Hawaii Extended Forecast Discussion NWS Weather Prediction Center College Park MD 811 AM EDT Tue Sep 26 2017 Valid 00Z Wed Sep 27 2017 - 00Z Wed Oct 04 2017 Into late this week expect trades to become a little more brisk as the surface ridge to the north of the state strengthens a bit and after a weakening trough initially just to the east passes over the islands. Within this flow regime showers will tend to favor windward terrain, with the passage of the surface trough possibly bringing a brief enhancement of activity. After Friday the focus of the forecast turns to a potential interaction of Bering Sea energy and a central Pacific trough/upper low. Most operational models end up closing off a farther south upper low near 30N latitude by around Monday but with wide spread on longitude. The 00z GFS (and UKMET through 00z Monday) are farthest east and 00z ECMWF/CMC are about ten degrees farther west. The full range of 00z GEFS/ECMWF/CMC ensembles is even broader, spanning greater than 20 degrees longitude. The 00z GFS is at least 3/4 toward the east side of the envelope with the 00z GEFS mean close to the 06z GFS which is a few degrees farther west. 00z ECMWF ensembles span nearly the entire envelope but with a higher proportion closer to the westward operational run. With CMC ensembles tending to lean westward as well, the more likely scenario currently appears to lie in the western half of the spread. Assuming such a solution, the leading surface front and associated heavier rainfall would remain farther northwest of the islands relative to the 00z/06z GFS runs. Winds should turn more southeasterly during the weekend and early next week with a continuation of scattered showers. Rausch