Prognostic Discussion for Long-Lead Hawaiian Outlooks NWS Climate Prediction Center College Park MD 830AM EDT Thu Jul 20 2023 MONTHLY FORECAST DISCUSSION VALID AUGUST 2023 Sea surface temperature (SST) anomalies from zero to positive one-half degrees Celsius were observed over the Hawaiian islands (Kauai, Oahu, Maui and the Big Island) during the previous week. For January through June 2023, rainfall total accumulations were: -Lihue Airport 29.55 inches (164 percent of normal) -Honolulu Airport 9.47 inches (115 percent of normal) -Kahului Airport 8.96 inches (97 percent of normal) -Hilo Airport 66.35 inches (122 percent of normal) The NCEP Climate Forecast System (CFS) and other climate models of the North American Multi-Model Ensemble (NMME) predict near-average SSTs (sea surface temperatures) around the Hawaiian Islands through August 2023. This supports Equal Chances (EC) for above-, near-, or below-normal temperatures over the Hawaiian Islands in August 2023. Enhanced chances for below-normal precipitation are predicted for all the Hawaiian Islands, as indicated by most dynamical model forecasts, consistent with the El Niño conditions over the tropical Pacific. TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV Hilo EC 76.6 0.4 B60 7.6 8.4 10.3 Kahului EC 79.8 0.4 B60 0.3 0.5 0.6 Honolulu EC 82.1 0.4 B60 0.1 0.2 0.4 Lihue EC 79.7 0.4 B60 1.4 1.8 2.5 SEASONAL FORECAST DISCUSSION VALID ASO 2023 - ASO 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. Weak El Niño conditions are observed across the Pacific Ocean. Equatorial SSTs are above average across the central and eastern Pacific Ocean. Positive subsurface temperature anomalies dominate the equatorial Pacific Ocean. Low-level winds were near average across most of the tropical Pacific Ocean, while upper-level wind anomalies were easterly over the western tropical Pacific and westerly over the eastern tropical Pacific. Convection and rainfall were mainly enhanced around the International Date Line. The tropical Pacific atmospheric anomalies are consistent with weak El Niño conditions. There is a greater than 90% chance that El Nino will continue through the Northern Hemisphere winter. Equal chances (EC) for above-, near-, or below-normal temperatures are forecast over Hawaii from August-September-October (ASO) to November-December-January (NDJ) 2023, while enhanced probabilities for above-normal temperatures are indicated over Hawaii during December-January-February (DJF) and January-Februrary-March (JFM) 2024, consistent with most dynamical and statistical forecast tools, including dynamical models of the NMME and the constructed analog statistical model. The forecast signal weakens at longer leads, therefore Equal Chances (EC) for above, near or below normal temperatures are indicated for Hawaii beginning in February-March-April (FMA) 2024 and extending through longer leads. Dynamical models from the NMME show increased confidence this month in predicting enhanced probabilities of below-normal precipitation from ASO 2023 to FMA 2024, consistent with the impacts of EL Nino conditions. Due to considerable uncertainty in the precipitation forecasts from forecast tools at longer leads, EC is indicated over the Hawaiian Islands beginning in the March-April-May (MMA) 2024 season. Hilo TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV ASO 2023 EC 76.4 0.4 B60 26.1 28.8 33.3 SON 2023 EC 76.2 0.4 B60 24.3 30.2 40.8 OND 2023 EC 75.5 0.4 B60 28.3 34.5 42.0 NDJ 2023 EC 74.2 0.4 B60 26.4 36.6 43.0 DJF 2024 A40 72.8 0.4 B70 19.6 30.2 33.3 JFM 2024 A40 71.8 0.4 B70 22.0 32.0 44.5 FMA 2024 EC 71.7 0.4 B50 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 JAS 2024 EC 76.1 0.4 EC 25.2 28.6 33.4 ASO 2024 EC 76.4 0.4 EC 26.1 28.8 33.3 Kahului TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV ASO 2023 EC 79.4 0.4 B60 0.8 1.6 2.5 SON 2023 EC 79.1 0.4 B60 2.1 3.3 4.8 OND 2023 EC 77.8 0.4 B60 4.2 5.3 8.1 NDJ 2023 EC 75.9 0.4 B60 5.2 7.6 9.5 DJF 2024 A40 73.8 0.4 B70 4.6 6.9 8.7 JFM 2024 A40 72.5 0.4 B70 4.2 6.2 8.2 FMA 2024 EC 72.3 0.4 B50 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 JAS 2024 EC 79.0 0.4 EC 0.8 1.1 1.6 ASO 2024 EC 79.4 0.4 EC 0.8 1.6 2.5 Honolulu TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV ASO 2023 EC 81.7 0.4 B60 1.6 2.4 3.1 SON 2023 EC 81.4 0.4 B60 2.5 4.0 5.6 OND 2023 EC 80.0 0.4 B60 4.4 6.4 8.5 NDJ 2023 EC 77.7 0.5 B60 3.9 5.6 8.8 DJF 2024 A40 75.3 0.5 B70 3.7 5.6 8.6 JFM 2024 A40 73.9 0.4 B70 2.1 4.6 7.8 FMA 2024 EC 73.8 0.4 B50 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 JAS 2024 EC 81.3 0.4 EC 1.0 1.4 1.7 ASO 2024 EC 81.7 0.4 EC 1.6 2.4 3.1 Lihue TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV ASO 2023 EC 79.4 0.3 B60 6.2 7.9 8.4 SON 2023 EC 79.1 0.3 B60 9.2 10.0 11.2 OND 2023 EC 77.8 0.3 B60 9.2 11.7 15.6 NDJ 2023 EC 75.7 0.3 B60 8.6 12.1 16.9 DJF 2024 A40 73.6 0.4 B70 7.5 8.4 14.0 JFM 2024 A40 72.2 0.4 B70 6.5 8.8 13.8 FMA 2024 EC 72.1 0.5 B50 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 JAS 2024 EC 79.0 0.3 EC 5.3 6.1 7.8 ASO 2024 EC 79.4 0.3 EC 6.2 7.9 8.4 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 Aug 17, 2023. $$