Photo Credit: Jason Weingardt

West Kaua’i

Today: Mostly sunny with isolated showers. Highs around 83 near the shore to around 71 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 69 near the shore to around 59 above 3000 feet. Northeast winds 10 to 15 mph decreasing to up to 10 mph after midnight. Chance of rain 50 percent.

Friday: Mostly sunny with isolated showers. Highs around 83 near the shore to around 71 above 3000 feet. Northeast winds up to 10 mph. Chance of rain 20 percent.

South Kaua’i

Today: Breezy. Partly sunny with scattered showers. Highs around 80. Northeast winds 15 to 20 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 68. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Friday: Partly sunny with scattered showers. Highs around 80. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Breezy. Mostly cloudy with scattered showers. Highs 70 to 77 in the valleys to around 61 above 4000 feet. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows around 62 in the valleys to around 54 above 4000 feet. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

Friday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 70 to 77 in the valleys to around 61 above 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

North Kaua’i

Today: Partly sunny with scattered showers. Highs 73 to 83. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 62 to 70. East winds 10 to 15 mph. Chance of rain 70 percent.

Friday: Partly sunny with scattered showers. Highs 73 to 83. East winds around 10 mph. Chance of rain 50 percent.

East Kaua’i

Today: Mostly cloudy with scattered showers. Highs 73 to 82. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 60 to 71. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Friday: Partly sunny with scattered showers. Highs 73 to 82. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Breezy easterly trade winds will continue through tonight. Trade winds will weaken Friday into the weekend as an upper trough builds north of the region. Showers will favor windward and mauka locations for the next several days. A few heavier showers are possible Friday through early next week.

Discussion

Radar shows showers remain focused across windward areas this morning in lingering breezy trade wind flow. Shower intensity remained mainly light as limited moisture (PWs under 1.30″) continues, while sounding data at HLI and HTO showed stable low level inversions (around 9K FT) remain in place. However, radar estimates did suggest a few showers with locally heavier rainfall were embedded in the flow this morning.
Today through tonight…a large area of high pressure well north of the state will maintain breezy trade wind flow across the islands through tonight. Satellite data shows a band of slightly enhanced moisture remaining anchored east of the islands (PWs between 1.25″ to 1.40″), with much drier air lingering well to the northeast. This trade wind moisture pattern will continue to maintain a majority of showers across windward areas.
Friday through Monday…current trends continue to show the surface pressure gradient north of the state beginning to weaken, reducing the trade wind flow across the islands through the period. At upper levels, a trough will begin to sharpen northeast of the state early Friday, before deepening into an upper low during the weekend. Model trends show decreasing stability just north of the islands as a 500MB cold pool (temps around -14C) sinks southward, while PW values linger between 1.30″ and 1.50″. Moisture stability data suggests that this pattern could enhance showers across portions of the state through the weekend. However, the actual resultant shower pattern and location of any enhanced rainfall rates, will depend on the overall evolution and movement of the deepest moisture and instability. Currently, models resolve that the deepest moisture and pocket of instability will remain centered offshore of the islands, in the marine waters north of the state.
Tuesday through the remainder of next week…model solutions vary slightly through the period, with an area of high pressure trying to reorganize well northwest of the state, potentially reestablishing a trade wind pattern across the region. At upper levels, weak upper dynamics continue north of the state, though weakened since earlier in the weekend. This pattern could maintain some deeper layered moisture (modeled PWs in excess of 1.50″) and weakly organized insatiability, to continue the chance for showers with enhanced rainfall rates.

Aviation

Locally breezy trades will continue through the forecast period, focusing clouds and showers over windward and mauka areas. Increased moisture has allowed for greater coverage of showers and widespread MVFR conditions over windward areas of most islands. AIRMET Sierra for mountain obscuration is in effect for north through east facing sections of Oahu, Molokai, Maui, and the Big Island. Conditions are expected to improve later this morning. VFR conditions will prevail elsewhere across the state through today.
AIRMET Tango for low-level lee turbulence is in effect for all islands except Kauai, and expected to continue through this evening.

Marine

A high pressure system will remain north of the Hawaiian Islands producing moderate to locally strong trade winds into early Friday morning. A low pressure trough forming north through east of the islands will weaken the trade winds into the moderate range from Saturday into the first half of next week. A Small Craft Advisory (SCA) remains in effect for the windier waters and channels around Maui and Hawaii Counties. Wind speeds will decrease to moderate ranges and fall below SCA wind thresholds from Friday into the the middle of next week.
Small long period south to southwest swells (180-220 degree) will keep surf heights around the summer average along south facing shores through the week. Surf will slightly drop over the weekend, but will likely increase early next week as a new south-southwest (210 degree) swell arrives around Monday. Surf along east facing shores will remain near average and steadily decrease Friday into the weekend as the trade winds weaken.
North facing shores will see nearly flat conditions into Saturday, with a small long period northwest (310 degree) swell Sunday into Sunday night producing a slight bump in surf heights through Tuesday.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST this evening for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov