Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
770 FXHW60 PHFO 290617 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 817 PM HST Sun Apr 28 2024 .SYNOPSIS... Moderate trades will prevail over the eastern islands through the first half of the work week, while lighter trades over the western islands allow for some leeward land and sea breezes. Relatively dry weather will persist tonight through Tuesday, with a few showers affecting windward areas each night and developing over interior and leeward areas each afternoon. The trades will rebound Tuesday night and Wednesday, bringing a transition over to more typical trade wind weather. The trades will become breezy Thursday through next weekend, and the trade wind showers may increase as well due to a disturbance aloft moving over the islands. && .DISCUSSION... Currently at the surface, a weakening front is located around 500 miles west-northwest of Kauai, while a 1032 mb high is centered around 1450 miles northeast of Honolulu. Moderate trade winds prevail in unsheltered areas over the eastern end of the state, while lighter trades persist over the western islands. Infrared satellite imagery shows a combination of high and low clouds resulting in partly to mostly cloudy conditions across the state. Radar imagery shows scattered showers moving into east and southeast facing slopes and coasts of Maui and the Big Island, with a few showers also over the leeward slopes of Maui and the Big Island. Elsewhere, mainly dry conditions prevail. Main short term focus continues to revolve around trade wind trends and rain chances during the next few days. A front northwest of the islands will gradually weaken into a trough during the next couple days as it edges slowly eastward. Little change is expected in the overall wind forecast, with moderate trades holding on over the eastern end of the state, while lighter trades prevail over the western islands, allowing some leeward sea and land breezes to develop. We should see the trades start to rebound beginning Tuesday night as the trough west of the state begins to shift slowly westward. Moderate to locally breezy trades should overspread the island chain by late Wednesday, with the trades becoming breezy Thursday through next weekend. As for the remaining weather details, a band of moisture will bring some showers into east and southeast facing slopes of Maui and the Big Island tonight. Elsewhere, shower activity should be more sparse, with a few showers affecting mainly windward slopes and coasts, although a few showers will remain possible over leeward Big Island as well due to the east-southeast boundary layer flow. Relatively dry conditions should generally prevail across the island chain Monday through Tuesday. Brief passing showers will be possible in windward areas each night, with a few showers developing over interior and leeward areas each afternoon. A few showers could be a bit more robust over Kauai Monday afternoon, as some shortwave energy grazes by to the north. We should see a transition over to more typical trade wind weather Tuesday night and Wednesday, with wetter trade wind conditions potentially developing Friday through next weekend as upper troughing sets up over the state. && .AVIATION... Light to moderate ESE winds will continue through Monday. Drier air has filtered in across most of the area, with VFR conditions expected to generally prevail. However, a N-S oriented low cloud band is currently moving over the Big Island from the east, bringing periodic MVFR and even IFR conditions in the heavier showers. As such, AIRMET Sierra for tempo mountain obscuration is in effect for the Big Island and may need to be expanded as these conditions may also develop across windward portions of the smaller islands later tonight as the cloud band continues to move westward. Otherwise, with the lighter ESE flow and decreased cloud cover, afternoon sea breeze activity is expected across wind- sheltered areas, with some inland/leeward cloud buildups and a few light showers possible. && .MARINE... Surface high pressure far northeast of Hawaii and an approaching weak front to the northwest will drive breezy east southeast winds through tonight. A Small Craft Advisory for winds is in effect for most waters and channels surrounding Big Island, Maui, and Molokai through tonight. The high will slide east while a low pressure system will edge closer Monday and Tuesday weakening the pressure gradient allowing winds to ease. By mid-week, high pressure will rebuild to the northeast transitioning back to typically fresh to locally strong trade winds. North facing shores will remain tiny through the week with tiny medium period background energy. Surf along east facing shores will continue to decline as winds begin to taper off Monday and Tuesday. Surf along south facing shores will see a mix of small, short- period southeast, and small south-southwest pulse filling in Monday and Tuesday before easing Wednesday. Surf heights along the south facing shores should remain near or slightly below seasonal norms. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 AM HST Monday for Maui County Windward Waters-Pailolo Channel-Alenuihaha Channel-Big Island Windward Waters-Big Island Leeward Waters. && $$ DISCUSSION...Jelsema AVIATION...Farris MARINE...Shigesato