West Kaua’i

Tonight: Mostly clear. Isolated showers in the evening. Lows around 69 near the shore to around 60 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Thursday: Sunny. Highs 82 to 87 near the shore to around 74 above 3000 feet. Northeast winds up to 15 mph.

Thursday Night: Mostly clear. Lows around 69 near the shore to around 60 above 3000 feet. East winds up to 10 mph.

South Kaua’i

Tonight: Partly cloudy. Breezy. Scattered showers in the evening, then isolated showers after midnight. Lows 68 to 73. Northeast winds 15 to 20 mph. Chance of rain 30 percent.

Thursday: Mostly sunny. Breezy. Isolated showers in the morning. Highs 76 to 86. Northeast winds 15 to 20 mph. Chance of rain 20 percent.

Thursday Night: Partly cloudy. Breezy. Lows 68 to 73. Northeast winds 10 to 20 mph.

Kaua’i Mountains

Tonight: Mostly cloudy with scattered showers. Lows around 65 in the valleys to around 56 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Thursday: Breezy. Mostly sunny with scattered showers. Highs 72 to 79 in the valleys to around 66 above 4000 feet. East winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 40 percent.

Thursday Night: Breezy. Partly cloudy with scattered showers in the evening, then mostly cloudy after midnight. Lows around 65 in the valleys to around 56 above 4000 feet. Northeast winds 10 to 20 mph. Chance of rain 40 percent.

North Kaua’i

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 61 to 72. East winds 10 to 15 mph. Chance of rain 50 percent.

Thursday: Breezy. Mostly sunny with isolated showers. Highs 69 to 83. East winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 20 percent.

Thursday Night: Partly cloudy. Breezy. Isolated showers in the evening. Lows 62 to 72. East winds up to 20 mph. Chance of rain 20 percent.

East Kaua’i

Tonight: Mostly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 64 to 74. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Thursday: Mostly sunny with isolated showers. Highs 75 to 83. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Thursday Night: Partly cloudy in the evening then becoming mostly cloudy. Isolated showers. Lows 64 to 74. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Breezy trades become moderate late this week through the weekend. Scattered showers focus windward and mauka into next week.

Discussion

High stability remains firmly entrenched over the state. Breezy trades are delivering showers to windward and mauka sections of the islands this morning beneath the resident 8kft trade inversion. No change in the large scale pattern is anticipated for the next several days as the islands reside under or equatorward of the subtropical jet placing the region beneath a broad swath of large scale subsidence in maintenance of existing stability. Sensible weather will be largely modulated by periodic fluctuations in the trades which will weaken in concert with periodic height falls across the Central/North Pacific. The first such instance will be a gradual weakening of trades during the latter half of this week in response to a rapidly weakening 1040mb high migrating toward 35N and weakening considerably as it does so. It is certainly plausible that trades are briefly lost altogether early next week setting the stage for a period of land/sea breezes. Given the high stability environment in place, would expect little in the way of interior showers should that pattern develop. Otherwise, scattered showers will focus windward and mauka for the balance of the forecast period.

Aviation

AIRMET Sierra is in effect for mountain obscuration over Kauai as increased lower-level clouds create lower ceilings and visibility. This AIRMET will continue through the afternoon and possibly into the evening before the moisture passes to the west. Additional windward areas could possilby be added with incoming moisture tonight.
AIRMET Tango remains in effect across all islands for moderate turbulence due to breezy trades and will likely be needed through tonight.

Marine

A surface ridge north of the state will maintain breezy to strong trade winds across the Hawaiian coastal waters through this afternoon before a weakness developing in the ridge allows trade wind speeds to ease slightly during the latter part of the week into the weekend. With the ASCAT pass from earlier today showing wind speeds already starting weaken, the Small Craft Advisory has been scaled back to the typically windier waters around the Big Island and Maui County. A more significant weakening of the trade winds is likely this weekend into early next week as a large North Pacific low pressure system far north of the islands breaks the ridge down even further.
A small, long-period northwest swell is peaking as it fills in down the island chain this afternoon. North- and west-facing shores are experiencing near- to above-seasonal-average surf that will hold through the evening before gradually subsiding into the weekend.
A series of medium-period south swells will continue to bring small surf to south facing shores through Thursday. A more significant long-period south swell is expected to begin filling in Thursday night and will likely bring above-advisory-level surf to south-facing shores through the weekend. This swell originated from a storm-force low that passed south and east of New Zealand over the weekend, generating seas of 35 to 40 feet or greater within Hawaiis swell AIRMET Sierra is in effect for mountain obscuration over Kauai as increased lower-level clouds create lower ceilings and visibility. This AIRMET will continue through the afternoon and possibly into the evening before the moisture passes to the west. Additional windward areas could possilby be added with incoming moisture tonight.
AIRMET Tango remains in effect across all islands for moderate turbulence due to breezy trades and will likely be needed through tonight. window, though the peak of the energy may pass just east of the state. The buoys near American Samoa picked up a portion of this swell today, seeming to peak around 5 feet 16 seconds, with the peak of the swell also likely passing to their east. Elevated surf along south-facing shores will likely continue into the first week of June due to a continued active weather pattern near New Zealand sending swells toward Hawaii.
Rough surf along east-facing shores will gradually lower Thursday through the weekend as trade winds ease.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Thursday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov