West Kaua’i

Today: Breezy. Mostly cloudy with scattered showers. Highs around 79 near the shore to around 68 above 3000 feet. Northeast winds up to 25 mph increasing to 10 to 25 mph in the afternoon. Chance of rain 50 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows around 69 near the shore to around 57 above 3000 feet. East winds 10 to 20 mph decreasing to up to 20 mph after midnight. Chance of rain 20 percent.

Tuesday: Breezy. Mostly sunny with isolated showers. Highs around 81 near the shore to around 70 above 3000 feet. East winds up to 25 mph increasing to 10 to 25 mph in the afternoon. Chance of rain 20 percent.

South Kaua’i

Today: Mostly cloudy. Breezy. Numerous showers early in the morning, then scattered showers in the late morning and afternoon. Highs around 76. Northeast winds 15 to 25 mph. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 63 to 71. Northeast winds 15 to 25 mph. Chance of rain 50 percent.

Tuesday: Breezy. Partly sunny with scattered showers. Highs around 78. Northeast winds 15 to 25 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Breezy. Frequent showers in the morning, then numerous showers in the afternoon. Highs 67 to 73 in the valleys to around 59 above 4000 feet. East winds 10 to 20 mph. Chance of rain near 100 percent.

Tonight: Mostly cloudy. Breezy. Numerous showers in the evening, then scattered showers after midnight. Lows 55 to 64 in the valleys to around 51 above 4000 feet. East winds 10 to 25 mph. Chance of rain 60 percent.

Tuesday: Breezy. Mostly cloudy with scattered showers. Highs 69 to 75 in the valleys to around 61 above 4000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

North Kaua’i

Today: Breezy. Frequent showers early in the morning, then scattered showers in the late morning and afternoon. Highs 69 to 79. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain near 100 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 60 to 70. East winds 10 to 20 mph. Chance of rain 50 percent.

Tuesday: Breezy. Partly sunny with scattered showers. Highs 71 to 81. East winds 10 to 25 mph. Chance of rain 50 percent.

East Kaua’i

Today: Breezy. Frequent showers in the morning, then numerous showers in the afternoon. Highs 68 to 78. Northeast winds 10 to 20 mph. Chance of rain near 100 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 56 to 72. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Tuesday: Breezy. Partly sunny with scattered showers. Highs 70 to 80. East winds 10 to 25 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

A wet and windy trade wind pattern will persist today as the remnants of a cold front drift southward through the islands. While most showers will favor windward and mauka locations, some will periodically reach leeward areas of the smaller islands. Drier conditions will move in by Tuesday as the boundary shifts away from the area. Breezy to windy trades will continue through midweek before gradually easing by Friday as the ridge weakens to the north.

Discussion

Model guidance remains in good agreement, showing a strong low- to mid-level ridge anchored north of the islands holding firm through the first half of the week. This setup will maintain breezy to windy trade winds. A weak upper trough lingering nearby will keep the inversion weak and slightly elevated, allowing for occasional increases in windward showers as shallow bands of moisture move through.
This morning, the remnants of a cold front, shown on satellite as a shallow band of clouds and moisture, has settled southward into the islands. This feature is supporting a wet trade wind pattern, with frequent windward and mauka showers that are occasionally reaching leeward areas of the smaller islands. The latest rainfall summary showed peak totals over the past 12 hours (through 2 AM HST) up to 3 inches on Kauai and up to around an inch on Oahu and Maui. The band will continue drifting southward through the islands today before shifting away by Tuesday, allowing drier air to fill in.
Trade winds will remain in the breezy to windy range today, with a gradual strengthening trend expected by Tuesday as high pressure builds north of the state. This will likely bring stronger trades, likely reaching wind advisory levels across the typically windier areas of Maui County and the Big Island. Despite the drier air expected, spotty showers will remain in the forecast, particularly for windward and mauka areas overnight through the mornings as areas of moisture move through.
By late week into next weekend, the ridge could weaken, allowing trade winds to gradually ease. Easterly winds may also veer slightly more east-southeast as a trough aloft develops well northwest of the islands. This shift could lead to a further weakening trend in the trades heading into the weekend.

Aviation

A long band of unstable clouds, associated with the remnants of an old cold front, continues to drift into the Hawaiian Islands from the north today. Expect wet and breezy trade wind weather bringing periods of MVFR conditions in showers to all islands over the next 24 hours.
AIRMET Sierra for mountain obscuration is currently in effect for north and east facing slopes of Kauai, Oahu, Molokai, Maui and the Big Island as the remnant cloud band continues to drift southward into the islands.
AIRMET Tango remains in effect for moderate low level turbulence over and downwind of island terrain. This AIRMET is expected to continue over the next several days. AIRMET Tango was also issued for moderate turbulence aloft between FL270 and FL360 due to a lingering subtropical jet stream.

Marine

Strong surface high pressure centered far north of Hawaii will maintain a very tight pressure gradient between itself and lower equatorial pressure, resulting in an extended period of fresh to strong trade winds. The remnant moisture from a dissipated cold front will drift south over the state today and bring gusty scattered showers to much of the local waters. Tuesday through early Thursday, expect strong- to near gale-force trade winds, with the strongest over the typically windier waters and channels surrounding Maui County and Big Island. The Small Craft Advisory for all Hawaiian waters has been extended through Wednesday morning for the strong winds and resulting rough seas.
The current moderate, medium period, north-northwest swell (340 degree) will steadily ease through Tuesday. A slightly larger, long-period north-northwest (330 degree) swell will arrive Tuesday night into Wednesday, with a reinforcing long-period northwest swell (310 degree) on its heels to close out the week.
Rough surf will continue along east facing shores through the week in response to the persistent strong trade winds over and upstream of the islands. Surf will near High Surf Advisory criteria Tuesday through midweek as trades peak in strength.
Surf along south-facing shores will remain small, aside from the possibility of some wrap from the easterly wind waves making it into the more eastern-facing southern exposures.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Wednesday for all Hawaiian waters,