Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
627 FXHW60 PHFO 181353 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 353 AM HST Mon Aug 18 2025 .SYNOPSIS... Breezy trade winds will gradually return today as weak trough moves west of the state tonight. Isolated to scattered clouds and showers will persist through the morning hours mainly along windward and mauka regions with few showers spilling over the leeward areas at times. A gradual drying trend is expected tonight into Tuesday with 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 continue to move west over the state today, allowing trade wind speeds to increase throughout the day. This morning sounding from Lihue shows tradewind inversion height around 9 kft with precipitable water vapor values around 1.68 inches. Scattered, light to moderate showers can be seen on the radar early this morning, mainly focused over windward and mountain areas with some showers spilling over to leeward areas at times. Expect showers to ease slightly during the day as drier air filters in from the east, expect for the Kona slopes of the Big Island, which will see some clouds and shower development this afternoon as seabreezes develop. As this trough exits the area tonight, we should see less clouds and drier conditions on Tuesday. Trade winds will continue to 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 will persist through the forecast period. Low cigs and SHRA will continue over windward and mauka areas through the early morning hours generating MVFR conds in SHRA, otherwise VFR prevails. AIRMET Sierra has been issued for MTN OBSC overnight due to an increase in low clouds and SHRA along windward and mauka regions. Conds may become VFR during the afternoon hours has inversion heights increase and SHRA decrease. AIRMET Tango may be needed later today as wind speeds increase below the inversion. && .MARINE... Fresh to locally strong trades will persist through the week as ridging stays situated north of the state. The Small Craft Advisory (SCA), for the typical windy waters around Maui and the Big Island, will remain in effect through at least Wednesday morning with a likely extension into the weekend. The ongoing small, medium period south (180-190) swell will hold through tomorrow and generate waist to near head high surf within higher sets. A slightly larger, medium to long period, south swell is progged to arrive on Wednesday, adding a little bump to surf heights along south facing shores through the remainder of the work week. Choppy conditions will continue for east-facing shores through the forecast period due to the persistent fresh trades. Meanwhile, expect surf to be flat to tiny along north facing shores. && .FIRE WEATHER... Conditions should remain below critical fire weather thresholds through the first half of this week. A weak low-level trough will continue to move across the state today, bringing an increase in humidity and shower activity and weakening the trade wind inversion. 12Z sounding from Lihue shows the trade wind inversion has lifted from 5000 feet Sunday afternoon to 9000 feet early this morning. 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...Almanza AVIATION...Almanza MARINE...Thomas FIRE WEATHER...Almanza