Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
233 FXHW60 PHFO 221325 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 325 AM HST Fri Aug 22 2025 .SYNOPSIS... High pressure north of the islands will maintain moderate to locally breezy trade winds through the weekend, followed by a slight decrease in winds early next week. Stable summertime conditions will bring periods of mainly windward and mauka showers, while most leeward areas remain rather dry. && .DISCUSSION... No significant changes to the forecast this morning. The forecast has been nudged towards the latest National Blend of Models, which does boost PoPs over the windward slopes of the Big Island later today in response to an area of low clouds upstream of the islands being carried in on the trades. This solution also lowers PoPs a bit over the Big Island windward slopes on Monday and Tuesday, and the windward sides of all the islands Thursday. Broad high pressure remains to north and northeast of the islands, with mid level ridging over the islands. Although the high is not particularly strong, the ITCZ is near 10N, making it a little further north than normal. This combination will continue to bring a stable and relatively dry weather pattern over the islands with moderate to locally breezy trades. The overnight soundings continue to show an inversion based between 5,000 and 7,000 ft, and little to no organized moisture is noted in the trade wind flow. Anticipate windward rainfall totals to remain low. Little change is expected to the relatively dry and stable trade wind weather pattern through Sunday. Trades may ease a notch and shift out of a more easterly direction for Monday and Tuesday as the surface ridge to the north is briefly weakened. The mid-level ridge should remain strong enough to maintain stable conditions, and an area of tropical moisture may clip the Big Island on Monday or Tuesday, though odds favor the moisture passing to the south. Longer term guidance suggests moderate trades and continued modest shower activity for the second part of next week. && .AVIATION... High pressure remains to the north and northeast of the islands and will maintain moderate to breezy trades. Mid level ridging will help to provide a stable airmass overhead that will limited rainfall totals. Clouds and showers will remain focused primarily over the windward and mountain areas, particularly overnight and into the morning hours. MVFR conditions will be possible in showers, otherwise VFR will likely prevail. No AIRMETs are currently in effect, and none are expected to be issued today. && .MARINE... A high pressure ridge north of the Hawaiian Islands will maintain fresh to locally strong trade winds through early next week. The Small Craft Advisory (SCA) was extended in time through Sunday for the windier waters and channels near Maui County and the Big Island through Saturday. This SCA will likely continue for these windier waters into early next week. A series of small overlapping medium and long period south (170-190 degree) swells will continue through Saturday, with surf heights near the summertime average through Friday along south facing shores. Surf heights should decrease to background levels early next week as the swell energy fades. Another small, long period south swell will arrive by next week Tuesday. Choppy conditions will continue for east facing shores through the forecast period due to the persistent fresh trades. Surf along north facing shores will remain nearly flat through next week. Peak high tides associated with the lunar cycle will lead to minor coastal flooding along shorelines and low lying coastal areas during this afternoon`s high tide. A Coastal Flood Statement remains in effect for minor coastal flooding. These coastal high water levels will decrease on Saturday. && .FIRE WEATHER... Trade winds will remain in the moderate to locally breezy range into Sunday, while a ridge aloft maintains an inversion between 5,000 and 7,000 ft. Under this stable and rather dry weather pattern, relative humidity will drop into the low to mid 40s percent range each afternoon, bringing near critical fire weather conditions. We do not anticipate fire weather headlines through the weekend, but fire weather concerns will be elevated. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 PM HST Sunday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...M Ballard AVIATION...M Ballard MARINE...Bohlin FIRE WEATHER...M Ballard