PROGNOSTIC DISCUSSION FOR LONG-LEAD HAWAIIAN OUTLOOKS NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD 830AM EDT THU SEP 21 2017 MONTHLY FORECAST DISCUSSION VALID OCTOBER 2017 SEA SURFACE TEMPERATURE (SST) ANOMALIES SURROUNDING THE HAWAIIAN ISLANDS ARE CURRENTLY BETWEEN POSITIVE ONE-HALF DEGREE AND ONE DEGREE C, WITH THE GREATEST ANOMALIES NEAR THE NORTHWESTERN ISLANDS. FOR JANUARY 2017 THROUGH THE END OF AUGUST 2017, RAINFALL TOTAL ACCUMULATIONS WERE: - LIHUE AIRPORT 17.88 INCHES (83 PERCENT OF NORMAL) - HONOLULU AIRPORT 15.89 INCHES (179 PERCENT OF NORMAL) - KAHULUI AIRPORT 15.10 INCHES (141 PERCENT OF NORMAL) - HILO AIRPORT 53.62 INCHES (67 PERCENT OF NORMAL) THE NCEP CLIMATE FORECAST SYSTEM (CFS) AND OTHER CLIMATE MODELS RUN AS A PART OF THE NORTH AMERICAN MULTI-MODEL ENSEMBLE (NMME) PREDICT ABOVE NORMAL SSTS AROUND THE HAWAIIAN ISLANDS TO CONTINUE FOR OCTOBER 2017. THIS ELEVATES THE CHANCES OF ABOVE NORMAL MONTHLY MEAN AIR TEMPERATURES FOR THE HAWAIIAN ISLANDS IN OCTOBER 2017. EQUAL CHANCES (EC) FOR ABOVE, NEAR, OR BELOW MEDIAN PRECIPITATION ARE INDICATED BY DYNAMICAL MODEL FORECASTS FOR HAWAII DURING OCTOBER 2017. TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV HILO A55 75.7 0.5 EC 7.8 8.6 12.1 KAHULUI A60 78.2 0.4 EC 0.3 0.6 1.1 HONOLULU A65 80.2 0.5 EC 0.5 1.3 1.9 LIHUE A65 78.1 0.3 EC 2.5 3.3 4.2 SEASONAL FORECAST DISCUSSION VALID OND 2017 - OND 2018 REFER TO THE PROGNOSTIC DISCUSSION ON LONG-LEAD SEASONAL OUTLOOKS FOR THE CONUS AND ALASKA, DISCUSSION OF THE FORECASTS OF EQUATORIAL PACIFIC SSTS, AND FOR THE GENERAL BACKGROUND FOR THE SEASONAL FORECAST, INCLUDING DETAILS ON THE CURRENT STATE OF THE ATMOSPHERE AND OCEAN. ENSO-NEUTRAL CONDITIONS REMAIN ACROSS THE EQUATORIAL PACIFIC OCEAN, HOWEVER RECENT CONDITIONS INDICATE AN INCREASING CHANCE OF THE DEVELOPMENT OF LA NINA CONDITIONS BY WINTER. EQUATORIAL SEA SURFACE TEMPERATURES (SSTS) WERE BELOW AVERAGE ACROSS THE CENTRAL AND EASTERN PACIFIC OCEAN IN THE LAST MONTH. NEGATIVE SUBSURFACE TEMPERATURE ANOMALIES STRENGTHENED AT DEPTH BETWEEN 150W AND 100W. ATMOSPHERIC CONVECTION, AS INDICATED BY OUTGOING LONGWAVE RADIATION ANOMALIES, WAS NEAR AVERAGE OVER THE EASTERN PACIFIC, ENHANCED OVER THE MARITIME CONTINENT, AND SUPPRESSED OVER THE CENTRAL PACIFIC OCEAN TO THE NORTH OF THE EQUATOR. THE LOWER-LEVEL TRADE WINDS WERE NEAR AVERAGE OVER THE CENTRAL AND EASTERN PACIFIC AND ENHANCED OVER THE WESTERN PACIFIC, WHILE UPPER-LEVEL WINDS WERE NEAR AVERAGE OVER MOST OF THE TROPICAL PACIFIC OCEAN. THE NCEP CFS AND DYNAMICAL MODELS FROM THE NMME ARE NOW INDICATING AN INCREASED PROBABILITY OF LA NINA CONDITIONS DEVELOPING BY WINTER. STATISTICAL MODELS AND THE CPC NINO 3.4 SST CONSOLIDATION FORECAST INDICATE AN INCREASED BUT RELATIVELY LOWER PROBABILITY OF LA NINA, COMPARED TO THE NMME MODELS. IN THE OFFICIAL OUTLOOK, A LA NINA IS LIKELY TO DEVELOP FOR NORTHERN HEMISPHERE WINTER 2017-18. ENHANCED PROBABILITIES FOR ABOVE NORMAL TEMPERATURES ARE INDICATED FOR HAWAII FROM OND 2017 TO FMA 2018 DUE TO PREDICTED ANOMALOUSLY ABOVE NORMAL SEA SURFACE TEMPERATURES ACROSS THE REGION. EQUAL CHANCES (EC) FOR ABOVE, NEAR, OR BELOW NORMAL TEMPERATURES ARE INDICATED AT ALL LOCATIONS FOR MAM 2018 AND BEYOND. THERE IS SOME UNCERTAINTY WITH THE PRECIPITATION FORECAST FROM DYNAMICAL AND STATISTICAL TOOLS FOR HAWAII FOR OND TO NDJ 2017. EQUAL CHANCES (EC) FOR ABOVE, NEAR, OR BELOW NORMAL PRECIPITATION ARE INDICATED FOR HAWAII FROM OND TO NDJ 2018. FOR THE WINTER SEASONS FROM DJF 2018 TO JFM 2018, A GREATER PROBABILITY OF ABOVE NORMAL PRECIPITATION IS INDICATED BY AVAILABLE TOOLS. THE DYNAMICAL MODEL FORECASTS FROM THE NMME INDICATE A MORE RAPID ONSET OF LA NINA ALONG WITH GREATER PROBABILITIES FOR ABOVE NORMAL PRECIPITATION BEGINNING IN EARLIER MONTHS, COMPARED TO STATISTICAL FORECASTS, AS WELL AS CONTINUATION OF HIGHER PROBABILITIES FOR ABOVE NORMAL PRECIPITATION INTO EARLY SPRING. THE CPC CONSTRUCTED ANALOG (CA), CANONICAL CORRELATION ANALYSIS (CCA), AND ENSO REGRESSIONS BASED ON THE CPC NINO 3.4 SST CONSOLIDATION INDICATE GREATER UNCERTAINTY IN EARLY LEADS, BUT INCREASING PROBABILITY FOR ABOVE NORMAL PRECIPITATION IN DJF AND JFM 2018, AND A TRANSITION TO GREATER LIKELIHOOD FOR BELOW NORMAL PRECIPITATION FOR HAWAII BY MAM AND AMJ 2018. EQUAL CHANCES (EC) FOR ABOVE, NEAR, OR BELOW NORMAL PRECIPITATION ARE FORECAST FOR LIHUE, HONOLULU, KAHULUI, AND HILO IN MJJ 2018 AND LONGER LEADS. HILO TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV OND 2017 A65 75.5 0.4 EC 28.3 34.5 42.0 NDJ 2017 A60 74.2 0.4 EC 26.4 36.6 43.0 DJF 2018 A60 72.8 0.4 A40 19.6 30.2 33.3 JFM 2018 A55 71.8 0.4 A40 22.0 32.0 44.5 FMA 2018 A45 71.7 0.4 EC 24.6 34.1 45.5 MAM 2018 EC 72.0 0.5 B40 22.5 28.4 34.0 AMJ 2018 EC 72.9 0.5 B40 21.4 23.7 29.0 MJJ 2018 EC 74.0 0.4 EC 20.2 27.5 29.1 JJA 2018 EC 75.2 0.4 EC 19.4 27.2 31.4 JAS 2018 EC 76.1 0.4 EC 25.2 28.6 33.4 ASO 2018 EC 76.4 0.4 EC 26.1 28.8 33.3 SON 2018 EC 76.2 0.4 EC 24.3 30.2 40.8 OND 2018 EC 75.5 0.4 EC 28.3 34.5 42.0 \N KAHULUI TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV OND 2017 A65 77.8 0.4 EC 4.2 5.3 8.1 NDJ 2017 A60 75.9 0.4 EC 5.2 7.6 9.5 DJF 2018 A60 73.8 0.4 A40 4.6 6.9 8.7 JFM 2018 A55 72.5 0.4 A40 4.2 6.2 8.2 FMA 2018 A45 72.3 0.4 EC 3.2 4.1 6.4 MAM 2018 EC 73.0 0.4 B40 2.5 3.5 4.6 AMJ 2018 EC 74.3 0.5 B40 1.2 1.6 2.2 MJJ 2018 EC 76.0 0.5 EC 0.7 1.1 1.8 JJA 2018 EC 77.7 0.4 EC 0.7 1.1 1.5 JAS 2018 EC 79.0 0.4 EC 0.8 1.1 1.6 ASO 2018 EC 79.4 0.4 EC 0.8 1.6 2.5 SON 2018 EC 79.1 0.4 EC 2.1 3.3 4.8 OND 2018 EC 77.8 0.4 EC 4.2 5.3 8.1 \N HONOLULU TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV OND 2017 A70 80.0 0.4 EC 4.4 6.4 8.5 NDJ 2017 A65 77.7 0.5 EC 3.9 5.6 8.8 DJF 2018 A60 75.3 0.5 A40 3.7 5.6 8.6 JFM 2018 A55 73.9 0.4 A40 2.1 4.6 7.8 FMA 2018 A45 73.8 0.4 EC 1.9 3.2 4.7 MAM 2018 EC 74.8 0.4 B40 1.8 2.6 3.0 AMJ 2018 EC 76.3 0.4 B40 1.2 1.6 1.8 MJJ 2018 EC 78.2 0.4 EC 0.8 1.4 1.6 JJA 2018 EC 79.9 0.4 EC 0.7 0.8 1.3 JAS 2018 EC 81.3 0.4 EC 1.0 1.4 1.7 ASO 2018 EC 81.7 0.4 EC 1.6 2.4 3.1 SON 2018 EC 81.4 0.4 EC 2.5 4.0 5.6 OND 2018 EC 80.0 0.4 EC 4.4 6.4 8.5 \N LIHUE TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV OND 2017 A70 77.8 0.3 EC 9.2 11.7 15.6 NDJ 2017 A65 75.7 0.3 EC 8.6 12.1 16.9 DJF 2018 A65 73.6 0.4 A40 7.5 8.4 14.0 JFM 2018 A60 72.2 0.4 A40 6.5 8.8 13.8 FMA 2018 A50 72.1 0.5 EC 5.8 8.4 9.9 MAM 2018 EC 72.8 0.5 B40 5.3 6.6 8.0 AMJ 2018 EC 74.2 0.5 B40 4.7 5.5 6.0 MJJ 2018 EC 76.0 0.5 EC 4.9 5.4 5.9 JJA 2018 EC 77.7 0.4 EC 4.4 5.3 6.9 JAS 2018 EC 79.0 0.3 EC 5.3 6.1 7.8 ASO 2018 EC 79.4 0.3 EC 6.2 7.9 8.4 SON 2018 EC 79.1 0.3 EC 9.2 10.0 11.2 OND 2018 EC 77.8 0.3 EC 9.2 11.7 15.6 \NFORECASTER: DAN COLLINS ANOMALIES BASED ON 1981-2010 MEANS CLARIFICATION: EC INDICATES EQUAL CHANCES THAT THE CLIMATE WILL FALL INTO ANY ONE OF THE THREE RANGES OR CATEGORIES WHOSE BOUNDARIES ARE SPECIFIED IN THE TABLES ABOVE. A FORECAST SPECIFICATION OF EC MEANS THERE IS NO PARTICULAR TILT OF THE ODDS TOWARD ABOVE-NORMAL OR BELOW-NORMAL CONDITIONS IN THE OUTLOOK. FOR EXAMPLE A40 MEANS A 40% CHANCE THAT TEMPERATURE OR PRECIPITATION WILL BE IN THE ABOVE CLASS, B40 MEANS A 40% PROBABILITY THAT TEMPERATURE OR PRECIPITATION WILL BE IN THE BELOW CLASS, AND N35 MEANS A 35% PROBABILITY THAT TEMPERATURE OR PRECIPITATION WILL BE IN THE NEAR-NORMAL CLASS. WHEN EC IS SPECIFIED, ALL CATEGORIES ARE EQUALLY LIKELY. NOTE - THESE OUTLOOKS ARE INTENDED FOR USE PRIOR TO THE START OF THEIR VALID PERIODS. WITHIN ANY VALID PERIOD OBSERVATIONS AND SHORTER RANGE FORECASTS SHOULD BE CONSULTED. ALSO - THIS SET OF OUTLOOKS WILL BE SUPERSEDED BY THE ISSUANCE OF THE NEW SET NEXT MONTH ON THU OCT 19, 2017. $$