FXUS05 KWBC 211330 PMD90D PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD 830 AM EST THU DEC 21 2017 SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS LA NINA CONDITIONS CONTINUE ACROSS THE EQUATORIAL PACIFIC OCEAN, AS REPRESENTED IN CURRENT OCEANIC AND ATMOSPHERIC OBSERVATIONS. THE OFFICIAL CPC ENSO FORECAST INDICATES THAT LA NINA IS LIKELY TO PERSIST THROUGH THE NORTHERN HEMISPHERE WINTER 2017-18. A TRANSITION TO ENSO-NEUTRAL CONDITIONS DURING THE MID-TO-LATE SPRING IS FORECAST. ENSO-NEUTRAL CONDITIONS ARE FAVORED TO PERSIST THROUGH AT LEAST THE BOREAL SUMMER. THE JANUARY-FEBRUARY-MARCH (JFM) 2018 TEMPERATURE OUTLOOK FAVORS ABOVE-NORMAL TEMPERATURES ACROSS THE SOUTHERN TIER OF THE CONUS, WITH THE HIGHEST ODDS (GREATER THAN 50 PERCENT) FORECAST ACROSS THE SOUTHWEST. A SLIGHT TILT IN THE ODDS TOWARD ABOVE-NORMAL TEMPERATURES IS FORECAST ALONG THE EAST COAST. ABOVE-NORMAL TEMPERATURES ARE ALSO FAVORED FOR NORTHERN MAINLAND ALASKA AND THE ALEUTIANS. INCREASED CHANCES FOR BELOW-NORMAL TEMPERATURES DURING JFM ARE FORECAST FROM PARTS OF THE PACIFIC NORTHWEST EAST TO THE NORTHERN GREAT PLAINS, UPPER MISSISSIPPI VALLEY, AND GREAT LAKES. BELOW-NORMAL TEMPERATURES ARE ALSO FAVORED FOR SOUTHEAST MAINLAND ALASKA AND THE ALASKA PANHANDLE. THE JFM 2018 PRECIPITATION OUTLOOK INDICATES ENHANCED PROBABILITIES OF ABOVE-NORMAL PRECIPITATION AMOUNTS FOR PARTS OF THE PACIFIC NORTHWEST ALONG WITH NORTHERN AREAS OF THE GREAT BASIN, ROCKIES, AND GREAT PLAINS. INCREASED CHANCES OF ABOVE-NORMAL PRECIPITATION ARE ALSO FAVORED FROM THE GREAT LAKES SOUTH TO THE OHIO AND TENNESSEE VALLEYS ALONG WITH NORTHERN AND WESTERN MAINLAND ALASKA. BELOW-NORMAL PRECIPITATION IS FAVORED FOR PARTS OF THE SOUTHEAST, GULF COAST, CENTRAL AND SOUTHERN GREAT PLAINS, SOUTHWEST, AND MUCH OF CALIFORNIA. THE MOST LIKELY AREA TO RECEIVE BELOW-NORMAL PRECIPITATION AMOUNTS IS SOUTHERN GEORGIA AND FLORIDA. EQUAL CHANCES (EC) ARE FORECAST AMONG AREAS WHERE SEASONAL MEAN TEMPERATURES AND SEASONAL ACCUMULATED PRECIPITATION AMOUNTS ARE EXPECTED TO BE SIMILAR TO CLIMATOLOGICAL PROBABILITIES. 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 OBSERVATIONS INDICATE THAT LA NINA CONDITIONS STRENGTHENED DURING THE PAST TWO MONTHS AS EQUATORIAL SSTS ANOMALIES BECAME INCREASINGLY NEGATIVE FROM THE DATE LINE TO THE SOUTH AMERICAN COAST. ABOVE-NORMAL SSTS ARE CURRENTLY OBSERVED OVER THE WEST PACIFIC. ALTHOUGH SUB-SURFACE TEMPERATURE ANOMALIES WEAKENED SLIGHTLY SINCE OCTOBER, THE EQUATORIAL UPPER-OCEAN ANOMALIES REMAINED LARGELY NEGATIVE FROM 180-100W. THE MOST RECENT ONI VALUE (SEPTEMBER ? NOVEMBER 2017), BASED ON SST DEPARTURES FROM AVERAGE IN THE NINO 3.4 REGION, IS -0.7 DEGREES C. THE RECENT ATMOSPHERIC OBSERVATIONS REMAIN CONSISTENT WITH LA NINA WITH ENHANCED (SUPPRESSED) CONVECTION CENTERED OVER THE MARITIME CONTINENT (DATE LINE). SINCE OCTOBER 2017, THE MADDEN-JULIAN OSCILLATION (MJO) WAS QUITE ACTIVE BUT THE LOW-FREQUENCY STATE REMAINS THE MAJOR INFLUENCE ON ANOMALOUS TROPICAL CONVECTION. ANOMALOUS EASTERLY WINDS AT 850-HPA WERE OBSERVED ACROSS THE CENTRAL EQUATORIAL PACIFIC DURING THE PAST MONTH. THE ENHANCED PHASE OF THE MJO IS FORECAST TO PROPAGATE EAST ACROSS THE WESTERN HEMISPHERE DURING THE NEXT TWO WEEKS AND MAY REEMERGE OVER THE INDIAN OCEAN DURING EARLY JANUARY 2018. THIS EVOLUTION OF THE MJO MAY PLAY A ROLE IN THE CIRCULATION PATTERN AND TEMPERATURES ACROSS THE MID-LATITUDES OF NORTH AMERICA LATER IN JANUARY 2018. PROGNOSTIC DISCUSSION OF SST FORECASTS THE CPC SST CONSOLIDATION FORECAST, WHICH INCLUDES THREE STATISTICAL FORECASTSALONG WITH THE CFS, PREDICTS A TRANSITION FROM LA NINA TO ENSO-NEUTRAL CONDITIONS DURING SPRING 2018 WITH ENSO-NEUTRAL CONDITIONS FAVORED THEREAFTER. THE NORTH AMERICAN MULTI MODEL ENSEMBLE (NMME) ENSEMBLE MEAN FORECAST FOR THE NINO-3.4 SST ANOMALY IS SIMILAR TO THE PREVIOUS MONTH, WITH A GRADUAL TRANSITION TO ENSO-NEUTRAL CONDITIONS AFTER THE NORTHERN HEMISPHERE WINTER. BASED ON THE LATEST OBSERVATIONS AND MODEL FORECASTS, THE OFFICIAL CPC/IRI ENSO OUTLOOK FAVORS ENSO-NEUTRAL CONDITIONS BY AMJ 2018. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS THE TEMPERATURE AND PRECIPITATION OUTLOOKS FOR JFM 2018 WERE BASED ON DYNAMICAL MODEL GUIDANCE AND STATISTICAL TOOLS THAT INCLUDE A CONSTRUCTED ANALOG BASED ON GLOBAL SST ANOMALY PATTERNS AND CANONICAL CORRELATION ANALYSIS THAT USES THE EVOLUTION OF SST AND SEA-LEVEL PRESSURE AS PREDICTORS. CLIMATE EFFECTS TYPICALLY ASSOCIATED WITH LA NINA DURING THE WINTER WERE ALSO USED IN CREATING THE OUTLOOKS FOR JFM 2018. DURING THE NEXT FOUR LEADS (FMA THROUGH MJJ 2018), THE PRIMARY FACTORS IN CREATING THE SUBSEQUENT OUTLOOKS WERE THE CALIBRATED PROBABILISTIC FORECASTS FROM THE NMME. THE LATER OUTLOOKS THROUGH NEXT WINTER 2018-19 WERE BASED ON TRENDS AND THE CPC CONSOLIDATION FORECAST. PROGNOSTIC DISCUSSION OF OUTLOOKS - JFM 2018 TO JFM 2019 TEMPERATURE ABOVE-NORMAL TEMPERATURES DURING JFM 2018 ARE MOST LIKELY (ABOVE 50 PERCENT) TO BE OBSERVED ACROSS THE SOUTHWESTERN CONUS, WHICH IS CONSISTENT WITH LA NINA TEMPERATURE COMPOSITES, VARIOUS STATISTICAL TOOLS, DYNAMICAL MODEL FORECASTS, AND TRENDS. ABOVE-NORMAL TEMPERATURES, ALBEIT WITH LOWER PROBABILITIES, ARE ALSO FAVORED FOR THE GULF COAST STATES AND ALONG THE EAST COAST, BASED ON GOOD AGREEMENT AMONG THE DYNAMICAL MODELS. LA NINA TEMPERATURE COMPOSITES DURING JFM SUPPORT BELOW-NORMAL TEMPERATURES ACROSS THE PACIFIC NORTHWEST, NORTHERN ROCKIES, NORTHERN GREAT PLAINS, AND UPPER MISSISSIPPI VALLEY. STATISTICAL METHODS CONTINUE TO OFFER A COLDER SOLUTION ACROSS THESE AREAS COMPARED TO THE DYNAMICAL MODELS. BELOW-NORMAL TEMPERATURES ARE SLIGHTLY FAVORED FROM THE PACIFIC NORTHWEST TO THE GREAT LAKES REGION, GIVEN THE WELL-ESTABLISHED LA NINA CONDITIONS AND ASSOCIATED TELECONNECTIONS. BELOW-NORMAL TEMPERATURES ARE EXPECTED ACROSS THE CENTRAL AND EASTERN U.S., NORTH OF THE 40TH PARALLEL, TO BEGIN JANUARY 2018. THE MADDEN-JULIAN OSCILLATION (MJO) MAY PLAY A ROLE IN THE OBSERVED TEMPERATURES ACROSS THE MID-LATITUDES OF THE CONUS LATER IN JANUARY. AS OF DECEMBER 19, DYNAMICAL MODEL FORECASTS INDICATE THAT THE ENHANCED PHASE OF THE MJO IS LIKELY TO PROPAGATE EAST TO THE INDIAN OCEAN AT THE BEGINNING OF JANUARY. IF THE MJO EVOLVES IN THIS MANNER, THEN A PATTERN CHANGE FAVORING ABOVE-NORMAL TEMPERATURES MAY OCCUR ACROSS THE CENTRAL AND EASTERN U.S. DURING THE LATTER HALF OF JANUARY. THIS MJO EVOLUTION DURING THE NEXT FEW WEEKS AND THE POTENTIAL FOR CONTINUED SUBSEASONAL VARIABILITY THROUGH THE WINTER ARE A LIMIT FORECAST CONFIDENCE AND PROBABILITIES IN THE TEMPERATURE OUTLOOK FOR JFM 2018. THE TEMPERATURE OUTLOOK FOR FMA 2018 IS SIMILAR TO JFM WITH LITTLE CHANGE AMONG THE DYNAMICAL AND STATISTICAL TOOLS. AS A SHIFT TO ENSO-NEUTRAL CONDITIONS IS LIKELY TO OCCUR DURING THE SPRING, THE TEMPERATURE OUTLOOKS FROM MAM THROUGH MJJ 2018 ARE BASED LARGELY ON THE CALIBRATED PROBABILITY FORECASTS FROM THE NMME ALONG WITH TRENDS. PROBABILITIES FOR ABOVE-NORMAL TEMPERATURES WERE INCREASED SLIGHTLY ACROSS THE SOUTHERN GREAT PLAINS FROM AMJ THROUGH JJA 2018, COMPARED TO THE PREVIOUS OUTLOOK, DUE TO AN INCREASING CHANCE OF DROUGHT AND LOW SOIL MOISTURE CONDITIONS AT THOSE TIME LEADS. DURING THE FALL AND WINTER 2018-19, THE TEMPERATURE OUTLOOKS WERE BASED PRIMARILY ON TRENDS. PRECIPITATION THE JFM 2018 PRECIPITATION OUTLOOK IS BASED ON LA NINA COMPOSITES AND INPUTFROM THE VARIOUS DYNAMICAL MODELS. PRECIPITATION TOOLS FAVOR A TIGHT GRADIENT BETWEEN AREAS FAVORED TO RECEIVE BELOW- AND ABOVE-NORMAL PRECIPITATION ACROSS THE SOUTHERN TO NORTHERN TIER OF THE CONUS, RESPECTIVELY. BASED ON GOOD AGREEMENT AMONG MOST OF THE DYNAMICAL MODEL FORECASTS INCLUDING THE NMME AND IMME, A SLIGHT TILT IN THE ODDS FOR BELOW-NORMAL PRECIPITATION WAS EXPANDED TO INCLUDE NEARLY ALL OF CALIFORNIA THROUGH THEIR WET SEASON. THIS FAVORED AREA FOR BELOW-NORMAL PRECIPITATION IS ALSO CONSISTENT WITH PRECIPITATION COMPOSITES FROM BACK-TO-BACK LA NINA WINTERS. THE HIGHEST PROBABILITIES (EXCEEDING 50 PERCENT FOR BELOW) IN THE PRECIPITATION OUTLOOK FOR JFM ARE FORECAST ACROSS SOUTHERN GEORGIA AND FLORIDA. BASED ON THE LATEST NMME CALIBRATED PROBABILITY FORECAST, BELOW-NORMAL PRECIPITATION IS FAVORED ACROSS THE SOUTHERN HIGH PLAINS THROUGH MJJ 2018. COVERAGE OF FAVORED AREAS FOR ANOMALOUS PRECIPITATION DECREASE DURING THE SUMMER AS FORECAST CONFIDENCE DIMINISHES WITH A WEAKENING SIGNAL AMONG TOOLS AND CONVECTIVE PRECIPITATION BECOME MORE DOMINANT. DURING JJA AND JAS 2017, BELOW (ABOVE)-MEDIAN PRECIPITATION FAVORED FOR THE PACIFIC NORTHWEST (NORTHEAST) IS RELATED TO HISTORICAL TRENDS. FORECASTER: BRAD PUGH THE CLIMATIC NORMALS ARE BASED ON CONDITIONS BETWEEN 1981 AND 2010, FOLLOWING THE WORLD METEROLOGICAL ORGANIZATION CONVENTION OF USING THE MOST RECENT 3 COMPLETE DECADES AS THE CLIMATIC REFERENCE PERIOD. THE PROBABILITY ANOMALIES FOR TEMPERATURE AND PRECIPITATION BASED ON THESE NEW NORMALS BETTER REPRESENT SHORTER TERM CLIMATIC ANOMALIES THAN THE FORECASTS BASED ON OLDER NORMALS. 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/LONG_RANGE/TOOLS.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/PRODUCTS/SOILMST_MONITORING/US/OUTLOOK/OUTLOOK.SHTM L (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 JAN 18 2018 1981-2010 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 19, 2011 FORECAST RELEASE. $$ O