251 FXHW60 PHFO 080625 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 825 PM HST Thu May 7 2020 .SYNOPSIS... A trade wind weather pattern will continue through the weekend, due to high pressure far north of the area. Clouds and passing showers will favor windward and mauka areas, with a few showers briefly spreading to select leeward locations. Winds will become weaken toward the middle of next week as the high moves to a position far northeast of the area. && .DISCUSSION... A 1027 mb high far NW of the islands is supporting moderate to locally breezy NE trade winds, with embedded moisture providing passing showers over windward and mauka areas. Winds are sufficiently strong enough to blow a few showers to some leeward locations. This general weather pattern is expected to persist through the weekend as the eastward-moving surface high passes far N of the islands, allowing winds to shift to the E. As the high moves into the NE Pacific Tuesday and Wednesday, a front will pass far N of the area, and winds will diminish, likely becoming light and variable over land through the end of the week. A low aloft is forecast to develop W of the area late in the weekend, then pass over the islands on Monday. This feature will likely destabilize the island atmosphere, and potentially lead to increased shower coverage and intensity, especially windward and mauka. After the low departs to the NE Tuesday, a trough aloft may linger near islands through mid-week. Afternoon and evening clouds that form over the islands in response to daytime heating/sea breeze convergence will likely drop a few showers. && .AVIATION... A moderate northeast trade wind flow will continue into Friday as an area of high pressure remains far northwest of the main Hawaiian Islands. VFR will be the prevailing flying condition overnight, although there will be brief periods of MVFR ceilings and vis associated with embedded showers riding in with this northeast wind flow. Satellite and radar show scattered low clouds and showers extending far upwind of the islands east of Oahu, and this is where most of the showers will be overnight. To a lesser degree, Oahu and Kauai will get a stray shower or two. The showers will not be limited to the windward and mountain areas, as the trades are strong enough to carry the showers well into the lee areas of the smaller islands. The evening clouds covering mainly the lower half of leeward Big Island, will slowly clear out. A shower or two is possible overnight along the coastline there and adjacent waters. Tops of the showers are around 10k feet with higher tops to 15k feet in the heavier showers. No AIRMETs are currently in effect. && .MARINE... Moderate to fresh northeast trade winds will continue through Friday, then shift out of the east over the weekend as high pressure builds north of the islands. Although Small Craft Advisory-level winds are not expected, brief periods with pockets of fresh to strong breezes can't be ruled out across the windier areas and channels. For next week, guidance shows a weakness in the ridge developing as a front passes far to the north. If this evolves, light winds will become a possibility by the midweek time frame. Surf along north facing shores will trend up later tonight through Friday as a moderate northerly swell arrives from a gale that passed far north of the state over the past few days. This source should hold through Saturday, then fade through the day Sunday. Low pressure that has developed over the far northwest Pacific near the Kurils (around 2500 nm away from the islands) has intensified into a storm over the past 24-hrs. Recent satellite data reflected this and showed a favorable fetch aimed at the islands within the 300-310 deg directional band. Guidance remains in decent agreement and shows a small, long-period west-northwest swell arriving from this source by Tuesday. Surf along south facing shores will trend up Friday through the weekend as a small south and southwest swell fill in from recent southern hemisphere activity. Looking ahead into next week, latest data and analysis showed a decent sized fetch setting up over Hawaii's swell window southeast of New Zealand today. An altimeter pass showed seas in this area up to 30 ft. As this system continues eastward across the far southern Pacific this weekend, guidance shows this fetch aimed at the islands holding. As a result, a long- duration event seems possible that should begin around Wednesday, then carry into next weekend (15th/16th) as the swell shifts more out of the south. Surf along east facing shores will remain small into the weekend due to the lack of trades upstream of the state across the eastern Pacific. A downward trend appears possible by midweek as the trades diminish. && .HFO WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Birchard AVIATION...Lau MARINE...Gibbs