903
FXUS05 KWBC 161231
PMD90D
PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD
830 AM EDT THU JUL 16 2009
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.
SEA SURFACE TEMPERATURES (SSTS) IN THE EASTERN AND CENTRAL EQUATORIAL PACIFIC
OCEAN ARE NOW WELL ABOVE NORMAL AND CPC HAS DECLARED AN EL NINO IN EFFECT.
WATER TEMPERATURES ARE WELL ABOVE NORMAL IN THE UPPER 200 METERS OF THE
TROPICAL PACIFIC OCEAN, MAKING IT LIKELY THAT ABOVE NORMAL SSTS WILL CONTINUE
INTO THE REST OF SUMMER, FALL AND WINTER. THE CFS MODEL CORRECTLY ANTICIPATED
THIS RAPID TRANSITION IN ITS FORECASTS FOR THE LAST FEW MONTHS, AND ITS CURRENT
FORECAST SHOWS SST ANOMALIES APPROACHING 2 KELVIN IN THE COMING FEW MONTHS,
SUGGESTING THAT MODERATE EL NINO CONDITIONS WILL CONTINUE THROUGH THE END OF
THE YEAR. OTHER TOOLS HAVE JOINED IN THIS ASSESSMENT. THE OUTLOOKS FOR
TEMPERATURE AND PRECIPITATION FROM OND 2009 TO MAM 2010 ARE HEAVILY INFLUENCED
BY THE POSSIBILITY OF EL NINO. IT IS STILL A BIT EARLY TO PREDICT THE EL NINO
STRENGTH FOR THE WINTER MONTHS, WHEN ITS INFLUENCE ON U.S. CLIMATE IS
STRONGEST. THE EVOLUTION OF SSTS IN THE EQUATORIAL PACIFIC IN THE COMING MONTHS
WILL BE CRITICAL TO THE WINTERTIME FORECAST IN THE U.S.
THE TEMPERATURE OUTLOOK FOR ASO 2009 CALLS FOR AN ENHANCED LIKELIHOOD OF ABOVE
NORMAL TEMPERATURES ACROSS THE SOUTH FROM ARIZONA TO FLORIDA. ABOVE NORMAL
TEMPERATURES ARE FAVORED IN NORTHERN NEW ENGLAND. CHANCES FOR BELOW NORMAL
TEMPERATURES ARE ENHANCED IN THE MIDWEST AND UPPER PLAINS. ELSEWHERE, EQUAL
CHANCES OF BELOW, NEAR, AND ABOVE NORMAL TEMPERATURES ARE PREDICTED.
THE CHANCE OF BELOW MEDIAN PRECIPITATION IS ENHANCED FOR ASO 2009 FOR PARTS OF
THE PACIFIC NORTHWEST INTO THE NORTHERN ROCKY MOUNTAINS. ABOVE MEDIAN
PRECIPITATION AMOUNTS ARE FAVORED FROM PARTS OF THE SOUTHWESTERN U.S. TO SOUTH
DAKOTA. ABOVE MEDIAN PRECIPITATION AMOUNTS ARE FAVORED FOR FLORIDA. ELSEWHERE,
EQUAL CHANCES OF BELOW, NEAR, AND ABOVE MEDIAN PRECIPITATION ARE PREDICTED.
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
SSTS IN THE EAST-CENTRAL EQUATORIAL PACIFIC CURRENTLY AVERAGE AROUND 0.5 TO 1
DEGREES C ABOVE NORMAL, AND ANOMALIES HAVE INCREASED MARKEDLY IN THE PAST FEW
MONTHS. THE HEAT CONTENT IN THE UPPER 300 METERS OF THE CENTRAL AND EASTERN
PACIFIC ALONG THE EQUATOR HAS ALSO INCREASED IN THE LAST FEW MONTHS AND NOW
AVERAGES 1 TO 1.5 DEGREE C ABOVE NORMAL. SST ANOMALIES IN THE NINO 3.4 REGION
AVERAGED AROUND .75 DEGREES C IN THE FIRST HALF OF JULY. REMARKABLY THE ENTIRE
TROPICAL PACIFIC IS WARMER THAN AVERAGE FROM INDONESIA TO SOUTH AMERICA.
ATMOSPHERIC CONDITIONS OVER THE EQUATORIAL PACIFIC OCEAN DURING JUNE AND JULY
ARE TRANSITIONING FROM LA NINA AND ENSO NEUTRAL CONDITIONS TO EL NINO.
ATMOSPHERIC CONVECTION OVER THE CENTRAL EQUATORIAL PACIFIC HAS RETURNED TO AT
LEAST NEAR NORMAL VALUES AFTER HAVING BEEN SUPRESSED FOR MOST OF THE PAST YEAR
IN THE LA NINA EVENT. INTRASEASONAL ACTIVITY HAS COMPLETELY STALLED FOR THE
LAST MONTH.
PROGNOSTIC DISCUSSION OF SST FORECASTS
THE MOST RECENT DYNAMICAL SST FORECASTS FROM THE CFS AND OTHER MODELS PREDICT
SST ANOMALIES OF BETWEEN .5 AND 2 DEGREES C FOR THE REMAINDER OF THIS YEAR.
FORECASTS FROM THE STATISTICAL MODELS ARE NOW CONSIDERABLY WARMER THAN THEIR
FORECASTS ONLY TWO MONTHS AGO, ALTHOUGH SOME STILL LAG BEHIND THE DYNAMIC
MODELS. THE CONSTRUCTED ANALOGUE METHOD IS THE MOST BOLD AMONG THE EMPIRICAL
METHODS AND REACHES +1.5 BY NEXT WINTER IN SEVERAL OF ITS MEMBERS, WHILE CCA
AND MARKOV HARDLY REACH 0.5. THE CPC CONSOLIDATION SEEKS MIDDLE GROUND BETWEEN
THE VERY WARM CFS AND CONSERVATIVE CCA AND MARKOV AND FINDS A CONSENSUS
SOMEWHAT BELOW THE CA. THE CONSOLIDATION NINO 3.4 SST ANOMALY FORECAST
INDICATES THE SST ANOMALIES WILL STAY ABOVE THE CRITICAL THRESHOLD FOR EL NINO
CONDITIONS OF .5 DEGREES C THROUGH FMA2010.
PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS
THE TEMPERATURE AND PRECIPITATION OUTLOOKS ARE BASED ON THE CONSOLIDATION
FORECAST (CON), A SKILL-WEIGHTED AND CALIBRATED PROBABILISTIC FORECAST DERIVED
FROM THE CFS, SMLR, OCN, CCA, AND ECCA FORECAST TOOLS. EL NINO COMPOSITES ARE
VERY MUCH RELIED UPON NOW THAT A WARM EVENT IS IN EFFECT. THE OUTLOOKS FOR
BEYOND MAM 2010 ARE BASED ON THE CON FORECASTS WHICH MEANS MOSTLY TRENDS.
BECAUSE OF THE ADVANCED SEASON, SOIL MOISTURE CONSIDERATIONS HARDLY PLAY A ROLE
ANY MORE.
PROGNOSTIC DISCUSSION OF OUTLOOKS - ASO 2009 TO ASO 2010
TEMPERATURE:
THE TEMPERATURE OUTLOOK FOR ASO 2009 FAVORS ABOVE NORMAL TEMPERATURES ACROSS
THE SOUTH FROM THE CONSOLIDATION FORECAST TOOL. THIS AREA IS MOSTLY DUE TO
RECENT TEMPERATURE TRENDS. TO ITS NORTH THE UPWARD TREND IS NEGATED BY SMLR,
THE CFS AND ENSO COMPOSITES. BELOW NORMAL TEMPERATURES ARE INDICATED IN A SWATH
FROM SOUTH DAKOTA TO ILLINOIS BY A NUMBER OF FORECAST TOOLS. THE ABOVE NORMAL
TEMPERATURES INDICATED ON LAST MONTHS OUTLOOK FOR ASO IN NEW ENGLAND HAVE BEEN
REDUCED DUE TO CONTRADICTING INDICATIONS FROM THE CFS.
THE TEMPERATURE OUTLOOKS FOR SON2009 THROUGH MAM2010 ARE MAINLY BASED ON THE
CON FORECAST AND ENSO COMPOSITES. THE TEMPERATURE FORECAST WAS REVISED FROM
LAST MONTHS FORECASTS FOR THE CORRESPONDING SEASONS MAINLY DUE TO INCREASED
CONFIDENCE THAT EL NINO WILL INFLUENCE THE WINTERTIME CIRCULATION.
TEMPERATURES IN EL NINO WINTERS TEND TO BE BELOW NORMAL OVER MUCH OF THE
SOUTHERN CONUS, PARTIALLY COUNTERACTING TRENDS FOR WARMER WINTER TEMPERATURES
IN THE SOUTHWEST, AND ENTIRELY COUNTERACTING TRENDS IN THE SOUTHEAST WHERE WE
ISSUE OUTLOOKS OF ENHANCED PROBABILITY FOR BELOW NORMAL TEMPERATURES IN DJF AND
FMA. CONFIDENCE IN ABOVE NORMAL TEMPERATURES OVER THE NORTHERN GREAT PLAINS AND
IN ALASKA IS INCREASED DUE TO ENSO TELECONNECTIONS.
REMAINING FORECAST LEADS FROM AMJ 2010 THROUGH ASO 2010 ARE BASED ON THE
CONSOLIDATION FORECAST AND LARGELY REFLECT TEMPERATURE TRENDS.
PRECIPITATION:
THE PRECIPITATION OUTLOOKS FOR ASO2009 ARE BASED PRIMARILY ON THE CONSOLIDATION
FORECAST, AND INDICATE INCREASED CHANCES OF ABOVE MEDIAN PRECIPITATION AMOUNTS
OVER PARTS OF THE CENTRAL ROCKY MOUNTAINS AND THE SOUTHWEST, BASED MOSTLY ON
FORECASTS FROM THE CFS AND ENSO COMPOSITES. A TREND-RELATED DRY FORECAST IS
INDICATED FOR THE PACIFIC NORTHWEST. TRENDS INDICATE ENHANCED PROBABILITY FOR
ABOVE MEDIAN PRECIPITATION IN FLORIDA.
EL NINO PRECIPITATION COMPOSITES WERE USED TOGETHER WITH THE CFS FORECAST FROM
OND 2009 THROUGH MAM 2010. THESE INDICATE INCREASED CHANCES OF ABOVE MEDIAN
PRECIPITATION FOR THE SOUTHERN CONUS, BEGINNING IN CENTRAL SECTIONS OF THE
REGION IN OND, EXPANDING TO MAXIMUM COVERAGE IN LATE WINTER, AND THEN
DIMINISHING IN AREA BY MAM. RELATIVE TO THE SET OF FORECASTS ISSUED A MONTH
AGO WE EXPANDED THE AREAL EXTENT SOMEWHAT. BELOW MEDIAN PRECIPITATION IS
FAVORED IN EL NINO WINTERS FOR THE PACIFIC NORTHWEST AND PARTS OF THE OHIO AND
TENNESSEE RIVER VALLEYS. THERE ARE NO CLEAR SIGNALS FOR PRECIPITATION FROM AMJ
TO MJJ 2010, RESULTING IN A FORECAST FOR EQUAL CHANCES FOR BELOW, NEAR, OR
ABOVE MEDIAN PRECIPITATION AMOUNTS NATIONWIDE. A TREND-RELATED SIGNAL FOR
ENHANCED CHANCES OF BELOW MEDIAN PRECIPITATION IN THE PACIFIC NORTHWEST, AND
ABOVE MEDIAN PRECIPITATION FOR FLORIDA APPEARS IN THE OUTLOOK FOR JJA 2010 AND
BEYOND.
VERY FEW RELIABLE INDICATIONS WERE FOUND FOR PRECIPITATION IN AK. EXCEPT FOR
TRENDS INDICATING ABOVE MEDIAN IN NORTHERN ALASKA IN NDJ AND DJF WE HAVE EC
THROUGHOUT.
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 AUG 20 2009
1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17, 2001
FORECAST RELEASE.
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