONSISTENT WITH A 
WEAKENING OF LA NINA CONDITIONS.  WEAKENING LA NINA CONDITIONS WERE ALSO 
OBSERVED AT THIS TIME OF YEAR DURING THE LAST STRONG LA NINA EPISODE IN BOTH 
1999 AND 2000.

FORECASTS GENERALLY INDICATE WEAK LA NINA CONDITIONS FOR MJJ 2008, FOLLOWED BY 
SIGNIFICANT UNCERTAINTY THEREAFTER.  THE CONSENSUS OF MODEL FORECASTS FOR NINO 
3.4 SSTS INDICATE THAT THE CURRENT SST ANOMALY OF -0.9 DEGREE C BELOW NORMAL 
WILL DECREASE SLIGHTLY DURING MJJ 2008.  THE CONSENSUS ALSO INDICATES THAT A 
BORDERLINE WEAK COLD OR NEUTRAL ENSO PHASE IS EXPECTED THROUGH EARLY WINTER.
 
THE TEMPERATURE OUTLOOK FOR MJJ 2008 DEPICTS AN INCREASED PROBABILITY OF ABOVE 
AVERAGE TEMPERATURES FOR MOST OF THE WESTERN CONUS, PENINSULAR FLORIDA, NEW 
YORK, NEW ENGLAND, SOUTHWEST ALASKA, AND PARTS OF THE ALASKAN NORTH SLOPE.  
BELOW AVERAGE TEMPERATURES ARE PREDICTED FOR THE ALASKA PANHANDLE AND WESTERN 
WASHINGTON.  EQUAL CHANCES (EC) OF ABOVE, NEAR AND BELOW AVERAGE TEMPERATURES 
ARE EXPECTED ELSEWHERE.  FOR ALL LONGER LEADS ENHANCED PROBABILITIES OF ABOVE 
NORMAL TEMPERATURE COVER DIFFERENT REGIONS OF THE U.S.  GREATER PROBABILITIES 
OF ABOVE NORMAL TEMPERATURES ARE PRIMARILY IN THE WEST FROM MJJ THROUGH ASO 
2008 AND PRIMARILY IN THE SOUTHWEST AND CENTRAL STATES AS WE PROGRESS INTO NEXT 
WINTER. THE WIDESPREAD WARMTH PREDICTED OVER MOST OF THE CONUS DURING DJF 
2008-09, JFM 2009, AND FMA 2009 IS INDICATED BY THE CONSOLIDATION TOOL, WHICH 
IS LARGELY DOMINATED BY TRENDS THIS FAR INTO THE FUTURE.

THE PRECIPITATION OUTLOOK FOR MJJ 2008 INDICATES AN ENHANCED PROBABILITY OF 
BELOW AVERAGE PRECIPITATION AMOUNTS OVER MUCH OF THE WESTERN CONUS (BASED ON 
THE CAS, CFS, IRI AND ECCA TOOLS), AND OVER THE SOUTHERN AND CENTRAL RIO GRANDE 
VALLEY (BASED ON THE CFS AND IRI TOOLS).  THIS LATTER AREA OF DRYNESS IS ALSO 
BASED ON THE INFLUENCE OF CURRENT AND EXPECTED SOIL MOISTURE CONDITIONS.  
ELSEWHERE, THE FORECAST CALLS FOR EQUAL CHANCES (EC) OF ABOVE, NEAR AND BELOW 
AVERAGE PRECIPITATION.

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

SEA SURFACE TEMPERATURES (SSTS) ACROSS THE EQUATORIAL PACIFIC REMAIN BELOW 
AVERAGE BETWEEN 110W AND 150E.  BY THE START OF APRIL, SSTS OVER MUCH OF THIS 
REGION AVERAGED 1 TO 2 DEG C BELOW AVERAGE.  OCEAN TEMPERATURES WITHIN 75 
METERS OF THE SURFACE OVER THE CENTRAL EQUATORIAL PACIFIC (155E TO 130W) RANGED 
BETWEEN 1.0 AND 2.0 DEG C BELOW AVERAGE...  WITH THE LARGER NEGATIVE ANOMALIES 
(BETWEEN -2 C AND -4 C) LOCATED BETWEEN 155W AND 135W.  IN THE WESTERN PACIFIC, 
SUBSURFACE OCEAN TEMPERATURES ARE GENERALLY FROM 2 C TO PERHAPS AS MUCH AS 6 C 
ABOVE AVERAGE BETWEEN 100 AND 250 METERS DEPTH... IMPLYING AN ANOMALOUSLY DEEP 
THERMOCLINE.  IN THE EASTERN PACIFIC, A VERY SHALLOW LAYER OF RELATIVELY WARM 
WATER IS UNDERLAIN BY ANOMALOUSLY COLD WATER BETWEEN 25 AND 150 METER DEPTH.  
OVER THE PAST 30 DAYS, TROPICAL CONVECTION HAS BEEN FOCUSED OVER THE WESTERN 
PACIFIC, INCLUDING INDONESIA, WITH SUPPRESSED CONVECTION PERSISTING OVER THE 
EQUATORIAL REGION NEAR THE DATE LINE. IN ADDITION... LOW LEVEL (850-HPA) 
EASTERLY WIND ANOMALIES WERE OBSERVED BETWEEN 140E AND 160W... AND UPPER LEVEL 
(200-HPA) WESTERLY WIND ANOMALIES WERE OBSERVED OVER THE CENTRAL PACIFIC IN 
ASSOCIATION WITH CYCLONIC ANOMALIES IN THE SUBTROPICS OF BOTH HEMISPHERES. 
THESE ATMOSPHERIC CIRCULATION ANOMALIES ARE ALL CONSISTENT WITH MODERATE LA 
NINA CONDITIONS.

PROGNOSTIC DISCUSSION OF SST FORECASTS

THE STATISTICAL TOOLS (CCA, MARKOV MODEL AND CONSTRUCTED ANALOG) PREDICT SSTS 
REMAINING BELOW AVERAGE THROUGH MJJ 2008... PREDICTING A NINO 3.4 SST INDEX 
VALUE BETWEEN -0.4 C AND -1.0 C.  WEAK LA NINA CONDITIONS ARE PREDICTED TO 
CONTINUE BY THE CFS, CONSTRUCTED ANALOG (CA) AND THE CCA UNTIL NEXT WINTER. 
THEREAFTER ALL TECHNIQUES FEATURE SOME DEGREE OF WARMING.   IN COMPARISON, THE 
MARKOV MODEL MAINTAINS A MODERATE STRENGTH COLD EVENT UNTIL DJF 2008-09... WITH 
SUBSEQUENT WARMING.  THIS SOLUTION IS THE COLDEST OF ALL THESE MODELS.  A 
CONSOLIDATION (CON) FORECAST BASED ON THE CCA, CONSTRUCTED ANALOG (CA), MARKOV 
AND CFS MODELS PREDICTS WEAK LA NINA CONDITIONS FOR MJJ 2008, AND POSSIBLY 
THROUGHOUT THE SUMMER, WITH A SLIGHT STRENGTHENING DURING AUTUMN AND EARLY 
WINTER BEFORE FINALLY WEAKENING TO A NEUTRAL EVENT BY LATE WINTER. IT IS TOO 
EARLY TO MAKE A CONFIDENT FORECAST FOR NEXT WINTER, ALTHOUGH IT IS CLEAR FROM 
THESE MODEL RUNS THAT WEAK LA NINA OR BORDERLINE ENSO-NEUTRAL CONDITIONS MAY 
DOMINATE FOR THE REMAINDER OF THIS YEAR.

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 AND OCN FORECAST TOOLS.  THE CON TOOL IS NOT AVAILABLE FOR 
ALASKA, SO THE FORECAST THERE IS BASED MOSTLY ON THE TRENDS FROM OCN.  THE CFS 
AND IRI TOOLS WERE USED FOR ALASKA ONLY FOR THE MJJ 2008 SEASON.  LA NINA 
COMPOSITES WERE CONSIDERED FOR THE CONUS FOR THE FIRST LEAD FORECAST. THE 
PRECIPITATION OUTLOOK FOR MJJ 2008 IS BASED ON THE CFS, IRI, ECCA AND CAS 
TOOLS. THE REMAINDER OF THE SUITE OF PRECIPITATION FORECASTS IS BASED LARGELY 
ON ANY AVAILABLE WEAK TRENDS, AS WELL AS THE CON TOOL.

PROGNOSTIC DISCUSSION OF OUTLOOKS - MJJ 2008 TO MJJ 2009

TEMPERATURE:

THE TEMPERATURE OUTLOOK FOR MJJ 2008 INDICATES GREATER THAN NORMAL CHANCES OF 
ABOVE AVERAGE TEMPERATURES FOR MOST OF THE WESTERN CONUS, THE FLORIDA 
PENINSULA, NEW YORK, NEW ENGLAND, SOUTHWESTERN ALASKA, AND MUCH OF THE ARCTIC 
COAST OF ALASKA.  FOR THE LOWER 48 STATES, THIS IS LARGELY BASED ON THE 
CONSOLIDATION (CON) TOOL, ECCA, IRI AND CAS TOOLS... WITH CONSIDERATION GIVEN 
TO MJJ LA NINA COMPOSITES.  THE ALASKA MJJ 2008 TEMPERATURE FORECAST IS MOSTLY 
ATTRIBUTED TO LONG-TERM TRENDS, AND TO A LESSER EXTENT THE CCA TOOL. BELOW 
AVERAGE TEMPERATURES ARE PREDICTED FOR THE ALASKA PANHANDLE AND WESTERN 
WASHINGTON.  THIS IS ATTRIBUTED TO THE CAS, CFS AND IRI TOOLS. ELSEWHERE, THE 
FORECAST CALLS FOR EQUAL CHANCES (EC) OF ABOVE, NEAR AND BELOW AVERAGE 
TEMPERATURES.

PRECIPITATION:

THE PRECIPITATION OUTLOOK FOR MJJ 2008 INDICATES AN ELEVATED PROBABILITY OF 
BELOW MEDIAN PRECIPITATION FOR MOST OF THE WEST, AND ALSO FOR THE SOUTHERN AND 
CENTRAL RIO GRANDE VALLEY.  FORECASTS FOR ALL LEADS ARE BASED TO A LARGE DEGREE 
ON THE CONSOLIDATION AND LONG-TERM TRENDS... WITH CONSIDERATION GIVEN TO LA 
NINA COMPOSITES FOR THE FIRST LEAD FORECAST. THE CHANCES OF BELOW MEDIAN 
PRECIPITATION ARE INCREASED FOR THE PACIFIC NORTHWEST FROM MJJ THROUGH ASO 
2008.  AN ENHANCED PROBABILITY OF ABOVE MEDIAN PRECIPITATION IS INDICATED FOR 
FLORIDA FROM JAS THROUGH SON 2008, ASSOCIATED WITH LONG TERM TRENDS IN 
PRECIPITATION POSSIBLY RELATED TO INCREASED TROPICAL ACTIVITY SINCE 1995.  FOR 
SON AND OND 2008, AN AREA OF BELOW MEDIAN PRECIPITATION IS ANTICIPATED OVER THE 
CENTRAL MISSISSIPPI VALLEY, DUE TO THE OCN - CFS - AND ECCA (SON 2008 ONLY) 
TOOLS.

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 15 2008

1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17, 2001 
FORECAST RELEASE.

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