Photo Credit: Jason Weingardt

West Kaua’i

Today: Mostly sunny. Breezy. Highs around 84 near the shore to around 71 above 3000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Lows around 67 near the shore to around 57 above 3000 feet. Northeast winds up to 10 mph.

Monday: Partly sunny. Highs around 83 near the shore to around 70 above 3000 feet. East winds up to 15 mph.

South Kaua’i

Today: Mostly sunny. Breezy. Isolated showers in the morning. Highs 77 to 83. East winds 15 to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Isolated showers. Lows around 67. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Monday: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 76 to 83. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Kaua’i Mountains

Today: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 71 to 78 in the valleys to around 62 above 4000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 60 to 65 in the valleys to around 55 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Monday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 70 to 77 in the valleys to around 62 above 4000 feet. East winds up to 10 mph. Chance of rain 70 percent.

North Kaua’i

Today: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 73 to 83. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 30 percent.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 60 to 70. Southeast winds up to 15 mph. Chance of rain 50 percent.

Monday: Partly sunny with scattered showers. Highs 72 to 83. East winds up to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Isolated showers. Highs 70 to 80. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 61 to 70. East winds up to 15 mph. Chance of rain 50 percent.

Monday: Partly sunny with scattered showers. Highs 69 to 79. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Breezy trade winds will ease late tonight and Monday as mid to high clouds spread over the eastern half of the island chain. High pressure will rebuild north of the state on Wednesday, leading to breezy and gusty trade winds through at least Friday. Rainfall will favor typical windward slopes through much of the week.

Discussion

A strong 1033 mb surface high remains parked about 900 miles northeast of the state and is driving the gusty trades. A mid- level ridge is maintaining a well-defined inversion between 6,000 to 8,000 ft. Under these stable conditions, localized areas on the Big Island could experience Wind Advisory conditions with gusts as high as 50 mph. Rainfall has been modest and confined to windward slopes overnight. Radar shows a few light to moderate showers. An upper- level trough has shifted over the central island chain and continues to support a 500 mb low a couple hundred miles to the south. This low and associated trough is sending some mid to high clouds over the eastern portion of the state this morning. The easterly winds on the flank of the 500 mb low have not been as strong as forecasted overnight, but a Wind Advisory remains posted for the high Summits of the Big Island, where the potential for strong winds remains through the morning hours.
Trade winds will ease to moderate strength tonight and Monday as the high to the northeast weakens and drifts eastward. The mid- to upper- level low will weaken and drift a little closer to the islands. The latest guidance suggests that the main impact will be mid to high clouds over much of the state, with just enough low- level ridging to maintain some stability. The shift in the position and intensity of the low aloft will cause winds at the high summits to shift out of the south and likely ease. A return to breezy and gusty trade winds will occur Wednesday into at least Friday as another strong surface high sets up north of the state.
There is no clear signal for any enhancement to rainfall, but will continue to monitor for changes. Thus, the forecast favors a typical pattern of mainly windward showers through the forecast period.

Aviation

A high pressure system northeast of Hawaii will keep breezy and gusty trade winds in the forecast today with decreasing wind speed trends starting on Monday. Brief showers and MVFR conditions will favor windward and mountain areas during the overnight to early morning hours.
AIRMET SIERRA remains in effect for mountain obscuration for north through east facing slopes of the Big Island. This AIRMET will likely diminish after sunrise this morning.
AIRMET TANGO remains in effect for moderate low level mechanical turbulence over and downslope of the mountains. Expect this to remain in place through the rest of the weekend. AIRMET TANGO also continues for upper level turbulence between FL290 and FL410 between Oahu and the Big Island. This is due to a portion of the subtropical jet bending around an upper low over the islands, and is expected to continue through the afternoon hours.

Marine

Strong trade winds will continue today with high pressure to the northeast of the state. The high will drift east over the next couple of days, and by tomorrow the pressure gradient over the region will relax a bit, resulting in the trades weakening to moderate to locally fresh levels. Another high building north of the islands during the middle of the week will cause winds to increase again, reaching strong to near gale levels during the second half of the week. A Small Craft Advisory (SCA) remains in effect for all Hawaiian coastal waters through this afternoon due to the strong winds. An incoming northwest swell will help to boost wave heights tonight and Monday to SCA levels. As such, most coastal water zones have had the SCA extended through Monday due to winds and seas.
The current moderate long period northwest swell is slowly subsiding, with surf along exposed shores expected to continue to drop through the day. A slightly larger west-northwest to northwest swell is expected to reach the northwest offshore buoys this afternoon, and reach the islands tonight, raising surf along exposed shores to High Surf Advisory (HSA) levels tonight and Monday. As mentioned above, this swell is expected to raise wave heights above 10 feet over the coastal waters to the east of the islands tonight and Monday, which would maintain a SCA for those waters. Due to the westerly component of this swell, surf heights may approach HSA thresholds for west facing shores of the Big Island on Monday.
Short period easterly wind wave swell will remain elevated and choppy as the trade winds remain strong. As the trades strengthen even further later next week, we should see another uptick along east facing shores the second half of next week. South-facing shore surf will remain at background levels for the next several days.

HFO Watches/Warnings/Advisories

Wind Advisory until 6 PM HST this evening for Kohala, Big Island Interior, Big Island Summits, Big Island South, Big Island Southeast, Big Island North.
Small Craft Advisory until 6 PM HST Monday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Channel, Oahu Windward Waters, Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.
Small Craft Advisory until 6 PM HST this evening for Kauai Leeward Waters, Oahu Leeward Waters.

Data Courtesy of NOAA.gov