Photo Credit: Brendan Stephen

West Kaua’i

Today: Windy. Mostly sunny with scattered showers. Highs around 79 near the shore to around 67 above 3000 feet. East winds 15 to 30 mph. Chance of rain 50 percent.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening, then scattered showers after midnight. Lows around 66 near the shore to around 55 above 3000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Thursday: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 79 near the shore to around 67 above 3000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

South Kaua’i

Today: Windy. Partly sunny with scattered showers. Highs around 78. East winds 20 to 30 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 62 to 67. Northeast winds 20 to 25 mph. Chance of rain 50 percent.

Thursday: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs around 78. East winds 20 to 25 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Windy. Mostly cloudy with showers likely. Highs 66 to 74 in the valleys to around 61 above 4000 feet. East winds 25 to 30 mph. Chance of rain 70 percent.

Tonight: Windy. Mostly cloudy with showers likely. Lows 55 to 60 in the valleys to around 49 above 4000 feet. East winds 15 to 30 mph. Chance of rain 70 percent.

Thursday: Partly sunny. Windy. Showers likely in the morning, then scattered showers in the afternoon. Highs 66 to 74 in the valleys to around 61 above 4000 feet. East winds 15 to 30 mph. Chance of rain 70 percent.

North Kaua’i

Today: Partly sunny. Windy. Showers likely in the morning, then scattered showers in the afternoon. Highs 71 to 78. East winds 15 to 30 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then showers likely after midnight. Lows 58 to 67. East winds 10 to 25 mph. Chance of rain 70 percent.

Thursday: Breezy. Partly sunny with showers likely in the morning, then mostly sunny with scattered showers in the afternoon. Highs 71 to 78. East winds 10 to 20 mph. Chance of rain 70 percent.

East Kaua’i

Today: Partly sunny. Windy. Showers likely in the morning, then scattered showers in the afternoon. Highs 71 to 78. East winds 20 to 30 mph. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with showers likely. Lows 56 to 68. Northeast winds 15 to 25 mph. Chance of rain 70 percent.

Thursday: Breezy. Partly sunny with scattered showers. Highs 71 to 78. East winds 15 to 25 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Wet and windy trade wind weather will persist into Thursday, with enhanced showers and thunderstorms possible across the eastern third of the state. Expect the most rainfall over windward slopes of the Big Island. Trade winds should gradually decrease late Thursday into the weekend as a front approaches from the northwest. This front will likely bring an increase of heavy showers, especially across leeward areas during the first half of next week.

Discussion

Strong high pressure north of the state will drive blustery trade winds through Thursday. Satellite loop shows an upper low just northeast of the Big Island which is enhancing trade wind showers. The upper low will remain near the islands into the weekend and isolated thunderstorms remain in the forecast into Friday.
The latest Hilo sounding showed an unstable airmass with no capping trade wind inversion, thanks to the nearby upper low. Expect isolated thunderstorms across portions of Maui and the Big Island due to this instability. Highest rainfall will be over windward slopes of the Big Island and possibly east Maui during the next several days. Strong and gusty trade winds will continue through the rest of this work week. Today looks to be the windiest day of the week, with gusty winds of over 50 mph possible especially in areas downwind of terrain. As a result, an array of Wind Advisories and High Wind Warnings remain in effect and have been extended through early Thursday.
Trade winds will gradually weaken Thursday through the weekend and could become light and variable by Sunday as a front begins to approach the state from the northwest. Overall, expect a decrease in shower activity and lighter winds this weekend. Models show an active weather pattern setting up for next week as a front approaches Monday into Tuesday, likely triggering periods of heavy rainfall and isolated thunderstorms. With prefrontal winds shifting to the southwest, the rainfall focus will shift toward leeward areas.

Aviation

A strong high pressure system far north of the Hawaiian Islands will keep strong and gusty trade winds in the forecast through Thursday. An unstable upper low will anchor just east of the Big Island for the next few days. A combination of unstable conditions and strong winds will lift clouds up island mountain slopes and produce periods of showers over all windward and mountain areas, with more isolated to scattered showers over leeward sections. Expect periods MVFR conditions in showers along north through east sections of each island.
AIRMET Sierra remains in effect for mountain obscurations windward areas of most islands. This AIRMET will likely continue through early the morning hours and then decrease in coverage by noon HST today.
AIRMET Tango remains in effect for low level moderate to isolated severe turbulence over and downwind of all island mountains. AIRMET Tango also remains in effect for strong surface winds across the entire state. These AIRMETs will likely continue through Thursday.

Marine

Rough conditions out across the waters will continue into the second half of the week as strong high pressure (1038 mb) remains positioned to the north. Satellite data showed 25-35 kt winds with seas hovering in the 12-15 ft range, which line up well with buoy observations at the PacIOOS Mokapu station and a SOFAR drifter buoy east of Hilo this morning. Gales will continue through Thursday over the windier waters and channels of Maui County and the Big Island, while Small Craft Advisory conditions continue elsewhere due to winds and seas. For the extended, a pattern transition is likely late Friday through this weekend as a cold front approaches, which means a break in the strong winds/seas.
Surf along east facing shores will remain rough, with heights holding around the warning threshold of 15 ft (faces) through Thursday due to the aforementioned winds over and upstream of the islands. A downward trend is expected late Friday through the weekend as the ridge weakens and winds ease.
Surf along north facing shores will remain well below the seasonal average each day through early next week, with the exception of the shores exposed to the large easterly seas. A small west-northwest swell arriving Friday from a recent gale that tracked eastward from the Kurils to the Date Line will linger through the weekend. A small long-period pulse is possible Tuesday out of the north-northeast from a gale predicted to move through the Gulf of Alaska over the weekend. For the long-term (low confidence), despite the differences shown in the various model solutions, a more significant winter-like scenario unfolding will become a possibility through the second half of next week in response to broad low pressure evolving north-northwest of the islands. Confidence through the extended portion of the forecast should improve over the coming weekend.
Surf along south facing shores will remain near the seasonal average each day, with mainly wind swell wrapping into exposed areas.

HFO Watches/Warnings/Advisories

Wind Advisory until 6 AM HST Thursday for Kauai Leeward, Kauai Mountains, Waianae Coast, Oahu North Shore, Olomana, Central Oahu, Waianae Mountains, Lanai Mauka, Kahoolawe, Maui Windward West, Maui Leeward West, Big Island Interior, Kauai North, Kauai East, Kauai South, East Honolulu, Honolulu Metro, Ewa Plain, Koolau Windward, Koolau Leeward, 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.
High Surf Warning until 6 PM HST Thursday for Olomana, Maui Windward West, Kauai East, Kauai South, East Honolulu, Koolau Windward, Molokai Windward, Molokai Southeast, Windward Haleakala, Kipahulu, South Haleakala, Big Island Southeast, Big Island East, Big Island North.
High Wind Warning until 6 AM HST Thursday for Kohala, Big Island North.
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, Maui County Leeward Waters, Big Island Windward Waters.
Gale Warning until 6 PM HST Thursday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov