PROGNOSTIC DISCUSSION FOR LONG-LEAD HAWAIIAN OUTLOOKS NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD 830AM EDT THU SEP 20 2018 MONTHLY FORECAST DISCUSSION VALID OCTOBER 2018 SEA SURFACE TEMPERATURE (SST) ANOMALIES ARE CURRENTLY AROUND ZERO TO POSITIVE ONE HALF DEGREE C OVER THE NORTHWESTERN HAWAIIAN ISLANDS, AND ABOUT POSITIVE ONE-HALF DEGREE TO POSITIVE ONE DEGREE C OVER THE SOUTHEASTERN ISLANDS. FOR JANUARY 2018 THROUGH THE END OF AUGUST 2018, RAINFALL TOTAL ACCUMULATIONS WERE: - LIHUE AIRPORT 33.67 INCHES (157 PERCENT OF NORMAL) - HONOLULU AIRPORT 9.59 INCHES (112 PERCENT OF NORMAL) - KAHULUI AIRPORT 15.91 INCHES (149 PERCENT OF NORMAL) - HILO AIRPORT 129.81 INCHES (162 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 FOR OCTOBER 2018. THIS ELEVATES THE CHANCES OF ABOVE NORMAL MONTHLY MEAN AIR TEMPERATURES FOR HAWAII IN OCTOBER 2018. MOST DYNAMICAL TOOLS ALSO FAVOR ABOVE NORMAL PRECIPITATION FOR THE HAWAIIAN ISLANDS DURING OCTOBER 2018. TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV HILO A65 75.7 0.5 A45 7.8 8.6 12.1 KAHULUI A65 78.2 0.4 A45 0.3 0.6 1.1 HONOLULU A60 80.2 0.5 A45 0.5 1.3 1.9 LIHUE A60 78.1 0.3 A45 2.5 3.3 4.2 SEASONAL FORECAST DISCUSSION VALID OND 2018 - OND 2019 REFER TO THE PROGNOSTIC DISCUSSION ON LONG-LEAD SEASONAL OUTLOOKS FOR THE CONUS AND ALASKA FOR A 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 CURRENTLY ARE PRESENT ACROSS THE EQUATORIAL PACIFIC OCEAN. EQUATORIAL SEA SURFACE TEMPERATURES (SSTS) ARE ABOVE AVERAGE IN PARTS OF THE CENTRAL AND WESTERN PACIFIC OCEAN. POSITIVE SUBSURFACE TEMPERATURE ANOMALIES HAVE EXPANDED IN THE CENTRAL AND EAST-CENTRAL PACIFIC OCEAN, WHILE A SMALL AREA OF NEGATIVE SUBSURFACE TEMPERATURE ANOMALIES PERSISTS IN THE EASTERN PACIFIC OCEAN. CONVECTION RETURNED TO NEAR AVERAGE OVER THE DATE LINE. ANOMALOUS LOW-LEVEL WESTERLY WINDS WERE EVIDENT OVER THE EAST-CENTRAL AND WESTERN TROPICAL PACIFIC OCEAN, WHILE UPPER-LEVEL WINDS WERE WESTERLY OVER THE EASTERN PACIFIC OCEAN. MOST MODELS INDICATE ABOUT 50-55% CHANCE OF EL NINO ONSET DURING THE NORTHERN HEMISPHERE FALL 2018, INCREASING TO 65-70% DURING WINTER 2018-19. ENHANCED PROBABILITIES FOR ABOVE NORMAL TEMPERATURES ARE INDICATED FOR HAWAII FROM OND 2018 TO MAM 2019 DUE TO PREDICTED ABOVE NORMAL SEA SURFACE TEMPERATURES ACROSS THE REGION. EQUAL CHANCES (EC) FOR ABOVE, NEAR, OR BELOW NORMAL TEMPERATURES ARE INDICATED AT ALL LOCATIONS FOR AMJ 2019 AND BEYOND. MOST ENSO FORECAST MODELS PREDICT A WARM EVENT (EL NINO) BY THE NORTHERN HEMISPHERE AUTUMN OR WINTER 2018-19. IF CORRECT, HISTORICAL EL NINO COMPOSITES FAVOR INCREASED ODDS FOR DRY CONDITIONS FOR HAWAII IN WINTER AND SPRING , WHICH IS CONSISTENT WITH THE FORECASTS FROM THE DYNAMICAL TOOLS AND THE STATISTICAL TOOLS (CONSTRUCTED ANALOG AND ENSO-OCN). THERE IS CONSIDERABLE UNCERTAINTY ACROSS THE HAWAIIAN ISLANDS IN THE PRECIPITATION FORECAST AMONG AVAILABLE FORECAST TOOLS IN OND 2018, AND IN MJJ 2019 AND LONGER LEADS, SO EQUAL CHANCES (EC) FOR ABOVE, NEAR, OR BELOW NORMAL PRECIPITATION ARE INDICATED. HILO TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV OND 2018 A70 75.5 0.4 EC 28.3 34.5 42.0 NDJ 2018 A65 74.2 0.4 B60 26.4 36.6 43.0 DJF 2019 A60 72.8 0.4 B65 19.6 30.2 33.3 JFM 2019 A60 71.8 0.4 B70 22.0 32.0 44.5 FMA 2019 A50 71.7 0.4 B65 24.6 34.1 45.5 MAM 2019 A40 72.0 0.5 B60 22.5 28.4 34.0 AMJ 2019 EC 72.9 0.5 B50 21.4 23.7 29.0 MJJ 2019 EC 74.0 0.4 EC 20.2 27.5 29.1 JJA 2019 EC 75.2 0.4 EC 19.4 27.2 31.4 JAS 2019 EC 76.1 0.4 EC 25.2 28.6 33.4 ASO 2019 EC 76.4 0.4 EC 26.1 28.8 33.3 SON 2019 EC 76.2 0.4 EC 24.3 30.2 40.8 OND 2019 EC 75.5 0.4 EC 28.3 34.5 42.0 KAHULUI TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV OND 2018 A70 77.8 0.4 EC 4.2 5.3 8.1 NDJ 2018 A65 75.9 0.4 B60 5.2 7.6 9.5 DJF 2019 A60 73.8 0.4 B65 4.6 6.9 8.7 JFM 2019 A60 72.5 0.4 B70 4.2 6.2 8.2 FMA 2019 A50 72.3 0.4 B65 3.2 4.1 6.4 MAM 2019 A40 73.0 0.4 B60 2.5 3.5 4.6 AMJ 2019 EC 74.3 0.5 B50 1.2 1.6 2.2 MJJ 2019 EC 76.0 0.5 EC 0.7 1.1 1.8 JJA 2019 EC 77.7 0.4 EC 0.7 1.1 1.5 JAS 2019 EC 79.0 0.4 EC 0.8 1.1 1.6 ASO 2019 EC 79.4 0.4 EC 0.8 1.6 2.5 SON 2019 EC 79.1 0.4 EC 2.1 3.3 4.8 OND 2019 EC 77.8 0.4 EC 4.2 5.3 8.1 HONOLULU TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV OND 2018 A65 80.0 0.4 EC 4.4 6.4 8.5 NDJ 2018 A60 77.7 0.5 B60 3.9 5.6 8.8 DJF 2019 A55 75.3 0.5 B65 3.7 5.6 8.6 JFM 2019 A55 73.9 0.4 B70 2.1 4.6 7.8 FMA 2019 A45 73.8 0.4 B65 1.9 3.2 4.7 MAM 2019 A40 74.8 0.4 B60 1.8 2.6 3.0 AMJ 2019 EC 76.3 0.4 B50 1.2 1.6 1.8 MJJ 2019 EC 78.2 0.4 EC 0.8 1.4 1.6 JJA 2019 EC 79.9 0.4 EC 0.7 0.8 1.3 JAS 2019 EC 81.3 0.4 EC 1.0 1.4 1.7 ASO 2019 EC 81.7 0.4 EC 1.6 2.4 3.1 SON 2019 EC 81.4 0.4 EC 2.5 4.0 5.6 OND 2019 EC 80.0 0.4 EC 4.4 6.4 8.5 LIHUE TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV OND 2018 A60 77.8 0.3 EC 9.2 11.7 15.6 NDJ 2018 A55 75.7 0.3 B60 8.6 12.1 16.9 DJF 2019 A50 73.6 0.4 B65 7.5 8.4 14.0 JFM 2019 A50 72.2 0.4 B70 6.5 8.8 13.8 FMA 2019 A45 72.1 0.5 B65 5.8 8.4 9.9 MAM 2019 A40 72.8 0.5 B60 5.3 6.6 8.0 AMJ 2019 EC 74.2 0.5 B50 4.7 5.5 6.0 MJJ 2019 EC 76.0 0.5 EC 4.9 5.4 5.9 JJA 2019 EC 77.7 0.4 EC 4.4 5.3 6.9 JAS 2019 EC 79.0 0.3 EC 5.3 6.1 7.8 ASO 2019 EC 79.4 0.3 EC 6.2 7.9 8.4 SON 2019 EC 79.1 0.3 EC 9.2 10.0 11.2 OND 2019 EC 77.8 0.3 EC 9.2 11.7 15.6 FORECASTER: LUKE HE ANOMALIES ARE BASED ON THE 1981-2010 MEANS. CLARIFICATION: EC INDICATED EQUAL CHANCES THAT THE PREDICTED PARAMETER WILL FALL INTO ANY ONE OF THE THREE CATEGORIES, WHOSE BOUNDARIES ARE SPECIFIC IN THE TABLES ABOVE. A FORECAST SPECIFICATION OF EC MEANS THERE IS NO PARTICULATE TILT OF THE ODDS TOWARD ABOVE NORMAL OR BELOW NORMAL CONDITIONS IN THE OUTLOOK. FOR EXAMPLE A40 MEANS A 40% CHANCE THAT THE AVERAGE TEMPERATURE OR TOTAL PRECIPITATION WILL BE IN THE ABOVE NORMAL CLASS, B40 MEANS A 40% CHANCE THAT THE AVERAGE TEMPERATURE OR TOTAL PRECIPITATION WILL BE IN THE BELOW NORMAL CLASS, AND N35 MEANS A 35% PROBABILITY THAT THE AVERAGE TEMPERATURE OR TOTAL 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 THE VALID PERIODS. WITHIN ANY VALID PERIOD, OBSERVATIONS AND SHORTER RANGE FORECASTS SHOULD BE CONSULTED. ALSO, THIS SET OF OUTLOOKS WILL BE SUPERSEDED BY THE ISSUANCES OF THE NEW SET NET MONTH, ON THU OCT 18, 2018. $$