PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD 830 AM EST THU FEB 16 2017 SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS RECENT OCEANIC AND ATMOSPHERIC OBSERVATIONS SHOW THAT ENSO-NEUTRAL CONDITIONS HAVE RETURNED TO THE EQUATORIAL PACIFIC OCEAN. THE OFFICIAL CPC ENSO FORECAST FAVORS ENSO-NEUTRAL CONDITIONS TO PERSIST AT LEAST THROUGHOUT BOREAL SPRING, WITH SIGNIFICANT UNCERTAINTY IN THE PHASE OF ENSO BEYOND THAT TIME. THE MARCH-APRIL-MAY (MAM) 2017 TEMPERATURE OUTLOOK FAVORS ABOVE-NORMAL TEMPERATURES EAST OF A LINE THAT RUNS APPROXIMATELY FROM SOUTHERN CALIFORNIA THROUGH EASTERN WYOMING TO NORTHERN MINNESOTA, AND OVER WESTERN ALASKA. PROBABILITIES OF ABOVE-NORMAL TEMPERATURES EXCEED 50-PERCENT OVER PORTIONS OF THE SOUTHWESTERN AND SOUTH-CENTRAL CONUS, AND OVER MUCH OF THE NORTHEAST. THE MAM 2017 PRECIPITATION OUTLOOK INDICATES ENHANCED PROBABILITIES OF ABOVE-MEDIAN PRECIPITATION FROM MICHIGAN WESTWARD ACROSS THE NORTHERN TIER OF STATES TO THE PACIFIC NORTHWEST. BELOW-MEDIAN PRECIPITATION AMOUNTS ARE FAVORED OVER SOUTHWESTERN PORTIONS OF THE COUNTRY, AND ALONG MOST OF THE SOUTHERN COAST OF ALASKA. EQUAL CHANCES (EC) ARE FORECAST OVER AREAS WHERE ODDS OF ABOVE-, BELOW-, OR NEAR-NORMAL 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 AND ATMOSPHERIC OBSERVATIONS INDICATE THAT THE RECENT LA NINA THAT WAS IN PLACE ACROSS THE EQUATORIAL PACIFIC HAS GIVEN WAY TO ENSO-NEUTRAL CONDITIONS. THOUGH A RESIDUAL AREA OF RELATIVELY COOL WATER PERSISTS BETWEEN THE DATE LINE AND ABOUT 160W, SEA SURFACE TEMPERATURES (SSTS) FOR MOST AREAS EAST OF ABOUT 150W ARE NOW ABOVE-AVERAGE. ACCORDING TO THE LATEST ENSO DIAGNOSTIC DISCUSSION ISSUED BY CPC ON 9 FEBRUARY 2017, THE LATEST WEEKLY NINO INDEX VALUES WERE -0.3 DEG C IN THE WESTERNMOST NINO-4 AND NINO-3.4 REGIONS, AND +1.5 DEG C IN THE EASTERNMOST NINO 1+2 REGION. THE UPPER-OCEAN (TOP 300 METERS) HEAT CONTENT ANOMALY INCREASED DURING JANUARY, AND FOR THE FIRST TIME IN NEARLY 11 MONTHS, BECAME SLIGHTLY POSITIVE. THIS REFLECTS THE INCREASE OF ABOVE-AVERAGE TEMPERATURES AT DEPTH. LOW-LEVEL (850-HPA) EASTERLY WINDS WERE SLIGHTLY ENHANCED OVER THE WESTERN TROPICAL PACIFIC, AND UPPER-LEVEL (200-HPA) WINDS WERE NEAR-AVERAGE. THE DOMINANT OUTGOING LONGWAVE RADIATION (OLR) ANOMALY PATTERN FOR THE PAST FEW MONTHS FEATURED ENHANCED CONVECTION ACROSS THE MARITIME CONTINENT REGION, AND SUPPRESSED CONVECTION OVER APPROXIMATELY THE CENTRAL THIRD OF THE TROPICAL PACIFIC. THIS DICHOTOMY IN ANOMALOUS CONVECTION BEARS THE SIGNATURE OF THE LA NINA THAT WAS RECENTLY IN PLACE. THIS PATTERN OF ANOMALOUS CONVECTION IS ALSO CONSISTENT WITH, AND REFLECTIVE OF, A POSITIVELY PHASED INDIAN OCEAN DIPOLE (IOD), WHICH HAS ALSO BEEN IN PLACE FOR SOME TIME. THESE SLOWLY VARYING, LOWER FREQUENCY SIGNALS (THE ENSO AND IOD) HAVE BEEN MODULATING INTRA-SEASONAL SIGNALS AS THEY PASS THROUGH THESE REGIONS. CONSTRUCTIVE INTERFERENCE WOULD RESULT WHEN THE ENHANCED CONVECTIVE PHASES OF THESE INTRA-SEASONAL SIGNALS MOVED ACROSS THE MARITIME CONTINENT REGION, AND DESTRUCTIVE INTERFERENCE WOULD RESULT WHEN THE ENHANCED CONVECTIVE PHASES OF THESE INTRA-SEASONAL SIGNALS MOVED ACROSS THE CENTRAL PACIFIC. PROGNOSTIC DISCUSSION OF SST FORECASTS THE CPC SST CONSOLIDATION FORECAST, WHICH INCLUDES THREE STATISTICAL FORECASTS ALONG WITH THE CFS, PREDICTS ENSO-NEUTRAL CONDITIONS WILL PERSIST FROM NOW UNTIL THE UPCOMING WINTER SEASON, AFTER WHICH A WEAK LA NINA WOULD BE BRIEFLY FAVORED. IN CONTRAST, THE CFS PREDICTS THE ONSET OF A WEAK EL NINO IN MAM 2017, WHICH STRENGTHENS TO MODERATE INTENSITY BY THE UPCOMING SUMMER. THE AMPLITUDE-CORRECTED NMME (NATIONAL MULTI-MODEL ENSEMBLE) PLUME OF NINO 3.4 SST FORECASTS IS GENERALLY IN-BETWEEN THE CFS AND THE CPC CONSOLIDATION FORECAST. THE CPC-IRI-CONSENSUS FORECAST DEPICTS DECREASING ODDS OF ENSO-NEUTRAL DURING THE NEXT FEW MONTHS, AND INCREASING ODDS OF A WARM EVENT. BY JJA AND JAS, THE PROBABILITY OF EITHER SCENARIO BECOMES AROUND 45 PERCENT EACH, WITH ONLY 10 PERCENT REMAINING FOR A COLD EVENT. THOUGH THERE IS A REASONABLE CHANCE OF AN EL NINO OCCURRING DURING THE NEXT COLD SEASON, IT IS TOO EARLY, AND TOO UNCERTAIN AT THIS TIME, TO CONSIDER USING THIS INFORMATION IN THE SEASONAL TEMPERATURE AND PRECIPITATION OUTLOOKS. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS THE OUTLOOKS FOR MAM 2017 THROUGH JAS 2017 ARE BASED ON DYNAMICAL MODEL OUTPUTS FROM THE NMME AND ITS CONSTITUENT INPUTS, BALANCED WITH INPUT FROM THE CPC CONSOLIDATION AND CONSTRUCTED ANALOG BASED ON SSTS (CA-SST). BEYOND JAS 2017, THE OUTLOOKS ARE BASED ON HISTORICAL TRENDS, THE CPC CONSOLIDATION, AND CA-SST. PROGNOSTIC DISCUSSION OF OUTLOOKS - MAM 2017 TO MAM 2018 TEMPERATURE THE OUTLOOK FOR MAM 2017 WAS CHANGED LITTLE FROM LAST MONTH. PROBABILITIES FOR ABOVE-NORMAL TEMPERATURES WERE EXPANDED WESTWARD ACROSS THE GREAT LAKES REGION AND UPPER MISSISSIPPI VALLEY, BASED ON THE NMME AND MANY OF ITS COMPONENT INPUTS (SUCH AS THE CANADIAN CANCM3 AND CANCM4 MODELS, GFDL FLOR, CFS, NCAR, AND NASA). PROBABILITIES FOR ABOVE-NORMAL TEMPERATURES WERE ALSO INCREASED TO 50-PERCENT IN NEW ENGLAND, BASED ON MANY OF THESE SAME DYNAMICAL MODELS. PROBABILITIES FOR RELATIVE WARMTH WERE ALSO INCREASED ACROSS MUCH OF THE EAST, FROM BETWEEN 33-40 PERCENT, TO BETWEEN 40-50 PERCENT. THE FAVORED ABOVE-NORMAL TEMPERATURES IN WESTERN ALASKA (ESPECIALLY THE ALEUTIANS) FOR THE MAM SEASON ARE BASED PRIMARILY ON DYNAMICAL MODEL INPUTS. ONE REGION THAT WAS ORIGINALLY CONSIDERED FOR A FORECAST OF BELOW-NORMAL TEMPERATURES WAS THE NORTH-CENTRAL CONUS, WHERE A ENSO-TREND BASED FORECAST TOOL THAT USES THE CPC SST CONSOLIDATION AS A PREDICTOR INDICATED THIS POTENTIAL. HOWEVER, WITH THE RECENT TRANSITION OF LA NINA TO ENSO-NEUTRAL CONDITIONS, AS WELL AS LITTLE DYNAMICAL MODEL SUPPORT, IT WAS DECIDED NOT TO INCLUDE THIS AREA OF BELOW-NORMAL TEMPERATURES ON THE MAP. FROM AMJ THROUGH JAS 2017, ONLY MINOR ADJUSTMENTS WERE MADE TO THE PREVIOUS OUTLOOKS, BASED PRIMARILY ON DYNAMICAL AND STATISTICAL MODEL GUIDANCE. ACROSS THE WESTERN CONUS, PROBABILITIES FAVORING ABOVE-NORMAL (UPPER-TERCILE) TEMPERATURE ANOMALIES EXPANDED GENERALLY TOWARDS THE NORTHWEST. THE PROBABILITIES IN EXCESS OF 50-PERCENT ACROSS THE SOUTHWEST ARE CONSISTENT WITH SPRINGTIME TEMPERATURE TRENDS. BY MJJ, THE PREDICTED AREA OF EC IS CONFINED TO THE NORTH-CENTRAL CONUS, AND A NOTICEABLE WEAKNESS IN THE PROBABILITIES FOR ABOVE-NORMAL TEMPERATURES TAKES SHAPE FROM THE MIDWESTERN STATES TOWARDS THE CAROLINAS. THIS IS A FEATURE THAT IS PREDICTED BY MANY OF THE DYNAMICAL AND STATISTICAL MODELS, AND THIS SUGGESTS THE POTENTIAL FOR COLDER AIR MASSES TO MOVE THROUGH THIS CORRIDOR. ABOVE-NORMAL TEMPERATURES ARE FAVORED FOR ALL OF ALASKA BY MJJ. IN JJA, THE PROBABILITIES FOR ABOVE-NORMAL TEMPERATURES EXCEEDS 50-PERCENT ACROSS NEW ENGLAND, BASED ON SUCH MODELS AS THE CFS, CALIBRATED NMME AND IRI. BY JAS, THE CORRIDOR OF RELATIVE WEAKNESS NOTED EARLIER (WHICH ALSO CONTAINED SOME EC) FILLS IN COMPLETELY WITH MODEST PROBABILITIES FOR UPPER-TERCILE WARMTH. FROM ASO ONWARD, THE CPC CONSOLIDATION TOOL (WHICH INCORPORATES HISTORICAL TRENDS) AND THE SST-CA TOOL WERE USED. THE GENERAL SHAPE OF THE PREDICTED PATTERN FAVORING RELATIVE WARMTH CONTINUES ACROSS THE CONUS AND ALASKA, THOUGH WITH DIMINISHED PROBABILITIES. DURING THE SON AND OND SEASONS, PROBABILITIES FOR UPPER-TERCILE TEMPERATURE ANOMALIES INCREASE TO OVER 60-PERCENT FOR THE NORTH SLOPE OF ALASKA. THIS IS PRIMARILY ATTRIBUTED TO THE DELAYED ONSET, AND REDUCED COVERAGE OF, SEA ICE FORMATION IN RECENT YEARS. BY FMA AND MAM 2018, THE FAVORED ABOVE-NORMAL TEMPERATURES OVER THE EASTERN CONUS GRADUALLY GIVE WAY TO EC, WHILE THE WARM SIGNAL TREND PERSISTS OVER THE WESTERN CONUS AND ALASKA. PRECIPITATION THE MAM 2017 PRECIPITATION OUTLOOK DEPICTS A FEW DIFFERENCES WITH THE PREVIOUS OUTLOOK. BASED PRIMARILY ON THE DYNAMICAL MODEL SUITE, THE FAVORED AREA OF ABOVE-MEDIAN PRECIPITATION WAS EXPANDED WESTWARD ACROSS THE NORTHERN ROCKIES AND THE PACIFIC NORTHWEST. THE AREA OF FAVORED BELOW-MEDIAN PRECIPITATION OVER THE SOUTHEAST WAS REMOVED DUE TO THE LARGE DIFFERENCES (AND HENCE LARGE UNCERTAINTIES) BETWEEN THE VARIOUS MODELS. THE AREA OF PREDICTED BELOW-MEDIAN (OR LOWER-TERCILE) PRECIPITATION ACROSS THE SOUTHWEST WAS INCREASED IN SIZE, WHILE A SLIVER OF LOWER-TERCILE PRECIPITATION WAS ADDED TO THE SOUTHERN COAST OF ALASKA. THIS LATTER FEATURE IS OFTEN OBSERVED DURING LA NINA WINTERS, AND IS SUPPORTED BY THE NMME, THE CANADIAN CANCM3 MODEL, GFDLS FLOR AND CM2.1 MODELS, AND NCARS CCSM4 AND CESM MODELS. THE CFS AND INTERNATIONAL MULTI-MODEL ENSEMBLE (IMME), HOWEVER, DID NOT PREDICT THIS FEATURE. DURING AMJ AND MJJ 2017, THE ONLY SIGNAL CONSIDERED RELIABLE WAS AN AREA OF ABOVE-MEDIAN PRECIPITATION ACROSS THE NORTHWESTERN PORTION OF THE LOWER 48 STATES. THE NMME AND CFS ALSO PREDICTED EXTENSIONS OF THIS WET AREA INTO THE SOUTHWEST, BUT THESE WERE DEEMED UNRELIABLE. BY JJA AND JAS, AN AREA OF BELOW-MEDIAN PRECIPITATION IS FAVORED ACROSS THE NORTHWEST, WHICH IS A FAIRLY RELIABLE TREND SIGNAL, AS IS THE FAVORED WET SIGNAL OVER THE NORTHEAST. THE LATTER SIGNAL CONTINUES THROUGH ASO. FOR SON AND OND, THERE ARE NO RELIABLE PRECIPITATION SIGNALS, HENCE THE NATIONAL FORECAST OF EC. FROM NDJ 2017 THROUGH MAM 2018, THE PRECIPITATION OUTLOOKS ARE PRIMARILY BASED ON HISTORICAL TRENDS, BUT ALSO ON THE SST-CA TOOL. LOWER-TERCILE PRECIPITATION IS FAVORED FOR PARTS OF THE WEST COAST AND GULF COAST IN BOTH NDJ AND DJF. THIS SIGNAL OF RELATIVE DRYNESS CONTINUES ACROSS THE EASTERN GULF COAST REGION AND EXPANDS ACROSS THE CAROLINAS OUT TO MAM 2018, WHILE A DRY SIGNAL EMERGES OVER THE DESERT SOUTHWEST DURING THE FMA AND MAM 2018 SEASONS. FORECASTER: ANTHONY ARTUSA 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 MAR 16 2017 1981-2010 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 19, 2011 FORECAST RELEASE. $$