Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
682 FXHW60 PHFO 301333 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 333 AM HST Thu May 30 2024 .SYNOPSIS... A high far northeast of the state will drive breezy to locally windy trade winds through the remainder of the week. Showers will favor windward areas, becoming more prevalent at night. Upper troughing will move over the islands Friday into early next week, setting up periods of increased trade showers coverage and intensity. && .DISCUSSION... Surface troughing west of the main Hawaiian Islands, combined with high pressure far to the northeast, maintains a pressure gradient sufficiently steep to support moderate to breezy trade winds across local waters this morning. Overnight soundings show our airmass has dried out a bit since yesterday, with 1.1 to 1.3 inches of PW. Slight instability is noted along with subsidence inversions near 6000 feet. Radar shows isolated to scattered light showers within trade flow, embedded within patchy broken low clouds across windward areas depicted in satellite loops. Models show high pressure to our northeast will strengthen a bit and drift south-southeast as troughing to our west slowly lifts northward. This will provide a minor uptick in wind speeds into the weekend. The trough will wash out through the weekend as high pressure northeast of the state inches a bit southwestward and closer to the islands early to mid next week, providing another slight boost to trades for the first few days of June. Models also show upper troughing will drift south across the islands Friday into next week, possibly increasing trade wind shower coverage and intensity. && .AVIATION... Moderate to breezy easterly trades will continue for the next couple of days, with clouds and showers favoring windward slopes. Brief MVFR conditions will be possible with this activity, particularly overnight when there will be a slight uptick in shower coverage. VFR conditions will generally prevail across leeward areas. A weak mid-level ridge will maintain stable conditions with an inversion based between 6,000 to 8,000 ft. Easterly trade winds at and below the inversion level will likely remain in the 15 to 20 kt range, which will produce some low-level turbulence. With these borderline conditions, AIRMET Tango isn`t expected to be needed. However, model cross sections show 25 kts under the inversion over the central part of the state this afternoon, which may be enough to produce some moderate low-level turbulence, so we will continue to monitor for the potential need for AIRMET Tango. && .MARINE... High pressure centered far northeast of the area will maintain moderate to locally strong easterly trade winds through Friday and back towards the east- northeast. Fresh to strong east- northeast trade winds should persist through the weekend as a ridge of high pressure remains anchored far north of the state. A Small Craft Advisory (SCA) remains in effect for majority of the waters around Maui County and the Big Island through Friday and additional zones around Oahu and Kauai waters will likely need to be included by Friday. Surf along exposed south-facing shores will remain small through Friday. A series of south swells will bring a prolonged period of above average surf along south facing shores through the start of June. Forerunners from the first swell could arrive as early as Friday, build and peak late Saturday into Sunday. A reinforcing pulse should arrive on Monday and will likely maintain surf heights near or just below the High Surf Advisory threshold of 10 feet. Surf heights should gradually trend down Tuesday through Wednesday as the south- southwest (200 degree) swell declines. A gale low currently developing just east of New Zealand, will likely bring another south (190 degree) swell Thursday into Friday of next week. Surf along exposed east-facing shores will continue to remain rough and choppy due to the windswell generated by the breezy trade winds and will likely increase slightly by this weekend. Surf along north-facing shores will continue to remain nearly flat over the next few days. A developing storm force low near Kamchatka should produce an out of season northwest swell, which should steadily fill in Sunday night into Monday. Latest guidance is showing 3 to 4 feet of swell from 320 degrees Monday into Tuesday. A typhoon tracking off the coast of Japan will likely bring a small reinforcing swell from the west-northwest to northwest Tuesday into the middle of next week. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 PM HST Friday for Kaiwi Channel- Maui County Windward Waters-Maalaea Bay-Pailolo Channel- Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Powell AVIATION...Farris MARINE...Shigesato