Hawaii Extended Forecast Discussion NWS Weather Prediction Center College Park MD 715 AM EST Fri Dec 30 2016 Valid 00Z Sat Dec 31 2016 - 00Z Sat Jan 07 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 has converged nicely here since yesterday, with the residual problems linked to the shape of the upper level system. For this reason alone (more elongated east-west), the 00z Canadian is likely not the best choice. The 06z GFS, 00z ECMWF, and 00z UKMET appear to be handling this closed feature north-northeast of the 50th state reasonably well, with the 06z GFS in particular showing the most reasonable pressure distribution in the subtropical north-central Pacific. The trades weaken early in the period as the deep cyclone becomes established to the north-northeast of Hawai'i. With the deep moisture offset east of Hawai'i, 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, which could increase rain chances back towards climatological norms by mid next week. Roth