PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD 830 AM EST THU JAN 18 2018 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, WITH A PREDICTED TRANSITION TO ENSO-NEUTRAL CONDITIONS DURING THE NORTHERN HEMISPHERE SPRING. ENSO-NEUTRAL CONDITIONS ARE FAVORED TO PERSIST THROUGH AT LEAST THE BOREAL SUMMER. THE FEBRUARY-MARCH-APRIL (FMA) 2018 TEMPERATURE OUTLOOK FAVORS ABOVE-NORMAL TEMPERATURES ACROSS THE SOUTHERN TIER OF THE CONUS, WITH THE HIGHEST ODDS (GREATER THAN 60 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 THE NORTH SLOPE OF ALASKA, THE WESTERN COAST OF ALASKA, AND THE ALEUTIANS. INCREASED CHANCES FOR BELOW-NORMAL TEMPERATURES DURING FMA ARE FORECAST FROM PARTS OF THE PACIFIC NORTHWEST EAST TO THE NORTHERN GREAT PLAINS, UPPER AND MIDDLE MISSISSIPPI VALLEYS, AND GREAT LAKES. BELOW-NORMAL TEMPERATURES ARE ALSO FAVORED FOR SOUTHEAST MAINLAND ALASKA AND THE ALASKA PANHANDLE. THE FMA 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 TENNESSEE VALLEY, 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 SOUTHERN 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 CONTINUED DURING THE PAST MONTHS AS EQUATORIAL SSTS ANOMALIES REMAINED NEGATIVE, AT APPROXIMATELY THE SAME MAGNITUDE, FROM THE DATE LINE TO THE SOUTH AMERICAN COAST. THE LATEST WEEKLY NINO-3.4 INDEX VALUE WAS -0.8 DEG C, AND THE NINO-3 AND NINO-1+2 INDICES WERE AT OR BELOW -1.0 DEG C DURING MUCH OF THE MONTH. NEGATIVE SUB-SURFACE TEMPERATURE ANOMALIES IN THE CENTRAL AND EAST-CENTRAL EQUATORIAL PACIFIC WEAKENED AT THE END OF THE MONTH AS ANOMALOUSLY WARM WATERS IN THE WESTERN PACIFIC AT DEPTHS GREATER THAN 100 M PROPAGATED EASTWARD TO APPROXIMATELY 140W. THE MOST RECENT ONI VALUE (OCTOBER – DECEMBER 2017), BASED ON SST DEPARTURES FROM AVERAGE IN THE NINO 3.4 REGION, IS -0.9 DEGREES C. THE ATMOSPHERIC CONDITIONS OVER THE TROPICAL PACIFIC OCEAN ALSO REFLECTED LA NINA, WITH SUPPRESSED CONVECTION NEAR AND EAST OF THE INTERNATIONAL DATE LINE AND ENHANCED CONVECTION TO THE NORTH OF INDONESIA. ALSO, THE LOW-LEVEL TRADE WINDS CONTINUED TO BE STRONGER THAN AVERAGE OVER THE WESTERN AND CENTRAL PACIFIC. THE ENHANCED PHASE OF THE MJO IS FORECAST TO PROPAGATE EAST ACROSS THE MARITIME CONTINENT DURING THE NEXT TWO WEEKS AND MAY REEMERGE OVER THE PACIFIC DURING EARLY FEBRUARY 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 FEBRUARY 2018. LONGER-TERM IMPACTS OF THE MJO ARE UNCERTAIN. PROGNOSTIC DISCUSSION OF SST FORECASTS THE CPC SST CONSOLIDATION FORECAST, WHICH INCLUDES THREE STATISTICAL FORECASTS ALONG 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, THOUGH A LITTLE COOLER THROUGH APRIL, 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 FMA 2018 WERE BASED ON DYNAMICAL MODEL GUIDANCE AND STATISTICAL TOOLS THAT INCLUDE A CONSTRUCTED ANALOG BASED ON GLOBAL SST ANOMALY PATTERNS AND REGRESSIONS OF TEMPERATURE/PRECIPITATION ON THE CPC CONSOLIDATED NINO3.4 OUTLOOKS. DURING THE NEXT FOUR LEADS (MAM THROUGH JJA 2018), THE FACTORS IN CREATING THE SUBSEQUENT OUTLOOKS WERE THE CALIBRATED PROBABILISTIC FORECASTS FROM THE NMME, TRENDS, THE CPC CONSOLIDATION, AND REGRESSIONS OF TEMPERATURE/PRECIPITATION ON THE CPC CONSOLIDATED NINO3.4 OUTLOOKS. THE LATER OUTLOOKS THROUGH NEXT WINTER 2018-19 WERE BASED ON TRENDS AND THE CPC CONSOLIDATION FORECAST. PROGNOSTIC DISCUSSION OF OUTLOOKS - FMA 2018 TO FMA 2019 TEMPERATURE ABOVE-NORMAL TEMPERATURES DURING FMA 2018 ARE MOST LIKELY, WITH A GREATER THAN 60 PERCENT CHANCE, TO BE OBSERVED ACROSS THE SOUTHWESTERN CONUS, WHICH IS CONSISTENT WITH REGRESSIONS OF TEMPERATURE ON LA NINA RELATED OCEANIC CONDITIONS, 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. THE ODDS FOR ABOVE-NORMAL TEMPERATURES FOR THE AREAS FROM THE TENNESSEE VALLEY TO THE MID-ATLANTIC COAST, AND FOR THE CENTRAL CALIFORNIA COAST, ARE SLIGHTLY LOWER THAN WHAT WAS INDICATED FOR FMA 2018 FROM THE DEC 2017 RELEASE. MODELS OUTPUT AND CONSTRUCTED ANALOGS BASED ON SST PATTERNS INDICATE A SLIGHTLY COOLER PATTERN FOR SOME AREAS EAST OF THE ROCKIES, WHEN COMPARED TO LAST MONTH, SO THAT NEWER INFORMATION WAS INCORPORATED. LA NINA TEMPERATURE COMPOSITES DURING FMA SUPPORT BELOW-NORMAL TEMPERATURES ACROSS THE PACIFIC NORTHWEST, NORTHERN ROCKIES, NORTHERN GREAT PLAINS, AND UPPER MISSISSIPPI VALLEY. SOME 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 ALSO FAVORED OVER SOUTHERN ALASKA, SUPPORTED BY MODEL OUTPUTS AND STATISTICALLY BASED RELATIONSHIPS WITH LA NINA. THE TEMPERATURE OUTLOOK FOR MAM 2018 HAS MORE COVERAGE FOR ABOVE-NORMAL TEMPERATURES AND LESS FOR BELOW-NORMAL TEMPERATURES THAN FOR FMA. AREAS WHERE BELOW-NORMAL TEMPERATURES ARE NOW FAVORED ARE RESTRICTED TO THE PACIFIC NORTHWEST AND NORTHERN ROCKIES. TELECONNECTIONS FROM LA NINA TYPICALLY WEAKEN DURING THE SPRING AND A SHIFT TO ENSO-NEUTRAL CONDITIONS IS LIKELY TO OCCUR DURING THE SPRING. THE COOLER SHIFT, RELATIVE TO THE LAST RELEASE AS MENTIONED ABOVE, IS CONTINUED IN THE OUTLOOKS THROUGH AMJ 2018. THE TEMPERATURE OUTLOOKS FROM AMJ THROUGH JJA 2018 ARE BASED LARGELY ON THE CALIBRATED PROBABILITY FORECASTS FROM THE NMME ALONG WITH TRENDS. AN INCREASING CHANCE OF DROUGHT BECOMING ENTRENCHED OVER THE SOUTHWEST AND SOUTHERN PLAINS CONTRIBUTES TO ELEVATED ODDS FOR ABOVE NORMAL TEMPERATURES ELEVATED OVER THOSE REGIONS THROUGH JJA 2018. THE IMPACT OF SOIL MOISTURE ON TEMPERATURE IS MOST PRONOUNCED DURING THE WARM SEASON. PRECIPITATION THE FMA 2018 PRECIPITATION OUTLOOK IS BASED ON PRECIPITATION SIGNALS ASSOCIATED WITH LA NINA AND INPUT FROM THE SUITE OF NMME 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 COVERS PORTIONS OF CENTRAL CALIFORNIA AND ALL OF SOUTHERN CALIFORNIA. THIS FAVORED AREA FOR BELOW-NORMAL PRECIPITATION IS ALSO CONSISTENT WITH PRECIPITATION COMPOSITES FROM BACK-TO-BACK LA NINA WINTERS. THE AREA WHERE BELOW-NORMAL PRECIPITATION IS FAVORED DURING FMA 2018 IS SLIGHTLY SMALLER THAN THE AREA DEPICTED IN LAST MONTH'S FMA OUTLOOK, REFLECTING NEWER MODEL OUTPUT. THE HIGHEST PROBABILITIES (EXCEEDING 50 PERCENT CHANCE FOR BELOW-NORMAL PRECIPITATION) IN THE PRECIPITATION OUTLOOK FOR FMAARE FORECAST ACROSS SOUTHERN GEORGIA AND FLORIDA, AND PORTIONS OF THE SOUTHWEST. 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 BECOMES MORE DOMINANT. DURING JJA AND JAS 2017, BELOW (ABOVE)-NORMAL PRECIPITATION IS FAVORED FOR THE PACIFIC NORTHWEST (NORTHEAST), RELATED TO HISTORICAL TRENDS AND SIGNALS IN THE CPC CON. FORECASTER: MATTHEW ROSENCRANS 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 FEB 15 2018 1981-2010 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 19, 2011 FORECAST RELEASE. $$