Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
148 FXHW60 PHFO 292008 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 1008 AM HST Wed May 29 2024 .SYNOPSIS... Surface high pressure far northeast of the state will maintain breezy trade winds for the remainder of the week. Shower activity will primarily be focused along windward slopes and coastlines, becoming more prevalent during the nocturnal hours. Upper level troughing will move in from the northeast and be over the islands from Friday into early next week. This will likely introduce frequent periods of increased trade wind showers in both coverage and intensity. && .DISCUSSION... Surface troughing approximately 700 miles west-northwest of Kauai, along with a near 1030 mb surface high centered around 1,350 miles northeast of Oahu, are both supporting a breezy trade wind regime across the state. Winds will hold at Small Craft Advisory thresholds through the eastern island bays and channels the next several days. The regional atmosphere is fairly moist with morning sounding pwats of around 1.5 inches pushing the upper percentile climatological range for late May. This relatively higher moisture within this breezy trade flow is producing mainly scattered to broken mid level clouds, with occasional overcast windward mauka conditions. Radar is spotty with the highest rainfall amounts of just a few hundredths of an inch per hour confined to the higher elevations. Better organized showers may drift over into the smaller island leeward communities. The main short term forecast theme will center around rain chances and trade wind trends. High pressure will slightly strengthen northeast of the state and settle more south-southeast as the trough of low pressure west of the area lifts slowly northward the next couple of days. This will provide a minor pick up of wind speeds as winds remain breezy to locally windy into early June. The trough will wash out through the weekend as high pressure northeast of the state inches a bit southwestward and closer to the island chain early to mid next week. This may provide a slight boost to trades the first few days of June. A relatively drier air mass moves across the state the next few days. This scenario will have light showers favoring more windward slopes and coasts, particularly during the overnight hours. Heights will lower over the state from Friday into the weekend although extended guidance is a little out of agreement on the extent of this troughing. Regardless of these minor model differences, there is moderate confidence that next week`s upper troughing will increase areal shower coverage and intensity. && .AVIATION... Moderate to breezy easterly trades will continue for the next several days. Clouds and showers will favor wind ward slopes, where periods of MVFR CIGs/VSBYs will move through especially in the overnight and early morning hours. VFR conditions will prevail over most leeward areas, with the exception of afternoon and evening MVFR conditions over leeward Big Island. AIRMET Sierra is in effect for mountain obscuration across windward sections of most islands this morning. Conditions are improving and the AIRMET will likely be dropped by noon. && .MARINE... A trough northwest of the area and a high centered far northeast of the area will maintain moderate to locally strong easterly trade winds through today. As the trough weakens and drifts further away, the trade winds will slightly strengthen Thursday 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 Thursday and additional zones around Oahu and Kauai waters may need to be included for Thursday through the weekend. Surf along exposed south-facing shores will remain below the summer average (5 feet) through Friday. A series of south swells will move in over the weekend into next week and will likely bring a prolonged period of above average surf along south facing shores. Forerunners from the first swell could arrive as early as Friday, but should steadily fill in throughout the day Saturday 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. As the trades slightly strengthen Thursday into the weekend, we should see a slight increase of rough and choppy surf 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 Thursday for Kaiwi Channel- Maui County Windward Waters-Maalaea Bay-Pailolo Channel- Alenuihaha Channel-Big Island Windward Waters-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Blood AVIATION...Wroe MARINE...Kino