Hawaii Extended Forecast Discussion NWS Weather Prediction Center College Park MD 830 AM EDT Tue Sep 05 2017 Valid 00Z Wed Sep 06 2017 - 00Z Wed Sep 13 2017 Early in the forecast period, models show an inverted upper trough sliding westward which will begin to approach the Hawai`ian island chain by Thursday while flattening in time. The 00Z UKMET solution seems to be a bit slower as a myriad of vorticity centers linger over the region into the weekend. Gradually the flow to the north will amplify but should remain confined to the mid-latitudes. By early next week, the southern extent of these height falls may pinch off with a negative height anomaly spinning north of Kauai. The operational 00Z GFS/ECMWF are one of the more amplified solutions relative to their 70 ensemble members. At the surface, weak pressure gradients will initially lead to very light wind fields before an anticyclone to the north-northeast begins to strengthen. This will ultimately lead to a return of the climatological trade wind regime with a gradual uptick to around 20 knots by the end of the work week. Eventually a shift to low-level south-southeasterly flow is expected as warm advection ensues ahead of the mid-latitude height falls. The 06Z GFS is by far the most aggressive solution depicting much sharper gradients with a deep low just east of 160W by next Tuesday morning. Regarding precipitation threats, the trade driven showers should pick up in coverage and intensity as the wind field begins to strengthen later in the week. This is coupled with multiple spikes in precipitable water values across the islands. Some frontal showers may approach the northern most islands next week although this is primarily a 06Z GFS scenario. Rubin-Oster