Prognostic Discussion for Long-Lead Hawaiian Outlooks NWS Climate Prediction Center College Park MD 830AM EDT Thu May 18 2023 MONTHLY FORECAST DISCUSSION VALID JUNE 2023 During the previous weeks, sea surface temperature (SST) anomalies ranged from zero to one-half degree Celsius around the Big Island to positive one-half to one-degree Celsius (near Maui, Oahu and Kauai). For January through April 2023, rainfall total accumulations were: -Lihue Airport 24.63 inches (175 percent of normal) -Honolulu Airport 8.41 inches (122 percent of normal) -Kahului Airport 8.61 inches (103 percent of normal) -Hilo Airport 56.51 inches (141 percent of normal) The NCEP Climate Forecast System (CFS) and other climate models of the North American Multi-Model Ensemble (NMME) predict above-average SSTs around most of the Hawaiian Islands through June 2023, and near-average SSTs around the Big Island of Hawaii. These SST forecasts support a forecast favoring above-normal temperatures for most islands in June 2023, except Equal Chances (EC) of below, near, and above-normal temperatures are predicted for Hilo. Enhanced chances for below-normal precipitation are predicted for the Big Island of Hawaii in June, while EC is predicted for the northwestern Hawaiian Islands, as indicated by dynamical model forecasts. TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV Hilo EC 75.4 0.4 B40 5.3 6.3 8.7 Kahului A40 78.0 0.5 EC 0.1 0.1 0.2 Honolulu A50 80.3 0.4 EC 0.1 0.2 0.3 Lihue A60 78.1 0.4 EC 1.1 1.3 1.6 SEASONAL FORECAST DISCUSSION VALID JJA 2023 - JJA 2024 Refer to the prognostic discussion of the long-lead seasonal outlooks for the CONUS and Alaska for a description of the ENSO outlook and other climate conditions relevant to the seasonal outlook. ENSO-neutral conditions are observed across the Pacific Ocean. Equatorial SSTs were slightly above-average in the central Pacific Ocean with the most recent weekly Nino 3.4 anomaly around positive 0.5 degrees Celsius. Significantly warmer than average SST anomalies are currently observed in the eastern Pacific Ocean. Positive subsurface temperature anomalies have expanded eastward and increased in amplitude, while remaining mostly at depth except in the eastern Pacific Ocean. Low-level winds have been near their long-term averages in recent weeks, while upper-level wind anomalies were westerly over much of the tropical Pacific. The latest CPC ENSO Outlook, supported by most dynamical and statistical model forecasts, predicts that a transition to El Niño conditions is very likely by the Northern Hemisphere summer, with probabilities exceeding 80 percent. Probabilities exceed 90 percent favoring the persistence of El Niño into the Northern Hemisphere winter. Enhanced probabilities for above-normal temperatures are forecast for most of the Hawaiian Islands (except for the Big Island where EC is favored) from summer (June-July-August) 2023 through autumn (October-November-December) 2023, consistent with most dynamical model forecasts from the NMME and statistical forecasts. The forecast signal weakens at longer leads, therefore Equal Chances (EC) for above, near or below-normal temperatures is indicated for Hawaii beginning in November-December-January 2023 and extending through longer leads. Dynamical models from the NMME show increased confidence this month in predicting enhanced probabilities of below-normal precipitation from summer (June-July-August) through autumn (October-November-December). With the very likely persistence of El Niño conditions into winter, regressions of precipitation on the Niño 3.4 index support likely below normal precipitation continuing from autumn (October-November-December) into winter (December-January-February). Due to considerable uncertainty in the precipitation forecasts from forecast tools at longer leads, EC is indicated over the Hawaiian Islands beginning in the January-February-March 2024 season. Hilo TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV JJA 2023 EC 75.2 0.4 B40 19.4 27.2 31.4 JAS 2023 EC 76.1 0.4 B40 25.2 28.6 33.4 ASO 2023 EC 76.4 0.4 B40 26.1 28.8 33.3 SON 2023 EC 76.2 0.4 B40 24.3 30.2 40.8 OND 2023 EC 75.5 0.4 B50 28.3 34.5 42.0 NDJ 2023 EC 74.2 0.4 B50 26.4 36.6 43.0 DJF 2024 EC 72.8 0.4 B40 19.6 30.2 33.3 JFM 2024 EC 71.8 0.4 EC 22.0 32.0 44.5 FMA 2024 EC 71.7 0.4 EC 24.6 34.1 45.5 MAM 2024 EC 72.0 0.5 EC 22.5 28.4 34.0 AMJ 2024 EC 72.9 0.5 EC 21.4 23.7 29.0 MJJ 2024 EC 74.0 0.4 EC 20.2 27.5 29.1 JJA 2024 EC 75.2 0.4 EC 19.4 27.2 31.4 Kahului TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV JJA 2023 A40 77.7 0.4 B40 0.7 1.1 1.5 JAS 2023 A40 79.0 0.4 B40 0.8 1.1 1.6 ASO 2023 A40 79.4 0.4 B40 0.8 1.6 2.5 SON 2023 A40 79.1 0.4 B40 2.1 3.3 4.8 OND 2023 A40 77.8 0.4 B50 4.2 5.3 8.1 NDJ 2023 EC 75.9 0.4 B50 5.2 7.6 9.5 DJF 2024 EC 73.8 0.4 B40 4.6 6.9 8.7 JFM 2024 EC 72.5 0.4 EC 4.2 6.2 8.2 FMA 2024 EC 72.3 0.4 EC 3.2 4.1 6.4 MAM 2024 EC 73.0 0.4 EC 2.5 3.5 4.6 AMJ 2024 EC 74.3 0.5 EC 1.2 1.6 2.2 MJJ 2024 EC 76.0 0.5 EC 0.7 1.1 1.8 JJA 2024 EC 77.7 0.4 EC 0.7 1.1 1.5 Honolulu TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV JJA 2023 A50 79.9 0.4 B40 0.7 0.8 1.3 JAS 2023 A50 81.3 0.4 B40 1.0 1.4 1.7 ASO 2023 A50 81.7 0.4 B40 1.6 2.4 3.1 SON 2023 A50 81.4 0.4 B40 2.5 4.0 5.6 OND 2023 A40 80.0 0.4 B40 4.4 6.4 8.5 NDJ 2023 EC 77.7 0.5 B40 3.9 5.6 8.8 DJF 2024 EC 75.3 0.5 B40 3.7 5.6 8.6 JFM 2024 EC 73.9 0.4 EC 2.1 4.6 7.8 FMA 2024 EC 73.8 0.4 EC 1.9 3.2 4.7 MAM 2024 EC 74.8 0.4 EC 1.8 2.6 3.0 AMJ 2024 EC 76.3 0.4 EC 1.2 1.6 1.8 MJJ 2024 EC 78.2 0.4 EC 0.8 1.4 1.6 JJA 2024 EC 79.9 0.4 EC 0.7 0.8 1.3 Lihue TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV JJA 2023 A60 77.7 0.4 B40 4.4 5.3 6.9 JAS 2023 A60 79.0 0.3 B40 5.3 6.1 7.8 ASO 2023 A60 79.4 0.3 B40 6.2 7.9 8.4 SON 2023 A60 79.1 0.3 B40 9.2 10.0 11.2 OND 2023 A50 77.8 0.3 B40 9.2 11.7 15.6 NDJ 2023 EC 75.7 0.3 B40 8.6 12.1 16.9 DJF 2024 EC 73.6 0.4 B40 7.5 8.4 14.0 JFM 2024 EC 72.2 0.4 EC 6.5 8.8 13.8 FMA 2024 EC 72.1 0.5 EC 5.8 8.4 9.9 MAM 2024 EC 72.8 0.5 EC 5.3 6.6 8.0 AMJ 2024 EC 74.2 0.5 EC 4.7 5.5 6.0 MJJ 2024 EC 76.0 0.5 EC 4.9 5.4 5.9 JJA 2024 EC 77.7 0.4 EC 4.4 5.3 6.9 FORECASTER: Dan Collins Anomalies are based on the 1991-2020 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 Jun 15, 2023. $$