Photo Credit: Jason Weingardt

West Kaua’i

Today: Mostly sunny. Highs around 86 near the shore to around 74 above 3000 feet. East winds up to 15 mph.

Tonight: Partly cloudy. Lows 69 to 74 near the shore to around 60 above 3000 feet. East winds up to 15 mph.

Wednesday: Mostly sunny. Highs around 86 near the shore to around 74 above 3000 feet. East winds up to 10 mph shifting to the south in the afternoon.

South Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Breezy. Isolated showers. Highs around 83. Northeast winds 15 to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 67 to 73. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny. Isolated showers in the morning. Highs around 83. East winds 10 to 15 mph. Chance of rain 20 percent.

Kaua’i Mountains

Today: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 73 to 80 in the valleys to around 64 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly 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 30 percent.

Wednesday: 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 30 percent.

North Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Isolated showers. Highs 76 to 85. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 63 to 73. East winds up to 15 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny with isolated showers. Highs 76 to 85. East winds up to 15 mph. Chance of rain 20 percent.

East Kaua’i

Today: Mostly cloudy with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 76 to 84. East winds 10 to 15 mph. Chance of rain 30 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Isolated showers. Lows 61 to 74. East winds 10 to 15 mph shifting to the northeast after midnight. Chance of rain 20 percent.

Wednesday: Partly sunny in the morning then becoming mostly sunny. Isolated showers. Highs 76 to 84. East winds up to 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Breezy trades will continue today, before easing Wednesday and giving way to sea and land breezes Thursday and Friday. A fairly typical trade wind pattern will continue this morning, with trade wind showers then steadily decreasing through the middle of the week as a more stable airmass gradually settles overhead. Some lingering instability may allow for a thunderstorm to pop over interior Big Island this afternoon however. Very dry conditions will overspread the entire island chain Thursday through the weekend, greatly limiting shower activity. Returning and gradually strengthening trade winds could bring a slight increase in showers early next week.

Discussion

Currently at the surface, a 1025 mb high centered 950 miles northeast of Honolulu, is driving breezy trade winds across the island chain. Infrared satellite imagery shows partly to mostly cloudy conditions with cloud cover most prevalent over windward and mauka areas. Radar imagery shows isolated to scattered showers affecting windward slopes and coasts, with the occasional shower spilling leeward. Main short term focus revolves around trade wind trends and rain chances.
The high to the northeast of the islands will remain nearly stationary today, slowly weaken as it shifts eastward on Wednesday, with the ridge axis then moving over or very near the western islands Thursday and Friday. Breezy trade winds will continue today, then ease into the moderate range Wednesday. The winds will ease further and become light and variable over the smaller islands Thursday and Friday, allowing for daytime sea breezes and overnight land breezes to be dominant. Meanwhile, light trades will likely hold in the unprotected areas of the Big Island. The surface ridge axis is forecast to shift northward over the weekend into early next week, which should bring a return and gradual strengthening of the trade winds.
As for the remaining weather details, isolated to scattered windward showers should prevail this morning, with the trade wind inversion then expected to lower to around 5 kft greatly limiting trade wind showers this afternoon. There remains a slight chance that instability aloft could allow a thunderstorm to pop over the Big Island interior this afternoon as well.
Rather dry trade wind weather will continue tonight through Wednesday night as the trade wind inversion holds around 5 kft, with most leeward areas not seeing any rain. Little change in the trade wind inversion height is expected Thursday through the weekend, greatly limiting shower activity across the entire state. A slight increase in windward showers is possible late in the weekend into early next week as the trades gradually return and inversion heights begin to slowly rise.

Aviation

Breezy to locally strong trades will produce low cigs and SHRA on windward and mauka zones through the period. MVFR conds possible in any SHRA. The arrival of elevated instability favors a chance for isolated TS over interior and upslope sections of the Big Island this afternoon.
AIRMET Sierra is in effect for mtn obsc for windward Big Island and N thru SE sections of the smaller islands.
AIRMET Tango for lee turb remains in effect.

Marine

Broad high pressure north of the state will maintain fresh to strong trade winds today as a Small Craft Advisory (SCA) remains in effect for all waters around the Big Island and Maui County and select areas around Oahu and Kauai through this afternoon. The ridge will continue to weaken as the SCA will be trimmed back to the waters around Maui County and the Big Island through tonight. The ridge further erodes and displaces the ridge southward over the islands Thursday into Friday, causing the trades to diminish significantly and possibly become disrupted. The SCA will be dropped completely by this time. Increasing moderate trades are expected during the weekend as the ridge lifts northward.
An active south Pacific will continue the extended run of southerly swell almost certainly through mid June. The current south-southwest swell gotten another pulse overnight but just below High Surf Advisory Criteria. This swell will gradually decline through Thursday, followed by a reinforcing south- southwest swell late Thursday and Friday that will produce south shore surf around seasonal average. Coming into the weekend, a larger swell will move through the islands likely near or at the High Surf Advisory (HSA) criteria of 10 feet. Followed by a potentially larger swell in development looking increasingly likely to push surf well above the advisory level late next week.
A small northwest swell has continued to fill in overnight and looks to hold today. Another pulse from the northwest will follow Wednesday into Thursday. The fresh to strong trade wind flow is producing rough choppy elevated seas but the wind waves will diminish significantly after Wednesday coinciding with the light winds through the weekend.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST this evening for Kauai Northwest Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters.
Small Craft Advisory until 6 AM HST Wednesday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov