Hawaii Extended Forecast Discussion NWS Weather Prediction Center College Park MD 829 AM EDT Tue Sep 25 2018 Valid 00Z Wed Sep 26 2018 - 00Z Wed Oct 03 2018 An area of disturbed weather near 135W longitude will track westward underneath a sprawling west/east oriented ridge. Even if tropical cyclone development were to unfold, the latest guidance suggests this system should remain well to the south of Hawai`i. Otherwise, this mentioned ridge is forecast to maintain its presence throughout the forecast period. By early next weekend, models depict the southern extension of height falls approaching from near the International Dateline. However, it appears these should stay harmlessly to the north of the island chain. Regarding the surface wind fields and rainfall chances, broad warm advection ahead of a mid-latitude system will initially encourage east-southeasterly flow while gradually weakening in time. The upstream cold front should near the northern most islands but weaken as the upper forcing lifts farther into the mid-latitudes. Surface gradients should tighten by Friday given ridging to the north and possible tropical development to the south. This will ultimately enhance the trades over the region with potential gustier winds across the Big Island depending on the strength of the possible wave. Once this skirts well southwest of Hawai`i, the trades should slacken a bit by Sunday into early next week. The best threat for organized rainfall will be early in the period given precipitable water values jump to around 2 inches. It should be most focused over the northern islands given better surface convergence due to the presence of the approaching frontal zone. Rubin-Oster