382
FXUS05 KWBC 191430
PMD90D
PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD
830 AM EST THU FEB 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. 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 -1.0 DEGREES C ACROSS THE
BASIN IN THE LATEST WEEKLY ANALYSIS. SPECIFICALLY, THE VALUES FOR THE NINO
REGIONS ARE -0.7, -0.8, -0.6 AND +0.1 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 -0.3 DEGREES C DURING THE MAM SEASON WITH A TRANSITION TO SLIGHTLY
POSITIVE VALUES BY AMJ 2009. THE CPC CONSOLIDATION SST FORECAST - AN OBJECTIVE
COMBINATION OF SEVERAL STATISTICAL TOOLS AND THE CFS - ALSO INDICATES THAT THE
3-MONTH MEAN NINO 3.4 VALUE WILL BE NEAR -0.3 DEGREES C FOR THE MAM 2009
SEASON. NEAR AVERAGE VALUES ARE EXPECTED THEREAFTER THROUGH THE SUMMER AND INTO
THE EARLY 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 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 MAM 2009
SEASON ONLY.
PROGNOSTIC DISCUSSION OF OUTLOOKS - MAM 2009 TO MAM 2010
TEMPERATURE:
THE TEMPERATURE OUTLOOK FOR MAM 2009 INDICATES ABOVE-AVERAGE TEMPERATURES FOR
PARTS OF THE SOUTHWEST US, THE SOUTHERN ROCKIES AND SOUTHERN GREAT PLAINS.
BELOW-AVERAGE TEMPERATURES ARE FORECAST FOR PARTS OF THE PACIFIC NORTHWEST AND
COASTAL AREAS OF SOUTHERN ALASKA AND THE ALASKAN PANHANDLE. THERE IS STRONG
SUPPORT FROM NEARLY ALL THE FORECAST TOOLS - STATISTICAL AND DYNAMICAL
INCLUDING THE CONSOLIDATED CONSENSUS FORECAST - FOR WARM CONDITIONS ACROSS THE
SOUTHWEST, SOUTHERN ROCKIES AND SOUTHERN PLAINS. DRY SOIL MOISTURE CONDITIONS
ACROSS PORTIONS OF TEXAS AND OKLAHOMA ARE ALSO EXPECTED TO CONTRIBUTE TO
ABOVE-AVERAGE TEMPERATURES IN THESE AREAS. BELOW-AVERAGE TEMPERATURES ACROSS
THE PACIFIC NORTHWEST AND COASTAL SOUTHERN ALASKA ARE SUPPORTED BY LA NINA
COMPOSITES, THE CCA STATISTICAL TOOL, SOME DYNAMICAL MODEL FORECASTS AND
CURRENT PREVAILING COOLER-THAN-AVERAGE SSTS FOR COASTAL AREAS. EQUAL CHANCES
ARE DESIGNATED IN REMAINING AREAS FOR MAM 2009.
LA NINA CONDITIONS ARE NOT CONSIDERED FOR THE AMJ SEASON AND BEYOND. 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 2009 SEASON DUE TO
COOLER-THAN-AVERAGE SSTS.
REMAINING FORECAST LEADS FROM JJA 2009 THROUGH MAM 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. IN MANY SEASONS, THERE ARE SOME
INDICATIONS BASED ON TRENDS FOR ABOVE-NORMAL TEMPERATURES FOR ALASKA.
PRECIPITATION:
THE PRECIPTATION OUTLOOK FOR MAM 2009 INDICATES BELOW-MEDIAN PRECIPITATION FOR
A REGION STRETCHING FROM THE SOUTHWEST US AND SOUTHERN AND CENTRAL ROCKIES TO
THE SOUTHERN PLAINS AND EASTWARD TO ENCOMPASS MUCH OF THE SOUTHEAST US. THE
FORECAST ACROSS THE SOUTHEAST US IS BASED ON LA NINA COMPOSITES AND STRONG
RECENT TRENDS AND TO A LESSER EXTENT ON SOME OF THE DYNAMICAL MODEL FORECAST
OUTPUT. IN THE SOUTHWESTERN US AND THE ROCKIES, 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 MAM 2009.
LA NINA CONDITIONS WERE NOT CONSIDERED FOR THE AMJ 2009 SEASON. BELOW-MEDIAN
PRECIPITATION IS EXPECTED FOR PORTIONS OF THE INTERIOR WEST DURING AMJ 2009,
SHIFTING INTO THE PACIFIC NORTHWEST BY ASO 2009 - BASED ON THE CONSOLIDATED
CONSENSUS FORECAST AND DYNAMICAL MODEL FORECAST OUTPUT. THE ABOVE-MEDIAN
PRECIPITATION AMOUNTS FOR COASTAL AREAS IN THE SOUTHEAST FROM JJA 2009 THROUGH
SON 2009 ARE RELATED TO LONG TERM TRENDS CONSISTENT WITH INCREASED TROPICAL
ACTIVITY DURING RECENT YEARS. 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: JON GOTTSCHALCK
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 MAR 19 2009
1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17, 2001
FORECAST RELEASE.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page