Photo Credit: Brendan Stephen

West Kaua’i

Today: Sunny with isolated showers. Highs 83 to 88 near the shore to around 74 above 3000 feet. Northeast winds up to 10 mph shifting to the southwest in the afternoon. Chance of rain 20 percent.

Tonight: Mostly clear. Lows 66 to 71 near the shore to around 59 above 3000 feet. Northeast winds up to 10 mph in the evening becoming light.

Thursday: Sunny. Isolated showers in the afternoon. Highs 82 to 87 near the shore to around 73 above 3000 feet. Light winds. Chance of rain 20 percent.

South Kaua’i

Today: Partly sunny with scattered showers in the morning, then sunny with isolated showers in the afternoon. Highs 79 to 86. Northeast winds 10 to 15 mph. Chance of rain 30 percent.

Tonight: Partly cloudy with isolated showers. Lows around 70. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Thursday: Mostly sunny with isolated showers. Highs 78 to 86. Northeast winds around 10 mph. Chance of rain 20 percent.

Kaua’i Mountains

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 72 to 81 in the valleys to around 65 above 4000 feet. East winds up to 10 mph. Chance of rain 40 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 60 to 67 in the valleys to around 56 above 4000 feet. East winds around 10 mph. Chance of rain 50 percent.

Thursday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 73 to 80 in the valleys to around 64 above 4000 feet. East winds up to 10 mph. Chance of rain 40 percent.

North Kaua’i

Today: Mostly sunny with isolated showers. Highs 74 to 85. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 62 to 71. East winds up to 10 mph. Chance of rain 20 percent.

Thursday: Mostly sunny with isolated showers. Highs 74 to 84. East winds up to 10 mph. Chance of rain 20 percent.

East Kaua’i

Today: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 71 to 84. Northeast winds around 10 mph. Chance of rain 40 percent.

Tonight: Partly cloudy with isolated showers. Lows 62 to 74. Northeast winds around 10 mph. Chance of rain 20 percent.

Thursday: Mostly sunny with isolated showers. Highs 71 to 83. East winds around 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

With the exception of showers over windward Big Island, a general drying trend is expected beginning today and lasting through the next several days. Additionally, trade winds will be on a weakening trend, becoming light and variable by Friday. A weak cold front will bring a wind shift to the northwest and a chance of showers on Sunday. Northeasterly trade winds and mostly dry weather are expected early next week.

Discussion

The band of higher moisture that moved over the smaller islands during the evening and overnight hours is exiting the region early this morning, and is now confined to mainly the leeward Kauai waters as drier air nudges in from the east. This drier airmass is resulting in a significant decrease in windward showers and low clouds over the smaller islands when compared to yesterday evening. The exception, however, is the Big Island where latest satellite and radar imagery shows showers and low clouds embedded within the trade winds continuing to stream into windward locations. In the upper levels, a low aloft just south of the state is contributing to the continued shower activity for windward Big Island, but this feature will gradually weaken and drift off to the east over the next 24 hours. As this occurs, showers will gradually wane here too as the atmosphere becomes more stable.
Meanwhile, surface high pressure centered north of the islands is weakening as it moves south. Although locally breezy trade winds were observed in an Advanced Scatterometer (ASCAT) pass last night, winds will continue on a downward trend for the next few days as this high continues to weaken and several areas of low pressure pass north of the islands. The high is forecast to dissipate on Friday, at which point a ridge will extend over the area from the east. Light and variable winds and mostly dry weather will prevail as the mid-level ridge persists. This regime will continue Saturday.
Guidance continues to indicate that a weak or dissipating front will move over the islands from the northwest on Sunday, bringing a renewed chance of showers (though rainfall accumulations will be minimal). Ensemble consensus indicates high pressure will build north of the islands early next week, with Sunday's post-frontal northwest winds veering to the northeast Monday and Tuesday. A mid-level ridge building over the area will support a mostly dry regime through the first half of next week.

Aviation

Trades will decrease gradually through Friday. SHRA and low cigs should mainly be confined to windward and mauka locations with some limited spillover to leeward areas. Some brief MVFR conds will be possible in any SHRA. Otherwise, VFR conds should prevail.
No AIRMETs are currently in effect.

Marine

Surface high pressure settling in over the far north offshore waters will weaken regional trade winds to primarily gentle to locally moderate breezes by Thursday. The west-to-east orientated surface ridge axis of high pressure laying across the northern waters will result in generally light to gentle breezes across most coastal waters, with moderate trades over the Alenuihaha Channel and south of Big Island, the next several days. Light winds are favored ahead of the approach of a weak front nearing Kauai Sunday. Gentle breezes will veer northwest to northeast early next week behind this frontal passage.
No significant swells are expected the next few days with slowly subsiding trade wind waves; a more calm overall sea state going into the latter half of the week. Nearshore windward buoys are observing a near 5 foot trade wind swell that will maintain above seasonal average rough east shore surf through the day. This short period trade wind swell will decline to around 4 feet Thursday and then further fade throughout the weekend.
A small, medium period northwest (320 degree) swell is due Thursday and will pass by on Friday. A moderate size, lower period northwest (320 degree) swell developing from a pair of lows far northwest of the islands is scheduled to travel through this weekend and peak Sunday. A smaller reinforcing northwest pulse (320 degree) is due Monday and Tuesday. Northeast (30 degree) swell originating from a very large, powerful hurricane force low churning off the U.S. Pacific Northwest coast will begin arriving as a moderate size, medium to long period swell Friday and peak on Saturday. None of these swells are expected to produce advisory level surf.

Fire weather

KBDI values remain high across the state and a general drying trend is expected for the next several days. With the dry air moving overhead, relative humidity values will have the potential to reach the critical 45% threshold from late morning through the afternoon each day through Sunday. Fortunately, however, weak trade winds will mitigate fire weather concerns through the rest of this week.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov