805
FXUS05 KWBC 191231
PMD90D
PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD
830 AM EDT THU MAR 19 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.
BOTH OCEANIC AND ATMOSPHERIC DATA INDICATE LA NINA CONDITIONS CONTINUE. SEA
SURFACE TEMPERATURES (SSTS) ARE BELOW AVERAGE ALONG THE EQUATOR THROUGHOUT MOST
OF THE CENTRAL AND EASTERN PACIFIC OCEAN. WATER TEMPERATURES BELOW THE SURFACE
REMAIN BELOW AVERAGE BUT DEPARTURES FROM NORMAL HAVE DECREASED OVER THE LAST
FEW WEEKS. LA NINA CONDITIONS ARE EXPECTED TO CONTINUE INTO SPRING 2009.
THE TEMPERATURE OUTLOOK FOR MAM 2009 CALLS FOR ABOVE-AVERAGE TEMPERATURES FOR
MUCH OF THE SOUTHWEST US, THE SOUTHERN ROCKIES AND PARTS OF THE SOUTHERN GREAT
PLAINS. BELOW-AVERAGE TEMPERATURES ARE FORECAST FOR THE PACIFIC NORTHWEST AND
COASTAL AREAS OF SOUTHERN ALASKA AND THE ALASKAN PANHANDLE. THE TEMPERATURE
OUTLOOK IS BASED ON TYPICAL LA NINA CONDITIONS, STATISTICAL TOOLS, NUMERICAL
CLIMATE MODEL OUTPUT AND IN SOME CASES CURRENT SSTS. ELSEWHERE, EQUAL CHANCES
OF BELOW-, NEAR-, AND ABOVE-AVERAGE TEMPERATURES ARE PREDICTED.
BELOW-MEDIAN PRECIPITATION IS FORECAST FOR MAM 2009 FOR A REGION STRETCHING
FROM THE CENTRAL ROCKIES TO THE SOUTHERN PLAINS AND INTO THE SOUTHEAST US. THE
PRIMARY DRIVERS FOR THE PRECIPITATION OUTLOOK ARE TYPICAL LA NINA CONDITIONS,
RECENT TRENDS AND NUMERICAL CLIMATE MODEL OUTPUT. 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 LA NINA. THE PACIFIC DECADAL OSCILLATION
IS IN A STRONG NEGATIVE PHASE. NEGATIVE SST ANOMALIES EXTEND FROM THE BERING
SEA AND ALEUTIAN ISLANDS ALONG THE WESTERN COAST OF NORTH AMERICA AS FAR SOUTH
AS NORTHERN MEXICO, AND THEN SOUTHWESTWARD THROUGH THE HAWAIIAN ISLANDS TO JUST
WEST OF THE DATE LINE AT THE EQUATOR. 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 TO ASIA. TROPICAL PACIFIC SEA SURFACE TEMPERATURES (SSTS) REMAIN
BELOW-AVERAGE ACROSS MUCH OF THE EQUATORIAL CENTRAL AND EASTERN PACIFIC OCEAN
WITH DEPARTURES GENERALLY RANGING FROM -0.5 TO -2.0 DEGREES C ACROSS THE BASIN
IN THE LATEST WEEKLY ANALYSIS. SPECIFICALLY, THE VALUES FOR THE NINO REGIONS
ARE -0.3, -0.4, -0.8 AND -0.2 DEGREES C FOR NINO 4, NINO 3.4, NINO 3, AND NINO
1+2 RESPECTIVELY. THE SUBSURFACE OCEANIC HEAT CONTENT ANOMALIES IN THE CENTRAL
PACIFIC OCEAN (THE AVERAGE WATER TEMPERATURES IN THE UPPER 300 M) WEAKENED
DURING THE LAST MONTH AS POSITIVE SUBSURFACE TEMPERATURE ANOMALIES FROM THE
WESTERN PACIFIC EXPANDED EASTWARD INTO THE CENTRAL PACIFIC.
ATMOSPHERIC CONDITIONS WERE CONSISTENT WITH LA NINA DURING THE LAST 30 DAYS.
TROPICAL CONVECTION REMAINS SUPPRESSED ALONG THE EQUATOR NEAR THE DATE LINE IN
THE PACIFIC OCEAN WHILE ENHANCED CONVECTION CONTINUED ACROSS MUCH OF INDONESIA,
NORTHERN AUSTRALIA, THE PHILIPPINES AND THE SOUTH PACIFIC CONVERGENCE ZONE
(SPCZ). LOW-LEVEL EASTERLIES REMAINED STRONGER THAN AVERAGE ACROSS MUCH OF THE
WEST-CENTRAL PACIFIC WHILE UPPER-LEVEL WESTERLY ANOMALIES WERE OBSERVED ACROSS
THE CENTRAL PACIFIC. MOREOVER, UPPER-LEVEL CYCLONIC CIRCULATIONS BOTH NORTH AND
SOUTH OF THE EQUATOR OVER THE CENTRAL PACIFIC WERE EVIDENT AND CONSISTENT WITH
ESTABLISHED LA NINA CONDITIONS.
PROGNOSTIC DISCUSSION OF SST FORECASTS
FORECASTS OF NINO 3.4 SST FROM BOTH THE CLIMATE FORECAST SYSTEM (CFS) AND THE
CPC CONSOLIDATION SST FORECAST INDICATE WEAKENING LA NINA CONDITIONS AS WE MOVE
THROUGH SPRING 2009. THE ENSEMBLE MEAN FORECAST FROM THE CFS SHOWS A DECREASE
TO NEAR -0.2 DEGREES C DURING THE AMJ SEASON WITH A TRANSITION TO SLIGHTLY
POSITIVE VALUES BY MJJ 2009. THE CPC CONSOLIDATION SST FORECAST - AN OBJECTIVE
COMBINATION OF SEVERAL STATISTICAL TOOLS AND THE CFS - INDICATES THAT THE
3-MONTH MEAN NINO 3.4 VALUE WILL BE NEAR -0.3 DEGREES C FOR THE AMJ 2009
SEASON. NEAR-TO SLIGHT BELOW-AVERAGE VALUES ARE EXPECTED THEREAFTER THROUGH THE
SUMMER AND INTO FALL 2009.
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 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 DYNAMICAL MODEL (CFS, IRI, ECPC)
FORECASTS, AND THE CCA, CFS, OCN, AND SMLR FORECASTS. NEAR COAST SSTS WERE
UTILIZED AT TIMES FOR THE TEMPERATURE OUTLOOKS WHILE RECENT SOIL MOISTURE
CONDITIONS CONTRIBUTED TO BOTH TEMPERATURE AND PREDICTION OUTLOOKS AT EARLY
LEADS. LA NINA COMPOSITES WERE CONSIDERED FOR THE AMJ AND MJJ 2009 SEASONS. LA
NINA COMPOSITES STRATIFIED BY THE PHASE OF THE PDO WERE ALSO CONSIDERED.
PROGNOSTIC DISCUSSION OF OUTLOOKS - AMJ 2009 TO AMJ 2010
TEMPERATURE:
THE TEMPERATURE OUTLOOK FOR AMJ 2009 INDICATES ENHANCED LIKELIHOOD OF
ABOVE-AVERAGE TEMPERATURES FOR PARTS OF THE SOUTH-CENTRAL AND SOUTHWEST US,
INCLUDING THE SOUTHERN ROCKIES AND SOUTHERN GREAT PLAINS. BELOW-AVERAGE
TEMPERATURES ARE FORECAST FOR PARTS OF THE PACIFIC NORTHWEST THROUGH MONTANA,
SOUTHERN ALASKA AND THE ALASKAN PANHANDLE.
SUPPORT FROM NEARLY ALL THE FORECAST TOOLS - STATISTICAL AND DYNAMICAL
INCLUDING THE CONSOLIDATED CONSENSUS FORECAST - INCREASE THE LIKELIHOOD FOR
EXTRA WARMTH ACROSS THE SOUTHWEST, SOUTHERN ROCKIES AND SOUTHERN GREAT PLAINS.
DRY SOIL MOISTURE CONDITIONS ACROSS PORTIONS OF TEXAS AND OKLAHOMA ARE ALSO
EXPECTED TO CONTRIBUTE TO ABOVE-AVERAGE TEMPERATURES IN THESE AREAS, ALTHOUGH
SOIL MOISTURE LEVELS THERE IMPROVED IN MID-MARCH. ENHANCED CHANCES OF
BELOW-AVERAGE TEMPERATURES ACROSS THE PACIFIC NORTHWEST AND COASTAL SOUTHERN
ALASKA ARE SUPPORTED BY LA NINA/PDO COMPOSITES, THE CCA STATISTICAL TOOL,
DYNAMICAL MODEL FORECASTS AND CURRENT PREVAILING COOLER-THAN-AVERAGE SSTS FOR
COASTAL AREAS. EQUAL CHANCES ARE DESIGNATED IN REMAINING AREAS FOR AMJ 2009.
LA NINA CONDITIONS ARE LIKELY TO CONTINUE THROUGH SPRING AND ARE CONSIDERED
THROUGH MJJ. INCREASED CHANCES FOR ABOVE-AVERAGE TEMPERATURES CONTINUE TO BE
FORECAST FOR THE SOUTHWEST, SOUTHERN ROCKIES AND PARTS OF THE SOUTHERN PLAINS
THROUGH JJA AND ARE INDICATED BY MOST STATISTICAL AND DYNAMICAL FORECAST TOOLS.
DRY SOIL MOISTURE CONDITIONS CONTINUE TO PLAY A ROLE IN THE OUTLOOK ACROSS
PORTIONS OF THE SOUTHERN PLAINS DURING THIS PERIOD. BELOW-AVERAGE TEMPERATURES
ARE EXPECTED TO PERSIST FOR COASTAL AREAS OF ALASKA INTO THE AMJ AND MJJ 2009
SEASONS DUE TO COOLER-THAN-AVERAGE SSTS, AND POSSIBLE LINGERING OF COLD LA
NINA/PDO CONDITIONS.
REMAINING FORECAST LEADS FROM JAS 2009 THROUGH AMJ 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 AMJ 2009 INDICATES AN ENHANCED LIKELIHOOD OF
BELOW-MEDIAN PRECIPITATION FOR A REGION STRETCHING FROM THE CENTRAL ROCKIES TO
THE NORTHWESTERN CONUS AND NORTHERN CALIFORNIA. AN INCREASED LIKELIHOOD OF
SUB-MEDIAN RAINFALL ACROSS THE SOUTHERN HALF OF THE FLORIDA PENINSULA IS BASED
ON LA NINA COMPOSITES AND STRONG RECENT TRENDS, DYNAMICAL MODEL FORECAST OUTPUT
SUPPORTED BY THE EXISTENCE OF COLDER THAN NORMAL SSTS IN THE REGION. IN THE
ROCKIES AND NORTHWEST, THE CONSOLIDATED CONSENSUS FORECAST WAS THE MAIN TOOL
ALTHOUGH LA NINA COMPOSITES WERE ALSO CONSISTENT WITH THE EXPECTATIONS FOR
BELOW-MEDIAN PRECIPITATION. DRY SOIL MOISTURE CONDITIONS ACROSS THE SOUTHERN
PLAINS ALSO CONTRIBUTED TO THE FORECAST FOR BELOW-MEDIAN PRECIPITATION IN THESE
AREAS. EQUAL CHANCES ARE DESIGNATED IN REMAINING AREAS FOR AMJ 2009.
LA NINA CONDITIONS WERE CONSIDERED THROUGH THE MJJ 2009 SEASON. THERE IS
ENHANCED LIKELIHOOD OF BELOW-MEDIAN PRECIPITATION FOR PORTIONS OF THE INTERIOR
WEST AND THE NORTHWEST DURING AMJ 2009. THIS INCREASED CHANCE OF RELATIVE
DRYNESS IN THE REGION CONTINUES THROUGH ASO 2009 - BASED ON THE CONSOLIDATED
CONSENSUS FORECAST AND DYNAMICAL MODEL FORECAST OUTPUT. THE INCREASED RISK OF
ABOVE-MEDIAN PRECIPITATION AMOUNTS FOR COASTAL AREAS IN THE SOUTHEAST FROM ASO
2009 THROUGH SON 2009 IS RELATED TO LONG TERM TRENDS, AND IS CONSISTENT WITH
INCREASED TROPICAL ACTIVITY DURING RECENT YEARS. THE PRECIPITATION OUTLOOK FOR
ALASKA THROUGH MID-WINTER INDICATES AN ENHANCED LIKELIHOOD OF ABOVE-MEDIAN
PRECIPITATION IN VARIOUS SECTIONS OF THE STATE, AS INDICATED BY ALL TOOLS,
EARLY-ON IN THE FORECAST, AND BY STATISTICAL TOOLS AFTER SON 2009.
THE REGION OF ENHANCED CHANCE OF ABOVE-MEDIAN RAINFALL PREDICTED FOR THE
ARIZONA-NEW MEXICO REGION IN MJJ AND JJA COMES FROM THE CON FORECAST. ALL THE
STATISTICAL TOOLS CONTRIBUTED TO THIS SIGNAL, AND IT IS ALSO SUPPORTED BY THE
CAS, CFS, AND ECPC MODELS. THERE IS ALSO SUPPORT FOR ENHANCED US SOUTHWEST
MONSOON CONDITIONS IN THESE SEASONS FROM THE PDO-STRATIFIED LA NINA COMPOSITES.
NOTE - AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL
PROBABILITIES) ARE NOW LABELED EC (EQUAL CHANCES).
FORECASTER: ED O'LENIC
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 APR 16 2009
1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17, 2001
FORECAST RELEASE.
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