Hawaii Extended Forecast Discussion NWS Weather Prediction Center College Park MD 811 AM EDT Sat Aug 20 2016 Valid 00Z Sun Aug 21 2016 - 00Z Sun Aug 28 2016 Latest models and ensemble means offer similar evolution over the next seven days though with some differences in moisture during the most active period of weather in the first half of the week. Trades will fluctuate depending on combined strength and proximity of eastern Pacific high pressure. Expect winds to trend gradually weaker from now to about 12Z Tuesday, stronger into Thursday, then weaker again during Friday-Saturday. There is agreement in principle upon a band of enhanced moisture reaching the islands from the east/southeast around Sunday night-Wednesday. This moisture combined with a modest weakness aloft as well as potential sea breeze boundaries allowed by weak trade flow may promote some areas of heavy rainfall in that time frame. However beyond the loose agreement there are meaningful differences in specifics with recent ECMWF runs notably lower and farther westward with the axis of highest precipitable water values. What trends exist over the past two 12-hourly ECMWF runs and 6-hourly GFS runs seem to suggest an end result somewhere between the two sides of the range. Note that maximum PWATs in the 00z GEFS mean are slightly lower than in the 00Z/06Z GFS runs but still reach 2.5-3.0 standard deviations above normal over the Big Island around Monday-Tuesday. There should be a drying trend over the latter half of the week with higher heights aloft and a decrease in deep moisture. Rausch