Prognostic Discussion for Long-Lead Hawaiian Outlooks NWS Climate Prediction Center College Park MD 830AM EDT Thu Apr 16 2020 MONTHLY FORECAST DISCUSSION VALID MAY 2020 Positive sea surface temperature (SST) anomalies from about positive one half to one degree Celsius are surrounding the Hawaiian Islands during the previous week. For March 2020, rainfall total accumulations were: - Lihue Airport 19.61 inches (170 percent of normal) - Honolulu Airport 5.77 inches (91 percent of normal) - Kahului Airport 6.59 Inches (91 percent of normal) - Hilo Airport 49.46 Inches (153 percent of normal) The NCEP Climate Forecast System (CFS) and other climate models of the North American Multi-Model Ensemble (NMME) predict above normal SSTs around the Hawaiian Islands for May 2020. This elevates the chances of above normal monthly mean air temperatures for Hawaii in May 2020. Most dynamical models from the NMME indicate Equal Chances (EC) for above, near or below normal precipitation over the Hawaiian Islands during May 2020. TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV Hilo A65 74.0 0.5 EC 4.1 7.4 8.7 Kahului A65 75.8 0.6 EC 0.2 0.5 0.8 Honolulu A65 78.0 0.6 EC 0.2 0.4 0.8 Lihue A65 75.8 0.6 EC 1.3 1.5 2.3 SEASONAL FORECAST DISCUSSION VALID MJJ 2020 - MJJ 2021 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, including details on the current state of the atmosphere and ocean. ENSO-neutral conditions currently are present across the equatorial Pacific Ocean. Equatorial sea surface temperatures (SSTs) are near to above average across the Pacific Ocean. Subsurface temperature anomalies remain positive across most of the Pacific Ocean near the surface, while the anomalies decreased during last month due to the expansion of below-average temperatures into the central Pacific at depth. Tropical convection is suppressed over parts of Indonesia and is near average near the Date Line. Low-level wind anomalies were easterly in the eastern Pacific, and upper-level wind anomalies were westerly over the central and eastern portions of the basin. The tropical atmospheric circulation is generally consistent with ENSO-neutral. ENSO-neutral is likely to continue through Northern Hemisphere summer 2020 with probabilities about 60 percent and through autumn 2020 with probabilities about 50 percent. Enhanced probabilities for above normal temperatures are indicated across the Hawaiian Islands in the outlook from MJJ 2020 to SON 2020, due to predicted persistence of above normal sea surface temperatures in the NMME dynamical model forecasts, and supported by statistical models including the Constructed Analog (CA) and Optimum Climate Normals (OCN) through OND 2020. The signal weakens at longer leads, therefore Equal Chances (EC) for above, near or below normal temperatures are indicated for Hawaii in NDJ 2020 and thereafter. Now Hawaii is into a dry season. The NMME and the CA predict greater probabilities for below normal precipitation over northwestern islands (Lihue and Honolulu) in MJJ 2020. The NMME and the consolidation of dynamical and statistical tools also favor below normal precipitation from JJA 2020 through SON 2020 over all Hawaiian Islands, though some statistical tools such as the CA indicate above normal is more likely for Hawaii during this period. There is considerable uncertainty in the precipitation forecasts among available dynamical and statistical tools over the Hawaiian Islands in OND 2020 and longer leads, so equal chances (EC) for above, near or below normal precipitation are indicated. Hilo TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV MJJ 2020 A65 74.0 0.4 EC 20.2 27.5 29.1 JJA 2020 A60 75.2 0.4 B50 19.4 27.2 31.4 JAS 2020 A55 76.1 0.4 B45 25.2 28.6 33.4 ASO 2020 A50 76.4 0.4 B45 26.1 28.8 33.3 SON 2020 A45 76.2 0.4 B40 24.3 30.2 40.8 OND 2020 A40 75.5 0.4 EC 28.3 34.5 42.0 NDJ 2020 EC 74.2 0.4 EC 26.4 36.6 43.0 DJF 2021 EC 72.8 0.4 EC 19.6 30.2 33.3 JFM 2021 EC 71.8 0.4 EC 22.0 32.0 44.5 FMA 2021 EC 71.7 0.4 EC 24.6 34.1 45.5 MAM 2021 EC 72.0 0.5 EC 22.5 28.4 34.0 AMJ 2021 EC 72.9 0.5 EC 21.4 23.7 29.0 MJJ 2021 EC 74.0 0.4 EC 20.2 27.5 29.1 Kahului TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV MJJ 2020 A65 76.0 0.5 EC 0.7 1.1 1.8 JJA 2020 A60 77.7 0.4 B50 0.7 1.1 1.5 JAS 2020 A55 79.0 0.4 B45 0.8 1.1 1.6 ASO 2020 A50 79.4 0.4 B45 0.8 1.6 2.5 SON 2020 A45 79.1 0.4 B40 2.1 3.3 4.8 OND 2020 A40 77.8 0.4 EC 4.2 5.3 8.1 NDJ 2020 EC 75.9 0.4 EC 5.2 7.6 9.5 DJF 2021 EC 73.8 0.4 EC 4.6 6.9 8.7 JFM 2021 EC 72.5 0.4 EC 4.2 6.2 8.2 FMA 2021 EC 72.3 0.4 EC 3.2 4.1 6.4 MAM 2021 EC 73.0 0.4 EC 2.5 3.5 4.6 AMJ 2021 EC 74.3 0.5 EC 1.2 1.6 2.2 MJJ 2021 EC 76.0 0.5 EC 0.7 1.1 1.8 Honolulu TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV MJJ 2020 A65 78.2 0.4 B50 0.8 1.4 1.6 JJA 2020 A60 79.9 0.4 B50 0.7 0.8 1.3 JAS 2020 A55 81.3 0.4 B45 1.0 1.4 1.7 ASO 2020 A50 81.7 0.4 B45 1.6 2.4 3.1 SON 2020 A45 81.4 0.4 B40 2.5 4.0 5.6 OND 2020 A40 80.0 0.4 EC 4.4 6.4 8.5 NDJ 2020 EC 77.7 0.5 EC 3.9 5.6 8.8 DJF 2021 EC 75.3 0.5 EC 3.7 5.6 8.6 JFM 2021 EC 73.9 0.4 EC 2.1 4.6 7.8 FMA 2021 EC 73.8 0.4 EC 1.9 3.2 4.7 MAM 2021 EC 74.8 0.4 EC 1.8 2.6 3.0 AMJ 2021 EC 76.3 0.4 EC 1.2 1.6 1.8 MJJ 2021 EC 78.2 0.4 EC 0.8 1.4 1.6 Lihue TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV MJJ 2020 A65 76.0 0.5 B50 4.9 5.4 5.9 JJA 2020 A60 77.7 0.4 B50 4.4 5.3 6.9 JAS 2020 A55 79.0 0.3 B45 5.3 6.1 7.8 ASO 2020 A50 79.4 0.3 B45 6.2 7.9 8.4 SON 2020 A45 79.1 0.3 B40 9.2 10.0 11.2 OND 2020 A40 77.8 0.3 EC 9.2 11.7 15.6 NDJ 2020 EC 75.7 0.3 EC 8.6 12.1 16.9 DJF 2021 EC 73.6 0.4 EC 7.5 8.4 14.0 JFM 2021 EC 72.2 0.4 EC 6.5 8.8 13.8 FMA 2021 EC 72.1 0.5 EC 5.8 8.4 9.9 MAM 2021 EC 72.8 0.5 EC 5.3 6.6 8.0 AMJ 2021 EC 74.2 0.5 EC 4.7 5.5 6.0 MJJ 2021 EC 76.0 0.5 EC 4.9 5.4 5.9 FORECASTER: Luke He Anomalies are based on the 1981-2010 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 May 21, 2020. $$