Hilo

Tonight: Mostly cloudy. Occasional showers in the evening, then numerous showers after midnight. Lows 61 to 68 near the shore to 49 to 56 at 4000 feet. North winds up to 15 mph. Chance of rain 90 percent.

Thursday: Occasional showers. Highs 76 to 81 near the shore to around 65 at 4000 feet. Northeast winds up to 15 mph. Chance of rain near 100 percent.

Thursday Night: Occasional showers. Lows 62 to 70 near the shore to 53 to 60 at 4000 feet. Northeast winds up to 15 mph. Chance of rain near 100 percent.

Kona

Tonight: Mostly clear. Lows around 70 near the shore to 42 to 50 near 5000 feet. Light winds becoming east up to 10 mph after midnight.

Thursday: Sunny. Highs around 85 near the shore to around 70 near 5000 feet. Northeast winds up to 10 mph shifting to the north in the afternoon.

Thursday Night: Mostly clear. Lows around 72 near the shore to 47 to 53 near 5000 feet. Northeast winds up to 10 mph in the evening becoming light.

Waimea

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Windy. Scattered showers. Lows 62 to 70 near the shore to 51 to 60 near 3000 feet. East winds 10 to 30 mph with gusts to 55 mph. Chance of rain 50 percent.

Thursday: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs 63 to 82. East winds 10 to 25 mph. Chance of rain 50 percent.

Thursday Night: Mostly cloudy. Breezy. Numerous showers in the evening, then scattered showers after midnight. Lows 63 to 71 near the shore to 56 to 64 near 3000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Kohala

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Windy. Scattered showers. Lows 62 to 70 near the shore to 51 to 60 near 3000 feet. East winds 10 to 30 mph with gusts to 55 mph. Chance of rain 50 percent.

Thursday: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs 63 to 82. East winds 10 to 25 mph. Chance of rain 50 percent.

Thursday Night: Mostly cloudy. Breezy. Numerous showers in the evening, then scattered showers after midnight. Lows 63 to 71 near the shore to 56 to 64 near 3000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

South Big Island

Tonight: Mostly clear. Windy. Lows around 73 near the shore to around 51 near 5000 feet. East winds 10 to 30 mph.

Thursday: Sunny and windy. Isolated showers in the afternoon. Highs around 86 near the shore to around 69 near 5000 feet. East winds 10 to 30 mph. Chance of rain 20 percent.

Thursday Night: Breezy. Partly cloudy with isolated showers. Lows around 74 near the shore to around 53 near 5000 feet. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Puna

Tonight: Mostly cloudy. Occasional showers in the evening, then numerous showers after midnight. Lows 61 to 68 near the shore to 49 to 56 at 4000 feet. North winds up to 15 mph. Chance of rain 90 percent.

Thursday: Occasional showers. Highs 76 to 81 near the shore to around 65 at 4000 feet. Northeast winds up to 15 mph. Chance of rain near 100 percent.

Thursday Night: Occasional showers. Lows 62 to 70 near the shore to 53 to 60 at 4000 feet. Northeast winds up to 15 mph. Chance of rain near 100 percent.

Waikoloa

Tonight: Mostly clear. Windy. Lows 68 to 73 near the shore to 47 to 53 above 4000 feet. Southeast winds up to 30 mph with gusts to 50 mph.

Thursday: Sunny and breezy. Highs 81 to 89 near the shore to 66 to 73 above 4000 feet. Northeast winds up to 20 mph.

Thursday Night: Mostly clear. Lows around 73 near the shore to around 54 above 4000 feet. East winds up to 10 mph.

Detailed Forecast

Synopsis

Strong trades will focus showers over windward and mauka areas through tomorrow, particularly for the eastern end of the state. Trades then ease for the weekend and into next week with limited shower activity.

Discussion

At the surface, broad high pressure north of the islands and a trough associated with a well-defined low aloft south of the islands are resulting in a tight pressure gradient over the state. This is resulting in locally strong trade winds this afternoon. Latest satellite and radar imagery shows dry and stable conditions over most of the smaller islands, while showers are more common over windward portions of the Big Island in closer proximity to the trough and its associated upper low.
The main focus continues to be the strong trade winds in response to the high pressure ridge to our north and the low aloft south of the islands that is deepening and migrating westward. Winds will generally peak through tonight at breezy to strong levels, then begin to decline Thursday through the rest of the week. The pressure gradient is strongest over the eastern end of the state, as confirmed by observations across Maui and the Big Island this afternoon. Therefore, a Wind Advisory remains in effect through tonight for the typically windier areas of the Big Island and portions of Maui County. Additionally, based on recent trends, the High Wind Warning that was previously in effect for the Big Island Summits has been downgraded to a Wind Advisory and will also be in effect through tonight.
For Thursday and Friday, the fairly dry and stable breezy trade wind pattern will persist for the western end of the state, while slightly higher shower chances can be expected over the eastern end. This will be due to a combination of the proximity of the upper level low moving westward to our south and deeper moisture edging up from the south near the Big Island. This weekend and early next week, trade winds will not be as strong as the low south of the islands dissipates and a series of fronts passing to our north weaken the surface ridge. In addition, drier air will filter across the region, putting a damper on trade wind showers throughout this period.

Aviation

AIRMET Tango remains in effect for low-level turbulence to the lee of the mountains across the state and for strong surface winds east of Molokai. Both elements of this AIRMET will likely be needed into Thursday due to strong high pressure north of the islands and associated blustery trade winds. Clouds and showers riding in on the trades will continue to focus rainfall over windward sides of the islands, with isolated MVFR conditions. At this time no widespread mountain obscuration is expected.

Marine

High pressure north of the Hawaiian Islands will keep strong trade winds in place tonight before gradually easing to fresh by Friday into the weekend. The Gale Warning for Maalea Bay, the Pailolo and Alenuihaha Channels, and waters south of the Big Island will remain in effect through tomorrow afternoon. A Small Craft Advisory is in effect for the remaining waters where winds will still be fresh to strong and seas are expected to remain near 10 feet.
Surf along north and west-facing shores will continue to lower today through tonight and remain elevated through Friday then decline over the weekend. A larger long period west-northwest swell is possible next week.
Surf along east-facing shores will remain rough and choppy through the Friday due to the fresh to strong trade winds.Surf heights will then decrease over the weekend as trade speeds decrease.
Surf along south-facing shores will remain small through the forecast period.

Fire weather

Gusty trades will stick around through Thursday, though will be on a gradual decline. Observations from earlier today showed that relative humidity values briefly dropped to 45% at Honolulu, and tomorrow should be similar to today with little change to the moisture field expected. Therefore, a Red Flag Warning remains in effect until 6 PM HST Thursday, though red flag conditions are expected to be met from Thursday morning through Thursday afternoon.

HFO Watches/Warnings/Advisories

Red Flag Warning until 6 PM HST Thursday for Niihau, Kauai South, Kauai Southwest, Honolulu Metro, Ewa Plain, Waianae Coast, Oahu North Shore, Central Oahu, Waianae Mountains, Molokai West, Molokai Leeward South, Lanai Windward, Lanai Leeward, Lanai South, Lanai Mauka, Maui Leeward West, Maui Central Valley North, Maui Central Valley South, South Maui/Upcountry, South Haleakala, Big Island South, Big Island Southeast, Kohala, Big Island Interior.
Wind Advisory until 6 AM HST Thursday for Lanai Mauka, Kahoolawe, Maui Windward West, Maui Leeward West, Kohala, Big Island Interior, Lanai Windward, Lanai Leeward, Lanai South, Maui Central Valley North, Maui Central Valley South, South Haleakala, Big Island South, Big Island Southeast, Big Island North.
Wind Advisory until 6 AM HST Thursday for Big Island Summits.
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.

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Data Courtesy of NOAA.gov