Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
771 FXHW60 PHFO 050157 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 357 PM HST Tue Jun 4 2024 .SYNOPSIS... Breezy trades will gradually ease over the next few days with light trades expected by Thursday. Trades should be light enough for daytime sea breezes across select areas on Thursday. A slight strengthening of the trades is expected Friday into the weekend. Otherwise, very dry conditions will overspread the entire island chain Thursday through the weekend, greatly limiting shower activity. Breezy trades returning early next week should bring the return of some windward showers. && .DISCUSSION... This afternoon`s satellite imagery shows stable stratocumulus clouds anchored over select windward areas. Although we do have some decent amount of cloud cover in select areas, it has been a fairly dry day today with all of our rain gauges reporting less than 0.05 inches during the past 6 hours. Latest water vapor imagery shows a upper level trough just north of the Big Island drifting northeast. This trough could provide enough instability for some isolated thunderstorms over on the Kona slopes of the Big Island through this evening. This upper level trough should gradually move northeast and away from the state over the next 24 hours. Trades are expected to weaken another notch on Wednesday as the ridge of high pressure north of the state drifts closer to the state. By Thursday, the ridge of high pressure will be very close to the state and we should the winds weaken another notch. Latest ECMWF and NBM models are in good agreement with a light trade wind pattern for Thursday, while the GFS remains the outlier with the ridge very close to the state and a very light wind pattern. The latest wind forecast has been updated to show winds closer to consensus. Although the trades will likely still be light enough for sea breezes to develop during the day time. From Friday into Saturday, winds will likely pick up a touch and we should see a light to moderate trade wind pattern. As far as precipitation, there will be little of it through the weekend. The Kona slopes should have a chance for showers each afternoon, but as a drier and very stable air mass moves in over the next few days, any shower activity will remain light. Elsewhere, with a strong mid level ridge overhead and drier than normal low level moisture, clouds will still develop, but very little vertical development is expected of the clouds. Thus, little to no precipitation is expected through the weekend. && .AVIATION... Breezy easterly trades will continue through this evening, then gradually weaken into tomorrow as the pressure gradient relaxes. Clouds and showers will favor windward and mauka locations with periods of MVFR conditions possible. Otherwise, VFR conditions will generally prevail. Lingering elevated atmospheric instability over the state will allow for the potential development of isolated thunderstorms over interior and upslope sections of the Big Island through this evening. Stability will increase heading into Wednesday as mid level ridging strengthens over the state, ending the thunderstorm potential. 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 by Wednesday morning 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 along 30N continues to bring trades to the region. The ridge is sinking southward, and the result is a downward trend to the winds. The Small Craft Advisory (SCA) has been scaled back to the typical windier waters around the Big Island and Maui County for tonight. Winds are expected to weaken further tonight, and fall below SCA levels by morning. Over the weekend, the ridge is expected to lift northward, allowing moderate trades to return from south to north. 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. An 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 reinforcement from the northwest will follow Wednesday into Thursday. 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...Kino AVIATION...Farris MARINE...M Ballard