Hawaii Extended Forecast Discussion NWS Weather Prediction Center College Park MD 715 AM EST Sat Dec 31 2016 Valid 00Z Sun Jan 01 2017 - 00Z Sun Jan 08 2017 A very strong 500 hPa positive anomaly near the Alaska panhandle forced by an amplified trough near 160E teleconnects to a deep cyclone under the ridge's base somewhere to the north of Hawai'i. While separation between such systems is normally 20 degrees latitude, the breadth/strength of the positive anomaly is forcing greater separation than usual. The negative anomaly under its base could be composed of multiple, merging closed lows which is advertised nicely by the global guidance. The global and ensemble mean guidance remains relatively close here, with the residual problems linked to whether or not another system offshore the CA/OR as seen on the 00z ECMWF can try to distend it somewhat along an east-west axis in four days (late Tuesday) which shows up as an eastward shift in its surface low position. For the time being, a compromise of the 00z UKMET, 00z GFS, and 00z ECMWF is advised to deal with this detail issue. The trades should be weaker than average due to the proximity of the deep cyclone north-northeast of Hawai'i. With the deep moisture offset east of the archipelago, a generally quiet pattern is expected with windward focused showers less numerous than usual. A cold front/shear line will drag out of the Papahanaumokuakea Marine National Monument into the northwestern main islands Tuesday/Wednesday, with the boundary clearing the Big Island on Friday, which could increase rain chances back towards climatological norms mid to late next week as the feature passes by. Roth