Hawaii Extended Forecast Discussion NWS Weather Prediction Center College Park MD 816 AM EDT Wed Oct 24 2018 Valid 00Z Thu Oct 25 2018 - 00Z Thu Nov 01 2018 ...Heavy rain threat for parts of the Aloha state next week... Ensembles agree on developing significant troughing between 160-170W early next week which will support an increasingly wet pattern for much of the region. A cold front currently north of 30N will dip southward but stay north of Hawai'i and dissipate over the weekend as a lead trough over the North Pacific pushes eastward. In its wake (and over the Western Pacific near 160E) upper ridging will build which will help dig troughing to the west of the state. The ECMWF ensembles were generally bit quicker than the GEFS ensembles with the trough axis due to how the northern piece progresses eastward along 40-50N, but for now would recommend an intermediate solution. To the south, some models spin off a coherent surface low off the ITCZ and bring it northeastward over the western islands next week which may act to enhance an already wet pattern. Predictability is low in such a solution. Trades will veer from ENE to E to SE and eventually south as the trough and surface cold front approach next week. Total rainfall potential is high with this pattern given the amplitude of the trough (500mb heights about 3 standard deviations below average) and surge of tropical moisture from the ITCZ (probability of precipitable water values greater than 2 standard deviations above average > 50% per the GEFS). Several inches of rain are possible over especially the western islands but the entire state has the potential for significant rain next week. Fracasso