PROGNOSTIC DISCUSSION FOR LONG-LEAD OUTLOOKS
CLIMATE PREDICTION CENTER NCEP
NATIONAL WEATHER SERVICE  WASHINGTON DC
3 PM EDT THURSDAY AUGUST 16 2001

     BASIS AND SUMMARY OF THE CURRENT LONG-LEAD OUTLOOK
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THESE OUTLOOKS PRIMARILY REFLECT THE EXPECTED U.S. CLIMATE ANOMALIES FOR ENSO-
NEUTRAL CONDITIONS ... AND THE LONG-TERM TREND AS ESTIMATED BY OCN.  SOIL
MOISTURE CONDITIONS FACTOR INTO THE OUTLOOK FOR SON.  EQUATORIAL PACIFIC SSTS
ARE NOW SLIGHTLY ABOVE NORMAL IN THE WEST AND CENTRAL PACIFIC AND SLIGHTLY BELOW
NORMAL NEAR SOUTH AMERICA.  SOME STATISTICAL AND DYNAMIC PREDICTIONS OF NINO 3.4 
SSTS INDICATE WEAK WARM EPISODE (EL NINO) CONDITIONS BY THE END OF THE YEAR - 
WHILE OTHERS PREDICT ANOMALIES VERY NEAR ZERO THROUGHOUT THE UPCOMING COOL
SEASON.  WHILE IT IS LIKELY THAT EQUATORIAL PACIFIC SSTS WILL BE ABOVE AVERAGE -
THE ANOMALIES ARE WEAK AND NOT LIKELY TO PRODUCE THE LARGE-SCALE ATMOSPHERIC
EFFECTS ASSOCIATED WITH STRONG EL NINO EVENTS THIS COOL SEASON.
 
     CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS

NEAR-NORMAL ATMOSPHERIC AND OCEANIC CONDITIONS CONTINUE TO PREVAIL IN THE
TROPICAL PACIFIC IN JULY.  SST ANOMALIES ALONG THE EQUATOR CURRENTLY ARE JUST
OVER 0.5 DEG C IN THE CENTRAL PACIFIC  AND ARE STILL AROUND -1 DEG C NEAR
THE SOUTH AMERICAN COAST.  THE ABOVE NORMAL OCEAN TEMPERATURE EXTEND FROM THE
SURFACE TO OVER 200 M DEPTH OVER MOST OF THE CENTRAL PACIFIC OCEAN AND THIS AREA
OF POSITIVE SUB-SURFACE TEMPERATURE ANOMALIES CONTINUES TO MOVE EASTWARD.  THE
ATMOSPHERIC CIRCULATION IN THE TROPICAL PACIFIC HAS BEEN VERY CLOSE TO NORMAL
FOR SEVERAL MONTHS NOW.  TAKEN TOGETHER - THESE OBSERVATIONS SIGNIFY AN END TO
THE COLD EVENT CONDITIONS THAT HAVE PREVAILED FOR OVER 3 YEARS.
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     PROGNOSTIC DISCUSSION OF SST FORECASTS

WEAK WARM ENSO CONDITIONS ARE PREDICTED TO SLOWLY DEVELOP OVER THE NEXT SEVERAL
SEASONS.  MOST  DYNAMIC  MODELS (NCEP - ECMWF - SCRIPPS) GRADUALLY INCREASE NINO
3.4 SSTS TO BETWEEN 0.5 AND 1 DEG C ABOVE NORMAL BY YEARS END.  ON THE OTHER
HAND - MANY STATISTICAL MODELS (CONSTRUCTED ANALOG - MARKOV MODEL - LINEAR
INVERSE MODELING) PREDICT NEUTRAL OR COOL NINO 3.4 SSTS FOR THIS COOL SEASON -
ALTHOUGH THE CCA PREDICTION IS FOR ABOVE NORMAL SSTS.  NONE OF THE MODELS
PREDICT STRONG ANOMALIES FOR THE EQUATORIAL PACIFIC IN THE NEXT FEW SEASONS.
A CONSOLIDATION OF THREE NCEP TOOLS BASED ON THEIR PAST PERFORMANCE INDICATES
NEAR NORMAL CONDITIONS WILL PREVAIL THROUGH THE WINTER - WITH GRADUALLY
INCREASING ANOMALIES THAT REACH AROUND 0.5 DEGREES BY LATE NEXT SPRING.
CONSIDERING THAT TEMPERATURES ANOMALIES ARE ALREADY POSITIVE - NINO 3.4 SEA
SURFACE TEMPERATURES ARE EXPECTED TO REMAIN POSITIVE FOR THE REMAINDER OF THE
YEAR - GRADUALLY INCREASING TO MARGINALLY WARM ENSO CONDITIONS BY LATE IN THE
WINTER.

     PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOK

THE STATISTICAL TOOLS ... CCA - OCN AND SMLR ... WERE CONSULTED AT ALL LEAD
TIMES.  THE CONSTRUCTED ANALOG SOIL MOISTURE-BASED FORECAST TOOL (CAS) WAS USED 
ONLY FOR THE FIRST LEAD.  BECAUSE THE INITIAL ENSO STATE IS NEAR ZERO AND IS 
FORECAST TO BE WEAK - THE NCEP COUPLED MODEL WAS CONSIDERED ONLY WHERE IT AGREED 
WITH A CONSENSUS OF OTHER GENERAL CIRCULATION MODELS RUN AT OTHER CENTERS FOR 
CLIMATE PREDICTION.  
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     PROGNOSTIC DISCUSSION OF OUTLOOKS - SON 2001 TO SON 2002

TEMPERATURE:

MOST FORECAST TOOLS INDICATE WARMER-THAN-NORMAL TEMPERATURES FOR SON 2001 - DJF
2001 IN THE SOUTHWEST U.S..  DRY INITIAL SOIL MOISTURE CONDITIONS IN TEXAS
EXTENDS THIS AREA OF ABOVE NORMAL TEMPERATURES INTO MOST OF TEXAS FOR SON.
OCN - CCA - AND SMLR PREDICT ABOVE NORMAL TEMPERATURES FOR SOUTHERN FLORIDA
THROUGH OND.  CCA GIVES STRONG INDICATIONS FOR BELOW NORMAL TEMPERATURES IN 
WESTERN ALASKA IN THE FALL.  EQUATORIAL PACIFIC SSTS ARE WARMER THAN ANTICIPATED 
IN LAST MONTHS FORECAST.  THIS SKEWS THE EXPECTED SEASONAL CLIMATE RESPONSE 
SLIGHTLY FROM NEUTRAL TOWARD WARM ENSO EVENT COMPOSITES (ALTHOUGH THE OUTLOOK 
STILL PRIMARILY REFLECTS NEUTRAL EVENTS) AND RESULTS IN A CHANGE IN THE OUTLOOK 
FOR THE UPPER MIDWEST FROM THE BELOW NORMAL TEMPERATURES ISSUED LAST MONTH TO 
CLIMATOLOGY ON THE CURRENT OUTLOOK.  WITH WEAK ENSO FORCING THE PRIMARY FACTOR 
INFLUENCING THE SEASONAL CLIMATE ANOMALIES OVER THE EASTERN U.S. THIS WINTER 
WILL BE THE PHASE OF THE ARCTIC OSCILLATION (AO).  THE AO IS NOT PREDICTABLE 
BEYOND THE LIMITS OF WEATHER PREDICTION MODELS - BUT RECENT TRENDS SUGGEST THAT 
THE SEASONAL FREQUENCY OF THE AO NEGATIVE PHASE IS GREATER THAN IT WAS IN THE 
EARLY AND MID 1990S.  SINCE THE NEGATIVE AO PHASE IS ASSOCIATED WITH COOLER 
THAN NORMAL CONDITIONS THROUGHOUT THE EAST - THE AO TREND COUNTERACTS RECENT 
TRENDS TOWARD WARMER-THAN-NORMAL WINTER TEMPERATURES OVER MUCH OF THE EASTERN 
U.S. IN FAVOR OF CLIMATOLOGICAL ODDS.  THE AO HAS LITTLE INFLUENCE IN THE 
WESTERN U.S. AND THEREFORE TEMPERATURE TRENDS ACCOUNT FOR THE LARGE AREA OF 
ABOVE NORMAL TEMPERATURES PREDICTED IN THE WESTERN U.S. FROM JFM THROUGH AMJ.  
THE TEMPERATURE OUTLOOK FOR NEXT SUMMER AND FALL IS BASED ON OCN.  THE RECENT 
COOL SUMMERS IN THE EASTERN U.S. AND WARM SUMMERS IN THE MIDWEST ARE OPPOSITE 
THE DECADAL TRENDS IN BOTH AREAS AND REDUCE THE PROBABILITY ANOMALIES IN EACH 
OF THOSE AREAS TOWARD CLIMATOLOGY WHEN COMPARED TO LAST MONTHS FORECAST. 

NOTE: THE CHANGE IN NORMALS IMPLEMENTED IN MAY 2001 HAS NOT RESULTED IN ANY 
MAJOR CHANGES IN THE OUTLOOK PATTERNS... ALTHOUGH SLIGHT WEAKENING IS SHOWN IN 
SOME OF THE TRENDS FOR WARMTH... AS MIGHT BE EXPECTED.  
 
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PRECIPITATION:

ABOVE MEDIAN PRECIPITATION OVER PORTIONS OF THE SOUTHEAST IN SON IS INDICATED
BY OCN AND WILL BE AIDED BY INITIALLY WET SOIL CONDITIONS SUPPORTING THE
RECYCLING MOISTURE LOCALLY.  THE PRECIPITATION OUTLOOK FOR OND 2001 THROUGH JFM
2002 INCLUDES A REGION OF ABOVE MEDIAN PRECIPITATION IN THE SOUTH-CENTRAL U.S.
WHICH COMES FROM OCN.   CCA - SMLR - AND CMP INDICATE BELOW MEDIAN
PRECIPITATION IN THE DESERT SOUTHWEST FOR NDJ AND DJF 2001.  OCN INDICATES ABOVE
MEDIAN PRECIPITATION IN THE PACIFIC NORTHWEST FOR AMJ AND MJJ 2002 - HOWEVER
THE SIGNAL IS WEAKER THAN LAST MONTHS FORECAST BECAUSE OF THE DRY CONDITIONS
EXPERIENCED THERE IN SPRING 2001.  ABOVE MEDIAN PRECIPITATION OVER THE NORTHERN
PLAINS IN JJA AND JAS 2002 IS BASED ON OCN.
  
FOR A DESCRIPTION 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/MULTI-SEASON/
13_SEASONAL_OUTLOOKS/TOOLS  (USE LOWER CASE LETTERS)

INFORMATION ON THE FORMULATION AND SKILL OF THE CAS FORECASTS MAY BE FOUND AT:
HTTP://WWW.CPC.NCEP.NOAA.GOV/SOILMST/FORECASTS.HTML  (USE LOWER CASE LETTERS)

NOTES - THESE CLIMATE OUTLOOKS ARE INTENDED FOR USE PRIOR TO THE START OF
THEIR VALID PERIODS.  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 THURSDAY SEPTEMBER 13 2001.

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

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