034 FXHW60 PHFO 010128 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 328 PM HST Sat May 31 2025 .SYNOPSIS... Moderate to breezy easterly trade winds will briefly shift out of the east-southeast tonight through Monday as a broad surface trough develops far northwest of the islands. Increasing moisture and instability may lead to enhanced shower activity Sunday into Monday, particularly over the western end of the state. Breezy easterly trades and drier conditions are expected to return during the first half of next week as the trough weakens and shifts away from the region. && .DISCUSSION... Moderate to breezy trades will veer east-southeast tonight through Monday as a strengthening high well to our northeast interacts with a broad trough approaching from the northwest. This slightly veered wind direction will disrupt the trade wind flow across the smaller islands and allow for the development of land and sea breezes across leeward areas. An upper-level trough approaching from the northwest will lower 500 mb heights and temperatures, introducing some instability over the western half of the state Sunday through early next week. The instability associated with this feature and an influx of low level moisture may help to enhance windward showers overnight and sea breeze- induced clouds and showers over leeward areas during the afternoons, particularly over the western half of the state. This east-southeasterly flow may also transport vog to a majority of the island chain through early next week. A return to breezy and more stable trade wind conditions is expected by Monday night as upper-level heights rise, drier air filters in from the east, and the surface trough weakens and moves away from the state. This will result in a more typical easterly trade wind pattern through Thursday, with showers favoring windward and mauka areas and generally dry conditions prevailing elsewhere. For the latter end of the week and into the weekend, a weak upper-level trough will move overhead, introducing some more instability to the region. However, the instability and available moisture look rather unimpressive, so not expecting much more than perhaps a slight enhancement of trade wind showers for the end of the forecast period at this time. && .AVIATION... AIRMET Tango in effect for tempo moderate turbulence below 7000 feet south through west of mountains due to breezy trade winds. The winds will maintain strength into Sunday, but veer southeasterly and partially block some leeward areas from the full strength of the winds, and moving the main turbulence area to the northwest sector of the islands. LLWS possible through the rest of this afternoon and Sunday afternoon at near PHOG terminal. Low clouds and showers may fill in a bit overnight with possible MVFR ceilings and visibility across all windward areas. && .MARINE... Moderate to locally strong trade winds will veer out of the east to east-southeast late tonight and Sunday as the subtropical ridge is pushed closer to the islands by a developing trough northwest of Kauai. The Small Craft Advisory (SCA) has been adjusted slightly from the typically windy waters around the Big Island and Maui to account for enhanced winds north of these islands. On Monday, the trough will move westward, and the surface ridge to the north will rebuild, causing trade winds to shift back to a more easterly direction. The SCA will likely be reconfigured to the typically windy waters by Monday and should remain in place through at least midweek. A late season northwest swell is peaking this afternoon, bringing surf well above seasonal average. Nearshore PacIOOS buoys at Hanalei and Waimea Bay showed the 320-330 degree swell at 6 to 7 feet at 13 to 14 seconds, producing surf just below High Surf Advisory levels. The swell will decline tonight and Sunday, with north shore surf dropping to near June average for the first half of the work week. Tiny surf is expected by Thursday. Surf along south-facing shores will continue to see a mix of small background swell for the next few days, followed by a small inconsistent southwest swell late Tuesday and Wednesday. A storm low moved into the Hawaii swell window southeast of New Zealand yesterday and is generating seas in excess of 30 feet today. The resulting long-period south-southwest swell will build on Friday and peak next weekend, leading to surf well above June average. Surf along east-facing shores will remain small and choppy through Sunday, then gradually build to near or above seasonal average Monday through Wednesday due to a return of fresh to strong trades over and upstream of the islands. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 AM HST Monday for Maui County Windward Waters-Pailolo Channel-Alenuihaha Channel-Big Island Windward Waters-Big Island Leeward Waters. && $$ DISCUSSION...Farris AVIATION...Foster MARINE...Wroe