702
FXUS05 KWBC 211231
PMD90D
PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD
830 AM EDT THU MAY 21 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.
DURING THE MONTH OF APRIL 2009, EQUATORIAL PACIFIC ATMOSPHERIC AND OCEANIC
CONDITIONS TRANSITIONED FROM LA NINA TO ENSO-NEUTRAL. MONTHLY SEA SURFACE
TEMPERATURE (SST) ANOMALIES ARE NEAR-ZERO ACROSS THE CENTRAL PACIFIC OCEAN AND
POSITIVE IN THE EASTERN PACIFIC OCEAN. UPPER-OCEAN HEAT CONTENT FROM 50 TO 200
METERS BELOW THE SURFACE SHOWS A SIGNIFICANT POSITIVE ANOMALY ACROSS THE
PACIFIC OCEAN FROM ABOUT 140 E TO 110 W LONGITUDE. ENSO-NEUTRAL CONDITIONS ARE
EXPECTED TO PERSIST INTO SUMMER 2009.
THE TEMPERATURE OUTLOOK FOR JJA 2009 CALLS FOR AN ENHANCED LIKELIHOOD OF
BELOW-NORMAL TEMPERATURES FOR THE NORTHERN PLAINS INTO MINNESOTA. THE
LIKELIHOOD OF ABOVE NORMAL TEMPERATURES IS ENHANCED FOR MOST OF THE WESTERN
U.S., ALONG THE GULF COAST AND FOR THE EASTERN SEABOARD FROM FLORIDA TO NEW
ENGLAND. ELSEWHERE, EQUAL CHANCES OF BELOW, NEAR, AND ABOVE NORMAL TEMPERATURES
ARE PREDICTED.
THE PROBABILITY OF BELOW MEDIAN PRECIPITATION IS ENHANCED FOR JJA 2009 FOR THE
PACIFIC NORTHWEST INTO THE NORTHERN INTER-MOUNTAIN WEST. ABOVE MEDIAN
PRECIPITATION AMOUNTS ARE MORE LIKELY FOR AN AREA OF THE SOUTHWEST NEAR THE
FOUR CORNERS REGION. ELSEWHERE, EQUAL CHANCES OF BELOW, NEAR, AND ABOVE MEDIAN
PRECIPITATION IS PREDICTED.
THE TEMPERATURE AND PRECIPITATION OUTLOOKS ARE BASED PRIMARILY ON THE OBJECTIVE
CONSOLIDATION OF THE STATISTICAL TOOLS AND DYNAMICAL CLIMATE MODEL OUTPUT. THE
INFLUENCE OF SOIL MOISTURE AND THE INFLUENCE SSTS ALONG SOME COASTAL AREAS ARE
ALSO CONSIDERED.
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
FOLLOWING LA NINA CONDITIONS LAST WINTER INTO EARLY SPRING, ATMOSPHERIC AND
OCEANIC CONDITIONS CURRENTLY INDICATE ENSO-NEUTRAL CONDITIONS. WEEKLY SST
ANOMALIES FROM ALONG THE WESTERN COAST OF CANADA SOUTHWARD TO CENTRAL
CALIFORNIA REMAIN BELOW NORMAL, WHILE SEA SURFACE TEMPERATURES HAVE RECENTLY
WARMED TO NEAR NORMAL OFF THE COAST OF ALASKA. A POSITIVE SST ANOMALY REMAINS
IN THE PACIFIC NORTH OF HAWAII NEAR 150 W LONGITUDE AND 40 N LATITUDE. SEA
SURFACE TEMPERATURES (SSTS) ARE NOW NEAR NORMAL ACROSS MUCH OF THE EQUATORIAL
WESTERN AND CENTRAL PACIFIC OCEAN, ACCORDING TO THE LATEST WEEKLY ANALYSIS. THE
WEEKLY NINO 3.4 SST INDEX VALUE IS AROUND 0.3 DEGREES C. THE UPPER-OCEAN HEAT
CONTENT IN THE CENTRAL PACIFIC OCEAN INDICATED BY THE TEMPERATURE ANOMALY FROM
180-100 W LONGITUDE IN THE UPPER 300 METERS HAS INCREASED TO ABOUT 0.5 DEGREES
C, AS POSITIVE SUBSURFACE TEMPERATURE ANOMALIES STRETCH FROM THE WESTERN
PACIFIC TO ABOUT 100 W LONGITUDE.
ATMOSPHERIC TROPICAL CONVECTION REMAINED SUPPRESSED NEAR THE DATE LINE, WHILE
ENHANCED CONVECTION IS DECREASING OVER INDONESIA. LOW-LEVEL EASTERLY WINDS ARE
NEAR-AVERAGE ACROSS THE EQUATORIAL PACIFIC, AND UPPER-LEVEL WESTERLY WINDS ARE
ALSO NEAR-AVERAGE EXCEPT OVER PARTS OF THE WESTERN PACIFIC. OVERALL, THE
ATMOSPHERIC AND OCEANIC STATE INDICATES THAT THE PREVIOUS LA NINA CONDITIONS
HAVE TRANSITIONED TO ENSO-NEUTRAL CONDITIONS.
PROGNOSTIC DISCUSSION OF SST FORECASTS
THE CPC CONSOLIDATION NINO 3.4 SST ANOMALY FORECAST INDICATES THAT THE GREATEST
PROBABILITY IS FOR ENSO-NEUTRAL CONDITIONS THROUGH JJA 2009. THE CPC
CONSOLIDATION SST FORECAST, WHICH IS A SKILL-WEIGHTED COMBINATION OF SEVERAL
STATISTICAL SST FORECASTS AND THE CLIMATE FORECAST SYSTEM (CFS) MODEL
FORECASTS, PREDICTS THAT ENSO-NEUTRAL CONDITIONS ARE MOST LIKELY TO PERSIST
THROUGH 2009 INTO THE SPRING OF 2010. HOWEVER, THE IRI SST-FORECAST PLUME
SHOWS THAT MOST DYNAMICAL MODEL FORECASTS ARE PREDICTING EL NINO CONDITIONS BY
THE END OF SUMMER 2009 CONTINUING INTO NEXT WINTER, WHILE THE STATISTICAL
MODELS WHICH ARE GENERALLY LESS SENSITIVE TO SUBSURFACE OCEAN TEMPERATURES
INDICATE ENSO-NEUTRAL CONDITIONS PERSISTING. THE RECENT ENSEMBLE MEMBERS OF
THE CLIMATE FORECAST SYSTEM COUPLED OCEAN-ATMOSPHERE MODEL INDICATE A VERY
RAPID WARMING, WITH THE NINO 3.4 SST ANOMALY EXCEEDING +0.5 DEGREES C BY JULY
AND A POSSIBLE EL NINO NEXT WINTER, EVEN AFTER CORRECTING FOR MODEL BIASES.
THOUGH THE CPC CONSOLIDATION NINO 3.4 SST FORECAST INDICATES ENSO-NEUTRAL
CONDITIONS ARE MORE LIKELY TO PERSIST FOR SOME TIME, THE CHANCE OF AN EL NINO
EVENT BY THIS WINTER HAS INCREASED.
PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS
THE TEMPERATURE AND PRECIPITATION OUTLOOKS FOR ALL LEAD TIMES ARE BASED
PRIMARILY ON THE CONSOLIDATION FORECAST (CON), A SKILL-WEIGHTED AND CALIBRATED
PROBABILISTIC FORECAST DERIVED FROM THE CFS, SMLR, OCN, CCA, AND ECCA FORECAST
TOOLS. THE IRI MULTI-MODEL ENSEMBLE FORECASTS BASED ON SEVERAL DYNAMICAL
CLIMATE MODELS, THE ECPC CLIMATE FORECAST, AND THE CAS TOOL ARE ALSO USED. THE
CONSOLIDATION FORECAST IS NOT AVAILABLE FOR ALASKA, SO THE FORECAST THERE IS
BASED ON A SUBJECTIVE COMBINATION OF DYNAMICAL MODEL FORECASTS AND THE CCA,
OCN, AND SMLR STATISTICAL FORECASTS. NEAR THE COASTS FOR EARLY LEADS, SST
ANOMALIES ARE CONSIDERED FOR THE TEMPERATURE OUTLOOKS, WHILE RECENT SOIL
MOISTURE CONDITIONS CONTRIBUTE TO BOTH TEMPERATURE AND PRECIPITATION OUTLOOKS
AT EARLY LEADS.
PROGNOSTIC DISCUSSION OF OUTLOOKS - JJA 2009 TO JJA 2010
TEMPERATURE:
THE TEMPERATURE OUTLOOK FOR JJA 2009 INDICATES GREATER THAN CLIMATOLOGICAL
PROBABILITIES FOR ABOVE NORMAL TEMPERATURES FOR MOST OF THE WESTERN U.S., PARTS
OF THE SOUTHERN PLAINS, AS WELL AS THE EAST COAST, AS INDICATED BY THE
CONSOLIDATION OF FORECAST TOOLS. GREATER THAN CLIMATOLOGICAL PROBABILITIES FOR
BELOW NORMAL TEMPERATURES, AS IN THE SMLR, CFS AND ECPC FORECASTS, ARE
INDICATED FOR THE NORTHERN PLAINS.
ALL OF THE STATISTICAL TOOLS WITH SOME SUPPORT FROM THE CFS INDICATE THE
INCREASED LIKELIHOOD FOR ABOVE NORMAL MEAN TEMPERATURES IN THE WEST FOR JJA AND
JAS 2009. BELOW NORMAL SEA-SURFACE TEMPERATURES OFF THE COASTS OF WASHINGTON,
OREGON AND NORTHERN CALIFORNIA HAVE CONTRIBUTED TO NEAR CLIMATOLOGICAL
PROBABILITIES OF ALL TEMPERATURE CATEGORIES NEAR THE PACIFIC COAST COMPARED TO
THE ENHANCED PROBABILITY FOR ABOVE NORMAL FOR THE INTERIOR WEST. THE ENHANCED
LIKELIHOOD FOR ABOVE NORMAL TEMPERATURES IN THE SOUTHWEST PERSISTS THROUGH ALL
LEADS INTO JJA 2010 DUE TO LONG-TERM TEMPERATURE TRENDS AS REPRESENTED IN THE
CONSOLIDATION. THE LIKELIHOOD OF ABOVE NORMAL TEMPERATURES ARE ENHANCED IN THE
NORTHEAST THROUGH SON 2009 LARGELY DUE TO TEMPERATURE TRENDS. GREATER THAN
CLIMATOLOGICAL PROBABILITIES FOR ABOVE NORMAL TEMPERATURES FOR THE NORTHERN AND
CENTRAL PLAINS AND NORTHERN INTER-MOUNTAIN WEST IN OND 2009 THROUGH JFM 2010
ARE DUE TO BOTH TRENDS AND SOME INFLUENCE OF A TILT IN THE PROBABILITY TOWARDS
EL NINO CONDITIONS.
REMAINING FORECAST LEADS FROM FMA 2010 THROUGH JJA 2010 ARE BASED ON THE
CONSOLIDATION FORECAST.
PRECIPITATION:
ALL FORECAST LEADS FROM JJA 2009 THROUGH JJA 2010 ARE BASED PRIMARILY ON THE
CONSOLIDATION FORECAST, WITH SOME ADJUSTMENTS MADE FOR THE UNCERTAIN STATE OF
ENSO AT LONGER LEADS. THE PRECIPITATION OUTLOOKS FOR JJA THROUGH ASO 2009
INDICATE GREATER THAN CLIMATOLOGICAL PROBABILITIES FOR PRECIPITATION AMOUNTS
FALLING WITHIN THE LOWER TERCILE OVER THE PACIFIC NORTHWEST AS INDICATED BY THE
CONSOLIDATION. RECENT ATMOSPHERIC CONDITIONS INDICATE AN INCREASED LIKELIHOOD
FOR AN EARLY ONSET AND AN ABOVE NORMAL NORTH AMERICAN MONSOON LEADING TO AN
ENHANCED PROBABILITY FOR ABOVE MEDIAN PRECIPITATION AMOUNTS PARTICULARLY AROUND
THE FOUR CORNERS REGION IN JJA AND JAS 2009. LONG-TERM PRECIPITATION TRENDS
LEAD TO AN ENHANCED LIKELIHOOD FOR ABOVE MEDIAN PRECIPITATION AMOUNTS FOR THE
FLORIDA PENINSULA FROM JJA THROUGH SON 2009. THE GREATER THAN CLIMATOLOGICAL
PROBABILITY OF BELOW MEDIAN PRECIPITATION IN THE INTERIOR AND PACIFIC NORTHWEST
FROM OND 2009 INTO FMA 2010 IS A RESULT OF BOTH TRENDS AND THE INFLUENCE OF A
GREATER THAN NORMAL CHANCE OF EL NINO CONDITIONS. THE AREA OF GREATER THAN
CLIMATOLOGICAL PROBABILITY OF BELOW MEDIAN PRECIPITATION IN THE SOUTHEAST FROM
DJF TO MAM 2010 IS INDICATED BY THE CONSOLIDATION DUE TO SIGNIFICANT
PRECIPITATION TRENDS; HOWEVER, THERE IS SOME UNCERTAINTY ALONG THE GULF AND
ATLANTIC COASTS DUE TO THE POSSIBILITY OF EL NINO CONDITIONS.
IN REGIONS WHERE PRECIPITATION SIGNALS WERE WEAK OR IN CONFLICT, EQUAL CHANCES
(EC) OF BELOW, NEAR, AND ABOVE MEDIAN PRECIPITATION IS PREDICTED.
NOTE - AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL
PROBABILITIES) ARE NOW LABELED EC (EQUAL CHANCES).
FORECASTER: DAN COLLINS
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 JUN 18 2009
1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17, 2001
FORECAST RELEASE.
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