Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
531 FXHW60 PHFO 050635 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 835 PM HST Tue Jun 4 2024 .SYNOPSIS... Breezy trades this evening will ease to moderate levels Wednesday, then become light Thursday and Friday with land and sea breezes common across much of the state. The ridge will lift northward this weekend allowing the trades to gradually strengthen, with locally breezy conditions returning for the first half of next week. Very dry conditions will greatly limit shower activity through the weekend, with a slight increase in windward showers expected early next week as the trades strengthen to locally breezy levels. && .DISCUSSION... Currently at the surface, a 1026 mb high is centered around 1150 miles northeast of Honolulu, and is driving breezy trade winds across the island chain. Infrared satellite imagery shows partly to mostly cloudy skies across the state, with cloud coverage the greatest over windward and mauka areas. Radar imagery shows very little rainfall across the state, with nothing more than isolated very light showers affecting windward slopes at coasts from time to time. Main short term focus continues to revolve around trade wind trends during the next several days. High pressure northeast of the state will gradually weaken and shift eastward during the next few days, with the associated ridge shifting southward to a location just north of Kauai Thursday and Friday. Breezy trades this evening will ease to moderate levels Wednesday, then to light background trades Thursday and Friday with land and sea breezes common across much of the state. The ridge will begin to lift northward over the weekend allowing the trades to gradually strengthen, with moderate to locally breezy conditions returning for the first half of next week. As for the remaining weather details, very stable and dry conditions have now overspread the island chain, evident in the sharp trade wind inversions, below 4 kft at PHTO and below 5 kft at PHLI during the 00z soundings. Little change in the trade wind inversion is expected through the weekend, which will greatly limit shower activity across the entire state. The trade wind inversion will begin to lift early next week, which should bring a slight increase in trade wind showers, while still remaining drier than normal for this time of year. && .AVIATION... Trade winds will gradually weaken over the next twenty-four to thirty-six hours as the pressure gradient over the Islands relaxes. Bands of clouds and light showers will favor east and northeast facing slopes and coasts. Brief MVFR conditions are to be expected in showers, otherwise VFR conditions will prevail statewide. Lingering mid-level atmospheric instability will encourage convective showers over interior and upslope portions of the Big Island tomorrow afternoon and early evening. Stability is expected to increase later in the week as mid level ridging builds over the state. AIRMET Tango for low level turbulence lee of island terrain remains in effect. This AIRMET will be needed through this evening, but will likely be cancelled late tonight as winds below the inversion decrease. AIRMET Sierra remains in effect for mountain obscuration for windward sections of the smaller islands. This AIRMET may need to be extended through mid to late morning tomorrow before conditions improve into the afternoon, and windward portions of the Big Island may need to be included. && .MARINE... A ridge of high pressure north of the waters along 30N will continue to bring moderate to locally strong trades. The ridge is slowly sinking southward, and the result is a downward trend to the winds. The Small Craft Advisory (SCA) is in effect for the typical windier waters around the Big Island and Maui County through tonight. Trade winds are expected to continue to ease on Wednesday and diminish significantly Thursday and Friday. The SCA will be dropped completely through the end of the week. Increasing moderate trades are expected during the weekend as the ridge lifts northward. The active south Pacific will continue to generate southerly swells that will pass through the islands through the middle of the month. The current south-southwest swell has started to decline, and a continued gradual decline is expected through Thursday. Another reinforcing south-southwest swell is expected to arrive late Thursday and Friday, that is currently expected to bring south facing shore surf around the seasonal average. A larger swell is expected to move through the islands this coming weekend, which will likely be near or at HSA levels of 10 feet. A potentially even larger swell is looking increasingly likely late next week that would bring surf well above advisory levels. The current small northwest swell will get a second pulse from the northwest Wednesday into Thursday keeping surf elevated. The fresh to strong trade wind flow is producing rough choppy elevated seas but the wind waves will diminish significantly after Wednesday coinciding with the light winds through the weekend. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 AM HST Wednesday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Windward Waters- Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Jelsema AVIATION...Bedal MARINE...Shigesato