FXHW40 KWBC 211331 PMDHCO Prognostic Discussion for Long-Lead Hawaiian Outlooks NWS Climate Prediction Center College Park MD 830AM EST Thu Nov 21 2024 MONTHLY FORECAST DISCUSSION VALID DECEMBER 2024 Sea-surface temperatures (SSTs) surrounding the Hawaiian islands have been slightly above average during the past few weeks. From January through October 2024, rainfall total accumulations were: Lihue Airport 24.79 inches (90 percent of average) Honolulu Airport 10.28 inches (86 percent of average) Kahului Airport 11.26 inches (97 percent of average) Hilo Airport 83.14 inches (89 percent of average) Most climate models of the North American Multi-Model Ensemble (NMME) and the International Multi-Model Ensemble (IMME or C3S) favor near normal SSTs around the Hawaiian Islands in December 2024. A few solutions lean towards above normal SSTs, especially for Kauai, while only the NCEP Climate Forecast System (CFSv2) favors below normal SSTs for this period. Based primarily on these SST predictions, Equal Chances (EC) of below, near, and above normal temperatures are favored for the Big Island, Maui, and Oahu in December, and a slight tilt towards above normal temperatures is favored for Kauai. For the December 2024 precipitation outlook, the C3S generally favors near normal precipitation with two constituent models leaning towards relatively wet conditions (Meteo-France and ECMWF), two models supporting relatively dry conditions (DWD and CMCC), and two favoring mixed conditions (CFSv2 and UKMO). The NMME inputs depicted mixed results at best. Therefore, EC appears to be the best bet for the December 2024 precipitation outlook. These weak temperature and precipitation signals are to be expected given the weak ENSO forcing currently ongoing in the Pacific (see below). TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV Hilo EC 72.5 0.4 EC 6.8 10.2 13.6 Kahului EC 73.5 0.5 EC 1.9 2.7 3.4 Honolulu EC 74.9 0.6 EC 0.8 1.3 3.8 Lihue A40 73.3 0.5 EC 1.8 3.2 5.5 SEASONAL FORECAST DISCUSSION VALID DJF 2024 - DJF 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 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, with positive subsurface temperature anomalies continuing over the western Pacific. A relatively small area of low-level easterly wind anomalies was observed in the east-central equatorial Pacific Ocean, while upper-level wind anomalies were near average. Suppressed convection was observed over the vicinity of the Date Line and equator, while near to slightly enhanced convection was noted across eastern Indonesia. Collectively, the coupled ocean-atmosphere system reflected ENSO-neutral. La Niña is most likely to emerge in October-November-December (OND 2024) with a 57% 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 DJF (December-January-February) 2024-25, consistent with practically all C3S dynamical model forecasts, a majority of the NMME dynamical model forecasts, and (for the Big Island and Maui) the statistical ENSO-OCN tool. Probabilities favoring above normal temperatures are expected to increase from southeast to northwest across the island chain. Above normal temperatures are favored by practically all NMME and C3S model inputs during January-February-March (JFM) and February-March-April (FMA) 2025, though the ENSO-OCN favors near normal temperatures. Nearly all models that constitute the NMME favor relatively warm temperatures across the archipelago during March-April-May (MAM) and April-May-June (AMJ) 2025. Beyond AMJ 2025, the forecast signal weakens at longer leads, in large part due to the lack of clear forcing from ENSO and the climatological Spring Barrier. Therefore, EC is indicated for Hawaii beginning in May-June-July (MJJ) and extending through longer leads. For DJF 2024-25 precipitation, most NMME and C3S dynamical model forecasts depict above normal precipitation across Hawaii, with Meteo-France the main outlier favoring relatively dry conditions. The statistical consolidation tool (Stat-CON) and its constituents (Canonical Correlation Analysis (CCA), Optimal Climate Normals (OCN), Constructed Analog (CA) and ENSO-OCN) provide conflicting indications amid very weak precipitation signals from DJF through the winter months and into spring 2025. In JFM 2025, above normal precipitation continues to be favored by most NMME solutions, though the GFDL Spear forecasts mixed conditions over the islands. The IMME/C3S solutions also mostly favor relatively wet conditions, though once again the exception is the Meteo-France model which leans dry. For FMA, the C3S inputs Meteo-France and CMCC (Canadian) favor a mixed precipitation signal for Hawaii, with the majority of models favoring above normal precipitation. For the NMME, nearly all models predict above normal precipitation, except for the relatively dry GFDL-Spear solution. Most of the NMME suite of models continue to favor the theme of anomalous wetness through MAM 2025, though by AMJ the uncertainty increases significantly, favoring EC for the archipelago. The lack of strong forcing from ENSO warrants EC for the remaining precipitation leads. Hilo TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV DJF 2025 A40 72.8 0.4 A40 19.6 30.2 33.3 JFM 2025 A50 71.8 0.4 A50 22.0 32.0 44.5 FMA 2025 A50 71.7 0.4 A50 24.6 34.1 45.5 MAM 2025 A50 72.0 0.5 A40 22.5 28.4 34.0 AMJ 2025 A40 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 DJF 2026 EC 72.8 0.4 EC 19.6 30.2 33.3 Kahului TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV DJF 2025 A50 73.8 0.4 A45 4.6 6.9 8.7 JFM 2025 A55 72.5 0.4 A55 4.2 6.2 8.2 FMA 2025 A60 72.3 0.4 A55 3.2 4.1 6.4 MAM 2025 A55 73.0 0.4 A45 2.5 3.5 4.6 AMJ 2025 A45 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 DJF 2026 EC 73.8 0.4 EC 4.6 6.9 8.7 Honolulu TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV DJF 2025 A60 75.3 0.5 A50 3.7 5.6 8.6 JFM 2025 A60 73.9 0.4 A55 2.1 4.6 7.8 FMA 2025 A60 73.8 0.4 A55 1.9 3.2 4.7 MAM 2025 A55 74.8 0.4 A45 1.8 2.6 3.0 AMJ 2025 A45 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 DJF 2026 EC 75.3 0.5 EC 3.7 5.6 8.6 Lihue TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV DJF 2025 A60 73.6 0.4 A50 7.5 8.4 14.0 JFM 2025 A60 72.2 0.4 A60 6.5 8.8 13.8 FMA 2025 A60 72.1 0.5 A60 5.8 8.4 9.9 MAM 2025 A60 72.8 0.5 A50 5.3 6.6 8.0 AMJ 2025 A50 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 DJF 2026 EC 73.6 0.4 EC 7.5 8.4 14.0 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 Dec 19, 2024. $$