West Kaua’i

Tonight: Partly cloudy. Breezy. Isolated showers in the evening. Lows around 75 near the shore to around 65 above 3000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Thursday: Mostly sunny. Breezy. Highs 87 to 93 near the shore to around 80 above 3000 feet. East winds 15 to 20 mph.

Thursday Night: Partly cloudy. Breezy. Lows around 74 near the shore to around 65 above 3000 feet. Northeast winds 10 to 25 mph.

South Kaua’i

Tonight: Breezy. Partly cloudy with isolated showers. Lows 72 to 78. Northeast winds around 20 mph. Chance of rain 20 percent.

Thursday: Breezy. Mostly sunny with isolated showers. Highs 80 to 91. Northeast winds around 20 mph. Chance of rain 20 percent.

Thursday Night: Breezy. Partly cloudy with isolated showers. Lows 71 to 77. Northeast winds 20 to 25 mph. Chance of rain 20 percent.

Kaua’i Mountains

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 70 in the valleys to around 62 above 4000 feet. East winds 15 to 25 mph. Chance of rain 50 percent.

Thursday: Mostly sunny in the morning then becoming partly sunny. Windy. Scattered showers. Highs 76 to 84 in the valleys to around 69 above 4000 feet. East winds 15 to 30 mph. Chance of rain 50 percent.

Thursday Night: Mostly cloudy. Windy. Scattered showers in the evening, then isolated showers after midnight. Lows 67 to 72 in the valleys to around 61 above 4000 feet. Northeast winds 20 to 30 mph. Chance of rain 40 percent.

North Kaua’i

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Breezy. Scattered showers. Lows 67 to 76. East winds 15 to 20 mph. Chance of rain 40 percent.

Thursday: Breezy. Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 73 to 90. East winds 15 to 20 mph. Chance of rain 40 percent.

Thursday Night: Mostly cloudy in the evening then becoming partly cloudy. Breezy. Isolated showers. Lows 66 to 75. East winds 15 to 25 mph. Chance of rain 20 percent.

East Kaua’i

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 68 to 78. East winds 15 to 20 mph. Chance of rain 50 percent.

Thursday: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs 80 to 87. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Thursday Night: Mostly cloudy. Breezy. Scattered showers in the evening, then isolated showers after midnight. Lows 67 to 77. Northeast winds 15 to 25 mph. Chance of rain 40 percent.

Detailed Forecast

Synopsis

A strong pressure gradient is developing over the state as a strong high sits north of the state and Major Hurricane Lowell passes roughly 400 miles south of the Big Island. A Wind Advisory is in effect for portions of Oahu, Maui County and the Big Island. Trades are expected to continue to strengthen across the state through Thursday where portions of Kauai may be added to the wind advisory. Trades will gradually ease Friday into Saturday. Expect scattered clouds and showers to focus over windward and mauka areas, particularly during the overnight hours. Sunday through early next week the forecast remains uncertain due to both Lowell and Karina nearing the state over the coming days.

Discussion

A tight pressure gradient is developing over the state as Major Hurricane Lowell tracks west roughly 400 miles south of the Big Island this afternoon and a strong high remains far north of the state. Very windy and gusty trades have developed over Maui County and the Big Island and are anticipated to develop over Oahu this evening, thus have added portions of Oahu to the Wind Advisory. Portions of Kauai may need to be added to the Advisory Thursday as trade winds continue to strengthen across the state.
Current radar and satellite show clouds and showers have cleared significantly since this morning as drier air filters in. Expect typically trade wind showers to focus over windward and mauka areas, especially during the overnight and early morning hours with a few showers spilling over to leeward areas at times within the strong trade wind flow. This trend will carry in to the weekend with a slight uptick in showers expected Thursday night as a low level band of clouds and showers ride through the trades.
The National Hurricane Center (NHC) latest forecast on Lowell has the system continuing a westward track far south of the islands over the next couple of days, before turning northward late this weekend and early next week as major hurricane. While confidence is not high there is a possibility that a major hurricane can impact the state next week. We continue to closely monitor this system and update forecast as necessary. Now is the time to make a plan for worst case scenario in order to be able to take action if and when needed.
Meanwhile, Hurricane Karina is about 1360 miles east of Hilo this afternoon, and the latest forecast from the NHC has it moving west- northwest through Friday, before lifting further to the north over the weekend and weakening. As Karina moves northeast of the islands this weekend and early next week, it will help to disrupt the strong trade wind flow, helping our winds to return initially to more moderate levels. Early next week it could lead to lighter winds. Remnant moisture from Karina could significantly increase chances of showers over the weekend and interact with the moisture field with Lowell keeping cloudy and showery conditions into early next week. Due to the uncertainty with the forecast tracks of both Lowell and Karina this far out, confidence in the forecast is low as details of the forecast for this upcoming holiday weekend are still being flushed out.
Please visit the hurricanes.gov page for the official NHC forecast for Lowell and Karina.

Aviation

Wet start to the day with numerous showers passing through the islands leading to MVFR and pockets of IFR under heaviest showers. Satellite shows up stream clearing so showers will taper off 19-20Z with more VFR conditions. Still could see some VCSH/MVFR this afternoon/evening on windward locations and upper slopes. Moderate to locally strong trade winds will prevail today, especially later this afternoon. Will need to keep an eye on LLWS with highest chances for HOG and HKO. Hurricane Lowell is forecast to pass far south of the island chain the next couple of days. On this westerly track, regional trade winds will remain strong per a tight pressure gradient between the hurricane and high pressure to the far north.
AIRMET Sierra has been issued for IFR and SHRA for KAUAI OAHU MOLOKAI MAUI through 20Z.
AIRMET Tango remains in effect for moderate low level turbulence south through west downstream of high terrain. AIRMET Tango will likely be in effect for the foreseeable future.

Marine

As a strong surface high persists far north of the Hawaiian Islands and interacts with Hurricane Lowell passing to the south, trade winds will strengthen across the coastal waters to become fresh to locally near gale force. A Small Craft Advisory (SCA) remains in effect for all Hawaiian Waters through Thursday night and will likely get extended into Friday. The offshore waters is currently seeing tropical storm conditions over the far southern waters while the core of hurricane force winds remains just outside the area through Thursday. A Tropical Storm Warning remains in effect for the far southern offshore waters.
While there is still plenty of uncertainty regarding the exact track of Lowell, confidence is fairly high that the southwest and western offshore waters will see Hurricane conditions. How close it gets to the state, is yet to be determined. As for Hurricane Karina, confidence is increasing that Karina will pass to the north and northeast of the state.
Swells from Hurricane Lowell will steadily fill in across rest of the island chain tonight into Thursday and will likely produce advisory level surf for south and southeast exposures throughout the state. Swells from Lowell will likely linger through next week and will gradually veer from southeast to south tonight through Thursday and eventually towards the southwest early next week. While, the forecast for swells and seas for next week will highly depend on the eventual track and intensity of Lowell, confidence is beginning to increase for the potential of extra-large surf (exceeding warning levels) along south and western exposures early next week. Additionally, the current moderate long period south swell will peak tonight then gradually decline through the rest of the week.
A large, medium-period east swell from Hurricane Karina will steadily fill in Friday into the weekend and will likely produce high end advisory level surf or warning level surf along east facing shores by this weekend.

Fire weather

Trade winds will continue to strengthen and spread across the state tonight and remain strong and gusty into Friday. Gusts to, or over 50 mph, will be possible in the typical windy areas. Relative humidity values are forecast to remain too high for critical fire criteria to be reached, and fuels are currently rated as not critical. Therefore, the strong winds will not trigger fire weather watches or warnings. The trade inversion is forecast to be 6000 ft to 7000 ft today.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST Thursday for Niihau, Kauai Leeward, Waianae Coast, Kahoolawe, Maui Leeward West, Kona, Kauai South, East Honolulu, Honolulu Metro, Ewa Plain, Molokai West, Molokai Leeward South, Lanai Leeward, Lanai South, Maui Central Valley South, South Maui/Upcountry, South Haleakala, Big Island South, Big Island Southeast.
Wind Advisory until 6 AM HST Friday for Waianae Coast, Central Oahu, Waianae Mountains, Lanai Mauka, Kahoolawe, Maui Windward West, Maui Leeward West, Kohala, East Honolulu, Honolulu Metro, Ewa Plain, 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, Big Island North.
Small Craft Advisory until 6 AM HST Friday for all Hawaiian waters,

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Data Courtesy of NOAA.gov