A surface ridge will maintain light winds with land and sea breezes for the next couple of days. Isolated showers will affect windward sections of the eastern islands overnight into the early morning hours, and the island interiors each afternoon and early evening. A weak front could increase showers late Thursday night through Saturday as it moves southeastward into the islands. Another stronger front could increase shower coverage as well as bring breezy southwesterly winds late Sunday into early next week.
Currently at the surface, a 1028 mb high is centered to the distant northeast, with a ridge axis extending southwestward from the high to a location over the western end of the state. This is resulting in light winds with land breezes present across the island chain. Infrared satellite imagery shows mostly clear skies across the state, with radar imagery showing a few showers over the coastal waters and brushing east and southeast facing slopes of Maui and the Big Island. Main short term focus revolves around minimal rain chances during the next couple of days.
The ridge of high pressure over the western end of the state will shift slowly southeastward during the next couple of days as a cold front approaches from the northwest. This will keep a light wind regime in place across the state. As a result, a few showers will affect windward locations over the eastern end of the state overnight and during the morning hours, with a few showers then possible over the island interiors each afternoon before fizzing out in the early evening hours.
Models are in good agreement showing a cold front moving into Kauai late Thursday night, then decaying as it shifts southeastward down the island chain Friday and Saturday. The front will bring an increase in clouds and showers as it moves through, but with the best forcing remaining well north of the state, no significant rainfall is expected. The old front or its remnant moisture should lift back north of the islands on Sunday, as yet another front approaches from the northwest. This front appears stronger, with moderate to breezy southwesterly winds developing in advance late Sunday into Monday. The front appears to move through the state later Monday through Tuesday, accompanied by a line of heavier showers with potentially gusty winds.
Light southeasterly background flow will give way to a land and seabreeze pattern through the forecast period. This will provide some interior clouds during the afternoon, that will dissipate overnight. VFR conditions are expected to prevail.
Currently, no AIRMETS are in effect.
Light winds will prevail through Thursday as a surface ridge remains over the islands. The background flow will remain out of the southeast for Maui and the Big Island waters and out of the south to southwest over the Kauai and Oahu waters. While most coastal areas will experience typical overnight land breezes and afternoon sea breezes, terrain-induced accelerations will lead to brief periods of locally enhanced winds where the flow parallels to the coast, particularly through the afternoon hours. Moderate to fresh northerly winds will gradually fill in on Friday as a cold front moves into the area.
Surf along exposed north- and west-facing shores will remain around the advisory levels through the early morning hours today, then gradually lower by this afternoon. Offshore buoy observations to the northwest already show a downward trend, which should be reflected at the nearshore buoys later today as the swell eases.
A more significant northwest swell is expected through the second half of the week and weekend from a broad and complex low that has evolved over the far northwest Pacific in the past few days. Latest analysis and satellite imagery show this system positioned over the far northwest Pacific near the western Aleutians, with a captured fetch focused at the islands within the 290 to 315 degree directional bands. This swell will begin building down the island chain Thursday and will be a long-duration event, with a peak centered around the Friday through Saturday time frame. Heights will exceed advisory levels by Thursday, then warning levels Friday through Saturday.
Impacts associated with the warning-level surf Friday through Saturday will likely lead to some water reaching areas that typically remain dry along exposed coasts, including vulnerable low-lying roadways and infrastructure. This likelihood will especially increase if the peak surf coincides with the overnight high tide cycle Friday night.
Surf along east-facing shores will remain small due to the lack of trades locally and upstream of the state.
Surf along south-facing shores will remain up today before easing Thursday as a small, long-period south-southwest swell moves through.
High Surf Advisory until noon HST today for Niihau-Kauai Leeward- Waianae Coast-Oahu North Shore-Maui Windward West-Kauai North- Molokai Windward-Molokai North-Molokai West-Maui Central Valley North-Windward Haleakala.
