West Kaua’i

Tonight: Windy. Mostly cloudy with scattered showers and isolated thunderstorms. Locally heavy rainfall possible. Lows around 70 near the shore to around 61 above 3000 feet. Southwest winds 20 to 30 mph with gusts to 50 mph. Chance of rain 30 percent.

Sunday: Breezy. Cloudy with numerous showers and isolated thunderstorms. Locally heavy rainfall possible. Highs around 81 near the shore to around 69 above 3000 feet. West winds 10 to 20 mph. Chance of rain 70 percent.

Sunday Night: Mostly cloudy with showers. Lows around 69 near the shore to around 60 above 3000 feet. Southwest winds up to 10 mph. Chance of rain 80 percent.

South Kaua’i

Tonight: Breezy. Mostly cloudy with scattered showers and isolated thunderstorms. Locally heavy rainfall possible. Lows around 71. Southwest winds 20 to 25 mph. Chance of rain 30 percent.

Sunday: Breezy. Cloudy with numerous showers and isolated thunderstorms. Locally heavy rainfall possible. Highs 75 to 82. West winds 20 to 25 mph. Chance of rain 70 percent.

Sunday Night: Cloudy with numerous showers. Lows around 69. West winds 10 to 15 mph. Chance of rain 70 percent.

Kaua’i Mountains

Tonight: Windy. Mostly cloudy with scattered showers and isolated thunderstorms. Locally heavy rainfall possible. Lows 63 to 69 in the valleys to around 59 above 4000 feet. Southwest winds 15 to 35 mph with gusts to 55 mph. Chance of rain 30 percent.

Sunday: Breezy. Cloudy with numerous showers and isolated thunderstorms. Locally heavy rainfall possible. Highs 71 to 77 in the valleys to around 62 above 4000 feet. Southwest winds up to 25 mph becoming 10 to 20 mph in the afternoon. Chance of rain 70 percent.

Sunday Night: Mostly cloudy with numerous showers. Lows 62 to 68 in the valleys to around 58 above 4000 feet. Southwest winds up to 15 mph. Chance of rain 70 percent.

North Kaua’i

Tonight: Breezy. Mostly cloudy with scattered showers and isolated thunderstorms. Locally heavy rainfall possible. Lows 63 to 72. Southwest winds 15 to 25 mph with gusts to 45 mph. Chance of rain 40 percent.

Sunday: Breezy. Cloudy with numerous showers and isolated thunderstorms. Locally heavy rainfall possible. Highs 72 to 80. West winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 70 percent.

Sunday Night: Mostly cloudy with scattered showers. Lows 63 to 71. West winds up to 15 mph shifting to the southeast after midnight. Chance of rain 50 percent.

East Kaua’i

Tonight: Breezy. Mostly cloudy with scattered showers and isolated thunderstorms. Locally heavy rainfall possible. Lows 65 to 74. Southwest winds 15 to 25 mph. Chance of rain 30 percent.

Sunday: Breezy. Cloudy with numerous showers and isolated thunderstorms. Locally heavy rainfall possible. Highs 69 to 81. Southwest winds 10 to 20 mph. Chance of rain 70 percent.

Sunday Night: Mostly cloudy with numerous showers. Lows 64 to 73. Southwest winds up to 15 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

A powerful kona storm remains north of the state producing periods of hazardous weather impacts across the Hawaiian Islands through Sunday. Expect a combination of threats ranging from significant flash flooding, damaging winds, isolated thunderstorms, and snow and ice over the highest Big Island summits. Strong and damaging southwesterly wind gusts will hold into Sunday, particularly for the eastern half of the state. The highest threats for damaging winds remains along north and east slopes of island mountains. The kona storm will lift northeastward Sunday into Monday allowing chances of heavy rain and strong winds will decrease across the Hawaii region. Light and variable winds will develop Monday and hold through much of next week, however, periods unsettled wet weather will continue across the state through much of next week.

Discussion

A strong kona low roughly 950 sm north of the state continues to generate moderate to heavy showers within a broad band clouds currently centered over the eastern half of the state. The proximity of this low to the state is generating strong southerly winds that have been producing severe gusts, particularly for the eastern half of the state where a High Wind Warning remains in effect. Winds have eased slightly over the western half of the state thus a High Wind Advisory remains in effect for Kauai and oahu. Drier more stable air is filtering in over Kauai where more scattered clouds with light to moderate showers have been observed. Latest short term model guidance suggests rainfall accumulations will continue to trend down for Kauai thus have cancelled the Flood Watch for Kauai. A narrow band of moderate to heavy showers currently moving over the eastern half of Oahu is merging within a broader band of showers that has been center over Maui County through much of the and and is forecast to intensify overnight due to one last push of upper support. Due to already saturated soils, elevated streams the flooding threat will continue for Oahu through early morning Sunday and through early morning Monday for Maui County and the Big Island.
Sunday and Monday the kona low will shift northeast of the state allowing for an overall trend down in wind speeds and showers. Very strong, gusty southerly winds will ease to advisory levels over Maui County and the Big Island Sunday night before dropping to light to breezy levels across the state Monday. Thunderstorms will be possible over the Big Island each afternoon Monday due to lingering instability and afternoon convection within a light wind pattern. These light winds will hold through rest of the week. In addition shallow bands of clouds and showers associated the exiting kona low will move through the state generating periods of unsettled wet weather.

Aviation

Showers have continued to move through most of the state today, providing MVFR to IFR conditions from Oahu to the Big Island. Kauai remains VFR as showers have not impacted the island. Showers are expected to continue primarily impacting islands from Molokai to Big Island through tonight, with some lingering showers impacting Oahu through this evening. These showers will continue to bring MVFR to IFR conditions. Isolated thunderstorms, primarily over the eastern half of the state, are also possible through tonight. The S-SW Winds have slightly weakened over the western half of the state, while Maui and the Big Island can still see winds 30 kt or greater through tomorrow.
AIRMET Sierra is in effect for mountain obscuration and IFR conditions for islands from Oahu to Big Island. Oahu will likely have conditions improve tonight or early tomorrow morning, as showers gradually move out of the area. Conditions for islands from Molokai to the Big Island will likely remain through tonight, especially for Maui and the Big Island.
AIRMET Tango remains in effect for moderate mid-upper level turbulence between 130 and FL300. AIRMET Tango is also in effect for strong surface winds for Maui and the Big Island, and for turbulence downwind N through E of terrain statewide. These conditions are expected to primarily continue into tomorrow.
AIRMET Zulu remains in effect, as high clouds from these showers present icing concerns between 130 and FL260. These conditions are expected to continue into tomorrow.

Marine

Gale-force winds continue across the central and eastern coastal waters into Sunday as a strong kona storm continues impacting the region. Therefore, a Gale Warning remains in effect for these waters through 6 PM HST Sunday. Elsewhere (for the waters near Kauai and Oahu), a Small Craft Advisory remains in effect for both winds and elevated seas greater than 10 feet. Gusty winds, steep and fast seas, and low visibility in heavy showers will continue across all coastal waters through the rest of the weekend. As the winds diminish later on Sunday, the Gale Warning will be replaced with a Small Craft Advisory. Seas will gradually fall as the system moves off to the north.
Strong to gale-force southerly winds will create large and rough surf along south facing shores into Sunday, though recent observations show that surf along south facing shores has declined a bit today, particularly across the western end of the state where winds have decreased. Therefore, the High Surf Advisory has been cancelled. Winds will shift shift westerly and diminish early next week as the storm gains increasing distance far to the north of the islands. Additionally, a small long-period south swell will result in a slight bump in south shore surf Tuesday.
A small, short to medium period west to west-northwest swell will bring small to moderate surf to north and west facing shores through the rest of the weekend. An additional bump in north shore surf is expected on Tuesday. Additionally, a small, medium period north swell will peak this weekend before gradually declining. Another small north swell could arrive late in the week.

HFO Watches/Warnings/Advisories

Wind Advisory until 6 AM HST Sunday for Niihau, Kauai Leeward, Kauai Mountains, Waianae Coast, Oahu North Shore, Olomana, Central Oahu, Waianae Mountains, Kauai North, Kauai East, Kauai South, East Honolulu, Honolulu Metro, Ewa Plain, Koolau Windward, Koolau Leeward.
Flood Watch through late tonight for Oahu,
Flood Watch through late Sunday night for Lanai Mauka, Kahoolawe, Maui Windward West, Maui Leeward West, Haleakala Summit, Kona, Kohala, Big Island Interior, Molokai, Lanai Windward, Lanai Leeward, Lanai South, Maui Central Valley North, Maui Central Valley South, Windward Haleakala, Kipahulu, South Maui/Upcountry, South Haleakala, Big Island South, Big Island Southeast, Big Island East, Big Island North.
High Wind Warning until 6 PM HST Sunday for Lanai Mauka, Kahoolawe, Maui Windward West, Maui Leeward West, Haleakala Summit, Kona, Kohala, Big Island Interior, Big Island Summits, Molokai, Lanai Windward, Lanai Leeward, Lanai South, Maui Central Valley North, Maui Central Valley South, Windward Haleakala, Kipahulu, South Maui/Upcountry, South Haleakala, Big Island South, Big Island Southeast, Big Island East, Big Island North.
Winter Storm Warning until 6 AM HST Monday for Big Island Summits.
Small Craft Advisory until 6 PM HST Sunday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters.
Gale Warning until 6 PM HST Sunday for Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov