Prognostic Discussion for Long-Lead Hawaiian Outlooks NWS Climate Prediction Center College Park MD 830AM EDT Thu Aug 15 2019 MONTHLY FORECAST DISCUSSION VALID SEPTEMBER 2019 Sea surface temperature (SST) anomalies are around positive one half to about two degrees Celsius surrounding the Hawaiian Islands during the previous week. For January 2019 through July 2019, rainfall total accumulations were: - Lihue Airport 16.04 inches (83 percent of normal) - Honolulu Airport 8.88 inches (106 percent of normal) - Kahului Airport 9.68 Inches (95 percent of normal) - Hilo Airport 47.99 Inches (68 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 September 2019. Model guidance from the NMME and IMME indicate anomalies of 1-2 degrees C above normal.This elevates the chances of above normal monthly mean air temperatures for Hawaii in September 2019. Most dynamical models predict above normal precipitation over the Hawaiian Islands during September 2019, consistent with the Canonical Correlation Analysis (CCA) forecast tool. TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV Hilo A65 76.4 0.5 A45 8.0 9.3 11.0 Kahului A65 79.3 0.4 A45 0.1 0.2 0.5 Honolulu A65 81.8 0.4 A45 0.4 0.6 0.8 Lihue A65 79.4 0.3 A45 1.7 1.9 2.6 SEASONAL FORECAST DISCUSSION VALID SON 2019 - SON 2020 Refer to the prognostic discussion of the long-lead seasonal outlooks for the CONUS and Alaska for a discussion 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 above average across the western and central Pacific Ocean and are below average in the eastern Pacific. Positive subsurface temperature anomalies have weakened across the Pacific, but still remain in the central Pacific, while negative subsurface temperature anomalies have expanded in the eastern Pacific. Low-level wind anomalies were near average over the tropical Pacific Ocean, and upper-level winds were easterly over the east-central Pacific. ENSO-neutral is likely to continue through the Northern Hemisphere winter 2019-2020 (with a 50-55% chance). Enhanced probabilities for above normal temperatures are indicated across the Hawaiian Islands in the outlook from SON 2019 to JFM 2020, due to persistent above normal sea surface temperatures predicted by the NMME dynamical models, and also supported by statistical models including the Canonical Correlation Analysis (CCA) and Constructed Analog (CA). The signal weakens at longer leads, therefore Equal Chances (EC) for above, near, or below normal temperatures are indicated for Hawaii beginning in FMA 2020 and beyond. Most dynamical models predict larger signals for above normal precipitation over the Hawaiian Islands during SON 2019 to NDJ 2019-2020, though some statistical tools are on the drier side. Increasing uncertainty in the tropical climate state in DJF 2019-2020 and longer leads, leads to an indication of equal chances (EC) for above, near, or below normal precipitation for Hawaii. Hilo TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV SON 2019 A65 76.2 0.4 A50 24.3 30.2 40.8 OND 2019 A60 75.5 0.4 A45 28.3 34.5 42.0 NDJ 2019 A55 74.2 0.4 A40 26.4 36.6 43.0 DJF 2020 A50 72.8 0.4 EC 19.6 30.2 33.3 JFM 2020 A45 71.8 0.4 EC 22.0 32.0 44.5 FMA 2020 EC 71.7 0.4 EC 24.6 34.1 45.5 MAM 2020 EC 72.0 0.5 EC 22.5 28.4 34.0 AMJ 2020 EC 72.9 0.5 EC 21.4 23.7 29.0 MJJ 2020 EC 74.0 0.4 EC 20.2 27.5 29.1 JJA 2020 EC 75.2 0.4 EC 19.4 27.2 31.4 JAS 2020 EC 76.1 0.4 EC 25.2 28.6 33.4 ASO 2020 EC 76.4 0.4 EC 26.1 28.8 33.3 SON 2020 EC 76.2 0.4 EC 24.3 30.2 40.8 Kahului TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV SON 2019 A65 79.1 0.4 A50 2.1 3.3 4.8 OND 2019 A60 77.8 0.4 A45 4.2 5.3 8.1 NDJ 2019 A55 75.9 0.4 A40 5.2 7.6 9.5 DJF 2020 A50 73.8 0.4 EC 4.6 6.9 8.7 JFM 2020 A45 72.5 0.4 EC 4.2 6.2 8.2 FMA 2020 EC 72.3 0.4 EC 3.2 4.1 6.4 MAM 2020 EC 73.0 0.4 EC 2.5 3.5 4.6 AMJ 2020 EC 74.3 0.5 EC 1.2 1.6 2.2 MJJ 2020 EC 76.0 0.5 EC 0.7 1.1 1.8 JJA 2020 EC 77.7 0.4 EC 0.7 1.1 1.5 JAS 2020 EC 79.0 0.4 EC 0.8 1.1 1.6 ASO 2020 EC 79.4 0.4 EC 0.8 1.6 2.5 SON 2020 EC 79.1 0.4 EC 2.1 3.3 4.8 Honolulu TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV SON 2019 A65 81.4 0.4 A50 2.5 4.0 5.6 OND 2019 A60 80.0 0.4 A45 4.4 6.4 8.5 NDJ 2019 A50 77.7 0.5 A40 3.9 5.6 8.8 DJF 2020 A45 75.3 0.5 EC 3.7 5.6 8.6 JFM 2020 A40 73.9 0.4 EC 2.1 4.6 7.8 FMA 2020 EC 73.8 0.4 EC 1.9 3.2 4.7 MAM 2020 EC 74.8 0.4 EC 1.8 2.6 3.0 AMJ 2020 EC 76.3 0.4 EC 1.2 1.6 1.8 MJJ 2020 EC 78.2 0.4 EC 0.8 1.4 1.6 JJA 2020 EC 79.9 0.4 EC 0.7 0.8 1.3 JAS 2020 EC 81.3 0.4 EC 1.0 1.4 1.7 ASO 2020 EC 81.7 0.4 EC 1.6 2.4 3.1 SON 2020 EC 81.4 0.4 EC 2.5 4.0 5.6 Lihue TEMPERATURE PRECIPITATION FCST AVE LIM FCST BLW MEDIAN ABV SON 2019 A65 79.1 0.3 A50 9.2 10.0 11.2 OND 2019 A60 77.8 0.3 A45 9.2 11.7 15.6 NDJ 2019 A50 75.7 0.3 A40 8.6 12.1 16.9 DJF 2020 A45 73.6 0.4 EC 7.5 8.4 14.0 JFM 2020 A40 72.2 0.4 EC 6.5 8.8 13.8 FMA 2020 EC 72.1 0.5 EC 5.8 8.4 9.9 MAM 2020 EC 72.8 0.5 EC 5.3 6.6 8.0 AMJ 2020 EC 74.2 0.5 EC 4.7 5.5 6.0 MJJ 2020 EC 76.0 0.5 EC 4.9 5.4 5.9 JJA 2020 EC 77.7 0.4 EC 4.4 5.3 6.9 JAS 2020 EC 79.0 0.3 EC 5.3 6.1 7.8 ASO 2020 EC 79.4 0.3 EC 6.2 7.9 8.4 SON 2020 EC 79.1 0.3 EC 9.2 10.0 11.2 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 Sep 19, 2019. $$