Photo Credit: Braden Jarvis

West Kaua’i

Today: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs around 84 near the shore to around 72 above 3000 feet. Northeast winds 10 to 15 mph decreasing to up to 15 mph in the afternoon. Chance of rain 50 percent.

Tonight: Windy. Mostly cloudy with scattered showers. Locally heavy rainfall possible in the evening. Lows around 69 near the shore to around 59 above 3000 feet. Northeast winds up to 30 mph. Chance of rain 50 percent.

Wednesday: Breezy. Partly sunny with scattered showers. Highs around 81 near the shore to around 68 above 3000 feet. Northeast winds up to 25 mph. Chance of rain 50 percent.

South Kaua’i

Today: Breezy. Partly sunny with scattered showers. Highs 80 to 86. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Windy. Scattered showers in the evening, then numerous showers after midnight. Lows around 69. Northeast winds 20 to 30 mph. Chance of rain 70 percent.

Wednesday: Mostly cloudy. Windy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 76 to 82. Northeast winds 20 to 30 mph. Chance of rain 70 percent.

Kaua’i Mountains

Today: Mostly cloudy. Breezy. Scattered showers in the morning, then numerous showers in the afternoon. Highs 71 to 78 in the valleys to around 63 above 4000 feet. Northeast winds 10 to 25 mph. Chance of rain 70 percent.

Tonight: Windy. Cloudy with numerous showers. Locally heavy rainfall possible in the evening. Lows 61 to 67 in the valleys to around 57 above 4000 feet. Northeast winds 10 to 30 mph with gusts to 50 mph. Chance of rain 70 percent.

Wednesday: Mostly cloudy. Windy. Occasional showers in the morning, then numerous showers in the afternoon. Highs 67 to 74 in the valleys to around 60 above 4000 feet. Northeast winds 10 to 30 mph. Chance of rain 90 percent.

North Kaua’i

Today: Partly sunny. Breezy. Scattered showers in the morning, then numerous showers in the afternoon. Highs 73 to 84. Northeast winds 10 to 15 mph increasing to 10 to 25 mph in the afternoon. Chance of rain 70 percent.

Tonight: Windy. Mostly cloudy with numerous showers. Locally heavy rainfall possible in the evening. Lows 62 to 71. Northeast winds 15 to 30 mph with gusts to 50 mph. Chance of rain 70 percent.

Wednesday: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 70 to 81. Northeast winds 10 to 25 mph with gusts to 45 mph. Chance of rain 70 percent.

East Kaua’i

Today: Mostly cloudy. Breezy. Scattered showers in the morning, then numerous showers in the afternoon. Highs 71 to 82. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

Tonight: Cloudy and breezy. Scattered showers in the evening, then numerous showers after midnight. Lows 63 to 73. Northeast winds 15 to 25 mph. Chance of rain 70 percent.

Wednesday: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 67 to 79. Northeast winds 15 to 25 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Moderate to breezy easterly trade winds will back to a more northeasterly direction today as a front moves over Kauai late this afternoon, increasing clouds and showers. A strong high far northwest of the state will shift north of the state Wednesday through Thursday, driving the front southeast over the rest of the state. Expect wet conditions along the front and very windy northeasterly trade winds to follow behind the front. Drier than normal air will fill in across the state by Thursday afternoon. A more typical easterly trade wind pattern will then gradually return over the weekend and persist into early next week as the high weakens north of the state.

Discussion

A ridge of high pressure far north of the state that has been producing moderate to breezy easterly trades has weakened and shifted east overnight as a front inches closer to state from the northwest. ASCAT and surface observations show winds have already started to shift out of the northeast near Kauai from a strong 1038 mb high located roughly 1500 miles northwest of the state. Current radar and satellite imagery show scattered clouds and showers riding in with the easterly trades and along and area of convergence positioned from Kauai to nearly 200 miles north northeast of Kauai. Latest model guidance suggests winds will continue to shift out of the northeast today ahead of the front, clouds and showers will briefly become more limited along windward and mauka areas with some showers spilling over to leeward locales. The front will move over Kauai late this afternoon into the evening increasing clouds and shower coverage once again over windward and mauka areas. Very wind conditions are expected for Kauai tonight as the momentum and strength of the leading edge of the front is at the maximum. These very windy conditions may prompt a wind advisory for Kauai tonight.
The strong high is expected to shift north of the state Wednesday and Thursday, tightening the gradient over the state and driving the front and associated clouds and showers southeast down the island chain. Thus a wind advisory may be needed for other parts of the state as very windy conditions spread across the state. The wet weather associated with the front will continue to favor windward and mountain areas with some showers spilling over to leeward locations.
Dewpoints are expected to drop in the mid to upper 50's first for the western half of the state late Wednesday then for the rest of state by Thursday afternoon and persist into the weekend. This will make for drier conditions and seemingly cooler temperatures. Northeasterly trades will gradually ease Friday and may shift out of the east as the high weakens just north of the state and persist into early next week. Clouds and showers will be limited if any along windward and mauka areas. Dewpoint will return to more normals values late in the weekend into early next week.

Aviation

Moderate to breezy trade winds will become locally strong by the afternoon or evening as a cold front approaches Kauai from the northwest. Clouds and showers will continue to favor windward and mauka areas resulting in periods of MVFR conditions. Deeper moisture will move into the western end of the state and increase clouds and showers near Kauai and Oahu this morning. Otherwise, expect VFR to generally prevail across the state.
AIRMET Sierra is in effect for mountain obscuration across north through east sections of Kauai and Oahu this morning due to increased lower clouds and showers. Conditions should improve during the day today.
AIRMET Tango for tempo mountain lee turbulence will likely become necessary by this afternoon or evening as the trade winds strengthen.

Marine

A cold front will push southward through Kauai late this afternoon, then stall out just north of Oahu tonight into early Wednesday. The front will get driven southeastward down the island chain by a strong building high to the distant northwest late Wednesday and Wednesday night. Behind the front, northeast trades will ramp up to strong and near Gale force, with these winds then remaining steady through Friday. The trades will ease back to moderate and locally strong levels over the weekend as the high to the north weakens.
The combination of strengthening northeast trades and large rough seas will bring Small Craft Advisory conditions to most waters through Friday. The winds are expected to be particularly strong over the waters west of Kauai, and a Gale Warning is now in effect beginning 6 PM this evening and continuing through 6 AM Thursday.
A small medium-period north swell will continue to decline today. Long-period forerunners from in incoming long-period northwest swell have reached Kauai and Oahu, and will continue to build down the island chain through the day and peak around 10 feet tonight and Wednesday. While the resulting surf will easily exceed High Surf Advisory levels on north and west facing shores, the peak of the swell will coincide with fresh to near gale northeasterly winds, leading to rough conditions along some east facing shores due to large wind waves. Late Thursday into Friday, the swell will be reinforced and shift out of the north-northwest, likely keeping surf elevated above advisory levels. Another northerly swell reinforcement is possible on Saturday, potentially extending the advisory level surf for north facing shores. This swell is then forecast to lower Sunday into early next week.
Small short-period wind waves and wrapping northerly swell will produce small east shore surf today, followed by a rise around Kauai and Oahu tonight and Wednesday as strengthening northeast trade winds produce large wind waves. Above average east shore surf and rough conditions can be expected Thursday and Friday due to fresh to near gale trade winds and additional wrapping northerly swell. Tiny south shore surf will prevail through the weekend, followed by a small pulse from the south- southwest early next week.

HFO Watches/Warnings/Advisories

High Surf Advisory from noon today to 6 AM HST Thursday for north and west facing shores of Niihau and Kauai.
High Surf Advisory from 6 PM this evening to 6 AM HST Thursday for north and west facing shores of Oahu and Molokai and north facing shore of Maui.
Small Craft Advisory from noon today to 6 PM HST this evening for Kauai Northwest Waters, Kauai Leeward Waters.
Gale Warning from 6 PM this evening to 6 AM HST Thursday for Kauai Northwest Waters, Kauai Leeward Waters.
Small Craft Advisory from noon today to 6 PM HST Friday for Kauai Windward Waters.
Small Craft Advisory from 6 PM this evening to 6 PM HST Friday for Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters.
Small Craft Advisory until 6 PM HST Friday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov