Photo Credit: Jason Weingardt

West Kaua’i

Today: Cloudy and breezy. Frequent showers in the morning, then scattered showers in the afternoon. Highs around 81 near the shore to around 67 above 3000 feet. Southwest winds 10 to 20 mph. Chance of rain 90 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows around 67 near the shore to around 57 above 3000 feet. West winds 10 to 15 mph. Chance of rain 20 percent.

Thursday: Mostly sunny. Highs around 81 near the shore to around 68 above 3000 feet. Northwest winds around 10 mph.

South Kaua’i

Today: Cloudy and breezy. Frequent showers in the morning, then numerous showers in the afternoon. Highs 77 to 82. Southwest winds 20 to 25 mph decreasing to 10 to 25 mph in the afternoon. Gusts up to 45 mph. Chance of rain 90 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy after midnight. Lows around 64. West winds 10 to 15 mph. Gusts up to 35 mph. Chance of rain 30 percent.

Thursday: Mostly sunny. Highs around 81. West winds around 10 mph shifting to the southwest in the afternoon.

Kaua’i Mountains

Today: Cloudy and windy. Frequent showers in the morning, then numerous showers in the afternoon. Highs 73 to 80 in the valleys to around 62 above 4000 feet. Southwest winds up to 35 mph decreasing to up to 20 mph in the afternoon. Chance of rain 90 percent.

Tonight: Breezy. Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 57 to 65 in the valleys to around 55 above 4000 feet. West winds 10 to 20 mph. Chance of rain 40 percent.

Thursday: Mostly sunny. Highs 72 to 78 in the valleys to around 63 above 4000 feet. West winds 10 to 15 mph.

North Kaua’i

Today: Mostly cloudy. Breezy. Frequent showers in the morning, then scattered showers in the afternoon. Highs 70 to 82. South winds up to 25 mph shifting to the west up to 15 mph in the afternoon. Gusts up to 50 mph. Chance of rain 90 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 60 to 67. West winds 10 to 15 mph. Chance of rain 30 percent.

Thursday: Mostly sunny. Highs 71 to 80. Northwest winds around 10 mph.

East Kaua’i

Today: Cloudy and breezy. Frequent showers in the morning, then numerous showers in the afternoon. Highs 72 to 82. Southwest winds up to 25 mph with gusts to 45 mph. Chance of rain 90 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 59 to 69. West winds 10 to 15 mph decreasing to up to 10 mph after midnight. Chance of rain 40 percent.

Thursday: Mostly sunny. Highs 73 to 82. Light winds.

Detailed Forecast

Synopsis

Gusty south to southwest winds into Thursday, as a pair of fronts move through the island chain. Increased rain chances will accompany this system as well through Wednesday night. Drier conditions and light winds will follow over the western end of the state Thursday through Friday, while some moisture lingers over the eastern end as the front stalls and weakens. Moderate to breezy southwest winds and increasing moisture will return over the weekend as the next cold front approaches.

Discussion

Water vapor imagery shows a negatively-tilted upper trough advancing toward Kauai and beginning to lift northeastward. This trough is driving a cold front, currently around 400 miles northwest of Kauai, toward a stationary front located around 120 miles northwest of Kauai. A low cloud band and line of showers ahead of the frontal system are now over Kauai, along with some developing low cloud and shower bands moving over Oahu and Maui County in the southerly flow in advance of the front. The stationary front is forecast to be reinvigorated as it is pushed through the state today through Thursday.
As the fronts are pushed toward and through the state, a tightening of the pressure gradient will result in strong and gusty southwest winds into this evening. The high resolution model guidance overnight indicated low-end advisory level winds over the islands, so an update to the forecast was made to increase winds over and downwind of the island terrain. As a result, a Wind Advisory was issued for these areas of Niihau through Maui, excluding the summit of Haleakala for the time being, in effect until 6 PM this evening. The line of showers currently over and around Kauai will advance down the island chain today, reaching Oahu later this morning and the eastern end of the state late Wednesday through Thursday. Although significant rainfall is not anticipated, some showers could become locally heavy at times with some minor ponding on roadways and elevated stream levels possible.
As the front reaches and stalls over the eastern end of the state tonight and Thursday, the southerly winds out ahead of it will likely reach Wind Advisory speeds at the summits of the Big Island, and potentially Haleakala as well. Drier conditions and light winds will follow over the western end of the state Thursday through Friday. Some rain chances will linger for Maui County and the Big Island into Friday morning, as the moisture axis associated with diminishing front stalls over the eastern end of the island chain. Moderate to breezy southwest winds and increasing moisture will return over the coming weekend as the next cold front nears the state from the northwest.

Aviation

A cold front will approach Kauai from the west today, then slide eastward across the island chain through tonight. Ahead of the feature, scattered to numerous showers will first affect Kauai and Oahu, then Maui County, and by mid-day Thursday, to a lesser extend, the Big Island.
South to southwesterly flow will increase ahead of the aforementioned front and become windy by this afternoon. AIRMET TANGO will likely be needed at a later time along north through east sections of the islands, in the lee of the mountains, for tempo moderate turbulence.
AIRMET SIERRA remains in effect above 2500 feet for Kauai for tempo mountain obscuration from clouds and showers.

Marine

A front passing over Kauai early this morning will slowly move down the island chain through early Thursday. The passage of this boundary will result in fresh to locally strong southwesterlies in its wake with winds east of the front remaining southeasterly or southerly through tonight. Wind magnitudes over most of the coastal zones will achieve Small Craft Advisory (SCA) levels today and hold there through this evening in direct association with the tight west-to-east pressure gradient associated with the southeast advancing front into the central waters. As high pressure builds in over the state, moderate southwesterlies will gradually weaken and veer more westerly this weekend as the front washes out in the vicinity of the eastern waters. The next front is forecast to clip the northern waters this weekend. Today's large, generally medium period west northwest swell and another similar swell scheduled to arrive late tonight into Thursday will keep seas elevated…especially around Kauai and more exposed waters surrounding Oahu. While winds die off Thursday, the SCA will be scaled back to the west to account for these higher seas brought on by the arrival of the reinforcing west northwest swell.
The current west northwest (290-320 degree) swell will hold near High Surf Advisory (HSA) level surf along many north and west- facing shores today. This swell will gradually decline this morning but will still provide the occasional advisory level sets through the day. A reinforcing moderate size, medium period west northwest swell arriving tonight into Thursday will warrant holding onto the ongoing HSA. Because of the more westerly direction of these recent swells, Oahu and Maui's north-facing shores may experience some minor shadowing by Kauai. However, coastal areas of west Big Island better exposed to this west component will likely continue to see minor overwash onto the most vulnerable low lying roadways and partially-inundated beaches through the good part of the day. A large west-northwest (310 degree) swell early next week will again result in these coastal inundation hazards. East-facing shore light wind wave chop due to the absence of trades. South- facing shore surf will remain small except for those areas better exposed to west wrap.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 AM HST Friday for north and west facing shores of Niihau, Kauai, Oahu, Molokai, north facing shores of Maui, and west facing shores of Lanai and the Big Island.
Wind Advisory until 6 PM HST this evening for Niihau, Waianae Coast, Oahu North Shore, Olomana, Central Oahu, Waianae Mountains, Lanai Mauka, Maui Windward West, Maui Leeward West, Kauai North, Kauai East, Kauai South, East Honolulu, Koolau Windward, Koolau Leeward, Molokai, Lanai Windward, Lanai Leeward, Lanai South, Maui Central Valley North, Maui Central Valley South, Windward Haleakala.
Small Craft Advisory until 6 PM HST this evening for Maui County Leeward Waters, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters.
Small Craft Advisory until 6 PM HST Thursday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters.

Data Courtesy of NOAA.gov