Hawaii Extended Forecast Discussion NWS Weather Prediction Center College Park MD 719 AM EST Mon Nov 26 2018 Valid 00Z Tue Nov 27 2018 - 00Z Tue Dec 04 2018 Upper-level ridging will weaken across Hawaii over the next few days, with models showing good agreement that an anomalous trough will amplify across the Central Pacific by mid to late week. The trough is expected to remain north of Hawaii as it progresses eastward, but the system will push a surface cold front to Hawaii by Thu night. Moisture return ahead of the system does not look as impressive in the guidance as it did a few days ago, but PWs should rise to over 1.75 inches along and just ahead of the front, which should be sufficient to produce at least locally heavy rains as the front sweeps across Hawaii from west to east through Sat night. Additionally, expect trades to diminish by Thu as the low pressure system dominates the flow in the region, resulting in a period of light southerly or southeasterly winds for Hawaii, followed by northwest winds in the wake of the front by Sat-Sun. The GFS/CMC/ECMWF all show a second shortwave in the wake of the first one Sun-Mon, also deepening into a closed low just north of Hawaii. Given the time range (day 6-7), spread among the guidance is quite a bit larger with this system and an ensemble mean based forecast is likely best at this time. Whether this feature moves east more quickly as shown by the ECMWF or slowly drifts southeastward near Hawaii as shown by the GFS/CMC will play a crucial role in the sensible weather effects on Hawaii, which remain highly uncertain at this time. Ryan