Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
731 FXHW60 PHFO 031959 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 959 AM HST Mon Jun 3 2024 .SYNOPSIS... Trade winds will persist through Wednesday, then diminish and become light and variable for the second half of the week. The island atmosphere will be unstable the next couple of days, so windward trade showers will be a little more active than normal. Additionally, daytime heating of the slopes on the Big Island and Maui will bring the potential for afternoon thunderstorms. A trend toward much drier weather will start Wednesday, and continue through the weekend. && .DISCUSSION... Breezy and somewhat wet trade wind weather the next couple of days will trend much drier after mid-week as winds diminish and a ridge aloft builds over the area. In the meantime, a mid- and upper-level low centered just E of the islands will drift W today, stall near the islands through Tuesday, then move E on Wednesday. Although the atmosphere is not especially moist, the low has prompted the development of isolated, but somewhat unusual, high-based thunderstorms a couple hundred miles E of the islands, due to steep mid- and upper-level lapse rates. As the low`s associated cold pool moves closer to the islands, instability will increase, and the forecast contains a mention of isolated thunderstorms over Maui/Big Island slopes the next 1/2 afternoons respectively. Otherwise, windward showers may be a little more active than normal. The low will weaken and move E Wednesday as a strong mid-level ridge builds over the area from the NW, leading to a very stable island atmosphere, and significantly lowering inversion heights/rainfall chances. A surface ridge N of the islands will remain nearly stationary through Tuesday, supporting locally breezy trade winds. On Wednesday and Thursday, unseasonably strong low pressure rapidly developing N of the area will weaken the high and displace the ridge southward over the islands, with winds becoming light and variable Thursday and Friday. The ridge will gradually strengthen and move N over the weekend, and light to moderate trade winds are expected. With relatively light winds and a stable atmosphere, a mostly dry regime is anticipated. && .AVIATION... Breezy to locally strong trades will deliver clouds and showers to windward and mauka zones through today. MVFR conditions are most likely this morning with improvement expected by early afternoon. The arrival of elevated instability favors a chance for isolated thunderstorms over interior and upslope sections of the Big Island and Mount Haleakala on Maui. AIRMET Sierra for mountain obscuration remains in effect. AIRMET Tango for lee turb remains in effect. AMD NOT SKED for PMDY as equipment remains unavailable with no time table for return to service. && .MARINE... Broad high pressure north of the state will maintain fresh to strong trade winds through Tuesday, and a Small Craft Advisory (SCA) in effect for all waters around the Big Island and Maui County and select areas around Oahu and Kauai. Trades will decline Tuesday night and Wednesday as the ridge of high pressure is weakened and pushed southward, and the SCA will will likely be trimmed back to the typical windy waters around the Big Island and Maui. The ridge will erode further and be displaced farther south near Kauai Thursday into Friday, causing the trades to diminish significantly and possibly become disrupted. The SCA will be dropped completely by this time. Increasing moderate trades are expected during the weekend. An extended run of southerly swell will persist this week and almost certainly through mid June. The current south-southwest swell is peaking today at around 3 feet 15 seconds, leading to surf near the 10 foot High Surf Advisory level. This swell will gradually decline Tuesday into Thursday. Another south-southwest swell will arrive late Thursday and Friday, and as this swell declines, a larger swell will move during the weekend and into early next week. A potentially larger swell is looking increasingly likely late next week. A small, long-period north swell will fill in through the day and continue peak late tonight and Tuesday, with the potential for a small follow-up swell later in the week. The fresh to strong trade wind flow is producing elevated seas of 7 to 8 feet at 7 to 8 seconds. As trade winds decline Wednesday onward, rough surf along east facing shores will decline well below seasonal average. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 PM HST Tuesday for Kauai Northwest Waters-Oahu Leeward Waters-Kaiwi Channel-Maui County Windward Waters-Maui County Leeward Waters-Maalaea Bay-Pailolo Channel- Alenuihaha Channel-Big Island Windward Waters-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Birchard AVIATION...JVC MARINE...Wroe