Hawaii Extended Forecast Discussion NWS Weather Prediction Center College Park MD 818 AM EDT Wed Sep 13 2017 Valid 00Z Thu Sep 14 2017 - 00Z Thu Sep 21 2017 Models and ensembles show good agreement with respect to the large-scale pattern across the Central Pacific over the next week. A stationary frontal boundary currently situated north of Hawaii is expected to gradually wash out over the next few days as an upper-level weakness in the subtropical ridge drifts westward. The GFS and ECMWF both show the majority of precipitation associated with this front remaining north of the state. The front seems to be disrupting the low-level flow across the Central Pacific, and easterly trades are expected to remain relatively weak or even non-existent until the front dissipates. From Friday onward an upper-level ridge is forecast to amplify across the north central Pacific, and a strengthening surface high will result in increasing easterly low-level flow of 10-20 kt reestablishing across the Islands. Additionally, the ECMWF and GFS show agreement that drier air will filter into the Hawaiian Islands from the east, as evidenced by decreasing PWs to near or even slightly under 1 inch. The lower PWs are expected to result in below average shower activity despite the strengthening low-level easterly flow. Ryan