Prognostic Discussion for Long-Lead Hawaiian Outlooks NWS Climate Prediction Center College Park MD 830AM EST Thu Mar 21 2024 MONTHLY FORECAST DISCUSSION VALID APRIL 2024 Sea surface temperature (SST) anomalies were near-average over the Hawaiian islands (Kauai, Oahu, Maui and the Big Island) during the previous week. For January through February 2024, rainfall total accumulations were: -Lihue Airport 3.52 inches (55 percent of normal) -Honolulu Airport 2.94 inches (78 percent of normal) -Kahului Airport 5.77 inches (131 percent of normal) -Hilo Airport 8.98 inches (50 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 Kauai, Oahu, and Maui through April 2024 and near average SSTs for the Big Island through April 2024. Based primarily on these SST forecasts, surface temperatures are also favored to be relatively warm compared to normal for Kauai, Oahu and Maui, while Equal Chances (EC) for above, near or below normal temperatures are forecast for the Big Island in April 2024. For the April 2024 precipitation outlook, below normal precipitation chances are elevated for all of the island chain, as indicated by most dynamical model forecasts, and consistent with the El Nino conditions over the tropical Pacific. TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV Hilo EC 72.6 0.7 B60 7.4 8.9 11.2 Kahului A40 74.1 0.6 B60 0.5 0.9 1.3 Honolulu A40 76.3 0.5 B55 0.3 0.5 0.7 Lihue A40 74.0 0.6 B55 1.6 1.9 2.8 SEASONAL FORECAST DISCUSSION VALID AMJ 2024 - AMJ 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. El Niño conditions are observed over the tropical Pacific Ocean. Equatorial sea surface temperatures (SSTs) are above average across the central and eastern Pacific Ocean. Positive subsurface temperature anomalies have weakened across the equatorial Pacific but remain close to the surface in the central Pacific. Negative subsurface temperature anomalies expanded across the equatorial Pacific and below-average temperatures have reached the surface in the eastern Pacific Ocean. Low-level wind anomalies were easterly over the western tropical Pacific Ocean and Date Line, while upper-level wind anomalies were easterly over the east-central equatorial Pacific. Enhanced convection and precipitation were observed near the Date Line, while suppressed convection and precipitation were evident around Indonesia and the Philippines. Atmospheric and oceanic conditions over the tropical Pacific are generally consistent with El Niño conditions. There is a 83% chance of transition from El Nino to ENSO-neutral during April-June 2024, with increasing odds, about 62% chance, of La Niña developing in Summer 2024. Enhanced probabilities for above normal temperatures are forecast for Kauai, Oahu and Maui and Equal Chances (EC) for above, near or below normal temperatures are forecast for the Big Island in AMJ (April-May-June) 2024, consistent with most dynamical model forecasts from the NMME and the Constructed Analog (CA) tool. The forecast signal weakens at longer leads, therefore EC is indicated for Hawaii beginning in MJJ (May-June-July) 2024 and extending through longer leads. Enhanced probabilities for below normal precipitation are forecast over the Hawaiian Islands (Kauai, Oahu, Maui and the Big Island) from AMJ (April-May-June) 2024 to ASO (August-September-October) 2024, consistent with most dynamical and statistical model forecasts. Due to considerable uncertainty in the precipitation forecasts from dynamical and statistical models, EC is indicated over the Hawaiian Islands beginning in Fall (September-October-November) 2024 through longer leads. Hilo TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV AMJ 2024 EC 72.9 0.5 B60 21.4 23.7 29.0 MJJ 2024 EC 74.0 0.4 B60 20.2 27.5 29.1 JJA 2024 EC 75.2 0.4 B60 19.4 27.2 31.4 JAS 2024 EC 76.1 0.4 B50 25.2 28.6 33.4 ASO 2024 EC 76.4 0.4 B40 26.1 28.8 33.3 SON 2024 EC 76.2 0.4 EC 24.3 30.2 40.8 OND 2024 EC 75.5 0.4 EC 28.3 34.5 42.0 NDJ 2024 EC 74.2 0.4 EC 26.4 36.6 43.0 DJF 2025 EC 72.8 0.4 EC 19.6 30.2 33.3 JFM 2025 EC 71.8 0.4 EC 22.0 32.0 44.5 FMA 2025 EC 71.7 0.4 EC 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 Kahului TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV AMJ 2024 A40 74.3 0.5 B60 1.2 1.6 2.2 MJJ 2024 EC 76.0 0.5 B60 0.7 1.1 1.8 JJA 2024 EC 77.7 0.4 B55 0.7 1.1 1.5 JAS 2024 EC 79.0 0.4 B50 0.8 1.1 1.6 ASO 2024 EC 79.4 0.4 B40 0.8 1.6 2.5 SON 2024 EC 79.1 0.4 EC 2.1 3.3 4.8 OND 2024 EC 77.8 0.4 EC 4.2 5.3 8.1 NDJ 2024 EC 75.9 0.4 EC 5.2 7.6 9.5 DJF 2025 EC 73.8 0.4 EC 4.6 6.9 8.7 JFM 2025 EC 72.5 0.4 EC 4.2 6.2 8.2 FMA 2025 EC 72.3 0.4 EC 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 Honolulu TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV AMJ 2024 A40 76.3 0.4 B60 1.2 1.6 1.8 MJJ 2024 EC 78.2 0.4 B50 0.8 1.4 1.6 JJA 2024 EC 79.9 0.4 B50 0.7 0.8 1.3 JAS 2024 EC 81.3 0.4 B45 1.0 1.4 1.7 ASO 2024 EC 81.7 0.4 B40 1.6 2.4 3.1 SON 2024 EC 81.4 0.4 EC 2.5 4.0 5.6 OND 2024 EC 80.0 0.4 EC 4.4 6.4 8.5 NDJ 2024 EC 77.7 0.5 EC 3.9 5.6 8.8 DJF 2025 EC 75.3 0.5 EC 3.7 5.6 8.6 JFM 2025 EC 73.9 0.4 EC 2.1 4.6 7.8 FMA 2025 EC 73.8 0.4 EC 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 Lihue TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV AMJ 2024 A40 74.2 0.5 B60 4.7 5.5 6.0 MJJ 2024 EC 76.0 0.5 B50 4.9 5.4 5.9 JJA 2024 EC 77.7 0.4 B50 4.4 5.3 6.9 JAS 2024 EC 79.0 0.3 B45 5.3 6.1 7.8 ASO 2024 EC 79.4 0.3 B40 6.2 7.9 8.4 SON 2024 EC 79.1 0.3 EC 9.2 10.0 11.2 OND 2024 EC 77.8 0.3 EC 9.2 11.7 15.6 NDJ 2024 EC 75.7 0.3 EC 8.6 12.1 16.9 DJF 2025 EC 73.6 0.4 EC 7.5 8.4 14.0 JFM 2025 EC 72.2 0.4 EC 6.5 8.8 13.8 FMA 2025 EC 72.1 0.5 EC 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 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 Apr 18, 2024. $$