Prognostic Discussion for Long-Lead Hawaiian Outlooks NWS Climate Prediction Center College Park MD 830AM EDT Thu May 20 2021 MONTHLY FORECAST DISCUSSION VALID JUNE 2021 Sea surface temperature (SST) anomalies from zero degree to positive one-half degree Celsius were observed over the Hawaiian islands during the previous week. For January through April 2021, rainfall total accumulations were: - Lihue Airport 19.19 inches (139 percent of normal) - Honolulu Airport 9.42 inches (136 percent of normal) - Kahului Airport 14.66 Inches (167 percent of normal) - Hilo Airport 63.39 Inches (145 percent of normal) The NCEP Climate Forecast System (CFS) and other climate models of the North American Multi-Model Ensemble (NMME) predict below normal monthly mean air temperatures over southeastern Hawaiian Islands (Kahului and Hilo) and equal chances (EC) for above, near, or below normal temperatures for northwestern Hawaiian islands (Honolulu and Lihue) in June 2021. Equal chances (EC) for above, near, or below normal precipitation are indicated by most dynamical and statistical models for the Hawaiian Islands during June 2021. TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV Hilo B50 75.4 0.4 EC 5.3 6.3 8.7 Kahului B50 78.0 0.5 EC 0.1 0.1 0.2 Honolulu EC 80.3 0.4 EC 0.1 0.2 0.3 Lihue EC 78.1 0.4 EC 1.1 1.3 1.6 SEASONAL FORECAST DISCUSSION VALID JJA 2021 - JJA 2022 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 are present across the Pacific Ocean, with near-to-below average sea surface temperatures (SSTs) over the east-central and eastern equatorial Pacific Ocean. Positive subsurface temperature anomalies have shifted eastward and closer to the surface in the eastern Pacific Ocean, while negative subsurface temperature anomalies remain in a small region of the eastern Pacific Ocean down to ~150m depth. Low-level easterly wind anomalies were weakly observed in the east-central Pacific, while upper-level westerly wind anomalies were present across the central and east-central tropical Pacific. ENSO-neutral is likely to continue through the Northern Hemisphere summer with a 67 percent chance during June-August 2021. Enhanced probabilities for below normal temperatures are indicated over Hilo from JJA 2021 to OND 2021, over Kahului from JJA 2021 to SON 2021, and over Honolulu from JAS 2021 to SON 2021, while equal chances (EC) for above, near, or below normal temperatures are forecast over Lihue, supported by most dynamical and statistical forecast tools. Enhanced probabilities for below normal precipitation are likely over the Hawaiian Islands from summer(JJA) 2021 to OND 2021, consistent with most dynamical models. Due to considerable uncertainty in the precipitation forecasts from dynamical and statistical models over the Hawaiian Islands in NDJ 2021 and longer leads, equal chances (EC) for above, near or below normal precipitation are indicated. Hilo TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV JJA 2021 B60 75.2 0.4 B40 19.4 27.2 31.4 JAS 2021 B60 76.1 0.4 B50 25.2 28.6 33.4 ASO 2021 B50 76.4 0.4 B60 26.1 28.8 33.3 SON 2021 B50 76.2 0.4 B50 24.3 30.2 40.8 OND 2021 B40 75.5 0.4 B40 28.3 34.5 42.0 NDJ 2021 EC 74.2 0.4 EC 26.4 36.6 43.0 DJF 2022 EC 72.8 0.4 EC 19.6 30.2 33.3 JFM 2022 EC 71.8 0.4 EC 22.0 32.0 44.5 FMA 2022 EC 71.7 0.4 EC 24.6 34.1 45.5 MAM 2022 EC 72.0 0.5 EC 22.5 28.4 34.0 AMJ 2022 EC 72.9 0.5 EC 21.4 23.7 29.0 MJJ 2022 EC 74.0 0.4 EC 20.2 27.5 29.1 JJA 2022 EC 75.2 0.4 EC 19.4 27.2 31.4 Kahului TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV JJA 2021 B50 77.7 0.4 B40 0.7 1.1 1.5 JAS 2021 B50 79.0 0.4 B50 0.8 1.1 1.6 ASO 2021 B40 79.4 0.4 B60 0.8 1.6 2.5 SON 2021 B40 79.1 0.4 B50 2.1 3.3 4.8 OND 2021 EC 77.8 0.4 B40 4.2 5.3 8.1 NDJ 2021 EC 75.9 0.4 EC 5.2 7.6 9.5 DJF 2022 EC 73.8 0.4 EC 4.6 6.9 8.7 JFM 2022 EC 72.5 0.4 EC 4.2 6.2 8.2 FMA 2022 EC 72.3 0.4 EC 3.2 4.1 6.4 MAM 2022 EC 73.0 0.4 EC 2.5 3.5 4.6 AMJ 2022 EC 74.3 0.5 EC 1.2 1.6 2.2 MJJ 2022 EC 76.0 0.5 EC 0.7 1.1 1.8 JJA 2022 EC 77.7 0.4 EC 0.7 1.1 1.5 Honolulu TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV JJA 2021 EC 79.9 0.4 B40 0.7 0.8 1.3 JAS 2021 B40 81.3 0.4 B50 1.0 1.4 1.7 ASO 2021 B40 81.7 0.4 B60 1.6 2.4 3.1 SON 2021 B40 81.4 0.4 B50 2.5 4.0 5.6 OND 2021 EC 80.0 0.4 B40 4.4 6.4 8.5 NDJ 2021 EC 77.7 0.5 EC 3.9 5.6 8.8 DJF 2022 EC 75.3 0.5 EC 3.7 5.6 8.6 JFM 2022 EC 73.9 0.4 EC 2.1 4.6 7.8 FMA 2022 EC 73.8 0.4 EC 1.9 3.2 4.7 MAM 2022 EC 74.8 0.4 EC 1.8 2.6 3.0 AMJ 2022 EC 76.3 0.4 EC 1.2 1.6 1.8 MJJ 2022 EC 78.2 0.4 EC 0.8 1.4 1.6 JJA 2022 EC 79.9 0.4 EC 0.7 0.8 1.3 Lihue TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV JJA 2021 EC 77.7 0.4 B40 4.4 5.3 6.9 JAS 2021 EC 79.0 0.3 B50 5.3 6.1 7.8 ASO 2021 EC 79.4 0.3 B60 6.2 7.9 8.4 SON 2021 EC 79.1 0.3 B50 9.2 10.0 11.2 OND 2021 EC 77.8 0.3 B40 9.2 11.7 15.6 NDJ 2021 EC 75.7 0.3 EC 8.6 12.1 16.9 DJF 2022 EC 73.6 0.4 EC 7.5 8.4 14.0 JFM 2022 EC 72.2 0.4 EC 6.5 8.8 13.8 FMA 2022 EC 72.1 0.5 EC 5.8 8.4 9.9 MAM 2022 EC 72.8 0.5 EC 5.3 6.6 8.0 AMJ 2022 EC 74.2 0.5 EC 4.7 5.5 6.0 MJJ 2022 EC 76.0 0.5 EC 4.9 5.4 5.9 JJA 2022 EC 77.7 0.4 EC 4.4 5.3 6.9 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 Jun 17, 2021. $$