085
FXUS05 KWBC 201330
PMD90D
PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD
830 AM EST THU NOV 20 2008
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.
ENSO-NEUTRAL CONDITIONS CONTINUED DURING MID-OCTOBER TO MID-NOVEMBER 2008, AS
GENERALLY NEAR AVERAGE SEA SURFACE TEMPERATURES (SSTS) WERE OBSERVED ACROSS THE
EQUATORIAL PACIFIC OCEAN.
A CONSENSUS OF THE SST FORECASTS FOR NINO 3.4 MAINTAINS ENSO-NEUTRAL CONDITIONS
WELL INTO NEXT YEAR. THEREFORE THE SUITE OF TEMPERATURE AND PRECIPITATION
FORECASTS DOES NOT USE COMPOSITES BASED ON EL NINO OR LA NINA.
THE TEMPERATURE OUTLOOK FOR DJF 2008-09 CALLS FOR ABOVE AVERAGE TEMPERATURES
ACROSS MUCH OF ALASKA, AND THE CENTRAL AND SOUTHWESTERN SECTIONS OF THE
CONTINENTAL U.S. THESE EXPECTED AREAS OF ABOVE AVERAGE TEMPERATURES ARE
DUE PRIMARILY TO RECENT TEMPERATURE TRENDS AND FOLLOW FAIRLY CLOSELY THE
OBJECTIVE CONSOLIDATION FORECAST, WHICH INCLUDES THE STATISTICAL FORECAST TOOLS
AND THE CFS FORECAST. ELSEWHERE, EQUAL CHANCES OF BELOW-, NEAR-, AND ABOVE
AVERAGE TEMPERATURES ARE PREDICTED.
THERE IS AN ENHANCED LIKELIHOOD OF BELOW-MEDIAN PRECIPITATION FOR DJF 2008-09
ACROSS MUCH OF THE SOUTHERN CONTIGUOUS UNITED STATES AS INDICATED PRIMARILY
BY THE OBJECTIVE CONSOLIDATION AND THE CFS DYNAMICAL MODEL. ABOVE-MEDIAN
PRECIPITATION IS EXPECTED FROM THE NORTHERN PANHANDLE OF TEXAS TO MISSOURI.
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 CONTINUED DURING MID-OCTOBER TO MID-NOVEMBER 2008, AS
RECENT INCREASES IN SEA SURFACE TEMPERATURES (SSTS) ABATED ACROSS THE
EQUATORIAL PACIFIC OCEAN. FROM WEST TO EAST, THE LATEST WEEKLY SST INDEX
VALUES RANGE FROM -0.3 C IN THE NINO-4 REGION TO +0.2 C IN THE NINO 1+2 REGION.
THE SUBSURFACE OCEANIC HEAT CONTENT (AVERAGE TEMPERATURES IN THE UPPER 300M OF
THE OCEAN) REMAINED NEAR-CONSTANT AT ABOUT -0.5 DEGREES C BETWEEN 100W AND 180.
ENHANCED LOW-LEVEL EASTERLY WINDS AND UPPER-LEVEL WESTERLY WINDS PERSIST IN
THE CENTRAL AND WESTERN TROPICAL PACIFIC REGION, WHILE CONVECTION, ON AVERAGE,
REMAINS SUPPRESSED OVER THE CENTRAL PACIFIC, AND HAS BEEN INTERMITTENTLY
ENHANCED OVER INDONESIA.
PROGNOSTIC DISCUSSION OF SST FORECASTS
MOST DYNAMICAL AND STATISTICAL SST FORECASTS FOR THE NINO 3.4 REGION PREDICT
SST DEPARTURES IN THE RANGE BETWEEN -0.5 C AND +0.5 C, INDICATING ENSO-NEUTRAL
CONDITIONS THROUGH LATE FALL AND WINTER. MOST NCEP SST FORECASTS MAINTAIN
SLIGHTLY NEGATIVE NINO 3.4 SST ANOMALIES THROUGH 2008 INTO 2009. AN OBJECTIVE
CONSOLIDATION OF NCEP FORECASTS SUGGESTS THAT NINO 3.4 SST ANOMALIES ARE MOST
LIKELY TO REMAIN SLIGHTLY BELOW ZERO THROUGH THE SPRING OF 2009. CONSIDERING
CURRENT OBSERVATIONS AND SST FORECASTS FROM STATISTICAL AND DYNAMICAL MODELS
FROM NCEP AND FROM OTHER CENTERS NOT INCLUDED IN THE CONSOLIDATION FORECAST,
ENSO-NEUTRAL CONDITIONS ARE CONSIDERED MOST LIKELY THROUGH EARLY 2009 WITH NINO
3.4 SST ANOMALIES EXPECTED TO BE WITHIN ONE HALF OF ONE DEGREE
CELSIUS OF ZERO.
PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS
THE TEMPERATURE AND PRECIPITATION OUTLOOKS FOR ALL LEAD TIMES ARE BASED ON THE
CONSOLIDATION (CON), A SKILL-WEIGHTED AND CALIBRATED OBJECTIVE BLEND OF THE CFS,
SMLR, OCN, CCA AND ECCA FORECAST TOOLS. OTHER TOOLS - IRI, ECPC AND CAS - ARE
CONSIDERED AND USED MOSTLY FOR MINOR ADJUSTMENT OF THE FORECAST. THE CON
FORECAST IS NOT AVAILABLE FOR ALASKA, SO THE FORECAST THERE IS BASED ON THE
FORECASTERS COMBINING OCN, CCA, SMLR AND THE CFS FORECASTS. THE ENSO STATE IS
NOT EXPECTED TO HAVE A SIGNIFICANT IMPACT ON THE COMING SEASONAL TEMPERATURE
AND PRECIPITATION OUTLOOKS. THE TEMPERATURE AND PRECIPITATION OUTLOOKS FROM DJF
2008-09 TO DJF 2009-10 ARE GUIDED THE CON FORECAST AS A FIRST-GUESS.
PROGNOSTIC DISCUSSION OF OUTLOOKS - DJF 2008 TO DJF 2009
TEMPERATURE:
THE TEMPERATURE OUTLOOK FOR DJF 2008-09 INDICATES ENHANCED PROBABILITIES OF
ABOVE AVERAGE TEMPERATURES FROM THE NORTHERN PANHANDLE OF TEXAS TO MISSOURI, AS
WELL AS FOR MUCH OF ALASKA. WITH CURRENT ENSO-NEUTRAL CONDITIONS IN PLACE, THE
EXPECTATION FOR ABOVE AVERAGE TEMPERATURES DURING THE DJF 2008-09 SEASON ARE
LARGELY DUE TO RECENT TEMPERATURE TRENDS. ELSEWHERE, EQUAL CHANCES OF BELOW-,
NEAR- AND ABOVE-AVERAGE TEMPERATURES ARE PREDICTED. THIS INCLUDES THE WESTERN
CONTIGUOUS U.S. WHERE THE CONSOLIDATION SIGNAL IS VERY WEAK, AND THERE ARE
NOTABLE DISAGREEMENTS BETWEEN THE OTHER DYNAMICAL AND STATISTICAL TOOLS.
TEMPERATURE FORECASTS AFTER DJF 2008-09 PRIMARILY FOLLOW THE CONSOLIDATION
FORECAST DERIVED FROM THE CFS, CCA, OCN, ECCA AND SMLR. SUB-NORMAL
TEMPERATURES ARE PREDICTED OVER THE NORTHWEST IN JFM AND FMA BASED ON THE
DYNAMICAL MODELS AND THE SMLR. THIS FEATURE MAY BE RELATED TO THE POSSIBLE
INFLUENCE OF THE MULTI-DECADAL PDO. THE OUTLOOKS FOR ALASKA ARE DERIVED MAINLY
FROM THE RECENT TEMPERATURE TRENDS WITH SECONDARY SUPPORT FROM OTHER TOOLS.
PRECIPITATION:
GREATER THAN CLIMATOLOGICAL PROBABILITIES FOR BELOW MEDIAN PRECIPITATION OVER
MUCH OF THE SOUTHERN CONTIGUOUS U.S. DURING THE DJF 2008-09 SEASON ARE DERIVED
PRIMARILY FROM THE OBJECTIVE CONSOLIDATION, ECCA, SKILL-MASKED CFS, SMLR, AND
IRI FORECASTS. ELSEWHERE, EQUAL CHANCES OF BELOW-, NEAR- AND ABOVE-MEDIAN
PRECIPITATION ARE PROJECTED. FOR JFM 2008-09 AND FMA 2009 THE SAME TOOLS WERE
USED, IN ADDITION TO THE CAS TOOL WHICH SHOWED SKILL FOR THE AREA OF RELATIVE
WETNESS CENTERED NEAR OKLAHOMA. FOR FMA AND MAM 2009, THE DRY SIGNAL OVER THE
SOUTHEAST IS RETAINED, MAINLY DUE TO RECENT TRENDS. THE ABOVE AVERAGE
PRECIPITATION FORECAST FOR COASTAL AREAS IN THE SOUTHEAST IN JAS AND ASO 2009
ARE RELATED TO INCREASED TROPICAL ACTIVITY DURING RECENT YEARS. THE DRY SIGNAL
OVER THE PACIFIC NORTHWEST DURING JJA, JAS AND ASO 2009 RESULTS FROM
PREDICTABLE PRECIPITATION TRENDS AS INDICATED BY THE CONSOLIDATION. THE
PRECIPITATION OUTLOOK OVER 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: 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 DEC 18 2008
1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17, 2001
FORECAST RELEASE.
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