Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
612 FXHW60 PHFO 180148 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 348 PM HST Sun Aug 17 2025 .SYNOPSIS... Breezy trade winds will briefly weaken this evening and tonight as a weak low-level trough moves through the state. A slight increase of clouds and showers are expected through Monday, with drier conditions returning by Tuesday. Breezy trades will return by Tuesday afternoon with our typical summer time trade wind weather (stable and mostly dry conditions) expected during the second half of week. && .DISCUSSION... A weak surface trough associated with the remnants of former Tropical Cyclone Ivo will move through the state this evening into Monday, which will cause the trade winds to briefly weaken and veer toward the east- southeast. An increase of showers are also expected, although rainfall amounts should remain modest at best and mainly be focused over windward and mountain areas. Although it is the remnants of a former Tropical Cyclone, precipitable water amounts remain unimpressive with CIMSS MIMIC precipitable water showing values of around 1.4 inches. Due to the limited moisture, many leeward areas should continue to remain dry with the exception of the Kona slopes of the Big Island. As this trough exits the area Monday night, we should see less clouds and drier conditions on Tuesday. Trade winds should gradually strengthen Tuesday afternoon with moderate to locally breezy trades expected throughout the rest of the week. Typical summer time trade wind weather is expected throughout the second half of the week with stable and mostly dry conditions. Subtle increases of moisture will bring in some windward showers at times with mostly dry conditions persisting over leeward areas. Trade winds could slightly strengthen over next weekend. && .AVIATION... Moderate to locally breezy trades through the forecast period. Low cigs and SHRA expected over windward and mauka areas. Brief MVFR conds possible in SHRA, otherwise VFR prevails. No AIRMETs in effect at this time, however AIRMET Sierra may be needed for mtn obsc overnight due to increased SHRA. && .MARINE... Ridging north of the state will result in a continued stable weather pattern with fresh to locally strong trades persisting through the week. The Small Craft Advisory (SCA) has been scaled back to only include the notoriously windier waters surrounding Maui County and Big Island. This SCA will be in effect through at least Tuesday night with a time extension likely into late week. Trades may briefly weaken below SCA thresholds early Monday morning as a weak trough from the remnants of Tropical Cyclone Ivo pass north of the islands. Trades will restrengthen back to moderate to locally strong speeds Monday afternoon and likely maintain these magnitudes through the remainder of the week. The ongoing 2 to 3 foot, medium period south southwest (180-200) swell has held today and generated waist to near head high surf within higher sets. A series of very similar small, medium period south swells will pass around the islands through the week. These swells will help maintain seasonal south-facing shore surf heights. Expect east-facing shore chop to decline tonight into Monday morning as trades drop off a touch. Fresh trades will once again introduce elevated choppy conditions to eastern exposures from Monday afternoon through the rest of the week. && .FIRE WEATHER... Conditions should remain below critical fire weather thresholds through the first half of this week. A weak low-level trough will move across the state this evening through Monday, bringing an increase in humidity and shower activity and weakening the trade wind inversion. 00Z sounding from Lihue shows the trade wind inversion at around 5000 feet this afternoon, but we should the trade wind inversion weaken and rise to around 8000 to 10,000 feet by Monday afternoon. As the trough exits the area, we should see the return of stable and dry conditions by Tuesday afternoon. During the second half of the week we should see stable and dry conditions with a stronger trade wind inversion at around 5000-6000 ft. Breezy trades are also expected during this time, which could produce elevated fire weather concerns later in the week through next weekend. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 AM HST Wednesday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Kino AVIATION...Walsh MARINE...Blood FIRE WEATHER...Kino