West Kaua’i

Today: Sunny and breezy. Isolated showers in the morning. Highs 79 to 84 near the shore to around 69 above 3000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Breezy. Isolated showers after midnight. Lows around 65 near the shore to around 56 above 3000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.

Thursday: Partly sunny with isolated showers in the morning, then mostly sunny in the afternoon. Highs around 81 near the shore to around 69 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

South Kaua’i

Today: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 75 to 82. Northeast winds 10 to 25 mph increasing to 20 to 25 mph in the afternoon. Chance of rain 50 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Scattered showers. Lows around 66. Northeast winds 10 to 25 mph. Chance of rain 40 percent.

Thursday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 75 to 82. Northeast winds 10 to 20 mph. Chance of rain 40 percent.

Kaua’i Mountains

Today: Breezy. Partly sunny with numerous showers in the morning, then mostly sunny with scattered showers in the afternoon. Highs 69 to 75 in the valleys to around 59 above 4000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 58 to 64 in the valleys to around 53 above 4000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Thursday: Partly sunny with scattered showers. Highs 69 to 75 in the valleys to around 60 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

North Kaua’i

Today: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 71 to 81. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Breezy. Partly cloudy with scattered showers. Lows 59 to 68. East winds up to 20 mph. Chance of rain 50 percent.

Thursday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 71 to 80. East winds up to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 68 to 79. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Scattered showers. Lows 59 to 70. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Thursday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 68 to 79. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Moderate to locally breezy trades will taper off today and tomorrow becoming light and variable by this weekend. Shower activity will be kept to a minimum with just a few windward and mauka clouds and showers through the end of the week. Next week, models begin to hint at a front developing, which may bring precipitation to the Hawaiian islands.

Discussion

A quasi-stationary upper-level low persists just northeast of the Hawaiian Islands while a broad 1029 mb surface high remains centered just north of the state. As these features meander eastward and weaken, trades at the local level will begin to ease across the region. Moisture content continues to be sparse, with model depicted precipitable water anomalies portraying values two to three standard deviations below average through early next week. This remains the case due to a much cooler and drier airmass which has more or less engulfed the Hawaiian Islands. Precipitable water from the latest 12z soundings from Hilo and Lihue show 0.95 and 0.83 inches, respectively, so any instability associated with the upper-level low and orographic lifting may still bring a few windward showers. Even then, rainfall amounts will be limited across the state.
Model guidance depicts the aforementioned surface high will meander eastward toward CONUS as it weakens, opening the doors to another surface trough developing just east of Hawaii. The trough may funnel some small batches of moisture into windward and mauka areas by way of the trades, but ultimately will remain limited with the lack of moisture content. Furthermore, with the high well out of the area by this time, trades will weaken even more, eventually becoming light and variable by this weekend.
Within the longer range forecast, models have begun to hint on the development of a front that will approach from the west during the early part of next week. The local winds will veer southeasterly, then southward in response, resulting in a pre-frontal convergence band pulling tropical moisture northward across the Hawaiian Islands. There remains considerable model discrepancies in the long-range GFS and ECMWF within this scenario, especially in the sense of timing, location, and strength. This system will be monitored and refined in the coming days as the pattern continues to evolve.

Aviation

Moderate to locally breezy ENE trade winds are expected today, before gradually weakening through the rest of the week. Embedded isolated and brief showers continue to primarily impact windward and mountain areas. MVFR conditions are possible within showers while VFR prevails elsewhere.
No AIRMET's are currently in effect. However, AIRMET Tango for mid – upper level moderate turbulence may be necessary later this morning due to an upper level low NE of the islands. This area of turbulence is not expected to linger for too long, and will likely weaken by the afternoon.

Marine

High pressure north of Hawaii will shift eastward through the week, causing trade winds to diminish. A Small Craft Advisory is in effect for the typically windier waters around Maui County and the Big Island.
Moderate north and east-facing shore surf continues to be generated by a short period north-northeast (020 degree) swell which will gradually diminish today as it veers northeast. Shores better exposed to this NNE swell will experience decent wind wave chop generated by solid moderate trades.
Surf along west-facing shores will remain dominated by wrap around from the north-northeasterly swell and will gradually diminish in kind through the week. The next small, medium-period northwest and west-northwest swells arrive this weekend to bring a small bump in surf for west-facing shores. Along south-facing shores, expect continued impulses to sustain small surf through the week.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM 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