Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
291 FXHW60 PHFO 120120 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 320 PM HST Fri Jul 11 2025 .SYNOPSIS... High pressure far northeast of the state will lead to moderate to locally breezy trade winds. Expect to see fairly typical summertime weather as clouds and showers favor windward and mauka areas, with an uptick in showers this weekend and early next week. && .DISCUSSION... A 1033 mb high remains nearly stationary far northeast of the state. Water vapor imagery shows a compact upper level low several hundred miles north of us that is slowly drifting westward. Even with the upper low nearby, 00z soundings show a typical subsidence inversion just under 7kft at Lihue and down to 5kft at Hilo. Rainfall amounts across the state have been roughly a quarter to a half inch over the past 12 hours, with more of those reports across Kauai and Oahu. The high northeast of the state will gradually shift northward over the next couple days, but we`ll remain in a pretty consistent trade wind flow. While the upper low is expected to stay north of the state, a shortwave trough rotating around it will help raise inversion heights this weekend. A pocket of moisture just outside the offshore waters, apparent as a showery band of cumulus on satellite imagery, will enhance rainfall chances this weekend. Trade winds speeds may lower a bit but still remain borderline breezy. While the trades will focus most rainfall across windward sections, there will be some brief showers reaching leeward areas as well. 12z/18z models show another pocket of moisture farther east (east of 140W) tracking across the state early next week. MIMIC Total Precipitable Water imagery shows higher values in this area (about 1.6-1.8 inches) compared with the first band at the edge of our offshore waters (about 1.3-1.5 inches). The GFS is more aggressive bringing this moisture across the state Monday/Tuesday, with the ECMWF fading out the signal more. Either way should lead to an uptick in windward showers early next week, with some rain reaching leeward as well. It`s interesting to note that the NBM lights up showers across the Kona slopes on the Big Island Monday afternoon more than any day this forecast period. Beyond Tuesday, we return to a more typical summertime trade wind pattern with showers focused primarily at night and during the early morning. Wind speeds may also ramp back up a notch during next week as the high northeast of us strengthens slightly. && .AVIATION... High pressure to the northeast will maintain moderate to locally breezy easterly trade winds into the early evening, with a slight downward trend tonight and tomorrow. Clouds and showers will favor windward and mountain areas across all islands, with the best coverage late tonight into tomorrow morning, as well as the Kona slopes of the Big Island during daytime hours. Brief MVFR conditions will be possible in showers. Otherwise, VFR conditions will generally prevail. AIRMET Tango is in effect for moderate turbulence below 8000 feet to the lee of mountains for all Hawaiian islands, due to the locally breezy trades and the stable atmosphere. AIRMET Sierra might be needed later tonight into tomorrow morning due to incoming tradewind showers. && .MARINE... High pressure far northeast of the waters will continue to drive moderate to locally strong trade winds through tonight. The Small Craft Advisory (SCA) for the typical windy waters around Maui County and Big Island has been extended through tonight. There may be a short- lived lull in trade speeds Saturday as the high fluctuates in strength and position, reducing wind speeds below SCA criteria for some or all zones in the SCA. The high will strengthen next week while drifting north resulting in trade wind speeds increasing state wide and SCA conditions returning or remaining in effect for typically windy waters through the rest of the forecast period. Surf along south facing shores will remain small through the weekend as a small background south southwest swell moves through. A small, long period south swell is expected to gradually build at the start of next week, with surf peaking near average Tuesday before slowly tapering off through the second half of next week. Rough, choppy east-facing shore surf may drop a touch over the weekend as trade winds ease slightly locally and upstream but should pick right back up next week. A very small northwest swell may pass through early next week, providing tiny surf along north facing shores Monday and Tuesday before becoming nearly flat through the remain forecast period. && .FIRE WEATHER... Moderate to locally breezy trades will decrease slightly over the weekend before becoming locally breezy again next week. Despite the trade wind showers picking up across windward sections this weekend and early next week, afternoon relative humidities across leeward sections remain near summertime normals. Fairly typical fire weather conditions are expected. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 AM HST Saturday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Bravender AVIATION...Farris MARINE...Almanza FIRE WEATHER...Bravender