Prognostic Discussion for Long-Lead Hawaiian Outlooks NWS Climate Prediction Center College Park MD 830AM EDT Thu Oct 17 2024 MONTHLY FORECAST DISCUSSION VALID NOVEMBER 2024 Sea-surface temperatures (SSTs) near the Hawaiian islands of Kauai, Oahu, and Maui, have warmed during the past few weeks to slightly above average, while SSTs surrounding the Big Island remain close to the 30-year climatological average. From January through September 2024, rainfall total accumulations were: Lihue Airport 23.82 inches (98 percent of average) Honolulu Airport 9.77 inches (93 percent of average) Kahului Airport 10.79 inches (100 percent of average) Hilo Airport 74.97 inches (90 percent of average) The NCEP Climate Forecast System (CFS) and other climate models of the North American Multi-Model Ensemble (NMME) generally predict above average SSTs around the Hawaiian Islands through October 2024 into November 2024. Therefore, above normal temperatures are elevated for Kauai, Oahu, Maui, and the Big Island in November 2024. For the November 2024 precipitation outlook, Equal Chances (EC) of below, near, and above normal is forecast for all of the island chain, as indicated by most dynamical model forecasts, and consistent with a transition from ENSO-neutral to La Niña conditions over the tropical Pacific in the near future. TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV Hilo A40 74.4 0.4 EC 8.7 11.4 17.1 Kahului A50 76.0 0.6 EC 1.2 1.8 2.6 Honolulu A50 77.8 0.6 EC 0.9 1.4 2.1 Lihue A50 75.8 0.5 EC 2.6 3.5 5.5 SEASONAL FORECAST DISCUSSION VALID NDJ 2024 - NDJ 2025 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 continue to be observed over the Pacific Ocean. Equatorial sea surface temperatures (SSTs) are near-to-below-average in the central and eastern Pacific Ocean. Negative subsurface temperature anomalies remain at depth in the central and eastern Pacific Ocean, with positive subsurface temperature anomalies over the western Pacific Ocean. Low-level easterly wind anomalies were observed in the east-central equatorial Pacific Ocean, while upper-level westerly wind anomalies were observed across the eastern Pacific Ocean. Suppressed convection was observed over the Date Line and western equatorial Pacific Ocean. Collectively, the coupled ocean-atmosphere system reflected ENSO-neutral. La Niña is favored to emerge in September-October-November (SON) with a 60% chance, and is expected to persist through January-February-March (JFM) 2025. Enhanced probabilities favoring above normal temperatures are indicated for the Hawaiian islands (Kauai, Oahu, Maui, and the Big Island) in NDJ (November-December-January) 2024, consistent with most dynamical model forecasts from the NMME and C3S. Above normal temperatures are favored to continue through MAM (March-April-May) 2025 in association with the expected La Niña. The forecast signal weakens at longer leads, therefore EC is indicated for Hawaii beginning in AMJ (April-May-June) 2025 and extending through longer leads. Above normal precipitation is forecast throughout the Hawaiian Islands in NDJ 2024 through MAM 2025. This is supported by most dynamical models of the NMME, and to some extent the constructed analog (CA) statistical model. Cold season La Niñas often accentuate the usual trade wind pattern of the lower latitudes, and typically bring increased precipitation to windward locations and increased dryness to leeward locations.The primary exception to this involves the development of Kona Lows, which frequently bring increased rainfall to both windward and leeward sites. Thereafter, beginning in AMJ 2025 and extending through longer leads, the forecast signal decreases, leaving EC in the precipitation outlook. Hilo TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV NDJ 2024 A50 74.2 0.4 A45 26.4 36.6 43.0 DJF 2025 A60 72.8 0.4 A55 19.6 30.2 33.3 JFM 2025 A60 71.8 0.4 A55 22.0 32.0 44.5 FMA 2025 A50 71.7 0.4 A55 24.6 34.1 45.5 MAM 2025 A45 72.0 0.5 A45 22.5 28.4 34.0 AMJ 2025 EC 72.9 0.5 EC 21.4 23.7 29.0 MJJ 2025 EC 74.0 0.4 EC 20.2 27.5 29.1 JJA 2025 EC 75.2 0.4 EC 19.4 27.2 31.4 JAS 2025 EC 76.1 0.4 EC 25.2 28.6 33.4 ASO 2025 EC 76.4 0.4 EC 26.1 28.8 33.3 SON 2025 EC 76.2 0.4 EC 24.3 30.2 40.8 OND 2025 EC 75.5 0.4 EC 28.3 34.5 42.0 NDJ 2025 EC 74.2 0.4 EC 26.4 36.6 43.0 Kahului TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV NDJ 2024 A50 75.9 0.4 A45 5.2 7.6 9.5 DJF 2025 A60 73.8 0.4 A55 4.6 6.9 8.7 JFM 2025 A60 72.5 0.4 A55 4.2 6.2 8.2 FMA 2025 A50 72.3 0.4 A55 3.2 4.1 6.4 MAM 2025 A45 73.0 0.4 A45 2.5 3.5 4.6 AMJ 2025 EC 74.3 0.5 EC 1.2 1.6 2.2 MJJ 2025 EC 76.0 0.5 EC 0.7 1.1 1.8 JJA 2025 EC 77.7 0.4 EC 0.7 1.1 1.5 JAS 2025 EC 79.0 0.4 EC 0.8 1.1 1.6 ASO 2025 EC 79.4 0.4 EC 0.8 1.6 2.5 SON 2025 EC 79.1 0.4 EC 2.1 3.3 4.8 OND 2025 EC 77.8 0.4 EC 4.2 5.3 8.1 NDJ 2025 EC 75.9 0.4 EC 5.2 7.6 9.5 Honolulu TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV NDJ 2024 A50 77.7 0.5 A45 3.9 5.6 8.8 DJF 2025 A60 75.3 0.5 A55 3.7 5.6 8.6 JFM 2025 A60 73.9 0.4 A55 2.1 4.6 7.8 FMA 2025 A50 73.8 0.4 A55 1.9 3.2 4.7 MAM 2025 A45 74.8 0.4 A45 1.8 2.6 3.0 AMJ 2025 EC 76.3 0.4 EC 1.2 1.6 1.8 MJJ 2025 EC 78.2 0.4 EC 0.8 1.4 1.6 JJA 2025 EC 79.9 0.4 EC 0.7 0.8 1.3 JAS 2025 EC 81.3 0.4 EC 1.0 1.4 1.7 ASO 2025 EC 81.7 0.4 EC 1.6 2.4 3.1 SON 2025 EC 81.4 0.4 EC 2.5 4.0 5.6 OND 2025 EC 80.0 0.4 EC 4.4 6.4 8.5 NDJ 2025 EC 77.7 0.5 EC 3.9 5.6 8.8 Lihue TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV NDJ 2024 A50 75.7 0.3 A45 8.6 12.1 16.9 DJF 2025 A60 73.6 0.4 A55 7.5 8.4 14.0 JFM 2025 A60 72.2 0.4 A60 6.5 8.8 13.8 FMA 2025 A50 72.1 0.5 A55 5.8 8.4 9.9 MAM 2025 A45 72.8 0.5 A45 5.3 6.6 8.0 AMJ 2025 EC 74.2 0.5 EC 4.7 5.5 6.0 MJJ 2025 EC 76.0 0.5 EC 4.9 5.4 5.9 JJA 2025 EC 77.7 0.4 EC 4.4 5.3 6.9 JAS 2025 EC 79.0 0.3 EC 5.3 6.1 7.8 ASO 2025 EC 79.4 0.3 EC 6.2 7.9 8.4 SON 2025 EC 79.1 0.3 EC 9.2 10.0 11.2 OND 2025 EC 77.8 0.3 EC 9.2 11.7 15.6 NDJ 2025 EC 75.7 0.3 EC 8.6 12.1 16.9 FORECASTER: Luke He 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 Nov 21, 2024. $$