465
FXUS05 KWBC 151415
PMD90D
PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD
830 AM EST THU JAN 15 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.
OCEANIC AND ATMOSPHERIC INDICATORS SUGGEST WEAK LA NINA CONDITIONS ARE IN
PLACE. SEA SURFACE TEMPERATURES (SSTS) ARE BELOW NORMAL ALONG THE EQUATOR
THROUGHOUT MOST OF THE EASTERN PACIFIC OCEAN WITH WATER TEMPERATURES JUST UNDER
THE SURFACE SUBSTANTIALLY BELOW NORMAL. SST FORECASTING TOOLS INDICATE LA NINA
CONDITIONS IN EARLY 2009, BUT A RETURN TO NEUTRAL CONDITIONS COULD HAPPEN AS
EARLY AS FMA 2009.
THE TEMPERATURE OUTLOOK FOR FMA 2009 CALLS FOR ABOVE AVERAGE TEMPERATURES FROM
THE INTERIOR SOUTHWESTERN U.S. EXTENDING EASTWARD TO INCLUDE TEXAS, THE
SOUTHERN GREAT PLAINS, AND THE SOUTHEASTERN STATES. BELOW NORMAL TEMPERATURES
ARE FAVORED IN THE PACIFIC NORTHWEST, PORTIONS OF THE NORTHERN ROCKIES AND MOST
OF MONTANA. THIS TEMPERATURE PATTERN IS SUPPORTED BY A RANGE OF NUMERICAL
CLIMATE MODELS AND STATISTICAL TOOLS AND IS TYPICAL OF TEMPERATURES ASSOCIATED
WITH LA NINA. ABOVE NORMAL TEMPERATURES ARE EXPECTED FOR NORTHERN ALASKA DUE
TO LONG TERM TRENDS. ELSEWHERE, EQUAL CHANCES OF BELOW-, NEAR-, AND ABOVE
AVERAGE TEMPERATURES ARE PREDICTED.
THERE IS AN ENHANCED LIKELIHOOD OF BELOW MEDIAN PRECIPITATION AMOUNTS FOR FMA
2009 ACROSS MUCH OF THE SOUTHERN CONTIGUOUS U.S. AS INDICATED BY CFS DYNAMICAL
MODEL PREDICTIONS AND THE CONSOLIDATION FORECAST. ABOVE MEDIAN PRECIPITATION
AMOUNTS ARE EXPECTED IN THE OHIO VALLEY, DUE TO A COMBINATION OF CFS FORECASTS
AND LA NINA COMPOSITES.
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
ENSO-NEUTRAL CONDITIONS WHICH HAD CONTINUED BETWEEN MID-NOVEMBER AND
MID-DECEMBER, 2008, SUDDENLY TURNED INTO MODEST LA NINA CONDITIONS IN LATE
DECEMBER. SSTS ALONG THE EQUATOR ARE NOW MORE THAN 1 DEGREES C BELOW NORMAL
FROM THE DATE LINE TO ABOUT 110W LONGITUDE. THE LATEST WEEKLY SST INDEX VALUES
FOR THE NINO REGIONS, FROM WEST TO EAST ARE -0.8 IN NINO 4, -1.1 IN NINO 3.4,
-0.9 IN NINO 3, AND -0.6 IN THE NINO 1+2 REGIONS. THE SUBSURFACE OCEANIC HEAT
CONTENT ANOMALIES IN THE EASTERN PACIFIC OCEAN (THE AVERAGE WATER TEMPERATURES
IN THE UPPER 300M) HAVE BECOME INCREASINGLY NEGATIVE IN THE LAST MONTH AND ARE
NOW AROUND -1.5 C. LOW-LEVEL EASTERLY WIND ANOMALIES OF VARYING STRENGTH HAVE
CONTINUED IN RECENT WEEKS AND LARGE SCALE CONVECTION CONTINUES TO BE ENHANCED
IN THE WESTERN PACIFIC NEAR INDONESIA AND SUPPRESSED IN THE CENTRAL PACIFIC
NEAR THE DATE LINE.
PROGNOSTIC DISCUSSION OF SST FORECASTS
A CONSOLIDATION FORECAST BASED ON THE CFS AND SEVERAL STATISTICAL TOOLS FOR THE
NINO 3.4 SSTS INDICATES THAT 3 MONTH MEAN NINO 3.4 SSTS WILL DIP DOWN TO -.75 C
FOR THE EARLY PART OF 2009, BUT RETURN TO -0.5 ALREADY BY FMA WHICH IS THE
SHORTEST LEAD SEASON OF INTEREST AT THIS POINT. NEAR NORMAL VALUES ARE EXPECTED
TO APPEAR SOON THEREAFTER, REMAINING SOMEWHAT BELOW NORMAL THROUGH AT LEAST
EARLY SUMMER.
PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS
THE TEMPERATURE AND PRECIPITATION OUTLOOKS FOR ALL LEAD TIMES ARE BASED HEAVILY
ON THE CONSOLIDATION FORECAST (CON), A SKILL-WEIGHTED AND CALIBRATED OBJECTIVE
BLEND OF THE CFS, SMLR, OCN, CCA, AND ECCA FORECAST TOOLS. OTHER TOOLS, THE
IRI MULTI-MODEL ENSEMBLE FORECASTS BASED ON SEVERAL DYNAMIC CLIMATE MODELS, THE
ECPC CLIMATE FORECAST, AND THE CAS TOOL ARE ALSO CONSIDERED AND USED TO ADJUST
THE FORECAST. THE CONSOLIDATION FORECAST IS NOT AVAILABLE FOR ALASKA, SO THE
FORECAST THERE IS BASED ON A SUBJECTIVE COMBINATION OF CCA, CFS, OCN, AND SMLR
FORECASTS. LA NINA COMPOSITES WERE CONSULTED FOR THIS SERIES OF FORECASTS,
FROM FMA TO MAM.
PROGNOSTIC DISCUSSION OF OUTLOOKS - FMA 2009 TO FMA 2010
TEMPERATURE:
THE TEMPERATURE OUTLOOK FOR FMA 2009 CALLS FOR ABOVE AVERAGE TEMPERATURES FROM
THE INTERIOR SOUTHWESTERN U.S. EXTENDING EASTWARD TO INCLUDE TEXAS, THE
SOUTHERN GREAT PLAINS, AND MUCH OF THE SOUTHEASTERN U.S. BELOW NORMAL
TEMPERATURES ARE EXPECTED IN THE PACIFIC NORTHWEST, PORTIONS OF THE NORTHERN
ROCKIES, AND MOST OF MONTANA. THIS TEMPERATURE PATTERN IS SUPPORTED BY A RANGE
OF NUMERICAL MODELS AND STATISTICAL TOOLS AND IS TYPICAL OF LA NINA WINTERS.
ABOVE NORMAL TEMPERATURES ARE EXPECTED FOR NORTHERN ALASKA DUE TO LONG TERM
TRENDS. LA NINA EFFECTS ARE ASSUMED TO LINGER INTO MAM. WE INCREASED WARMTH IN
TEXAS FROM AMJ THROUGH JJA BASED ON THE DRY SOIL CONDITIONS CURRENTLY IN PLACE.
OTHERWISE, TEMPERATURES FOR OUTLOOKS FROM MAM 2009 THROUGH FMA 2010 ARE MAINLY
FROM LONG TERM TRENDS ADJUSTED TO SOME EXTENT BY WEAK SIGNALS FROM THE VARIOUS
OTHER TOOLS USED IN THE CONSOLIDATION FORECAST.
IN MANY SEASONS SOME INDICATIONS BASED ON TRENDS FOR ABOVE NORMAL TEMPERATURE
ARE GIVEN FOR ALASKA.
PRECIPITATION:
THERE IS CONSENSUS FOR BELOW MEDIAN PRECIPITATION AMOUNTS IN FMA 2009 OVER MUCH
OF THE SOUTHERN CONUS WITH GREATEST CONFIDENCE IN SOUTHERN NEW MEXICO AND IN
FLORIDA. WE EXTENDED BELOW MEDIAN CONDITIONS IN THE SOUTHWEST WESTWARD INTO
SOUTHERN CALIFORNIA. THERE IS SOME SUPPORT FROM LA NINA COMPOSITES FOR ABOVE
MEDIAN PRECIPITATION IN THE OHIO VALLEY. THE CFS FAVORS BELOW MEDIAN
PRECIPITATION IN THE SOUTHERN AND CENTRAL ROCKIES FOR MAM AND AMJ 2009. BY MJJ
2009 ENHANCED CHANCES OF BELOW MEDIAN PRECIPITATION APPEAR IN PARTS OF THE
NORTHERN GREAT BASIN AND THEN IN THE PACIFIC NORTHWEST BY JJA THROUGH ASO,
PRIMARILY REFLECTING LONG TERM TRENDS. THE ABOVE MEDIAN PRECIPITATION AMOUNTS
FOR COASTAL AREAS IN THE SOUTHEAST IN JAS THROUGH SON ARE RELATED TO INCREASED
TROPICAL ACTIVITY DURING RECENT YEARS. THE CONSOLIDATION FORECAST INDICATES
ABOVE MEDIAN PRECIPITATION FOR PARTS OF THE NORTHEASTERN CONUS FOR ASO AND SON
2009. SIGNALS FOR DJF2009 THROUGH FMA2010 REFLECT TRENDS. THE PRECIPITATION
OUTLOOK FOR ALASKA FOR ALL SEASONS IS LEFT AT CLIMATOLOGICAL PROBABILITIES,
WITH NO STRONG TRENDS IN PRECIPITATION EVIDENT DURING ANY SEASON.
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 FEB 19 2009
1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17, 2001
FORECAST RELEASE.
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