West Kaua’i

Tonight: Mostly cloudy with a 50 percent chance of showers. Haze. Lows around 68 near the shore to around 58 above 3000 feet. East winds up to 10 mph in the evening becoming light.

Thursday: Partly sunny with a 50 percent chance of showers. Highs 78 to 86 near the shore to around 72 above 3000 feet. Southeast winds up to 10 mph.

Thursday Night: Mostly cloudy with a 50 percent chance of showers. Lows around 68 near the shore to around 58 above 3000 feet. East winds 10 to 15 mph.

South Kaua’i

Tonight: Mostly cloudy with a 50 percent chance of showers. Haze. Lows around 68. West winds up to 10 mph.

Thursday: Partly sunny with a 50 percent chance of showers. Highs 79 to 86. Southwest winds up to 15 mph increasing to 10 to 15 mph in the afternoon.

Thursday Night: Mostly cloudy with a 50 percent chance of showers. Lows around 69. Light winds.

Kaua’i Mountains

Tonight: Mostly cloudy with a 50 percent chance of showers. Haze. Lows 58 to 68 in the valleys to around 57 above 4000 feet. Southwest winds up to 15 mph.

Thursday: Partly sunny with a 50 percent chance of showers. Highs 75 to 82 in the valleys to around 65 above 4000 feet. Southwest winds up to 10 mph.

Thursday Night: Mostly cloudy with a 50 percent chance of showers. Lows 58 to 69 in the valleys to around 57 above 4000 feet. Light winds becoming southwest 10 to 15 mph after midnight.

North Kaua’i

Tonight: Partly cloudy with a 20 percent chance of showers. Haze. Lows 61 to 68. South winds up to 15 mph.

Thursday: Mostly sunny with a 20 percent chance of showers. Highs 76 to 84. Southeast winds up to 10 mph shifting to the north in the afternoon.

Thursday Night: Mostly cloudy with a 40 percent chance of showers. Lows 61 to 69. South winds around 10 mph.

East Kaua’i

Tonight: Partly cloudy with a 50 percent chance of showers. Haze. Lows 62 to 71. Southwest winds up to 15 mph.

Thursday: Partly sunny with a 50 percent chance of showers. Highs 74 to 85. Southwest winds up to 15 mph.

Thursday Night: Mostly cloudy with a 50 percent chance of showers. Lows 62 to 72. Light winds becoming west around 10 mph after midnight.

Detailed Forecast

Synopsis

Light winds will favor a southerly direction into the weekend as a couple of fronts stall northwest of Kauai. Limited rainfall is expected, with the best chance for a few showers over leeward portions of Kauai and Oahu. Trade winds will return Sunday and become strong by Tuesday, likely bringing an increase in showers, mainly windward.

Discussion

A progressive pattern over the N Pacific will lead to little change in island weather over the next couple of days, with benign weather prevailing. Powerful surface lows passing well N of the area will keep a surface ridge over the islands through Saturday, with the light to occasionally moderate low-level flow favoring a S-SW direction over Kauai and an E-SE direction over the Big Island. The southerly flow has led to increased dew points (near 70F) that will make it feel somewhat muggy, especially in the afternoon hours.
Expect some subtle day-to-day variations in wind speed/direction as the ridge position fluctuates N and S. A couple of fronts will stall NW of Kauai through Saturday, bringing slightly stronger SW winds to Kauai overnight, and again on Friday. Guidance also indicates a few showers moving over Kauai and Oahu over the next couple of days. Atmospheric stability will remain high as a mid-level ridge extends over the area from the W, leading to limited shower coverage and intensity. With the prevailing southerly flow, leeward areas will be more likely to see a shower than windward areas. Chances for rainfall over the Big Island and Maui are low.
This type of flow regime typically spreads vog from the Big Island to the other islands, and GOES GeoColor and Optical Depth imagery confirm that vog is moving over most islands from the S this afternoon. USGS webcam at Kilauea shows that episode 11 of the ongoing eruption may be ending, which would lead to a reduction in emissions and vog coverage as the week progresses.
A pattern shift appears likely to develop late in the forecast period, with high pressure supporting a developing trade wind flow late Sunday and Monday that becomes strong by Tuesday. Moisture associated with one of the stalled fronts may fuel an increase in windward showers as trade winds increase and mid-levels cool, with a wet and windy pattern currently anticipated.

Aviation

Moderate southeasterly flow over the eastern end of the state transitions to southwesterlies over Kauai and Oahu as a front tracks north of the area. Enhanced low-level convergence in the vicinity of Oahu will support increased clouds and isolated showers there through at least the first half of the night. This band of convergence is expected to migrate westward perhaps focusing light showers over Leeward Kauai by Thursday morning. VFR prevails.
No AIRMETs in effect.

Marine

A pair of fronts approaching from the northwest will pass just north of the state and will maintain light to moderate southerly winds the next several days. A strong high will build far north of the state late Sunday into Monday. Light to moderate trade winds could return as early as Sunday and will continue to strengthen on Monday. A pair of strong highs will pass far north of the state next week, which should produce a prolonged period of strong trades next week.
Although offshore buoys reported a swell coming in quite a bit over guidance levels last night, near shore buoys did not get as large today. Thus the High Surf Warning has been scaled back to a High Surf Advisory. Buoy 51101 and 51001 continue to show a fast decline and surf should drop below advisory thresholds for most areas by the middle of the night tonight.
A larger northwest swell should fill in Thursday afternoon and peak Thursday night into Friday morning. Overnight ASCAT pass showed a large fetch of storm force winds directed towards the state, which increases the odds of extra-large surf. Surf should reach High Surf Warning thresholds Thursday night and hold at warning thresholds through Friday. This northwest swell will gradually decline over the weekend and will be followed by another moderate to large west- northwest to northwest swell on Monday.
Surf along south facing shores will remain tiny with mainly background energy through the week. Surf along east facing shores will also remain tiny to small through the week due to mostly light background wind flow. With the return of strong trades next week, surf along east facing shores will steadily rise Monday and may even get close to advisory thresholds by the middle of next week.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 AM HST Thursday for North and West facing shores of Niihau Kauai Oahu Molokai and for North facing shores of Maui.

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