Hawaii Extended Forecast Discussion NWS Weather Prediction Center College Park MD 821 AM EDT Sun Jul 09 2017 Valid 00Z Mon Jul 10 2017 - 00Z Mon Jul 17 2017 A prominent 594-dm mid-level ridge centered over the central Pacific will dominate the mid-latitudes while weaknesses within the subtropics are forecast to gradually slide westward. One particular feature is expected to peel off from a longwave trough across the eastern Pacific and slowly migrate westward nearing 150W longitude by 13/0000Z. Recent models seem to favor keeping this disturbance northeast of the Hawai`ian islands next week as a ridge re-establishes itself to the north, albeit in a more weakened state. By next weekend, ensemble mean solutions show an elongated longwave trough trying to set up as the ridge begins to flatten and shift westward. At the surface, recent guidance depicts an anticyclone to the north-northeast will strengthen by at least 5 mb the next few days which will continue to support moderate trades across Hawai`i. Eventually this ridge will weaken a tad toward the end of next week which should decrease the strength of the climatological trades. Regarding chances for precipitation, an increase in the coverage and intensity of shower activity is likely during the Tuesday through Thursday time frame as precipitable water values spike considerably. Recent solutions show such moisture content rising to above 1.50 inches with the 06Z GFS/GEFS mean being notably wetter across the northern most islands. Eventually drier air will work its way westward bringing conditions closer to normal where the usual windward showers will be favored with heavier amounts in orographically favored locations. Rubin-Oster