PROGNOSTIC DISCUSSION FOR LONG-LEAD OUTLOOKS
CLIMATE PREDICTION CENTER NCEP
NATIONAL WEATHER SERVICE  WASHINGTON DC
3 PM EDT THURSDAY MAY 17 2001

     BASIS AND SUMMARY OF THE CURRENT LONG-LEAD OUTLOOK
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THE JJA 2001 FORECASTS REFLECT SOIL MOISTURE CONDITIONS WHICH STRENGHTENED
DURING APRIL AND THE LONG-TERM TREND AS ESTIMATED BY OCN. TROPICAL PACIFIC OCEAN
TEMPERATURES ARE NOT EXPECTED TO HAVE ANY IMPACT ON JJA 2001 SINCE WATER
TEMPERATURES HAVE RETURNED TO NEAR NORMAL AND ARE EXPECTED TO REMAIN NEAR NORMAL
THROUGHOUT THE SEASON. SOME STATISTICAL AND DYNAMICAL PREDICTIONS OF NINO 3.4 
INDICATE THE POSSIBILITY OF VERY WEAK WARM EPISODE (EL NINO) CONDITIONS BY 
WINTER 2001/2002. HOWEVER OTHER FORECASTS INDICATE EITHER SOMEWHAT COOLER THAN 
NORMAL OR NEAR NORMAL CONDITIONS IN THE TROPICAL PACIFIC. GIVEN THE 
UNCERTAINTIES IN THE SST OUTLOOK - NEXT WINTERS US FORECASTS DO NOT REFLECT 
EITHER WARM OR COLD EPISODE US IMPACTS.   

     CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS

ATMOSPHERIC AND OCEANIC INDICES OF ENSO SHOW EITHER NEAR NORMAL OR WEAK LA NINA
CONDITIONS.  PACIFIC SST ANOMALIES ARE NEAR ZERO THROUGHOUT THE EQUATORIAL
PACIFIC. HOWEVER THE TRADE WINDS REMAIN STRONGER THAN NORMAL WEST OF 150W IN THE
TROPICAL PACIFIC. THE TRADE WINDS HAVE INCREASED IN INTENSITY THROUGHOUT THE
EASTERN TROPICAL PACIFIC RESULTING IN A COOLING OF OCEAN SURFACE TEMPERATURES
ALONG THE WEST COAST OF SOUTH AMERICA AND ALONG THE EQUATOR IN THE EASTERN 
PACIFIC. BELOW THE SURFACE THERE HAS BEEN A SLOW EASTWARD SHIFT OF THE POSITIVE
TEMPERATURE ANOMALIES IN THE WEST PACIFIC SINCE LATE 1998. RECENTLY 
THERE HAS BEEN A SERIES OF EASTWARD AND WESTWARD SHIFTS OF THE EASTERN 
EDGE OF THIS WARM POOL. THESE SHIFTS APPEAR TO BE RELATED TO THE 30-60 DAY 
(MJO) OSCILLATION. A PERSISTENT EASTWARD SHIFT COULD CONTRIBUTE TO SURFACE
WARMING FARTHER EAST AT A LATER TIME.

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     PROGNOSTIC DISCUSSION OF SST FORECASTS

THE NCEP DYNAMIC AND STATISTICAL MODELS (THE CONSTRUCTED ANALOG (CA) METHOD 
AND CANONICAL CORRELATION ANALYSIS (CCA)) PREDICT ESSENTIALLY NEAR NORMAL 
NINO 3.4 REGION (5N TO 5S AND 120-170W) SSTS FROM JJA 2001 FORWARD.  THE CA 
SST FORECAST HOLDS TEMPERATURES CLOSEST TO ZERO THROUGH THE END OF THE YEAR. 
THE CCA IS AT LEAST 0.5 DEGREE WARMER THAN CA THROUGH MOST OF THE YEAR.
THE COUPLED MODEL SST OUTLOOK INDICATES POSITIVE SST ANOMALIES BETWEEN 0.5
AND 1 DEGREE C BY THE END OF THE YEAR.

A CONSOLIDATION OF THE THREE MODELS BASED ON THEIR PAST PERFORMANCE PREDICTS 
THAT NINO 3.4 SST ANOMALIES WILL AVERAGE NEAR ZERO IN JJA AND THEN INCREASE
SLOWLY BEFORE GENERALLY LEVELING OFF AT AROUND 0.5 DEGREES C AT MOST DURING THE
SECOND HALF OF 2001. SINCE SST ANOMALIES OF THAT MAGNITUDE DO NOT HAVE ANY 
APPRECIABLE IMPACT ON TROPICAL RAINFALL UNTIL LATE WINTER - EARLY SPRING WE DO
NOT EXPECT ANY ENSO-RELATED IMPACTS DURING FALL 2001 AND EARLY WINTER 
2001-2002. SINCE THERE IS A LACK OF CONSISTENCY IN THE VARIOUS SST FORECASTS 
AT THE LONGER LEADS WE CHOSE ENSO-NEUTRAL AS THE MOST LIKELY STATE FOR THIS 
SERIES OF FORECASTS.
 

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

THE CCA - OCN AND SMLR WERE CONSULTED AT ALL LEAD TIMES.  THE CONSTRUCTED 
ANALOG SOIL MOISTURE-BASED FORECAST TOOL (CAS) WHICH INCORPORATES THE
HISTORICAL INFLUENCE OF SOIL MOISTURE ANOMALIES INTO FORECASTS OF 
TEMPERATURE AND PRECIPITATION WAS USED FOR THE WARM SEASON FORECASTS.
ALL TOOLS PLUS THE CMP INFLUENCED THE FORECAST FOR THE FIRST THREE LEAD 
TIMES. THE COUPLED MODEL HAD ONLY WEAK SIGNALS. THE STRENGTHENED SOIL MOISTURE
ANOMALY PATTERN OVER THE COUNTRY CONTRIBUTED TO OUR USING THIS TOOL MORE THAN
LAST MONTH. AT LONGER LEADS TWO TOOLS WERE USED - THE OCN AND CCA. 

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     PROGNOSTIC DISCUSSION OF OUTLOOKS - JJA 2001 TO JJA 2002.

TEMPERATURE:

THE OUTLOOK FOR JJA 2001 CALLS FOR WARMER THAN NORMAL TEMPERATURES FROM
ARIZONA INTO THE DEEP SOUTHEAST - BASED ON CAS AND CCA-OCN. 
WARM SEASON PROBABILITIES FOR ABOVE NORMAL TEMPERATURES ARE HIGHEST IN THE SOUTH
AND SOUTHWEST WHERE YEAR-TO-YEAR VARIABILITY IS SMALL IN RELATION TO THE TRENDS.
CLIMATOLOGICAL ODDS ARE FAVORED OVER MOST OF THE NORTHERN AND CENTRAL PARTS OF
THE COUNTRY EXCEPT FOR PORTIONS OF THE CENTRAL PLAINS IN JJA AND JAS WHEN OCN 
AND CAS FAVOR BELOW NORMAL. CAS INDICATES ABNORMALLY COLD TEMPERATURES IN THE 
CENTRAL AND NORTH-CENTRAL US IN JJA AND JAS AS WELL.      

COVERAGE OF THE WEST BY WARMTH PEAKS IN JAS AND ASO WHEN ABOVE NORMAL IS 
PREDICTED TO EXPAND NORTHWARD TO INCLUDE THE NORTHWEST AND THE CENTRAL ROCKIES.
THE AREA OF ABNORMAL WARMTH SHRINKS THEREAFTER WITH ONLY SOUTHERN SECTIONS OF 
CALIFORNIA AND NEVADA ALONG WITH ARIZONA AND SOUTHWESTERN NEW MEXICO INDICATED 
TO BE ABOVE NORMAL BY SON.  BY OND THE SOUTHWESTERN US IS EXPECTED TO BE NEAR 
NORMAL WITH ONLY SOUTHERN FLORIDA PREDICTED TO BE ABOVE NORMAL. OCN INDICATES A 
RETURN OF THE ABNORMAL WARMTH IN THE SOUTHWEST DURING NDJ. AT THE SAME TIME 
WARMER THAN NORMAL TEMPERATURES ARE PREDICTED FOR SOUTHERN ALASKA. 

ENSO-NEUTRAL CONDITIONS ARE ASSUMED FOR OND-MJJ 2001-2002 TEMPERATURE OUTLOOKS.
WE THUS INVOKED HIGH FREQUENCY NEUTRAL ENSO COMPOSITES THAT SHOW COLD IN SEVERAL
AREAS WHERE OCN AND CCA FAVOR WARMTH. THUS THE TREND MAY BE CONTRADICTED 
IN ENSO NEUTRAL YEARS ESPECIALLY IN THE NORTHEAST AND MIDWEST DURING NDJ, DJF
AND JFM. THIS EXPLAINS THE LACK OF WARMTH IN THIS SET OF FORECASTS FOR MUCH OF
THE EAST IN WINTER 2001/2002.  WITH THE EXCEPTION OF OND WE PREDICT WARMER THAN 
NORMAL IN ALL SEASONS IN THE SOUTHWEST. WIDESPREAD WARMTH IS ALSO FORECAST FOR 
THE WEST AND IN ALASKA FOR JFM 2002 FORWARD. 

NOTE: THE CHANGE IN NORMALS HAS NOT RESULTED IN ANY MAJOR CHANGES IN THE
OUTLOOK PATTERNS. 
 
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PRECIPITATION:


THE JJA PRECIPITATION OUTLOOK IS FOR CLIMATOLOGICAL PROBABLILITIES FOR AREAS
THAT HAVE BEEN SUFFERING LONG-TERM MOISTURE DEFICITS - THE SOUTHEAST AND THE 
NORTHWEST. THUS NO SUBSTANTIAL RELIEF IS EXPECTED IN THOSE AREAS DURING THE 
SUMMER SEASON. ALONG WITH BELOW NORMAL TEMPERATURE CAS INDICATES ABOVE NORMAL 
PRECIP IN THE HEARTLAND IN JJA AND JAS. IN THIS AREA CAS IS ACTING ON INITIALLY 
WET SOIL - RECYCLING MOISTURE AND DUMPING IT SOMEWHAT DOWNSTREAM FROM THE 
INITIAL WETNESS. OCN INDICATES BELOW MEDIAN PRECIPITATION IN JAS IN THE FAR WEST 
AND NORTHWEST. INDICATIONS FOR ASO AND SON WERE WEAK EVERYWHERE AND CL WAS 
PREDICTED.

WE SEE NO INDICATIONS THAT THE SOUTHWEST US MONSOON WILL BE EITHER STRONGER OR 
WEAKER THAN NORMAL. THIS IS PARTLY BECAUSE THE TROPICAL PACIFIC WATER 
TEMPERATURES ARE NEAR NORMAL AND THEY ARE EXPECTED TO REMAIN NEAR NORMAL THROUGH 
THE SUMMER SEASON. AN ADDITIONAL FACTOR THAT CONTRIBUTES TO UNCERTAINTY IS THE
TROPICAL MJO ACTIVITY WHICH STRONGLY MODULATED THE SOUTHWEST MONSOON DURING THE
SUMMER 2000.

THE PRECIPITATION OUTLOOK FOR OND THROUGH DJF INCLUDES A REGION OF ABNORMAL
WETNESS IN THE CENTRAL AND SOUTH-CENTRAL US WHICH COMES FROM OCN.  LIKEWISE THE 
CHANCE RISES FOR ABOVE MEDIAN PRECIPITATION OVER PORTIONS OF THE SOUTHERN U.S. 
- HOWEVER THE PROBABILITY SHIFT IS VERY SMALL - INDICATING A HIGH DEGREE OF 
UNCERTAINTY.  OCN DOES INDICATE ABOVE MEDIAN PRECIPITATION FOR PORTIONS OF THE 
PLAINS AND TEXAS FOR OND 2001 THROUGH JFM 2002. 

PRECIPITATION FORECASTS FOR FMA-MJJ ARE MAINLY CL EVERYWHERE - EXCEPT FOR A 
FORECAST OF ABOVE IN AMJ AND MJJ 2002 IN THE NORTHWEST 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 JUNE 14 2001.

1971-2000 BASE PERIOD MEANS HAVE BEEN IMPLEMENTED EFFECTIVE WITH TODAYS 
FORECAST RELEASE.


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