Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
089 FXHW60 PHFO 051325 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 325 AM HST Sun Oct 5 2025 .SYNOPSIS... Light to moderate winds will prevail through the rest of today. A broad surface trough will develop northeast of the state early next week, then propagate across the island chain. As this occurs, winds will weaken and become east-southeasterly, resulting in a daytime sea breeze and nighttime land breeze regime. Moderate trade winds will return near the end of the week. && .DISCUSSION... Latest observations and advanced scatterometer pass of the islands indicate light to locally moderate easterly trades prevail across the region this morning -- just weak enough to support localized sea breezes later today. Meanwhile reflectivity shows isolated showers trickling into the windward and mauka area of most islands, producing little to no precipitation. The only notable exception being the Hilo area on the Big Island, where a heavier shower developed briefly. This morning`s 12z sounding from Hilo shows the temperature inversion heights ranging from 6000 to 7000 feet, with precipitable water values slightly lower than yesterday, at around 1.24 inches. Light to locally moderate trades will continue through today. Latest model guidance of the GFS and ECMWF continue to depict a broad surface trough developing just northeast of the islands on Monday, with a well-defined low aloft. Models project this trough to slowly meander westward toward the islands and passing over between Monday and mid-week, then becoming less defined as it and the associated low aloft exits well north of the state. Winds across the islands during this time will become noticeably weaker, veering east-southeasterly, and transitioning to a more pronounced land and sea breeze pattern across the entirety of the Hawaiian Islands. In such a pattern where the local scale winds are virtually absent, island heating will support sea breezes during the day, which will enhance leeward and interior shower activity, and overnight cooling will drive land breezes at night, clearing the night skies and limiting showers. The land/sea breeze regime is progged to continue through the latter half of the week until the aforementioned surface trough and associated low aloft exit the vicinity of the islands late Friday. Thereafter, moderate trades are expected to return to the islands just in time for the weekend, persisting through the remainder of the outlook period. && .AVIATION... Light to locally moderate trades continue to prevail across the Hawaiian Islands, bringing periods of MVFR conditions in isolated showers across windward and mauka locations. Winds will begin to diminish into a more land and sea breeze pattern toward the latter end of the TAF outlook, increasing clouds and shower activity across leeward and interiors of the islands. Localized MVFR is possible within any shower activity, however, most sites will remain VFR. No AIRMETs are currently in effect. && .MARINE... High pressure the northeast will continue to bring moderate east- northeast trades to the region today. A dissipating front and trough to the northwest will continue to weaken today. A new trough is expected to develop northeast of the state over the next couple of days, and then move to the southeast, and will weaken winds to light and variable through the first half of next week. The current moderate, medium-period north-northwest (330 degree) swell continues to fill in, and is expected to peak today below High Surf Advisory (HSA) levels. The swell will then slowly fade over the next few days. A small medium to long-period swell from the northwest (320 deg) is expected to fill in Monday, peak Tuesday and decline through the middle of next week. The current small, long-period southwest (210 deg) swell will continue to slowly decline into early next week. A small, long- period southwest swell may arrive late today, and build into early next week before subsiding. Another small long-period southwest (200 deg) swell is possible by the later half of next week. Surf along east-facing shores will remain below average over the next several days, even with the slight boost today with the brief uptick in trades. && .FIRE WEATHER... Wind speeds and humidity will remain below critical fire weather thresholds for the next several days. Temperature inversion heights across the state will range from 6000 to 7000 feet through tonight. && .HFO WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Pierce AVIATION...Pierce MARINE...M Ballard FIRE WEATHER...Pierce