PROGNOSTIC DISCUSSION FOR LONG-LEAD OUTLOOKS
CLIMATE PREDICTION CENTER NCEP
NATIONAL WEATHER SERVICE  WASHINGTON DC
3 PM EST THURSDAY FEB 15 2001

     BASIS AND SUMMARY OF THE CURRENT LONG-LEAD OUTLOOK
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THESE OUTLOOKS REFLECT THE EXPECTED U.S. CLIMATE ANOMALIES FOR WEAK TO MODERATE
COLD ENSO CONDITIONS THROUGH MAM - TRENDING TO NEUTRAL BY AMJ-MJJ.  TROPICAL
INTRA-SEASONAL (MJO) ACTIVITY WHICH WAS STRONG EARLIER IN THE SEASON HAS
DIMINISHED RECENTLY.  AN ACTIVE MJO CAN INFLUENCE MID-LATITUDE CIRCULATION AND
ENHANCE THE VARIABILITY IN CLIMATE ANOMALIES ON WEEKLY TO MONTHLY TIME SCALES.

THE 1961-90 BASE PERIOD MEANS ARE STILL IN USE AS CLIMATOLOGY- MAKING IT
DIFFICULT TO REACH THE BELOW NORMAL TEMPERATURE CATEGORY IN MANY REGIONS AND
SEASONS WHEN TODAYS CLIMATE IS COMPARED TO THE GENERALLY COOLER CLIMATE OF
THE 1960S AND 70S.  THEREFORE THIS SET OF OUTLOOKS HAS A SKEW TOWARD WARMER
THAN NORMAL TEMPERATURES.  

1971-2000 BASE PERIOD MEANS WILL BE IMPLEMENTED BEGINNING WITH THE FORECAST
ISSUED APRIL 12, 2001.

THE MAM-AMJ 2001 FORECASTS REFLECT THE U.S. CLIMATE ANOMALIES EXPECTED IN A
WEAKENING ENSO COLD EVENT.  STATISTICAL PREDICTIONS OF NINO 3.4 INDICATE THE
POSSIBILITY OF NEUTRAL TO WEAK WARM ENSO CONDITIONS BY WINTER 2001/2002.

     CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS

ATMOSPHERIC AND OCEANIC INDICES OF ENSO CONTINUE TO SHOW MODERATE COLD PHASE
(LA NINA) CONDITIONS.  PACIFIC SSTS NEAR THE EQUATOR ARE AROUND 1 DEGREE C
BELOW NORMAL SSTS FROM 160W TO 160E.  THE TRADE WINDS ARE STRONGER THAN NORMAL
THROUGHOUT MUCH OF THE TROPICAL PACIFIC - WHILE CONVECTION IS ENHANCED IN THE
FAR WESTERN TROPICAL PACIFIC AND SUBNORMAL TO THE EAST.

THE ARCTIC OSCILLATION (A0) IS CURRENTLY IN THE POSITIVE PHASE WITH MODEST
AMPLITUDE.  THE POSITIVE AO CHARACTERIZED BY ABNORMAL NEGATIVE 200 MB HEIGHT
ANOMALIES AT HIGH LATITUDES ALONG WITH A POLAR JET STREAM CONTRACTED NORTHWARD
AND ABNORMAL POSITIVE HEIGHT ANOMALALIES IN MIDDLE LATITUDES.  THIS PHASE OF
THE AO FOSTERS WARM TEMPERATURES OVER NORTH AMERICA WHEN IT REACHES LARGE
AMPLITUDE.  CURRENT FORECASTS CALL FOR CONTINUED WEAK AO AMPLITUDE FOR THE
NEXT TWO WEEKS.

AS OF THIS WRITING A STRATOSPHERIC WARMING EVENT IS UNDERWAY IN NORTHERN HIGH
LATITUDES.  AS THIS EVENT PROPAGATES DOWNWARD TO THE TROPOSPHERE DURING THE
NEXT SEVERAL WEEKS IT MAY CAUSE THE HIGH LATITUDE JET TO SHIFT SOUTHWARD -
POSSIBLY CHANGING THE PHASE OF THE AO AT LEAST TEMPORARILY TO THE NEGATIVE
PHASE.  THIS COULD TAKE UP TO SEVERAL WEEKS TO OCCUR IF IT HAPPENS AT ALL.

     PROGNOSTIC DISCUSSION OF SST FORECASTS

THE NCEP DYNAMIC AND STATISTICAL MODELS (THE COUPLED MODEL, CONSTRUCTED ANALOG
(CA) METHOD AND CANONICAL CORRELATION ANALYSIS (CCA)) CONTINUE TO PREDICT
SLIGHTLY BELOW NORMAL NINO 3.4 REGION (5N TO 5S AND 120-170W) SSTS THROUGH MAM
2001.  ALL MODELS CROSS ZERO ANOMALY BETWEEN MAM AND AMJ AND THEN FORECAST
VARYING DEGREES OF POSITIVE ANOMALIES THROUGH FMA 2002.
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THE CA SST FORECAST HOLDS TEMPERATURES CLOSE TO NEAR-NORMAL THROUGH THE END OF
THE SUMMER AND THEN WARMS SLIGHTLY BY THE END OF THE YEAR.  THE CCA BEHAVES LIKE
THE CA BUT IS SLIGHTLY WARMER THROUGH MOST OF THIS YEAR BEFORE CONVERGING TO
THE CA EARLY IN 2002.  THE COUPLED MODEL INDICATES A WEAK WARM PHASE OF ENSO
MAY DEVELOP BY LATE SUMMER BUT THEN ITS FORECAST COOLS SLIGHTLY AND CONVERGES
WITH THE CCA BY WINTER AND A POSITIVE ANOMALY OF 0.5 DEGREES C.  A CONSOLIDA-
TION FORECAST BASED ON THE PAST PERFORMANCE OF THE THREE MODELS PREDICTS THAT
NINO 3.4 SST ANOMALIES WILL AVERAGE SLIGHTLY BELOW ZERO IN MAM - INCREASE TO
ZERO BY AMJ AND THEN CONTINUE TO INCREASE BEFORE GENERALLY LEVELING OFF AT
AROUND 0.5 DEGREES C DURING THE SECOND HALF OF 2001.

FORECASTS FROM THESE TOOLS FOR NEXT SUMMER HAVE BEEN TRENDING TOWARD COOLER
TEMPERATURES AS THE MODELS ARE UPDATED WITH MORE RECENT DATA EACH MONTH - SO
IT IS LIKELY THAT THE BEST FORECAST FOR ENSO FOR NEXT SUMMER AND INTO THE FALL
WOULD BE FOR THE OBSERVATION TO BE ON THE LOWER END OF THE FORECAST SPREAD -
SO EITHER NEUTRAL OR WEAK WARM ENSO CONDITIONS IS OUR CURRENT CHOICE FOR
WINTER 2001-2002 SST CONDITIONS IN THE TROPICAL PACIFIC.

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

THE CCA - OCN AND SMLR FORECASTS WERE CONSULTED AT ALL LEAD TIMES.  THE CMP
FORECAST CONSIDERABLY INFLUENCED THE FORECAST FOR THE FIRST THREE LEAD TIMES.
COLD EVENT ENSO COMPOSITES SUPPORT THE MAM AND AMJ OUTLOOKS.  AT LONGER LEADS
THE OCN WAS WEIGHTED MORE HEAVILY.

     PROGNOSTIC DISCUSSION OF OUTLOOKS - MAM 2001 TO MAM 2002.

THE FORECAST FOR MAM 2001 CALLS FOR WARMER THAN NORMAL TEMPERATURES ALONG THE
SOUTHERN TIER OF STATES.  ALTHOUGH BELOW NORMAL TEMPERATURES ARE INDICATED FOR
THE NORTHWESTERN STATES AND FAR NORTHERN PLAINS BY BOTH CMP AND CCA - THERE IS
A STRONG OCN SIGNAL FOR ABOVE - SO CL IS PREDICTED THERE.

CCA - CMP AND COLD EVENT COMPOSITES PREDICT ABOVE NORMAL TEMPERATURES OVER THE
SOUTHWESTERN STATES - TEXAS - ALONG THE GULF COAST AND OVER FLORIDA DURING MAM
AND AMJ.

DURING MAM OCN AND CMP FAVOR ABOVE NORMAL TEMPERATURE FOR WESTERN ALASKA.  THE
FORECAST FOR ABNORMALLY DRY CONDITIONS OVER THE SOUTHEAST AND THE SOUTHWEST
REFLECT THE LA NINA COMPOSITES AND CMP FORECAST - AS WELL AS INDICATIONS FROM
BOTH CCA AND SMLR.  ABOVE MEDIAN PRECIPITATION FROM THE UPPER MISSISSIPPI
VALLEY TO NEW ENGLAND IS PREDICTED BY THE CMP AND LA NINA COMPOSITES.  CMP
ALSO PREDICTS ABOVE MEDIAN PRECIPITATION FOR THE ALEUTIONS AND ALASKAN
PANHANDLE.  ABOVE MEDIAN PRECIPITATION IN THE NORTHWEST IS FROM CMP AND LA NINA
COMPOSITES.

THE AMJ FORECAST IS A COMPROMISE BETWEEN THE EFFECTS OF AN EXPECTED DWINDLING LA
NINA AND THE CMP.  THESE ARE IN AGREEMENT ON THE MAJOR FEATURES PREDICTED
INCLUDING WARMTH ACROSS THE SOUTHERN U.S. - CONTINUED ABNORMAL DRYNESS IN
FLORIDA AND ABNORMALLY WET CONDITIONS IN THE NORTHWEST AND GREAT LAKES TO THE
NORTHEAST.
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WITH ENSO CONDITIONS PREDICTED TO BE NEAR-NEUTRAL FOR MJJ THROUGH FALL - THE
FORECAST FOR THE SUMMER AND FALL LARGELY REFLECTS THE LONG TERM TRENDS TOWARD
ABOVE NORMAL TEMPERATURES OVER THE SOUTHERN HALF OF THE LOWER 48 STATES.

OCN INDICATES STRONG WARMING TRENDS IN ALASKA IN THE SPRING AND EARLY SUMMER.
THIS IS SUPPORTED BY THE CCA PREDICTION FOR THE INTERIOR AREAS BY JJA.
PRECIPITATION TRENDS FAVOR RELATIVELY WET SPRING AND EARLY SUMMER CONDITIONS
IN THE PACIFIC NORTHWEST -AND THIS IS SUPPORTED BY CMP AND CCA.  WET CONDITIONS
ARE PREDICTED IN THE INTERIOR SOUTHWEST BASED ON THE POSSIBLE LAGGED IMPACT OF
THE LA NINA DURING LATE WINTER ON THE GLOBAL MONSOON CIRCULATION.

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 MIDWEST IN JJA AND JAS WHEN OCN
SLIGHTLY FAVORS BELOW NORMAL.  POSITIVE TEMPERATURE ANOMALIES FROM OCN EXTEND
NORTH ALONG THE EASTERN SEABOARD DURING MJJ AND JJA.

THE FORECAST FOR JAS 2001 TROUGH OND 2001 IS FOR ABNORMAL WARMTH FOR MUCH OF THE
WEST - BASED ON TRENDS - AND IN PORTIONS OF THE SOUTHERN STATES - DIMINISHING
FROM JAS TO OND.  OCN INDICATES BELOW MEDIAN PRECIPITATION IN JAS AND ASO FOR
PORTIONS OF THE PACIFIC NORTHWEST AND THE GREAT BASIN - WITH SOME WEAK SUPPORT
FROM CCA.  THE SOUTHWEST MONSOON IS EXPECTED TO BE HEAVIER THAN NORMAL BASED ON
THE RELATIONSHIP BETWEEN IT AND A PRECEEDING LA NINA WINTER.
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THE FORECAST FOR OND 2001/02 THROUGH MAM 2002 REFLECTS ENHANCED LIKELIHOOD OF
NEUTRAL OR WEAK WARM EVENT CONDITIONS.  THIS INCREASES THE LIKELIHOOD OF ABOVE
NORMAL TEMPERATURES OVER MUCH OF THE NORTHERN AND WESTERN PORTIONS OF THE
COUNTRY.  CCA AND OCN PREDICT WARMER THAN NORMAL IN SOME EXTREME SOUTHERN AREAS.
OCN PREDICTS WARMER THAN NORMAL OVER MUCH OF THE EASTERN HALF OF THE NATION AND
PORTIONS OF THE SOUTHWEST DURING DJF 2001/2002.
  
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 DJF 2001/2002.

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

NOTE - 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 MARCH 15 2001.

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