West Kaua’i

Tonight: Mostly clear. Lows around 68 near the shore to around 58 above 3000 feet. Light winds.

Wednesday: Sunny. Highs around 82 near the shore to around 72 above 3000 feet. Northeast winds up to 10 mph shifting to the southwest around 10 mph in the afternoon.

Wednesday Night: Partly cloudy. Lows around 68 near the shore to around 58 above 3000 feet. Light winds.

South Kaua’i

Tonight: Mostly clear. Lows around 67. West winds around 10 mph.

Wednesday: Sunny. Highs 78 to 84. West winds 10 to 15 mph.

Wednesday Night: Partly cloudy. Lows around 68. Light winds.

Kaua’i Mountains

Tonight: Partly cloudy with isolated showers. Lows 60 to 67 in the valleys to around 57 above 4000 feet. Light winds. Chance of rain 20 percent.

Wednesday: Sunny with isolated showers. Highs 75 to 82 in the valleys to around 67 above 4000 feet. Southwest winds up to 10 mph. Chance of rain 20 percent.

Wednesday Night: Partly cloudy with isolated showers. Lows 60 to 68 in the valleys to around 57 above 4000 feet. West winds up to 10 mph. Chance of rain 20 percent.

North Kaua’i

Tonight: Mostly clear. Isolated showers in the evening. Lows 62 to 70. Light winds. Chance of rain 20 percent.

Wednesday: Sunny. Highs 76 to 82. East winds up to 10 mph shifting to the north in the afternoon.

Wednesday Night: Partly cloudy. Lows 62 to 70. Light winds.

East Kaua’i

Tonight: Mostly clear. Lows 62 to 71. West winds up to 10 mph in the evening becoming light.

Wednesday: Sunny. Highs 75 to 84. Southwest winds up to 15 mph.

Wednesday Night: Partly cloudy. Lows 62 to 72. Light winds.

Detailed Forecast

Synopsis

A surface ridge will maintain light southerly winds with local land and sea breezes for the next few days. Isolated showers will occasionally move over south facing areas. Additional cloud and shower buildups will be possible during the afternoons for interior portions of each island. Due to the stability of the ridge, showers should remain light for the most part. A weak front could increase showers early Friday morning through Saturday. Another stronger front could increase shower coverage as well as bring breezy southwesterly winds by early next week.

Discussion

Radar and satellite imagery this afternoon shows isolated, light showers across select island interiors. Slightly more showers can be observed over the leeward portions of the Big Island. This fair weather can be attributed to a stable atmospheric profile due to a surface and mid level ridge. The ridging will keep showers mostly light and isolated through Thursday, and keep winds light with sea and land breezes. Sea breezes will allow clouds and showers to build up over island interiors, with overnight land breezes clearing out the clouds. Weak island convergence with the southerly winds could also bring isolated showers to random areas.
By Friday morning, a weak cold front is expected to move down the island chain where it is then forecast to stall and wash out in between Maui County and the Big Island. The front is expected to reach Kauai by Friday morning, Oahu by Friday afternoon, and Maui County by Friday night into early Saturday morning. The front will initially bring moderate north winds in its wake, followed by northeast, then east. An increase in showers can be expected along the front as it moves through, however at the moment these showers are not expected to be heavy due to the shallow depth of moisture and the lack of upper level support. The front could end up stalling in between Maui and the Big Island on Saturday, keeping lingering showers in the area before it lifts up to the north on Sunday.
By Sunday, a ridge builds in temporarily. This would once again bring light southerly winds, focusing isolated showers back over south facing areas. Long range models then depict a stronger cold front approaching the islands early next week. This front appears to have deeper moisture, and a stronger upper level trough supporting it. The front could bring heavier showers as well as gusty southwest winds. Uncertainty on timing and intensity are in place as it is still a week away.

Aviation

VFR conditions will continue tonight into Wednesday. Winds will veer southerly between 8 and 12 kt at most terminals by midday Wednesday. Land and sea breeze development midday will lead to increased clouds and chances for showers which could temporarily lower ceilings and visibilities to MVFR.

Marine

Ridging at the surface will prevail over the region through at least mid-week, keeping winds generally light. The background flow will remain out of the southeast for Maui and Big Island waters, and out of the south to southwest over Kauai and Oahu waters. Model guidance continues to indicate that a front could move into the northern portions of the area on Friday. Moderate to fresh northerly winds will fill in behind the front as it moves down the island chain.
Surf along north and west facing shores will continue to trend up this evening and tonight as a medium- to long-period north northwest (330-340 degree) swell moves into the islands. Latest observations this afternoon from NW Hawaii offshore buoy 51001 show that swell height has increased significantly above guidance, at around 8 to 9 feet as of mid-afternoon. Based on these latest observations, a High Surf Advisory has been posted for north and west facing shores of Niihau, Kauai, Oahu, Molokai, and north facing shores of Maui through the overnight hours. This swell is expected to peak tonight, then gradually ease during the day on Wednesday.
A larger northwest swell is expected during the second half of the week from a broad and complex low over the far northwest Pacific. A large area of gale- to storm-force winds is associated with this low, and currently focused at the islands between roughly 290 and 320 degrees. This swell will begin building down the island chain Thursday. It could become a long duration event, with a peak centered around the Friday through Saturday time frame. Surf heights will likely exceed advisory levels by late Thursday afternoon, then exceed warning levels Friday into Saturday.
Surf along east-facing shores will remain small for the next several days due to a combination of the local winds shifting southerly and a lack of trade winds upstream of the state.
Surf along south-facing shores will generally hold steady through mid-week as a background, long-period south swell maintains some tiny surf. This background swell will slowly ease during the second half of the week.

HFO Watches/Warnings/Advisories

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.

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Data Courtesy of NOAA.gov