Prognostic Meteorological Discussion
Issued by NWS
Issued by NWS
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600 FXHW40 KWBC 191231 PMDHCO Prognostic Discussion for Long-Lead Hawaiian Outlooks NWS Climate Prediction Center College Park MD 830AM EDT Thu Sep 19 2024 MONTHLY FORECAST DISCUSSION VALID OCTOBER 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 August 2024, rainfall total accumulations were: Lihue Airport 23.18 inches (105 percent of average) Honolulu Airport 9.71 inches (101 percent of average) Kahului Airport 10.79 inches (105 percent of average) Hilo Airport 68.22 inches (91 percent of average) The NCEP Climate Forecast System (CFS) and other climate models of the North American Multi-Model Ensemble (NMME) generally predict near average SSTs around the Hawaiian Islands through October 2024, with the exceptions of the IMME and GFDL-SPEAR models which predict an SST anomaly pattern similar to current observations. Given the fact that ocean temperatures typically change very slowly over time, it was decided to go with the IMME and GFDL-SPEAR solutions which agree with current SST observations. Based primarily on the expected persistence of the current SST anomaly pattern, surface temperatures are slightly favored to be above normal for Kauai, Oahu, and Maui, and Equal Chances (EC) of below, near, and above normal for the Big Island through October. For the October 2024 precipitation outlook, below normal precipitation probabilities are elevated for all of the island chain, as indicated by most dynamical model forecasts, and consistent with a transition from ENSO-neutral to La Nia conditions over the tropical Pacific in the near future. TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV Hilo EC 75.7 0.5 B50 7.8 8.6 12.1 Kahului A40 78.2 0.4 B45 0.3 0.6 1.1 Honolulu A40 80.2 0.5 B40 0.5 1.3 1.9 Lihue A40 78.1 0.3 B40 2.5 3.3 4.2 SEASONAL FORECAST DISCUSSION VALID OND 2024 - OND 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 throughout August. Equatorial SSTs are near average throughout most of the 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 over most of the equatorial Pacific, while upper-level easterly wind anomalies were observed over the east-central Pacific. Convection was slightly enhanced over parts of Indonesia and was near average near the Date Line. Collectively, the coupled ocean-atmosphere system reflected ENSO-neutral. Though the onset of La Nia has been delayed from initial projections, it is still favored to emerge in September-October-November (SON) 2024 with a 71% 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 OND (October-November-December) 2024, consistent with most dynamical model forecasts from the NMME and C3S. Above normal temperatures are favored to continue throughout FMA 2025 in association with the expected La Nia, peaking in or around JFM 2025. The forecast signal weakens at longer leads, therefore EC is indicated for Hawaii beginning in MAM 2025 and extending through longer leads. For precipitation, OND 2024 is forecast to be a season of transition for the Hawaiian archipelago, with EC favored. From NDJ 2024 through FMA 2025, elevated probabilities for above normal precipitation are supported by most of the dynamical models and some of the statistical models. Cold season La Nias 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 MAM 2025 and extending through longer leads, the forecast signal decreases, leaving EC as the most likely outcome. Hilo TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV OND 2024 A40 75.5 0.4 EC 28.3 34.5 42.0 NDJ 2024 A40 74.2 0.4 A45 26.4 36.6 43.0 DJF 2025 A40 72.8 0.4 A55 19.6 30.2 33.3 JFM 2025 A40 71.8 0.4 A55 22.0 32.0 44.5 FMA 2025 A40 71.7 0.4 A45 24.6 34.1 45.5 MAM 2025 EC 72.0 0.5 EC 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 Kahului TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV OND 2024 A45 77.8 0.4 EC 4.2 5.3 8.1 NDJ 2024 A45 75.9 0.4 A40 5.2 7.6 9.5 DJF 2025 A45 73.8 0.4 A45 4.6 6.9 8.7 JFM 2025 A45 72.5 0.4 A45 4.2 6.2 8.2 FMA 2025 A45 72.3 0.4 A40 3.2 4.1 6.4 MAM 2025 EC 73.0 0.4 EC 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 Honolulu TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV OND 2024 A45 80.0 0.4 EC 4.4 6.4 8.5 NDJ 2024 A50 77.7 0.5 A40 3.9 5.6 8.8 DJF 2025 A50 75.3 0.5 A45 3.7 5.6 8.6 JFM 2025 A50 73.9 0.4 A45 2.1 4.6 7.8 FMA 2025 A50 73.8 0.4 A40 1.9 3.2 4.7 MAM 2025 EC 74.8 0.4 EC 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 Lihue TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV OND 2024 A45 77.8 0.3 EC 9.2 11.7 15.6 NDJ 2024 A50 75.7 0.3 A45 8.6 12.1 16.9 DJF 2025 A50 73.6 0.4 A55 7.5 8.4 14.0 JFM 2025 A50 72.2 0.4 A55 6.5 8.8 13.8 FMA 2025 A50 72.1 0.5 A45 5.8 8.4 9.9 MAM 2025 EC 72.8 0.5 EC 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 FORECASTER: Anthony Artusa 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 Oct 17, 2024. $$