Photo Credit: Braden Jarvis

West Kaua’i

Rest Of Today: Sunny. Isolated showers in the afternoon. Highs around 78 near the shore to around 65 above 3000 feet. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

Tonight: Clear in the evening then becoming partly cloudy. Lows around 62 near the shore to around 52 above 3000 feet. East winds 10 to 15 mph.

Washingtons Birthday: Sunny. Highs around 79 near the shore to around 65 above 3000 feet. East winds 10 to 15 mph.

South Kaua’i

Rest Of Today: Sunny and breezy. Highs 74 to 79. Northeast winds 15 to 25 mph.

Tonight: Breezy. Partly cloudy with isolated showers. Lows around 63. Northeast winds 15 to 25 mph. Chance of rain 20 percent.

Washingtons Birthday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny in the afternoon. Highs 74 to 79. East winds 15 to 20 mph. Chance of rain 40 percent.

Kaua’i Mountains

Rest Of Today: Breezy. Mostly sunny with isolated showers. Highs 66 to 73 in the valleys to around 55 above 4000 feet. Northeast winds up to 25 mph increasing to 10 to 25 mph in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Scattered showers. Lows 54 to 60 in the valleys to around 49 above 4000 feet. East winds 10 to 25 mph. Chance of rain 40 percent.

Washingtons Birthday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 69 to 75 in the valleys to around 58 above 4000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

North Kaua’i

Rest Of Today: Sunny and breezy. Isolated showers in the afternoon. Highs 68 to 78. East winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening, then scattered showers after midnight. Lows 55 to 65. East winds 10 to 20 mph. Chance of rain 40 percent.

Washingtons Birthday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 68 to 79. East winds 10 to 15 mph. Chance of rain 50 percent.

East Kaua’i

Rest Of Today: Sunny and breezy. Isolated showers in the afternoon. Highs 65 to 77. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 55 to 67. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Washingtons Birthday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 67 to 78. East winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Breezy to windy north-northeasterly trade winds will prevail over the island chain today. Relatively low dewpoints will keep the air feeling cool, especially over the western and central islands. Lingering moisture over the eastern end of the state will gradually erode today. A stable trade wind pattern will persist over the next several days, though trades will become more easterly. Shower chances will generally remain highest across windward and mauka locations.

Discussion

Although winds atop Mauna Kea dropped below advisory levels earlier in the night, over the last hour or so, they have flirted with advisory levels. The Wind Advisory that had been effect was dropped overnight, and with guidance showing winds on the decrease, feel there is no need to raise the advisory again. We will continue to keep an eye on the observations in case that changes.
Most of the forecast remains on track, particularly for the next couple of days. No significant changes were made to the grids through about Wednesday. Beyond that the forecast PoPs were boosted mainly for windward, and some north facing areas.
High pressure far northwest of Kauai will continue to move to the east. As a result, breezy to locally windy north-northeast trade winds are expected today. A dry and stable airmass over most of the smaller islands will limit rainfall amounts. Lingering moisture over the Big Island are evident by the amount of clouds over that end of the state. Those areas are expected to see scattered showers focused over windward areas.
Dewpoints in the 40s and 50s will make it feel rather cool despite the overall lack of trade wind showers, especially across the smaller islands. This stable airmass spreading over the region will gradually erode the lingering moisture over the eastern end of the state through the rest of the weekend, so expect showers to diminish by the end of the weekend.
The high pressure system will move north of the islands tomorrow, with breezy to locally windy conditions beginning to weaken and start to become more easterly. The surface high is then expected to weaken and sag southward towards the islands, which will maintain trades in the moderate category through Wednesday. Strong consensus exists in the global models that trades will restrengthen for the second half of next week. Showers throughout this period will continue to favor windward and mauka locations.

Aviation

A breezy to locally windy northeast trade wind pattern will continue through today. Clouds and showers will favor windward slopes and coasts, but will likely only be isolated in coverage as drier air filters over the islands. Winds will gradually become more east-northeasterly later today and more easterly tomorrow onward as the surface high pressure system slides to the east of the state. VFR conditions will generally prevail, with only brief periods of MVFR possible in any showers.
AIRMET Tango remains in effect statewide due to occasional moderate turbulence downwind of higher terrain. This AIRMET will likely remain for at least the western half of the state today, where the stronger ridgetop winds look to be concentrated.

Marine

A declining northwest swell will be reinforced by a large pulse of north swell through the day today. As expected, a rapid rise in north swell was observed at the nearshore PACIOOS buoys overnight. Surf will peak along north and some exposed east facing shores early this morning close to the High Surf Warning level. A High Surf Advisory (HSA) remains in effect for most north facing shores through tonight for north facing shores of most islands as well as some windward/east facing areas that will be exposed to the northerly swell. Due to the northerly (340-360 degrees) direction of the swell, Kahului and Hilo Harbors may experience surges, and even though the swell will be declining late today and Monday, a shift in the swell direction out of the north-northeast (360-020 degrees) may maintain some surges. A Marine Weather Statement remains posted to highlight this concern.
Looking ahead, a storm low in the distant Northwest Pacific will produce a moderate, long period northwest swell that will arrive late Monday through Wednesday, with peak surf below HSA levels. East shores will experience some wrapping north swell during the next few days, followed by moderate, short period wind swell through much of the work week. South shores will remain seasonably small.
Cool, fresh to strong northeasterly winds will persist today, then shift more easterly on Monday as high pressure passes north of the islands. A Small Craft Advisory (SCA) remains posted for all waters through tonight due to a combination of the gusty winds and elevated seas, which will rise tonight with the building north swell. As the swell subsides, the SCA may be trimmed back to the typically windy waters around the Big Island and Maui as early as Monday. Winds will ease slightly Tuesday and Wednesday as the high weakens northeast of the islands, but another high building far north of the islands may bring increasing easterly trade winds by late Wednesday or Thursday.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 AM HST Monday for Niihau, Oahu North Shore, Olomana, Maui Windward West, Kauai North, Kauai East, Koolau Windward, Molokai Windward, Molokai North, Maui Central Valley North, Windward Haleakala, Big Island East, Big Island North.
Small Craft Advisory until 6 AM HST Monday for all Hawaiian waters,

Data Courtesy of NOAA.gov