Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Frequent showers and slight chance of thunderstorms. Highs around 81 near the shore to around 69 above 3000 feet. Southwest winds 10 to 15 mph shifting to the west in the afternoon. Chance of rain near 100 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 67 near the shore to around 56 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Monday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 80 near the shore to around 68 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

South Kaua’i

Today: Frequent showers and slight chance of thunderstorms. Highs around 80. West winds 10 to 15 mph. Chance of rain near 100 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 63 to 68. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Monday: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs around 79. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Breezy. Frequent showers and slight chance of thunderstorms. Highs 68 to 76 in the valleys to around 63 above 4000 feet. Southwest winds up to 25 mph shifting to the west in the afternoon. Chance of rain near 100 percent.

Tonight: Mostly cloudy with frequent showers. Lows 56 to 61 in the valleys to around 50 above 4000 feet. North winds up to 15 mph shifting to the northeast after midnight. Chance of rain 90 percent.

Monday: Partly sunny. Frequent showers in the morning, then scattered showers in the afternoon. Highs 67 to 75 in the valleys to around 62 above 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 90 percent.

North Kaua’i

Today: Frequent showers and slight chance of thunderstorms. Highs 73 to 80. South winds up to 15 mph shifting to the northwest in the afternoon. Chance of rain near 100 percent.

Tonight: Breezy. Mostly cloudy with frequent showers. Lows 59 to 68. Northeast winds 10 to 20 mph. Chance of rain 90 percent.

Monday: Partly sunny. Breezy. Frequent showers in the morning, then scattered showers in the afternoon. Highs 72 to 79. Northeast winds 10 to 20 mph. Chance of rain 90 percent.

East Kaua’i

Today: Frequent showers and slight chance of thunderstorms. Highs 73 to 80. Southwest winds up to 15 mph. Chance of rain near 100 percent.

Tonight: Mostly cloudy with frequent showers. Lows 57 to 69. North winds 10 to 15 mph. Chance of rain 90 percent.

Monday: Partly sunny. Frequent showers in the morning, then scattered showers in the afternoon. Highs 72 to 79. Northeast winds 10 to 15 mph. Chance of rain 90 percent.

Detailed Forecast

Synopsis

Breezy south to southwest winds will overspread the state today as a cold front approaches from the northwest. Showers will be most prevalent on Kauai, where there will also be a slight chance for thunderstorms. The front will push through Oahu tonight, then stall out over Maui County on Monday. The front will bring some showery weather as it moves through, with winds shifting northeasterly and becoming breezy behind, with the shower focus shifting to windward slopes and coasts. The front will gradually dissipate Monday night and Tuesday, with light to moderate trades and fairly typical trade wind weather expected Tuesday through the end of the work week. Another front could shift winds southerly and bring an increase in showers next weekend.

Discussion

Currently at the surface, a cold front is located around 125 miles west-northwest of Kauai and is moving eastward at around 15 mph. Winds have responded and strengthened to breezy levels out of the south and southwest early this morning. Infrared satellite imagery shows partly to mostly cloudy conditions across the state, with cloud coverage the highest over Kauai. Radar imagery shows frequent showers moving through Kauai, and scattered pre-frontal showers moving into leeward sections of the remaining smaller islands. Meanwhile, only a few light showers are seen moving into the southeast facing slopes of the Big Island. Main short term focus remains on the incoming front and the associated weather it will bring to the islands.
The latest model solutions continue to exhibit some differences, but have remained remarkably consistent from run to run. The GFS remains more progressive with the front, allowing it to reach Maui County, while the ECMWF hangs the front up over Oahu. The two models haven't changed much during the past 24 hours, and the current forecast appears in good shape reflecting a blend of these solutions.
Breezy south to southwest winds will continue today in advance of the approaching front. The front will push through Kauai later today, Oahu tonight, then stall out in the vicinity of Maui County on Monday. Moderate to locally breezy north to northeasterly winds are expected to fill in following the frontal passage. The front will gradually dissipate over the central islands Monday night and Tuesday, with a weak ridge building in north of the state. The northeasterly trades will ease back to moderate levels Monday night, with light to moderate trades then prevailing Tuesday through Friday. Winds could shift southerly next weekend in advance of the next approaching front.
As for the remaining weather details, increasing south to southwest flow will bring some pre-frontal showers into leeward areas of Oahu and Maui County today as the front approaches from the northwest. The more showery conditions are expected on Kauai, where there will be enough instability for some heavier showers and possibly a few thunderstorms as well. The most unstable airmass appears to lift northeast of the islands by tonight, but we will continue to monitor this closely. The front and its associated band of moisture will push through Oahu tonight then stall out across Maui County on Monday, bringing some showery weather with it. The front will become increasingly west to east oriented with time, so the showery conditions will continue behind the front particularly for windward locales. Both the GFS and ECMWF continue to show the deepest moisture associated with the front remaining to the north of the Big Island, so rather dry weather will prevail here through Monday.
The front will gradually dissipate across the central islands Monday night and Tuesday, bringing a return of more typical trade wind weather featuring mainly windward and mauka showers which should continue through the end of the work week. The next approaching front could bring an increase in showers next weekend.

Aviation

Breezy southerly winds will usher showers and pockets of MVFR over Kauai, Oahu, and adjacent waters for the next several hours while a greater coverage of showers advances toward Kauai from the west. AIRMET Sierra for mountain obscuration will likely remain in effect for Kauai until the front passes later today. Showers will then expand in coverage in the vicinity of Oahu as the decaying frontal boundary arrives favorably during the onset of nocturnal cooling. AIRMET Sierra may be needed for Oahu late this evening. Prevailing VFR is anticipated for the remainder of the island chain. Southerlies transition to gusty northeast trades in the wake of the front.
AIRMET Sierra for tempo mtn obsc is in effect for Kauai.

Marine

An approaching front just west of our waters will cause winds to strengthen into the moderate to locally strong range out of the south to southwest today, especially for waters around Kauai and Oahu. The front will push down the island chain this afternoon into Monday, producing numerous showers, and fresh to locally strong trade winds as the high pressure ridge builds in behind the front. A Small Craft Advisory (SCA) is in effect for western waters through the day. This SCA may need to be altered through tonight as conditions warrant, especially with frontal passage.
A small, medium period northwest swell will continue to provide a a slight boost to west facing shores today. However, a large, medium period, north- northwest (340-350 deg) swell should start to arrive late tonight, providing large level surf. A High Surf Advisory (HSA) is likely to be issued starting tonight into Monday for north and select west facing shores. If observations come above guidance, a High Surf Warning (HSW) may be issued for mainly north facing shores. This swell will hold as it transitions to a more northerly direction Tuesday, then slowly subside Wednesday into Thursday. This could lead to moderate surges in harbors such as Hilo and Kahului from the northerly swell component, so the buoys will be closely monitored as the event unfolds. In the long range forecast, another potential HSW northwest swell may develop late next week for north facing shores.
An out of season south swell will continue today near the summertime average, then decline over the next few days. Surf along east facing shores will remain rough and choppy as the trade winds build back this week. Although, east facing shores exposed to the north swell wrap will see a rise coinciding with the north swell.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST this evening for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters.

Data Courtesy of NOAA.gov