A surface ridge will maintain light winds with land and sea breezes for the next few 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 through. 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 1026 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 or developing across the island chain. Infrared satellite imagery shows decaying daytime heating cloud cover, with clear to partly cloudy skies in most areas. Radar imagery shows showers have fizzled out over land areas, with only a few noted over the coastal waters. 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 showers will affect windward locations over the eastern end of the state overnight and during the morning, with a few showers possible over the island interiors each afternoon before fizzing out in the and evening hours.
Models are in good agreement with a cold front will move 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 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 developing in advance late Sunday into Monday. The front appears to move through the state later Monday through next Tuesday, bringing a line of heavier showers through the islands as it moves through.
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 build down the island chain overnight, with heights exceeding advisory- levels by midnight. Offshore buoy observations to the northwest climbed above predicted levels this afternoon, but have begun to trend back down this evening. As a result, a gradual downward trend is expected by around noon on Wednesday. This may result in the current advisory being extended through the early morning hours tomorrow before the surf dips below criteria.
A more significant northwest swell is expected through the second half of the week and upcoming weekend from a broad and complex low that has evolved over the far northwest Pacific in the past couple of days. Latest analysis and satellite imagery continues to show this system parked over the far northwest Pacific at 974 mb low centered west of the Date Line 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 could become a long-duration event, with a peak centered around the Friday through Saturday time frame. Heights will exceed advisory levels by Thursday night, 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 the coast, including vulnerable low- lying roadways and infrastructure. This likelihood will increase in the event the peak of the surf coincides with the large tides that are running higher than predicted.
Surf along east-facing shores will remain small each day due to a combination of the local winds shifting southerly and the lack of trades upstream of the state.
Surf along south-facing shores will remain up through midweek before easing Thursday as small, long-period south-southwest swell moves through.
High Surf Advisory until 6 AM HST Wednesday 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.
