Hawaii Extended Forecast Discussion NWS Weather Prediction Center College Park MD 816 AM EDT Sat Apr 11 2015 Valid 00Z Sun Apr 12 2015 - 00Z Sun Apr 19 2015 Synopsis--- For Hawai'i, the weather forecast will not change much with this current split-flow pattern aloft prevailing across much of the Pacific. The occasional high cloud migration in the southern branch of this flow (Subtropical Jet) begins to lift northward Monday and given the current satellite pictures, would expect some of the high cloud cover to be originating in the Tropics. By Thursday---the best prospects in the medium range period for 'phasing' of this split-flow pattern---remains to be centered upon a relatively small geographical area of the central Pacific---along 30N between 155W-160W. This small geographic area of the Pacific is chosen (or focused upon by me) because of the deep mid-latitude cyclone and 'locked-in' storm track for sensible weather changes forthcoming in southern Alaska and its Panhandle. Model consensus is extremely good and precise---for its migration (just south of the Aleutians) between next Monday and next Wednesday (days 2-4). Model Preferences--- The 11/00Z ECENS and NAEFS were accepted as the baseline guidance for the WPC Pacific and Mainland forecasts overnight. And this seemed reasonable across the mid-latitude and Subtropical Pacific---heading into next Friday (day 6). In the Subtropical Pacific and Hawai'i per se---the differences are small enough---through next Thursday (day 5)---to recommend this 2-mean 'blend'. With the operational GFS runs (11/00Z and 11/06Z) the slightly weaken solution at the surface (Subtropical ridge strength along 35N latitude)---the operational 11/00Z ECMWF run might help add some detail to the low-level trade wind flow (wind direction and speed)---for this weekend into next Thursday. For day 6-7...would try to lean away from the NAEFS solution in the central north Pacific. Primarily because the downstream flow pattern at this time frame along 130W should be amplifying---but the upper-level low may have a hard time migrating into the Gulf of Alaska---the NAEFS solution at the moment for days 6-7-8 and beyond. Lean towards the ECENS here. Logic being...there should be a broad but quasi-stationary upper low invof the sern Bering Sea (Bristol Bay AK) that is anchoring the flow pattern aloft east of 160W longitude---arguing for an amplified trough-ridge pattern that 'resets' a good deal west of the NAEFS and GEFS (the d+8 time frame). Vojtesak