Photo Credit: Braden Jarvis

West Kaua’i

Today: Breezy. Mostly sunny with isolated showers. Highs around 83 near the shore to around 71 above 3000 feet. East winds up to 25 mph increasing to 10 to 25 mph in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening, then scattered showers after midnight. Lows around 69 near the shore to around 61 above 3000 feet. East winds up to 25 mph increasing to 10 to 25 mph after midnight. Chance of rain 50 percent.

Friday: Breezy. Mostly sunny with isolated showers. Highs around 82 near the shore to around 71 above 3000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

South Kaua’i

Today: Partly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 80. Northeast winds 20 to 25 mph. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 68. Northeast winds 15 to 25 mph. Chance of rain 50 percent.

Friday: Partly sunny. Breezy. Showers likely in the morning, then scattered showers in the afternoon. Highs around 80. East winds 15 to 20 mph. Chance of rain 70 percent.

Kaua’i Mountains

Today: Mostly cloudy. Breezy. Showers in the morning, then scattered showers in the afternoon. Highs 70 to 77 in the valleys to around 61 above 4000 feet. East winds 10 to 25 mph. Chance of rain 80 percent.

Tonight: Mostly cloudy. Breezy. Numerous showers in the evening, then showers after midnight. Lows 61 to 67 in the valleys to around 58 above 4000 feet. East winds 10 to 25 mph. Chance of rain 90 percent.

Friday: Mostly cloudy. Breezy. Showers in the morning, then scattered showers in the afternoon. Highs 70 to 77 in the valleys to around 61 above 4000 feet. East winds 15 to 25 mph. Chance of rain 80 percent.

North Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs 73 to 82. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Gusts up to 40 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 63 to 70. East winds 10 to 20 mph. Chance of rain 50 percent.

Friday: Breezy. Partly sunny with scattered showers. Highs 73 to 82. East winds 10 to 20 mph. Chance of rain 50 percent.

East Kaua’i

Today: Partly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 73 to 81. East winds 10 to 20 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows 63 to 71. East winds 10 to 20 mph. Chance of rain 70 percent.

Friday: Mostly cloudy. Breezy. Showers likely in the morning, then scattered showers in the afternoon. Highs 72 to 81. East winds 15 to 20 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Drier air and strong trade winds are expected through Friday. An upper level system moving towards the eastern end of the state this weekend could bring a wetter trade winds.

Discussion

Have made some tweaks to the winds through the forecast period. Wind Advisory level winds remain in the forecast for the north portion and Kohala areas of the Big Island today. Winds will remain on the breezy to locally windy side over the coming days. However, have lowered the winds to just below advisory levels beyond today. Otherwise the forecast, and the forecast philosophy, remains largely the same as last evening.
The upper level low and surface trough continue to move west away from the main Hawaiian Islands this morning, but continues to be playing a role in the local weather. Thunderstorm activity associated with this system continues to be found west of the coastal waters this morning, and it is expected that these thunderstorms will also continue to move west with the trough.
High pressure to the far northeast, combined with the exiting trough to the west is helping to keep a tight pressure gradient over the islands. As the trough moves to the west, the high is expected to sink southward, maintaining the pressure gradient over the islands which will provide a boost to the winds. Combined with a drier airmass moving in, we can expect an uptick in the returning trade wind flow today. At this time, the highest confidence for advisory level winds is over and downslope of the Kohala Mountains on the Big Island today. Other downslope areas will also likely see some strong gusts at times over the next couple of days. Will monitor the situation before determining if the Wind Advisory needs to be extended or expanded.
Winds are expected to shift to a more easterly direction on Friday, as the high sinks slightly south, and the trough continues to move to the west. This will likely allow winds to decrease just a bit on Friday. Low clouds and light showers will focus over windward areas, with isolated showers passing to leeward sides of the smaller islands. Overall rainfall accumulation will be light.
The GFS and ECMWF global models show an upper level trough moving in from the northeast this weekend. The GFS hints at an upper level low forming along this trough Saturday afternoon for a brief time. Regardless of whether the upper low forms, the lowering upper level heights and increased stability could support an enhancement to the trade winds showers. Although the bulk of the showers will favor windward areas in the low level trade wind flow, the continued breezy trade winds will carry some of them onto leeward areas, especially through the overnight and early morning periods.
Although this upper level trough axis swings through late Sunday, the global models show another one swinging through a little further east early next week. High pressure remaining to the north of the islands will maintain breezy trades well into next week, but the upper level trough will likely enhance some of the showers upstream of the islands. These will be carried in on the trade winds during the first half of next week, focusing over windward areas and occasionally blowing over the leeward areas.

Aviation

Breezy to strong easterly trade winds are expected through the 24-hr forecast period and beyond, with clouds and mostly light showers favoring windward and mauka locations. Upper-level debris clouds associated with convection and the upper low several hundred miles to the west-southwest will continue to stream over the state. MVFR CIGS/VSBYS remain likely for some windward areas as pockets of moisture move through delivering light to moderate showers.
AIRMET Sierra for mountain obscuration remains in effect for all windward zones.
AIRMET Tango for lee turbulence below 080 will continue.
AIRMET Tango for moderate mid- to upper-level turbulence in the FL250/400 layer remains in effect.
Light icing potential is noted in the Zulu section of the AIRMET due to a band of mid/upper clouds moving through in the 140/FL250 layer. The best chance for icing will remain over the western end of the state.

Marine

Strong high pressure will hold in place northeast of the state through the end of the work week, then merge with a new strong high building north of the islands over the weekend into early next week. Strong to near-gale force trade winds will continue through the period. A Small Craft Advisory (SCA) is now in effect for all waters due to a combination of winds and rough seas through 6 PM Monday. The SCA will likely need to be extended at least through the middle of next week.
Surf along east facing shores will remain large and rough through the middle of next week due to persistent strong trade winds over and upstream of the islands. A High Surf Advisory (HSA) is now in effect for east facing shores through 6 AM Saturday. The HSA could briefly lower below advisory levels this weekend, then ramp back up to advisory levels Monday through Wednesday.
A series of small northwest swells (310-320 degrees) will move through the islands today through Monday, keeping some small surf in place along north and west facing shores. Northwest swell energy appears to fade entirely by the middle of next week. South shore surf will remain small through the middle of next week, with nothing more than background south swell energy moving through.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 AM HST Saturday for east facing shores of Kauai, Oahu, Molokai, Maui and the Big Island.
Wind Advisory from 6 AM this morning to 6 PM HST this evening for Kohala, Big Island North.
Small Craft Advisory until 6 PM HST Monday for all Hawaiian waters,

Data Courtesy of NOAA.gov