788
FXUS05 KWBC 161231
PMD90D
PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD
830 AM EDT THU APR 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.
ATMOSPHERIC AND OCEANIC CONDITIONS DURING THE PAST MONTH CONTINUED TO REFLECT
WEAK LA NINA CONDITIONS. THE MONTHLY SEA SURFACE TEMPERATURES (SST) REMAIN
BELOW AVERAGE ACROSS PARTS OF THE EAST-CENTRAL AND EASTERN PACIFIC OCEAN. WATER
TEMPERATURES BELOW THE SURFACE REMAIN BELOW AVERAGE BUT DEPARTURES FROM NORMAL
HAVE CONTINUED TO DECREASE. A TRANSITION TO ENSO-NEUTRAL CONDITIONS IS EXPECTED
DURING APRIL 2009.
THE TEMPERATURE OUTLOOK FOR MJJ 2009 CALLS FOR AN ENHANCED LIKELIHOOD OF
BELOW-AVERAGE TEMPERATURES FOR SOUTHERN ALASKA, THE PACIFIC NORTHWEST COAST,
AND THE UPPER MIDWEST. ABOVE-AVERAGE TEMPERATURES ARE EXPECTED FOR PORTIONS OF
THE INTERIOR PACIFIC NORTHWEST, THE SOUTHWEST, MOST OF THE ROCKIES AND MUCH OF
THE CENTRAL AND SOUTHERN GREAT PLAINS. THE TEMPERATURE OUTLOOK IS BASED ON
STATISTICAL TOOLS, NUMERICAL CLIMATE MODEL OUTPUT, THE INFLUENCE OF SOIL
MOISTURE, AND SSTS ALONG SOME COASTAL AREAS. ELSEWHERE, EQUAL CHANCES OF
BELOW-, NEAR-, AND ABOVE-AVERAGE TEMPERATURES ARE PREDICTED.
BELOW-MEDIAN PRECIPITATION IS ANTICIPATED FOR MJJ 2009 FOR A LARGE PORTION OF
THE INTERIOR WEST, AND FOR EXTREME SOUTHWESTERN ALASKA. ABOVE-MEDIAN
PRECIPITATION AMOUNTS ARE FORECAST FOR SOUTHEAST ALASKA, THE ALASKA PANHANDLE,
THE UPPER MIDWEST, AND SOUTHERN SECTIONS OF BOTH ARIZONA AND NEW MEXICO. THE
PRIMARY INPUTS FOR THE PRECIPITATION OUTLOOK ARE NUMERICAL CLIMATE MODEL
OUTPUT, CURRENT SOIL MOISTURE CONDITIONS AND LONG-TERM TRENDS. ELSEWHERE, EQUAL
CHANCES OF BELOW-, NEAR-, AND ABOVE-MEDIAN PRECIPITATION IS 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
OCEANIC CONDITIONS CURRENTLY REFLECT WEAK LA NINA CONDITIONS. THE PACIFIC
DECADAL OSCILLATION (PDO) CONTINUES TO BE IN ITS NEGATIVE PHASE. NEGATIVE SST
ANOMALIES EXTEND FROM THE BERING SEA AND ALEUTIAN ISLANDS ALONG THE WESTERN
COAST OF NORTH AMERICA AS FAR SOUTH AS CENTRAL CALIFORNIA, AND THEN
SOUTHWESTWARD TO AND BEYOND THE HAWAIIAN ISLANDS. THESE COLD ANOMALIES TAKE THE
FORM OF AN ARC, WHICH PARTIALLY ENCIRCLES A REGION OF POSITIVE SST ANOMALIES
JUST NORTH OF THE HAWAIIAN ISLANDS. THESE WARM ANOMALIES EXTEND WESTWARD ACROSS
THE NORTH PACIFIC OCEAN, PAST THE DATE LINE, TO APPROXIMATELY 170E LONGITUDE.
THE SEA SURFACE TEMPERATURES (SSTS) REMAIN NEAR- TO BELOW-AVERAGE ACROSS MUCH
OF THE EQUATORIAL CENTRAL AND EASTERN PACIFIC OCEAN, ACCORDING TO THE LATEST
WEEKLY ANALYSIS. THE NINO 3.4 SST INDEX VALUE HAS NOW DIMINISHED TO NEAR ZERO
DEG C. THE SUBSURFACE OCEANIC HEAT CONTENT ANOMALIES IN THE CENTRAL PACIFIC
OCEAN (THE AVERAGE WATER TEMPERATURES IN THE UPPER 300 M) WEAKENED FURTHER
DURING THE LAST MONTH TO ABOUT -0.1 DEG C, AS POSITIVE SUBSURFACE TEMPERATURE
ANOMALIES FROM THE WESTERN PACIFIC EXPANDED EASTWARD INTO THE CENTRAL PACIFIC.
ATMOSPHERIC TROPICAL CONVECTION REMAINED SUPPRESSED NEAR THE DATE LINE, AND
ENHANCED ACROSS INDONESIA, BUT WEAKENED DURING THE SECOND HALF OF MARCH DUE TO
MADDEN-JULIAN OSCILLATION (MJO) ACTIVITY. ENHANCED LOW-LEVEL EASTERLY WINDS AND
UPPER-LEVEL WESTERLY WINDS ALSO DECREASED ACROSS THE EQUATORIAL PACIFIC.
COLLECTIVELY, THE ATMOSPHERIC AND OCEANIC ANOMALIES ARE CONSISTENT WITH A
WEAKENING LA NINA.
PROGNOSTIC DISCUSSION OF SST FORECASTS
FORECASTS OF NINO 3.4 SST FROM THE CPC CONSOLIDATION SST FORECAST INDICATE THE
TRANSITION FROM WEAK LA NINA TO ENSO-NEUTRAL CONDITIONS AS SPRING 2009
PROGRESSES. THE CPC CONSOLIDATION SST FORECAST - AN OBJECTIVE COMBINATION OF
SEVERAL STATISTICAL TOOLS AND THE CLIMATE FORECAST SYSTEM (CFS) MODEL - ALSO
PREDICTS THAT ENSO-NEUTRAL CONDITIONS COULD PERSIST THROUGHOUT THE REMAINDER OF
2009. THE ENSEMBLE MEAN FORECAST FROM THE CLIMATE FORECAST SYSTEM MODEL SHOWS A
MORE RAPID WARMUP, WITH A TRANSITION TO SLIGHTLY POSITIVE VALUES DURING MJJ
2009, AND BORDERLINE WARM EVENT CONDITIONS BY LATE SUMMER. HOWEVER, THE GENERAL
CONSENSUS OF ABOUT A DOZEN OTHER STATISTICAL AND DYNAMICAL SST FORECASTS FROM
OTHER CENTERS LENDS MORE CREDENCE TO THE CPC CONSOLIDATION FORECAST.
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. THE IRI MULTI-MODEL
ENSEMBLE FORECASTS BASED ON SEVERAL DYNAMIC CLIMATE MODELS, THE ECPC CLIMATE
FORECAST, AND THE CAS TOOL WERE 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 DYNAMICAL MODEL (CFS, IRI, ECPC)
FORECASTS, AND THE CCA, OCN, AND SMLR STATISTICAL FORECASTS. NEAR THE WEST
COAST, SSTS WERE UTILIZED AT TIMES FOR THE TEMPERATURE OUTLOOKS WHILE RECENT
SOIL MOISTURE CONDITIONS CONTRIBUTED TO BOTH TEMPERATURE AND PRECIPITATION
OUTLOOKS AT EARLY LEADS.
PROGNOSTIC DISCUSSION OF OUTLOOKS - MJJ 2009 TO MJJ 2010
TEMPERATURE:
THE TEMPERATURE OUTLOOK FOR MJJ 2009 INDICATES GREATER THAN CLIMATOLOGICAL
PROBABILITIES FOR ABOVE-AVERAGE TEMPERATURES FOR MOST OF THE INTERIOR WEST, AS
WELL AS FOR MOST OF THE ROCKIES, THE CENTRAL HIGH PLAINS AND NEARLY ALL OF THE
SOUTHERN PLAINS. GREATER THAN CLIMATOLOGICAL PROBABILITIES FOR BELOW-AVERAGE
TEMPERATURES ARE INDICATED FOR SOUTHERN ALASKA, THE ALASKA PANHANDLE, COASTAL
AREAS OF THE PACIFIC NORTHWEST, AND THE UPPER MIDWEST.
MOST OF THE FORECAST TOOLS - STATISTICAL AND DYNAMICAL, INCLUDING THE
CONSOLIDATED CONSENSUS FORECAST - SUGGEST AN INCREASED LIKELIHOOD FOR RELATIVE
WARMTH ACROSS THE SOUTHWEST DURING MJJ 2009, EXTENDING EASTWARD INTO THE
CENTRAL AND SOUTHERN PLAINS, AND NORTHWARD INTO OREGON AND IDAHO. THE LONG,
NEAR-COASTAL ARC OF BELOW-AVERAGE TEMPERATURES DEPICTED ON THE OFFICIAL MJJ
2009 MAP IS SUPPORTED BY THE ECPC, IRI, THE PERSISTENCE OF COLD WATER ALONG THE
WESTERN COAST OF NORTH AMERICA, AND TO A MODEST DEGREE THE CFS AND CON TOOLS.
THE AREA OF ANOMALOUSLY COOL TEMPERATURES ANTICIPATED OVER THE UPPER MIDWEST IS
GENERALLY SUPPORTED BY THE CPC CONSOLIDATION (CON), THE ECPC, THE CFS, AND TO A
LESSER DEGREE THE SMLR AND CCA TOOLS. THIS AREA OF ANOMALOUS COLD ACROSS THE
UPPER MIDWEST DURING MJJ 2009 IS ALSO FORECAST BECAUSE OF EXPECTED SOIL
MOISTURE CIRCULATION FEEDBACK MECHANISMS WITHIN THE BOUNDARY LAYER.
THE SATURATED SOILS ACROSS THE UPPER MIDWEST COULD ALSO HAVE AN EFFECT ON THE
TEMPERATURE FORECAST FOR JJA 2009. THE CFS AND ECPC DYNAMICAL MODELS, AND TO A
LESSER DEGREE THE CON, LEND STRONG SUPPORT FOR THE BELOW-AVERAGE TEMPERATURES
PREDICTED IN THAT REGION. WITH THE LARGE EXTENT OF ANOMALOUS COLD PREDICTED BY
THE CFS AND ECPC ACROSS THE CENTRAL CONUS DURING JJA, AND THE CON NOT SHOWING
SIGNIFICANT TILTS IN THE ODDS FOR EITHER COLD OR WARM ACROSS MUCH OF THIS
REGION, IT WAS DECIDED THAT EQUAL CHANCES (EC) IS PROBABLY THE BEST FORECAST.
REMAINING FORECAST LEADS FROM JAS 2009 THROUGH MJJ 2010 ARE MAINLY BASED ON THE
CONSOLIDATED CONSENSUS FORECAST AND LONG TERM TRENDS ADJUSTED TO SOME EXTENT BY
WEAK SIGNALS FROM THE VARIOUS OTHER TOOLS.
PRECIPITATION:
THE PRECIPITATION OUTLOOK FOR MJJ 2009 INDICATES GREATER THAN CLIMATOLOGICAL
PROBABILITIES FOR PRECIPITATION AMOUNTS FALLING WITHIN THE UPPERMOST TERCILE
OVER THE UPPER MIDWEST, SOUTHERN PORTIONS OF BOTH ARIZONA AND NEW MEXICO,
SOUTHEAST ALASKA AND THE ALASKA PANHANDLE. GREATER THAN CLIMATOLOGICAL
PROBABILITIES FOR PRECIPITATION AMOUNTS FALLING WITHIN THE LOWEST TERCILE ARE
INDICATED OVER THE NORTHERN AND CENTRAL PORTIONS OF BOTH THE INTERMOUNTAIN WEST
AND THE ROCKIES, AS WELL AS OVER SOUTHWESTERN PARTS OF ALASKA.
THE LARGE AREA OF BELOW-AVERAGE PRECIPITATION PREDICTED OVER THE NORTHWEST IN
MJJ 2009 IS BASED ON THE CON, ECPC, ECCA, IRI, CFS AND CCA TOOLS. THE AREA OF
RELATIVE DRYNESS ANTICIPATED OVER SOUTHWESTERN ALASKA IS DUE TO THE CFS AND
ECPC FORECASTS. THE ABOVE-AVERAGE PRECIPITATION AMOUNTS DEPICTED OVER
SOUTHEASTERN ALASKA AND THE ADJOINING PANHANDLE ARE ATTRIBUTED TO THE CFS AND
ECPC FORECASTS. ELEVATED CHANCES FOR ABOVE-AVERAGE RAINFALL ALONG PORTIONS OF
THE US-MEXICAN BORDER IS SUGGESTIVE OF WHAT COULD BE AN ENHANCED MONSOON SEASON
FOR THE SOUTHWEST. THIS AREA HAS SUBSTANTIAL SUPPORT FROM BOTH THE CFS AND ECPC
TOOLS, WITH SOMEWHAT LESS SUPPORT INDICATED BY THE ENSEMBLE CCA (ECCA).
ALTHOUGH THE PREDICTION OF THE MAGNITUDE AND TIMING OF THE MONSOON IS VERY
DIFFICULT AT BEST, THERE ARE SOME OBJECTIVE INDICATIONS THAT TILT THE
PROBABILITIES TOWARD THE WETTEST TERCILE OF THE PRECIPITATION DISTRIBUTION.
MOVING INTO THE JJA AND JAS 2009 SEASONS, THE CFS, ECPC AND ECCA CONTINUE TO GO
WITH WETTER THAN AVERAGE CONDITIONS ACROSS THE MONSOON REGION OF THE SOUTHWEST.
THE CON, ECCA, CCA AND OCN CONTINUE TO SHOW GOOD SUPPORT FOR THE RELATIVE
DRYNESS PREDICTED OVER THE NORTHWEST. THE JAS, ASO, AND SON SEASONS FAVOR ABOVE
AVERAGE PRECIPITATION AMOUNTS OVER PORTIONS OF FLORIDA, BASED LARGELY ON
RAINFALL TRENDS ASSOCIATED WITH INCREASED TROPICAL ACTIVITY DURING RECENT
YEARS. IN THE NORTHEAST U.S. FOR JAS AND ASO 2009, WETTER THAN AVERAGE
CONDITIONS ARE FAVORED BY THE CON, WHICH IS CONSISTENT WITH A RECENT TREND FOR
WETNESS ACROSS THIS AREA. FOR SEASONS OND 2009 TO MJJ 2010, THE PRECIPITATION
FORECASTS ARE BASED HEAVILY ON THE OBJECTIVE CONSOLIDATION AND RECENT TRENDS.
IN REGIONS WHERE PRECIPITATION SIGNALS WERE WEAK, OR IN CONFLICT, EQUAL CHANCES
(EC) OF BELOW-, NEAR-, AND ABOVE-AVERAGE PRECIPITATION IS PREDICTED.
NOTE - AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL
PROBABILITIES) ARE NOW LABELED EC (EQUAL CHANCES).
FORECASTER: ANTHONY ARTUSA
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 MAY 21 2009
1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17, 2001
FORECAST RELEASE.
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