382
FXUS05 KWBC 151421
PMD90D
PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD
830 AM EST THU NOV 15 2007
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 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). THE OCN TOOL
REPRESENTS THE TREND.
3) THE TROPICAL 30-60 DAY OSCILLATION - 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) 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.
6) STATISTICAL FORECAST TOOLS - CANONICAL CORRELATION ANALYSIS (CCA)... AND
SCREENING MULTIPLE LINEAR REGRESSION (SMLR).
7) DYNAMICAL FORECAST MODELS... INCLUDING THE NCEP CLIMATE FORECAST SYSTEM
(CFS).
8) AN OBJECTIVE CONSOLIDATION (ABBREVIATED CON IN THE TEXT) OF THE OCN...
CCA... SMLR 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.
LA NINA CONDITIONS CONTINUE TO STRENGTHEN. SEA SURFACE TEMPERATURES (SSTS) ARE
BELOW AVERAGE THROUGHOUT THE CENTRAL AND EASTERN EQUATORIAL PACIFIC OCEAN, WITH
THE LATEST WEEKLY MEAN THERE AVERAGING BETWEEN 2 AND 3 DEGREES C BELOW NORMAL
FROM 140W TO 90W. SSTS IN THE NINO 3.4 REGION (FROM 5N TO 5S AND 170W TO 120W)
ARE A GOOD INDICATOR OF THE STRENGTH OF A LA NINA. SSTS IN THE NINO 3.4 REGION
AVERAGED 1.5 DEGREES C BELOW NORMAL IN EARLY NOVEMBER, WHERE A VALUE OF 1.0 TO
1.5 DEGREES BELOW NORMAL INDICATES THE EXISTENCE OF MODERATE LA NINA
CONDITIONS.
THESE OBSERVATIONS AGREE WITH WHAT MOST DYNAMICAL AND STATISTICAL MODELS HAVE,
FOR SOME TIME, BEEN PREDICTING FOR THIS FALL AND WINTER. THESE FORECASTS AND
OBSERVATIONS SUPPORT A PREDICTION OF MODERATE LA NINA CONDITIONS OVER THE NEXT
FEW MONTHS. THE CONSENSUS OF MODEL FORECASTS FOR NINO 3.4 SSTS INDICATE THAT
THE CURRENT SST ANOMALIES OF BETWEEN 1 AND 2 DEGREES C BELOW NORMAL ARE LIKELY
TO PERSIST THROUGH THE REMAINDER OF THE YEAR... AND THEN GRADUALLY DIMINISH IN
SPRING 2008.
THE TEMPERATURE AND PRECIPITATION OUTLOOKS FOR DECEMBER-JANUARY-FEBRUARY (DJF)
2007-2008 REFLECT LA NINA IMPACTS IN COMBINATION WITH RECENT TRENDS.
TEMPERATURES IN THE PACIFIC NORTHWEST, SECTIONS OF THE GREAT BASIN, NORTHERN
CALIFORNIA, THE NORTHERN ROCKIES AND NORTHERN GREAT PLAINS ARE EXPECTED TO BE
COOLER THAN THE AVERAGE OF RECENT YEARS AND SEASONAL MEANS SHOULD BE MORE IN
LINE WITH THOSE EXPECTED IN THE 1971-2000 CLIMATE BASE PERIOD. THE REMAINDER
OF THE NATION IS LIKELY TO EXPERIENCE ABOVE NORMAL TEMPERATURES, BASED ON A
COMBINATION OF TREND AND LA NINA INFLUENCES.
THE PRECIPITATION OUTLOOK FOR DJF 2007-08 FAVORS ABOVE MEDIAN PRECIPITATION
AMOUNTS IN THE PACIFIC NORTHWEST AND NORTHERN ROCKIES, AND FROM THE CENTRAL
MISSISSIPPI VALLEY NORTHEASTWARD TO THE CENTRAL GREAT LAKES. BELOW MEDIAN
PRECIPITATION AMOUNTS ARE EXPECTED IN THE SOUTHWEST... PARTS OF TEXAS... ALONG
THE GULF COAST AND THROUGHOUT MUCH OF THE SOUTHEASTERN U.S. INCLUDING FLORIDA,
THE MIDDLE ATLANTIC COAST STATES AND COASTAL SECTIONS FROM THE DELMARVA
PENINSULA TO FAR EASTERN SECTIONS OF MASSACHUSETTS. THESE PRECIPITATION
SIGNALS ARE THE EXPECTED RESPONSE TO A MODERATE LA NINA, ALONG WITH A
RELATIVELY SMALL INFLUENCE FROM TRENDS.
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
SEA SURFACE TEMPERATURES (SSTS) ARE SUBSTANTIALLY BELOW AVERAGE IN THE
EQUATORIAL PACIFIC FROM THE SOUTH AMERICAN COAST TO THE DATELINE. SST
ANOMALIES ARE BETWEEN -2 AND -3 C FROM 120W EASTWARD... WHILE TEMPERATURES IN
THE CENTRAL EQUATORIAL PACIFIC ARE MOSTLY BETWEEN 1 AND 2 DEGREES C BELOW
NORMAL. WEEKLY AVERAGE SSTS IN THE NINO 3.4 AND NINO 4 REGIONS IN EARLY
OCTOBER WERE -1.7 C AND -.75 C IN THOSE REGIONS RESPECTIVELY, AND ABOUT -1.5 C
AND -.9 C IN EARLY NOVEMBER. NINO 3 TEMPERATURE IS AT ABOUT -1.9 C, WHILE NINO
1+2 TEMPERATURE HAS WARMED SLIGHTLY FROM -2.4 C IN LATE OCTOBER, TO ABOUT -2.2
C IN EARLY NOVEMBER. OCEAN TEMPERATURES IN THE UPPER 200 M HAVE REMAINED WELL
BELOW NORMAL, WITH LARGEST DEPARTURES OF -4 TO -6 C BETWEEN 130W AND 100W. THE
UPPER OCEAN HEAT CONTENT (THE AVERAGE TEMPERATURE IN THE UPPER 300 METERS OF
THE OCEAN BETWEEN THE DATELINE AND 100W) IS CURRENTLY AT ABOUT -1.2 C BELOW
NORMAL, FURTHER REINFORCING THE LIKELIHOOD OF CONTINUED SUB-NORMAL SSTS.
ANOMALIES IN OUTGOING LONGWAVE RADIATION SHOW SUPRESSED CONVECTION (POSITIVE
ANOMALIES) OVER MUCH OF THE EQUATORIAL PACIFIC... ESPECIALLY NEAR AND JUST WEST
OF THE DATELINE. LOW LEVEL EASTERLY WINDS ARE STRONGER THAN NORMAL OVER THE
CENTRAL TROPICAL PACIFIC. THESE ATMOSPHERIC CIRCULATION ANOMALIES ARE
CONSISTENT WITH LA NINA CONDITIONS.
PROGNOSTIC DISCUSSION OF SST FORECASTS
THERE IS CONSENSUS AMONG SST PREDICTION METHODS THAT NINO 3.4 SSTS WILL REMAIN
AT AROUND 1 DEGREE C OR MORE BELOW NORMAL THROUGH THE REMAINDER OF THE YEAR AND
POSSIBLY INTO EARLY 2008. THE LATEST CFS FORECAST INDICATES DJF SST ANOMALIES
IN THE NINO 3.4 REGION OF AROUND -1.6 C BY NDJ, AND A CONTINUING DROP IN NINO
3.4 SST ANOMALIES TO ABOUT -2 C BELOW NORMAL BY THE JFM SEASON. THE
STATISTICAL TOOLS... THE MARKOV MODEL... CCA... AND CONSTRUCTED ANALOG PREDICT
SST ANOMALIES OF BETWEEN -0.9 AND -1.5 C. A CONSOLIDATION FORECAST BASED ON
CCA, CONSTRUCTED ANALOG (CA), MARKOV AND CFS MODELS PREDICTS GREATEST
ANOMALIES OF ABOUT -1.6 C IN NDJ, WITH A SLIGHT RISE TO -1.4 C IN DJF...
DIMINISHING TO ABOUT -1.1 C BY JFM 2008, -0.8 C BY FMA, AND ZERO BY JAS 2008.
THE CONSOLIDATION METHOD GIVES A 98% CONFIDENCE THAT THE NINO 3.4 SSTS WILL
REMAIN BELOW THE -.5 C THRESHOLD ASSOCIATED WITH LA NINA CONDITIONS THROUGH JFM
2008, AND 80% THROUGH FMA 2008 AND ABOUT A 50% CHANCE BY MAM.
PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS
THE TEMPERATURE OUTLOOKS FOR ALL LEAD TIMES ARE BASED ON THE CONSOLIDATION
(CON) TOOL... WHICH IS A SKILL-AND SPREAD-WEIGHTED OBJECTIVE BLEND OF THE
CFS... CCA... SMLR AND OCN FORECAST TOOLS, AND ON COMPOSITES OF MODERATE LA
NINA EVENTS FROM 1950-2006. PRECIPITATION OUTLOOKS FOR NDJ 2007-2008 THROUGH
MAM 2008 ARE DERIVED ALMOST ENTIRELY FROM COMPOSITES OF MODERATE LA NINAS...
WITH PROBABILITIES ADJUSTED TO REFLECT THE EXPECTED INTENSITY OF THE CURRENT LA
NINA CONDITIONS. THE CON IS NOT AVAILABLE FOR ALASKA... SO THE FORECAST THERE
IS BASED LARGELY ON ANALYSIS OF THE CFS WITH CONSIDERATION OF THE OCN... CCA
AND SMLR. PRECIPITATION OUTLOOKS FOR AMJ 2008 AND BEYOND REFLECT WEAK SIGNALS
FROM LONG TERM TRENDS.
PROGNOSTIC DISCUSSION OF OUTLOOKS - DJF 2007 TO DJF 2008
TEMPERATURE:
THE TEMPERATURE OUTLOOK FOR DJF 2007-08 CALLS FOR ENHANCED CHANCES OF ABOVE
NORMAL TEMPERATURES FOR LARGE PARTS OF THE CONUS, WITH THE EXCEPTION OF THE
WEST, NORTHWEST, THE GREAT BASIN AND SECTIONS OF THE NORTH-CENTRAL CONUS. CPC
TOOLS, WITH THEIR INFLUENCE REFLECTED IN THE CONSOLIDATION, AND ALSO NUMERICAL
MODELS RUN AT OTHER CENTERS. THE IRI MULTI-MODEL ENSEMBLE FORECAST, ALSO
INDICATES HIGH CONFIDENCE IN AN ABOVE NORMAL TEMPERATURE FORECAST IN THE
SOUTH-CENTRAL CONUS, SECTIONS OF THE SOUTHWEST, AND THE CENTRAL CONUS. THE
INFLUENCE OF LA NINA COMPOSITES IS INDICATED BY AN INCREASE IN CONFIDENCE FOR
ABOVE NORMAL TEMPERATURES FROM THE SOUTHERN GREAT PLAINS AND TEXAS TO THE
WESTERN GULF STATES... AND A DECREASE IN THE CHANCES OF TREND-RELATED ABOVE
NORMAL TEMPERATURES FOR THE NORTHERN GREAT PLAINS... THE NORTHERN ROCKIES...
THE PACIFIC NORTHWEST... GREAT BASIN, AND NORTHERN CALIFORNIA. THE SEASONAL
OUTLOOKS FOR DJF 2007-08 THROUGH MAM 2008 LARGELY REFLECT THIS SAME, RELATIVELY
COOL, SEASONAL TEMPERATURE PATTERN FOR THOSE REGIONS. TREND-ADJUSTED LA NINA
COMPOSITES FAVOR NEAR NORMAL TEMPERATURES IN PARTS OF THE NORTHWEST, THE
NORTHERN GREAT PLAINS AND UPPER MISSISSIPPI VALLEY IN JFM. THE TREND DOMINATES
THE TEMPERATURE CONSOLIDATION FORECAST OUTLOOKS BEYOND MAM.
PRECIPITATION:
THE PRECIPITATION OUTLOOK FOR DJF 2007-08 CALLS FOR ELEVATED CHANCES OF ABOVE
MEDIAN PRECIPITATION AMOUNTS IN THE PACIFIC NORTHWEST AND FROM THE CENTRAL
MISSISSIPPI VALLEY, THROUGH SECTIONS OF THE OHIO VALLEY AND TENNESSEE, TO THE
CENTRAL GREAT LAKES. FROM DJF 2007-08 TO MAM 2008... BELOW MEDIAN
PRECIPITATION IS EXPECTED ACROSS MOST OF THE SOUTHERN UNITED STATES WITH
HIGHEST PROBABILITIES IN THE SOUTHWEST, AND THE SOUTHEAST. BELOW-MEDIAN
PRECIPITATION IS ALSO EXPECTED ALONG THE MIDDLE ATLANTIC COAST STATES AND
COASTAL SECTIONS OF SOUTHEASTHERN NEW ENGLAND. THIS FORECAST IS SUPPORTED BY
BOTH THE CONSOLIDATION AND BY TREND-ADJUSTED COMPOSITES BASED ON LA NINA
CONDITIONS. FORECASTS FOR AMJ 2008 AND BEYOND ARE BASED ON LONG-TERM TRENDS
AND THE CONSOLIDATION TOOL. THE LIKELIHOOD OF ABOVE NORMAL PRECIPITATION IS
INCREASED IN FLORIDA FROM JAS-SON 2008, IN SECTIONS OF THE NORTHERN ROCKIES AND
THE NORTHERN GREAT PLAINS IN SON AND OND 2008, AND OVER THE SOUTHERN GREAT
PLAINS IN NDJ AND DJF 2008-09. BELOW MEDIAN PRECIPITATION AMOUNTS ARE EXPECTED
FOR THE PACIFIC NORTHWEST FROM JJA THROUGH SON 2008, AND FOR SECTIONS OF THE
NORTHERN ROCKIES FROM OND 2008-DJF 2008-09, AND FOR SECTIONS OF THE SOUTHEAST
IN DJF 2008-09.
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 20 2007
1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17, 2001
FORECAST RELEASE.
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