Hawaii Extended Forecast Discussion NWS Weather Prediction Center College Park MD 256 AM EST Sun Nov 19 2023 Valid 00Z Mon Nov 20 2023 - 00Z Mon Nov 27 2023 Today's models and ensembles show a variable pattern over the course of the period. A leading front will arrive Sunday, bringing the potential for some locally moderate to heavy rainfall to the western islands and switching brisk southerly winds to northeasterly. Rapid dissipation of the front and high pressure to the north/northeast will allow for a return of moderate trades and windward/mountain shower focus from Tuesday into late week. Then an amplifying and sharpening upper trough should bring in second front next weekend, with another increase of rainfall and a wind shift from southeasterly to north-northeasterly. As for details, yesterday's majority ECMWF cluster has since trended at least partially in the GFS/GEFS direction for evolution of the Sunday-Monday upper trough and with the surface front's band of enhanced moisture settling into approximately the central islands before dissipating and/or getting carried westward in the trades. There is still some spread for how much enhanced moisture initially southeast of the state may brush the Big Island and vicinity by Tuesday-Wednesday. Now the 00Z ECMWF shows the greatest moisture (a role played by the 00Z GFS 24 hours ago) while the GFS and the ensemble means keep the moisture more suppressed to varying degrees. An average of the guidance minus the ECMWF looks reasonable for this aspect of the forecast. Moisture specifics have decreasing predictability later in the week. By next weekend, typical detail differences with the approaching upper trough lead to some timing spread for the front reaching the islands. However this spread is fairly modest for a 6-7 day forecast and a compromise would provide a reasonable starting point for the forecast. Rausch