Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 79 near the shore to around 67 above 3000 feet. East winds up to 15 mph shifting to the south in the afternoon. Chance of rain 20 percent.

Tonight: Mostly clear. Isolated showers after midnight. Lows around 64 near the shore to around 53 above 3000 feet. Light winds. Chance of rain 20 percent.

Thursday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers and isolated thunderstorms in the afternoon. Highs around 81 near the shore to around 69 above 3000 feet. Southwest winds around 10 mph. Chance of rain 50 percent.

South Kaua’i

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 78. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly clear. Lows 60 to 65. Northeast winds around 10 mph shifting to the south after midnight.

Thursday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers and isolated thunderstorms in the afternoon. Highs around 80. Southwest winds 10 to 15 mph. Chance of rain 30 percent.

Kaua’i Mountains

Today: Partly sunny with scattered showers. Highs 66 to 74 in the valleys to around 61 above 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers. Lows 53 to 58 in the valleys to around 47 above 4000 feet. Light winds becoming south up to 15 mph after midnight. Chance of rain 20 percent.

Thursday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers and isolated thunderstorms in the afternoon. Highs 68 to 76 in the valleys to around 63 above 4000 feet. Southwest winds 10 to 15 mph. Chance of rain 50 percent.

North Kaua’i

Today: Mostly sunny with scattered showers in the morning, then partly sunny with isolated showers in the afternoon. Highs 71 to 78. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers. Lows 56 to 65. Light winds. Chance of rain 20 percent.

Thursday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers and isolated thunderstorms in the afternoon. Highs 73 to 80. Southwest winds 10 to 15 mph. Chance of rain 40 percent.

East Kaua’i

Today: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 71 to 78. East winds up to 15 mph becoming around 10 mph in the afternoon. Chance of rain 50 percent.

Tonight: Partly cloudy. Isolated showers in the evening. Lows 54 to 66. Light winds. Chance of rain 20 percent.

Thursday: Sunny in the morning, then partly sunny with scattered showers and isolated thunderstorms in the afternoon. Highs 73 to 80. Southwest winds around 10 mph. Chance of rain 40 percent.

Detailed Forecast

Synopsis

Wind speeds will gradually ease today, giving way to a land and sea breeze weather pattern Thursday as a front approaches from the northwest. The front will bring a period of wet weather, including the possibility of thunderstorms, to portions of the state Thursday afternoon into Saturday. Another round of unsettled conditions is likely early next week.

Discussion

Trade winds will continue to weaken today as high pressure retreats to the northeast and a front approaches from the northwest. Clouds and showers decreased dramatically overnight as trades decreased, leaving mostly clear skies across most areas statewide. Overnight soundings show the trend, with PW only around an inch with stable lapse rates. Thursday will see land and sea breezes mixed with light southerly flow. This will pull more moisture into the region and prompt an increase in cloud cover and showers once again.
Models show upper troughing will push 500 mb temperatures lower and instability higher by Thursday, when the front is just northwest of Kauai. The combination of higher PW and increased airmass instability may allow thunderstorms to develop. While the bulk of this combination will occur southwest of the islands over the coastal and offshore waters, thunderstorms remain possible near Kauai Thursday afternoon. Thunderstorm possibility spreads east to include Oahu and surrounding areas Thursday night. By Friday, the front will stall across the central islands and thunderstorms will be possible statewide before tapering back Friday night to the eastern half of the state. Potential heavy rainfall will be spotty, so we are not expecting widespread flooding at this time.
Winds will remain light Saturday before increasing ahead of another front. Showers will continue across the region between these fronts. This second front, expected to arrive in the Sunday to Monday time frame, looks to be stronger than the first one. We may have to add thunderstorms to the forecast for Sunday and Monday in the next day or two as more model data arrives. Expect the second front to bring stronger winds to the Big Island summits. Big Island summit temperatures will hover near freezing at times as cooler air moves in aloft, so expect a mix of snow and rain showers there. By Sunday, the temperatures are expected to be closer to freezing, so there is the possibility for more snow than rain.

Aviation

A front moving toward the region from the northwest is causing the surface ridge located north of the islands to weaken. This will result in the background trade wind flow becoming lighter, and shifting out of the east-southeast today. Expect some low clouds and isolated showers to be transported into the northeast through southeast sections of some of the islands. By this afternoon, the lighter winds will likely allow local sea breezes to develop over each of the individual islands. This may result in clouds and isolated showers forming over some leeward and interior sections of the islands later today. This will likely be followed by clearing skies as local land breezes develop this evening. Very brief MVFR conditions may occur over some areas today in some of the clouds and showers, but expect VFR conditions to prevail over most of the state through this evening.
AIRMET Tango will likely be cancelled later this morning for the islands from Molokai to the Big Island due to the weakening low- level trade wind flow. No additional AIRMETS are anticipated through this evening.

Marine

Surface high pressure centered far northeast of the state will be moving further northeast and far enough away from the region to relax the tight pressure gradient that has existed upstream and over the islands for days. A storm-force low will slowly move northwest of the region today as it fills the void left by this northeast-exiting high. Winds have fallen below Small Craft Advisory (SCA) thresholds and will remain below SCA criteria through Thursday, or until the next elevated northwest swell moves through and lifts combined seas to around 10 feet around more western islands Friday. An approaching front from the northwest will also be the impetus for much weaker veering breezes late this week. Light to gentle breezes are anticipated to become northerly Friday into Saturday before strengthening and turning south southwest ahead of a potentially stronger front moving in from the northwest early next week.
A series of small, medium period northwest and north northeast swells will hold waist to head high surf along many north and northeastern-facing exposures through Thursday. A large northwest swell arriving Friday could lift surf to near High Surf Warning (HSW) levels along many north and west-facing shores. There is a higher probability that a large, medium period northwest swell arriving early next week will have the potential to produce solid HSW-level surf along most north and west-facing shorelines. East surf will remain slightly elevated through Thursday in Maui and Big Island despite the lighter trades in response to the northeast swell. The low period, wind wave chop should subtly subside on Oahu and Kauai because of these much tamer winds. South shore surf will remain very small with only background south swell energy moving through the next several days.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov