Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
240 FXHW60 PHFO 220137 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 337 PM HST Fri Jun 21 2024 .SYNOPSIS... High pressure far north of the islands will maintain gusty trade winds through early next week. Passing showers will favor windward and mountain areas, especially during nights and mornings. Although some light rainfall could occasionally spread leeward, most leeward locations will remain dry. && .DISCUSSION... High pressure centered roughly 900 miles north of Kauai remains firmly in place this afternoon, producing a stable and gusty trade wind regime across the islands. Latest satellite and radar imagery shows isolated to scattered light showers moving into windward and mountain locations, primarily over the western islands of Kauai and Oahu. Farther east, fewer clouds and showers are noted upstream of and over windward Big Island. Gusty trades have been observed across the islands today, particularly in typically windier areas and valleys. However, speeds have generally hovered below Wind Advisory criteria. Guidance suggests that a subtle shortwave moving over the state tonight could increase windward and mauka shower activity through early Saturday morning. Otherwise, the overall weather pattern will remain largely unchanged through the weekend with high pressure remaining in place to the north. Trades on Saturday are expected to be similar to those experienced today, so have opted not to issue a Wind Advisory at this time. Breezy trade winds and a typical summertime rainfall pattern will prevail into early next week. Modest showers will be focused over windward areas, mainly at night and in the morning. With the exception of afternoon and evening showers over the Kona slopes of the Big Island, leeward areas will remain mostly dry. Trade winds will likely decline to moderate levels by Tuesday or Wednesday as the high to the north weakens and is displaced eastward. && .AVIATION... Breezy to locally gusty trades will continue across the region for the next few days. Brief SHRA are expected mainly over windward and mauka areas. While VFR conds are generally expected to prevail, we could see some brief MVFR conds in any SHRA. AIRMET Sierra remains in effect for mtn obsc for windward locations of Kauai, Oahu, Molokai, and Maui. AIRMET Tango remains in effect for mod low level turb over and downwind of island terrain due to the breezy trade winds. && .MARINE... Strong easterly trades and resulting rough seas will continue into early next week, supporting the Small Craft Advisory in place for all waters. Guidance shows a slight downward trend in wind speeds next week between Tuesday and midweek, due to the surface ridge potentially weakening to the north. Surf along east-facing shores will remain rough through early next week due to the aforementioned strong trades locally and upstream of the state. Surf along south-facing shores will trend up to around average this weekend as a small south swell arrives. This should be short- lived, with a downward trend expected early next week. Despite a blocking high that has set up over our typical swell window near/southeast of New Zealand, guidance shows a gale forming to its northeast this weekend with the head of the fetch aimed at the islands within the 170 to 190-degree directional band. Given the shorter travel distance, surf could trend up late next week. Surf along north-facing shores could trend up above flat levels early next week due to a small, medium-period northwest swell from a marginal gale currently lifting northeastward toward the Aleutians. On its heels is a gale- to storm-force low, currently a couple hundred miles east of Japan, that could send a similar northwest swell through the area late next week. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 PM HST Sunday for all Hawaiian waters- && $$ DISCUSSION...Vaughan AVIATION...Walsh MARINE...TS