Hawaii Extended Forecast Discussion NWS Weather Prediction Center College Park MD 723 AM EST Tue Nov 05 2019 Valid 00Z Wed Nov 06 2019 - 00Z Wed Nov 13 2019 Today's guidance agrees fairly well among each other and internally into the first part of the weekend. Then greater differences emerge, significantly lowering confidence in forecast details. An upper shortwave initially west/northwest of the main islands will progress northeastward, with an associated front sagging southeastward over the state. Weak high pressure behind the front will support a period of northeasterly winds that should last into Thursday. Weaker and more variable winds will follow as the high dissipates. The front may serve as a modest focus for rainfall but most activity should be on the lighter side as heights aloft rise, peaking around 12Z Thursday. Another upper trough amplifying into the region by late week/weekend will bring a front toward the region from the northwest. From Sunday onward individual models and ensemble members diverge regarding precise evolution of trough energy. For example the 00Z CMC closes off an upper low near the northwestern islands while GFS/ECMWF runs are more open and progressive. By next Monday-Tuesday there are a couple CMC ensemble members that are at least as extreme as the operational run and some 00Z GEFS members even have a closed low to the south/southwest of the main islands. Still there are enough progressive members to allow the GEFS mean to have some resemblance to the operational run. Strong mid-latitude flow upstream would seem to favor at least some progression. Meanwhile the models and means differ significantly over how much moisture will be over/near the main islands from the weekend into next week. At the very least, the relatively high precipitable water values depicted near the northwestern islands in GFS runs seem questionable in light of their deeper southern periphery of the upper trough. At least the ECMWF's moisture axis is accompanied by a more shallow upper trough. On the other hand both the GEFS/ECMWF means show a decent southeastward push of drier air from the northwest. Given the potential for the front to linger over the area, the drying trend could be a little premature. Current spread makes it difficult to favor one specific solution, favoring a middle-of-the-envelope approach for moisture and mid-level/surface evolution until better clustering emerges. Rausch