Photo Credit: Brendan Stephen

West Kaua’i

Today: Mostly sunny in the morning then becoming mostly cloudy. Isolated showers. Highs 80 to 85 near the shore to around 70 above 3000 feet. Light winds becoming southwest up to 10 mph in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 64 to 70 near the shore to around 57 above 3000 feet. Northeast winds up to 10 mph. Chance of rain 20 percent.

Monday: Mostly sunny in the morning then becoming mostly cloudy. Isolated showers. Highs 81 to 86 near the shore to around 71 above 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

South Kaua’i

Today: Partly sunny with isolated showers. Highs 77 to 85. Light winds. Chance of rain 20 percent.

Tonight: Mostly cloudy with isolated showers. Lows around 68. Northeast winds up to 10 mph increasing to 10 to 15 mph after midnight. Chance of rain 20 percent.

Monday: Breezy. Partly sunny with isolated showers. Highs 76 to 84. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Kaua’i Mountains

Today: Mostly sunny in the morning then becoming cloudy. Isolated showers. Highs 71 to 80 in the valleys to around 63 above 4000 feet. Light winds. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 61 to 67 in the valleys to around 55 above 4000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Monday: Mostly sunny in the morning then becoming cloudy. Breezy. Isolated showers. Highs 70 to 82 in the valleys to around 61 above 4000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

North Kaua’i

Today: Mostly sunny in the morning then becoming mostly cloudy. Isolated showers. Highs 74 to 82. Light winds becoming north up to 10 mph in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 61 to 69. East winds up to 10 mph. Chance of rain 20 percent.

Monday: Mostly sunny in the morning then becoming mostly cloudy. Isolated showers. Highs 74 to 83. East winds up to 15 mph. Chance of rain 20 percent.

East Kaua’i

Today: Mostly sunny in the morning then becoming mostly cloudy. Isolated showers. Highs 72 to 83. Light winds becoming northeast up to 10 mph in the afternoon. Chance of rain 20 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 62 to 73. North winds up to 10 mph. Chance of rain 20 percent.

Monday: Mostly sunny in the morning then becoming mostly cloudy. Isolated showers. Highs 70 to 82. East winds 10 to 15 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Light and variable winds continue through this evening as a cold front passing north of the state will weaken the subtropical ridge north of the islands. A high pressure system will move in and build north of the state from Sunday night into Tuesday causing the winds to briefly shift back into trades with a few showers windward and mountain areas. Another stronger cold front approaching the Hawaii region from the northwest will weaken the ridge once again and produce another light southeasterly wind pattern from Wednesday onward. A shallow cold front may stall out near Kauai by Friday producing a brief period of light showers.

Discussion

The subtropical ridge remains locked in place over the Hawaiian Islands this morning producing stable and dry conditions across the region. The satellite picture this morning shows almost no clouds around the Hawaiian Islands. A cold front passing north of the island chain will keep large scale winds light and variable today, with mostly sunny skies, onshore sea breezes during the day and offshore land breezes at night.
The weather pattern shift starts later tonight, where a building high pressure system passing north of the islands will bring moderate to locally breezy trade winds back through Tuesday. By Tuesday the high center will continue to drift farther eastward into the East Pacific basin. A cold front approaching the islands from the northwest will weaken the ridge north of the state and force the ridge axis to drift south over the Hawaiian Islands. This pattern change will bring another round of stable and dry conditions, with lighter southeasterly winds with expanding sea breezes on Christmas Day, becoming light and variable winds from Thursday through Friday.
A shallow cold front will move into and stall out near Kauai by Friday. Clouds and a few showers are possible along this weakening frontal band. However fairly stable conditions under the ridge will limit rainfall amounts with this next system. Eastern islands in Maui and Hawaii Counties will not see much rainfall activity with this next frontal system. Trade winds return next weekend with an upper level trough/low potentially enhancing windward and mountain shower activity. The latest model guidance show this front stalling out sooner than previous operational model runs. Confidence is therefore lower that any islands east of Kauai will see much in the way of rainfall with the weak frontal cloud band.

Aviation

A strong surface ridge over the Hawaiian Islands will keep light winds over the area. Sea/land breezes expected today. Some brief SHRA and MVFR conds are possible but VFR conds should prevail.
No AIRMETs in effect.

Marine

Hazardous marine conditions will persist into Monday, with the largest in a series of extra-large, overlapping northwest swells arriving today. Observations at the offshore buoys northwest of Kauai have been rapidly rising overnight, which will begin at our nearshore Hanalei and Waimea PacIOOS buoys by dawn, then to Pauwela later this morning through the afternoon. The swell will peak through the day today, and then gradually ease late tonight through Tuesday. Resulting surf should reach giant levels, in excess of 40 feet (faces) along coastlines with the highest exposure, during the peak today. Heights could hover at or above warning levels well into Monday before lowering to advisory levels by Tuesday.
This extended period of warning-level surf, which began last Wednesday, will produce significant coastal impacts, including considerable beach erosion along exposed shorelines and potential overwash onto vulnerable coastal roadways and properties, particularly during the peak today. These impacts will remain likely despite monthly tidal minima, underscoring the magnitude of this swell. Mariners should also anticipate hazardous conditions, including strong currents and occasional breaking waves near harbor entrances, making transits potentially dangerous.
Winds across coastal waters will remain light and variable today as a surface ridge lingers over the region. However, a fast- moving surface high approaching from the northwest will lead to a rapid increase in northeast winds tonight, followed by fresh to strong trade winds as the high passes north of the state on Monday. A Small Craft Advisory (SCA) remains in effect for seas exceeding 10 feet, and as winds increase, the SCA will be expanded to include wind-affected zones. Trades are expected to gradually decline and shift southeasterly on Tuesday and Wednesday as the high moves eastward.

Fire weather

No critical fire weather conditions are expected for the next seven days. Dry humidity levels will continue in a mostly lighter wind pattern. Wind speeds will be the limiting factor as drier leeward afternoon humidity levels continue to approach criteria for some of our fire zones on the Big Island.

HFO Watches/Warnings/Advisories

High Surf Warning until 6 AM HST Monday for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kona, Kohala, Kauai North, Molokai Windward, Molokai North, Molokai West, Maui Central Valley North, Windward Haleakala.
High Surf Advisory until 6 AM HST Monday for Big Island East, Big Island North.
Small Craft Advisory until 6 AM HST Monday for all Hawaiian waters except Maalaea Bay,

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