


Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
610 FXHW60 PHFO 060209 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 409 PM HST Sun Oct 5 2025 .SYNOPSIS... A surface trough will approach, and then move over, the western end of the state tonight through Monday. As the feature moves through, increased clouds and showers are expected over the western islands. Ahead of it, winds will weaken and become more southeasterly, resulting in a daytime sea breeze and nighttime land breeze regime through at least Wednesday night. Moderate trade winds will return near the end of the week. && .DISCUSSION... Regional satellite imagery shows a well-defined band of showers associated with a trough north of the main Hawaiian Islands, just inside the northern offshore waters this afternoon. In addition to this surface trough, a distinct upper low is located near 30N 150W as of 0100 UTC, where towering cumulus and heavier showers are observed roughly 550 to 800 miles northeast of Honolulu. Closer to the islands, a late morning ASCAT pass and surface observations from around the state throughout the day reveal moderate trade winds that are slightly more northeasterly over the western end of the state in closer proximity to the surface trough, and more easterly over the eastern end of the state farther away from the feature. Relatively few showers and low clouds are moving into the islands on the moderate trades at this time, though afternoon sea-breeze induced cloud buildups and a few showers have developed over the Big Island again today. As strong high pressure builds behind a cold front moving quickly eastward across the North Pacific well north of the region, the surface trough near the main Hawaiian Islands will be displaced southward near and then over western islands. The band of clouds and showers discussed earlier associated with this feature is expected to approach Kauai tonight, reaching and passing over the Garden Isle Monday morning. As it weakens, it could also reach Oahu by the early afternoon hours on Monday. With this afternoon`s forecast updates, shower chances have been adjusted upward for the western end of the state through Monday, though it is notable that neither the HREF (High Resolution Ensemble Forecast System) probabilities nor the NBM PQPF (Probabilistic Quantitative Precipitation Forecasts) get too carried away with rainfall accumulations, likely due to the band`s quick movement over the islands and weakening nature. As the trough approaches the western islands, the background moderate trade wind flow will weaken to become light out ahead of it. This will mark a return of daytime sea breezes and overnight land breezes, particularly for the eastern islands on Monday, then statewide from Monday night through at least Wednesday night as the light background winds become more southeasterly. With this pattern, increased leeward and interior shower activity can be expected from late morning through early evening each day, followed by clearing and limited showers each night. Moderate trades may begin to fill back into the region by Thursday or Friday as strong high pressure builds far to the northeast of the region and then moves southward near the end of the week. There is some uncertainty in this, however, as there are some differences between global models regarding another surface trough that could develop north of the islands mid- to late-week. && .AVIATION... Light to locally moderate trades bringing periods of MVFR cond in isol SHRA across windward and mauka locations. Winds will diminish into a land/sea breeze pattern increasing clds and SHRA across leeward and interiors of the islands. MVFR possible in any SHRA, otherwise VFR prevails. No AIRMETs in effect. && .MARINE... The current moderate, medium-period north-northwest (330 degree) swell filled in overnight well above model-predicted values and is currently still running around 8 feet at 12 seconds. Therefore, will extend the High Surf Advisory (HSA) through midnight tonight (HST). The swell should drop below advisory level later tonight, then continue to fade over the next few days. The Small Craft Advisory has also been extended until midnight tonight for 10 foot seas in areas exposed to this swell. 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. High pressure the northeast will continue to bring moderate east- northeast trades to the region tonight. A 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. && .FIRE WEATHER... Light winds and increased showers will mitigate any fire weather concerns through the week. && .HFO WATCHES/WARNINGS/ADVISORIES... High Surf Advisory until midnight HST tonight for north and west facing shores of Niihau, Kauai, Oahu, Molokai, and north facing shores of Maui.. Small Craft Advisory until midnight HST tonight for Kauai Northwest Waters-Kauai Windward Waters-Kauai Leeward Waters- Kauai Channel-Oahu Windward Waters-Kaiwi Channel-Maui County Windward Waters. && $$ DISCUSSION...Vaughan AVIATION...Walsh MARINE...TS FIRE WEATHER...Vaughan