Hawaii Extended Forecast Discussion NWS Weather Prediction Center College Park MD 821 AM EDT Sat Apr 27 2019 Valid 00Z Sun Apr 28 2019 - 00Z Sun May 05 2019 From now into Monday expect light trades with sea/land breeze boundaries providing a focus for shower activity, as a front drifts close to the main islands. An approaching shortwave aloft (reaching the state early next week) may promote locally heavy rainfall and some thunder. Then by Tuesday-Thursday northeasterly to east-northeasterly trades with relatively light windward focused showers should prevail, with surface high pressure tracking well north of the area and an upper ridge building over the region behind the departing shortwave. Model/ensemble differences are fairly minor into Thursday so a consensus of available guidance looks reasonable. Guidance continues to diverge considerably for details of central Pacific flow during the late week/weekend time frame. 00-06Z GFS runs are on the faster/flatter side of the spread with an upper trough reaching east of 180 longitude by early Thursday, though interestingly the 06Z GFS is so fast with an upstream low that it settles into a position close to the 00Z ECMWF by early Saturday. Among other solutions the 06Z FV3 GFS looks most extreme with a deep upper low reaching just northwest of the main islands. The 00Z ECMWF adjusted from the prior 12Z run that had a weaker overall system aloft but brought lower heights and more rainfall to the northwestern islands. Given the ongoing spread and model variability, the 00Z GEFS/ECMWF means provide the most reasonable forecast while waiting for better agreement from operational runs. Based on this solution expect trades to turn east-southeasterly as a front approaches from the northwest by next weekend. Rausch