Hawaii Extended Forecast Discussion NWS Weather Prediction Center College Park MD 751 AM EDT Sun Jun 11 2017 Valid 00Z Mon Jun 12 2017 - 00Z Mon Jun 19 2017 As mid/upper-level ridging exits toward the east, some sort of weakness pinching off the prevailing westerlies may affect the Hawai`ian island chain. The signal is not quite as strong as in recent days although model solutions do depict a break in the west-east ridge oriented along the subtropical/tropical Pacific. This particular weakness/inverted trough is forecast to track westward headed toward 170E longitude by the end of next weekend. The 06Z GFS/00Z ECMWF appear to be in agreement with this scenario while the 00Z CMC lags off toward the east a bit. Such clustering in the GFS/ECMWF solutions is nearly in phase with their respective ensemble means. At the surface, persistent trade winds should be the norm given a broad anticyclone to the north and east of the region. Later in the work week, there could be a gradual slackening of this wind regime given the approach of a weak north/south inverted trough accompanying the passing disturbance aloft. Relative to yesterday, the extent of troughing is much more subtle, thus indicative of weaker surface convergence fields. Otherwise, expect general trades to dominate the pattern through the remainder of the forecast. Regarding precipitation, the usual windward showers are expected amidst an active period of trades and high precipitable water air. Such values range from around 1.50 to 1.75 inches for the most part. An uptick in rainfall coverage is likely by mid-week, particularly in the 06Z GFS which has been its motif in recent days. Other solutions are quite a bit drier but do believe there should be an expansion in coverage/intensity given the weakness crossing overhead. While still uncertain, the heaviest rainfall is expected across the island of Kauai. This agrees with the 00Z ECMWF which has trended wetter for the Wednesday/Thursday timeframe. In the wake, the coverage of showers should diminish given the intrusion of lower precipitable water air into the region. Rubin-Oster