Prognostic Discussion for Long-Lead Hawaiian Outlooks NWS Climate Prediction Center College Park MD 830AM EDT Thu Jun 15 2023 MONTHLY FORECAST DISCUSSION VALID JULY 2023 During the previous few weeks, sea surface temperature (SST) anomalies ranged from zero to positive one-half degree Celsius around the Hawaiian Islands. For February through May 2023, rainfall total accumulations were: -Lihue Airport 28.53 inches (176 percent of normal) -Honolulu Airport 9.08 inches (117 percent of normal) -Kahului Airport 8.84 inches (97 percent of normal) -Hilo Airport 61.97 inches (131 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 most of the Hawaiian Islands through July 2023, and near-average SSTs around the Big Island of Hawaii. These SST forecasts favor above-normal temperatures for most islands in July 2023, except Equal Chances (EC) of below, near, and above-normal temperatures are predicted for Hilo. Enhanced chances for below-normal precipitation are predicted for all the Hawaiian Islands, as indicated by most dynamical model forecasts. TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV Hilo EC 76.2 0.4 B40 7.1 9.5 11.4 Kahului A40 79.2 0.4 B40 0.2 0.4 0.5 Honolulu A50 81.4 0.5 B40 0.2 0.4 0.5 Lihue A60 79.2 0.4 B40 1.5 1.7 1.9 SEASONAL FORECAST DISCUSSION VALID JAS 2023 - JAS 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. A weak El Nino recently emerged as above-average sea surface temperatures (SSTs) strengthened across the equatorial Pacific. The most recent weekly Nino 3.4 anomaly is +0.8 Celsius. Significantly warmer than average SSTs are currently observed in the eastern Pacific Ocean. A broad subsurface reservoir of positive temperature anomalies is evident across the uppermost 300 meters of the near-equatorial Pacific. For the western and central Pacific (130E to 150W), the larger subsurface anomalies range from 50 to 225 meters below the surface; whereas from about 150W to the South American coast positive temperature anomalies extend from the surface to a depth of 150 meters. In recent weeks, low-level wind anomalies were westerly over the western Pacific, while upper-level wind anomalies were westerly over the eastern Pacific. Tropical convection was enhanced over the equator and suppressed over Indonesia. The CPC ENSO Outlook, supported by most statistical and dynamical models, predicts at least a 90-percent chance that the El Nino will continue well into Northern Hemisphere winter. Odds for a moderate strength El Nino (Oceanic Nino Index (ONI) >= +1.0C) stand at 84%, and there is a 56 percent chance of a strong El Nino (ONI >= +1.5C). Enhanced probabilities for above-normal temperatures are forecast for most of the Hawaiian Islands (except for the Big Island where EC is favored) from Jul-Aug-Sep (JAS 2023) through JFM 2024, consistent with most dynamical model forecasts from the NMME. The forecast signal weakens at longer leads, therefore Equal Chances (EC) for above, near or below-normal temperatures is indicated for Hawaii beginning in 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 during JAS 2023. With the very likely persistence of El Niño conditions into winter, regressions of precipitation on the Niño 3.4 index support likely below normal precipitation continuing from ASO 2023 through JFM 2024. The statistical precipitation models were not as bullish on the dry signal as were the dynamical models, especially during the first few leads. Due to considerable uncertainty in the precipitation forecasts from forecast tools at longer leads, EC is indicated over the Hawaiian Islands beginning in the February-March-April (FMA) 2024 season. Hilo TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV JAS 2023 EC 76.1 0.4 B40 25.2 28.6 33.4 ASO 2023 EC 76.4 0.4 B40 26.1 28.8 33.3 SON 2023 EC 76.2 0.4 B40 24.3 30.2 40.8 OND 2023 EC 75.5 0.4 B40 28.3 34.5 42.0 NDJ 2023 EC 74.2 0.4 B50 26.4 36.6 43.0 DJF 2024 EC 72.8 0.4 B50 19.6 30.2 33.3 JFM 2024 EC 71.8 0.4 B40 22.0 32.0 44.5 FMA 2024 EC 71.7 0.4 EC 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 Kahului TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV JAS 2023 A40 79.0 0.4 B40 0.8 1.1 1.6 ASO 2023 A40 79.4 0.4 B40 0.8 1.6 2.5 SON 2023 A40 79.1 0.4 B40 2.1 3.3 4.8 OND 2023 A40 77.8 0.4 B40 4.2 5.3 8.1 NDJ 2023 A40 75.9 0.4 B50 5.2 7.6 9.5 DJF 2024 A40 73.8 0.4 B50 4.6 6.9 8.7 JFM 2024 A40 72.5 0.4 B40 4.2 6.2 8.2 FMA 2024 EC 72.3 0.4 EC 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 Honolulu TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV JAS 2023 A50 81.3 0.4 B40 1.0 1.4 1.7 ASO 2023 A50 81.7 0.4 B40 1.6 2.4 3.1 SON 2023 A50 81.4 0.4 B40 2.5 4.0 5.6 OND 2023 A50 80.0 0.4 B40 4.4 6.4 8.5 NDJ 2023 A50 77.7 0.5 B50 3.9 5.6 8.8 DJF 2024 A50 75.3 0.5 B50 3.7 5.6 8.6 JFM 2024 A50 73.9 0.4 B40 2.1 4.6 7.8 FMA 2024 EC 73.8 0.4 EC 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 Lihue TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV JAS 2023 A60 79.0 0.3 B40 5.3 6.1 7.8 ASO 2023 A60 79.4 0.3 B40 6.2 7.9 8.4 SON 2023 A60 79.1 0.3 B40 9.2 10.0 11.2 OND 2023 A60 77.8 0.3 B40 9.2 11.7 15.6 NDJ 2023 A60 75.7 0.3 B50 8.6 12.1 16.9 DJF 2024 A60 73.6 0.4 B50 7.5 8.4 14.0 JFM 2024 A60 72.2 0.4 B40 6.5 8.8 13.8 FMA 2024 EC 72.1 0.5 EC 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 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 Jul 20, 2023. $$