Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
045 FXHW60 PHFO 131322 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 322 AM HST Tue Aug 13 2024 .SYNOPSIS... Persistent high pressure far north of the islands will support locally breezy trade winds through the weekend. Passing showers will periodically dampen most windward areas, with some showers occasionally spreading leeward, especially night and morning. && .DISCUSSION... Persistent surface high pressure far N of the islands will support locally breezy trade winds for the foreseeable future. A slow-moving trough aloft just N of the islands will bring some modest mid-level cooling as it drifts S the next couple of days, elevating and weakening the subsidence inversion. This will allow orographic lift to produce a few showers, in addition to random shower clusters arriving on the trades. These will occasionally dampen windward areas, with some showers occasionally spreading leeward, most active night and morning. In contrast, daytime heating will lead to afternoon and evening showers over the Kona slopes. A low-level trough approaching from the E (remnants of former T.S. Emilia) is forecast to dampen out as it reaches the longitude of the islands Thursday and Friday, but there may be a brief period of slightly weaker winds from late Wednesday into Thursday. While PWAT may diminish tonight into Wednesday, the nearby passage of these remnants may lead to increased PWAT/windward showers. A mid-level ridge will rebuild over the islands by the weekend, likely reducing shower coverage/frequency. && .AVIATION... Moderate to locally breezy trades will deliver low cigs and SHRA to windward and mauka locations through the forecast period. Brief MVFR conds can be expected within SHRA but VFR should generally prevail. AIRMET Sierra is in effect for windward locations of all islands for mtn obsc. Conds should improve by mid-morning. && .MARINE... An area of surface high pressure north of the state will remain nearly stationary over the next several days and produce moderate to locally strong trade winds across the local waters. A Small Craft Advisory has been extended through Thursday morning for the typically windier waters around Maui County and the Big Island and will likely need to be extended through late this week. A small, medium- period, background south swell will linger this morning and produce small surf along south facing beaches. Another small, long- period, south swell is expected to arrive late today and peak on Wednesday, then decline through early this weekend. Guidance introduces a 3 foot, long- period, southerly swell late Sunday into early next week. This swell will have originated from a slow moving gale low, currently east of New Zealand. Expect a bump up in surf to above August averages. Seasonally flat to tiny surf is expected through this week for north facing shores. Breezy trade winds will bring choppy surf conditions to east facing shores through the remainder of this week. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 AM HST Thursday for Maalaea Bay-Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...TB AVIATION...SMW MARINE...JT