149
FXUS05 KWBC 171335
PMD90D
PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD
830 AM EST THU JAN 17 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 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 - 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) 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.
A RATHER STRONG COLD EVENT (LA NINA) CONTINUES ACROSS THE PACIFIC BASIN. SEA
SURFACE TEMPERATURES (SSTS) ARE WITH THE EXCEPTION OF WESTPAC BELOW AVERAGE
THROUGHOUT THE ENTIRE EQUATORIAL PACIFIC OCEAN. 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 DURING
DECEMBER, WHERE A VALUE OF 1.0 TO 1.5 DEGREES BELOW NORMAL INDICATES THE
EXISTENCE OF MODERATE LA NINA CONDITIONS. SO FAR THERE IS NO SIGN OF WEAKENING.
FORECASTS AND OBSERVATIONS SUPPORT A PREDICTION OF STRONG LA NINA CONDITIONS
FOR FMA 2008, FOLLOWED BY WEAKER LA NINA CONDITIONS THEREAFTER. 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 WILL GRADUALLY DIMINISH DURING FMA AND
MAM (SPRING) 2008.
MOST OF THE NATION, INCLUDING NORTHWEST ALASKA, IS LIKELY TO EXPERIENCE ABOVE
AVERAGE TEMPERATURES, BASED ON A COMBINATION OF TREND AND LA NINA INFLUENCES.
ELSEWHERE... THE FORECAST CALLS FOR EQUAL CHANCES (EC) OF ABOVE-, NEAR-, AND
BELOW AVERAGE TEMPERATURES.
THE PRECIPITATION OUTLOOK FOR FMA 2008 FAVORS ABOVE AVERAGE PRECIPITATION
AMOUNTS IN THE PACIFIC NORTHWEST AND NORTHERN ROCKIES, AND FROM THE CENTRAL
MISSISSIPPI VALLEY NORTHEASTWARD TO THE CENTRAL GREAT LAKES. BELOW AVERAGE
PRECIPITATION AMOUNTS ARE EXPECTED IN THE SOUTHWEST... THE SOUTHERN AND CENTRAL
PLAINS... 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 NEW ENGLAND. ELSEWHERE... THE
FORECAST CALLS FOR EQUAL CHANCES (EC) OF ABOVE-, NEAR-, AND BELOW AVERAGE
PRECIPITATION. THESE PRECIPITATION SIGNALS ARE THE EXPECTED RESPONSE TO A 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 FAR WEST OF THE DATE LINE.
SST ANOMALIES ARE BETTER THAN -2 C FROM 110W TO THE DATELINE. OCEAN
TEMPERATURES IN THE UPPERMOST 200 METERS IN THE EAST PACIFIC HAVE REMAINED WELL
BELOW NORMAL, WITH LARGEST DEPARTURES OF -3 C BETWEEN 130W AND 110W. IN THE
WESTPAC THE SUBSURFACE SHOWS AN EXTENSIVE POSITIVE ANOMALY OF 3.5 C OR A DEEP
THERMOCLINE. ANOMALIES IN OUTGOING LONGWAVE RADIATION SHOW SUPRESSED CONVECTION
(POSITIVE ANOMALIES) OVER MUCH OF THE EQUATORIAL PACIFIC... ESPECIALLY NEAR AND
JUST WEST OF THE DATE LINE. LOW LEVEL EASTERLY WINDS ARE STRONGER THAN NORMAL
OVER THE CENTRAL TROPICAL PACIFIC. THESE ATMOSPHERIC CIRCULATION ANOMALIES ARE
CONSISTENT WITH LA NINA CONDITIONS. AN MJO EVENT HAS BEEN MODULATING THE LA
NINA CONDITIONS FOR THE LAST 2 MONTHS AND AFTER A COMPLETE TOUR AROUND THE
EARTH THE MJO'S ENHANCED CONVECTION IS NOW HESITATING TO RE-ENTER THE PACIFIC.
PROGNOSTIC DISCUSSION OF SST FORECASTS
THE STATISTICAL TOOLS... THE MARKOV MODEL... CCA... AND CONSTRUCTED ANALOG
PREDICT SST ANOMALIES OF BETWEEN -0.5 AND -1.3 C FOR FMA. BUT THE CFS REACHES
-2.5 IN FMA BEFORE RELAXING. A CONSOLIDATION FORECAST BASED ON CCA, CONSTRUCTED
ANALOG (CA), MARKOV AND CFS MODELS PREDICTS GREATEST ANOMALIES OF ABOUT -1.0 C
IN FMA 2008, -0.9 C IN MAM 2008, AND CONTINUES TO STEADILY RISE TO NEAR -0.5 C
BY AMJ 2008. BEYOND THIS TIME, ENSO NEUTRAL CONDITIONS ARE PREDICTED BY THE
CONSOLIDATION TOOL AT LEAST THROUGH SON 2008. IT IS TOO EARLY TO SPECULATE
ABOUT NEXT WINTER ALTHOUGH WE NOTE THAT SOME TOOLS OR AT LEAST SOME OF THEIR
ENSEMBLE MEMBERS INDICATE THE POSSIBILITY OF NINO3.4 BEING THE ENTIRE YEAR 2008
ON THE COLD SIDE.
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. IN ADDITION, COMPOSITES OF MODERATE
(WEAK) LA NINA EVENTS FROM 1950-2006 WERE USED FOR FMA AND MAM 2008.
PRECIPITATION OUTLOOKS FOR FMA AND MAM 2008 ARE DERIVED ALMOST ENTIRELY FROM
COMPOSITES OF 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. IT WOULD HAVE BEEN
POSSIBLE TO USE SOIL MOISTURE TOOLS FOR SPRING AND SUMMER BUT THE PRESENT
INITIAL CONDITION ON A NATIONAL BASIS IS RATHER WEAK AND DISORGANIZED.
PROGNOSTIC DISCUSSION OF OUTLOOKS - FMA 2008 TO FMA 2009
TEMPERATURE:
THE TEMPERATURE OUTLOOK FOR FMA 2008 CALLS FOR ENHANCED CHANCES OF ABOVE
AVERAGE TEMPERATURES FOR MOST OF THE SOUTHERN AND CENTRAL CONUS AS WELL AS
NORTHWEST ALASKA. ALONG THE SOUTHERN CA COAST ENHANCED CHANCES FOR BELOW NORMAL
TEMPERATURES ARE PREDICTED DUE TO COLD SST IN THE CALIFORNIA CURRENT. EQUAL
CHANCES (EC) OF ABOVE-, NEAR- AND BELOW AVERAGE TEMPERATURES ARE EXPECTED
ELSEWHERE. THE FMA AND MAM 2008 TEMPERATURE FORECAST IS BASED LARGELY ON
TREND-ADJUSTED LA NINA COMPOSITES, AND CONSIDERATION OF THE CONSOLIDATION TOOL,
THE CFS AND IRI TOOLS, AND CURRENT AND ANTICIPATED LOCATIONS OF SIGNIFICANT
SNOW/ICE COVER. THE TREND DOMINATES THE TEMPERATURE CONSOLIDATION FORECAST
OUTLOOKS BEYOND AMJ. FOR ALL LONGER LEADS THERE ARE AREAS FOR ABOVE NORMAL
TEMPERATURE - PRIMARILY IN THE WEST FROM MJJ THROUGH ASO AND IN THE CENTRAL AND
NORTHERN STATES FOR NEXT WINTER. CHANGES MADE RELATIVE TO THE SET OF FORECASTS
RELEASED A MONTH AGO ARE SMALL.
PRECIPITATION:
THE PRECIPITATION OUTLOOK FOR FMA 2008 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. ELEVATED CHANCES FOR BELOW MEDIAN PRECIPITATION ARE
FORECAST FOR THE SOUTHWEST, THE SOUTHERN ROCKIES, THE SOUTHERN AND CENTRAL
PLAINS, THE SOUTHEAST, AND FROM VIRGINIA AND DELAWARE UP THE IMMEDIATE EAST
COAST TO FAR EASTERN MASSACHUSETTS. THE FAM AND MAM FORECASTS ARE BASED
PRIMARILY ON TREND-ADJUSTED LA NINA COMPOSITES AND TO A LESSER EXTENT ON THE
CONSOLIDATION TOOL. FORECASTS FOR AMJ 2008 AND BEYOND ARE BASED ON LONG-TERM
TRENDS AND THE CONSOLIDATION TOOL. THE LIKELIHOOD OF ABOVE AVERAGE
PRECIPITATION IS INCREASED ACROSS FLORIDA FROM JAS-SON 2008, WHICH COINCIDES
WITH THE EXPECTED BULK OF SEASONAL TROPICAL CYCLONE ACTIVITY. BELOW MEDIAN
PRECIPITATION AMOUNTS ARE EXPECTED FOR SECTIONS OF THE WEST AND PACIFIC
NORTHWEST FROM MAM THROUGH ASO 2008, AND FOR SECTIONS OF THE SOUTHEAST IN DJF
2008-09 AND JFM 2009. ABOVE MEDIAN PRECIPITATION AMOUNTS ARE EXPECTED FOR
SECTIONS OF THE CENTRAL SOUTHERN STATES IN DJF2008/09 THROUGH FMA2009 - THIS IS
BASED ON TREND.
NOTE - AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL
PROBABILITIES) ARE NOW LABELED EC (EQUAL CHANCES).
FORECASTER: HUUG VAN DEN DOOL
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 FEB 21 2008
1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17, 2001
FORECAST RELEASE.
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