Hilo

Tonight: Partly cloudy. Isolated showers in the evening. Lows 65 to 73 near the shore to 54 to 60 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny early in the morning, then partly sunny with scattered showers in the late morning and afternoon. Highs 81 to 88 near the shore to 68 to 74 at 4000 feet. North winds up to 10 mph shifting to the east in the afternoon. Chance of rain 50 percent.

Wednesday Night: Partly cloudy with isolated showers. Lows 67 to 72 near the shore to 55 to 60 at 4000 feet. East winds up to 10 mph shifting to the south after midnight. Chance of rain 20 percent.

Kona

Tonight: Mostly cloudy with isolated showers in the evening, then partly cloudy after midnight. Lows around 73 near the shore to 50 to 55 near 5000 feet. Light winds. Chance of rain 20 percent.

Wednesday: Partly sunny. Scattered showers in the late morning and afternoon. Highs 84 to 89 near the shore to around 71 near 5000 feet. Light winds. Chance of rain 50 percent.

Wednesday Night: Partly cloudy. Lows around 74 near the shore to 51 to 56 near 5000 feet. Light winds.

Waimea

Tonight: Breezy. Partly cloudy with isolated showers. Lows 64 to 71 near the shore to 55 to 62 near 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Wednesday: Partly sunny. Isolated showers early in the morning, then scattered showers in the late morning and afternoon. Highs 66 to 86. Northeast winds up to 15 mph. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy in the evening then becoming partly cloudy. Breezy. Isolated showers. Lows 65 to 73 near the shore to 57 to 64 near 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Kohala

Tonight: Breezy. Partly cloudy with isolated showers. Lows 64 to 71 near the shore to 55 to 62 near 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Wednesday: Partly sunny. Isolated showers early in the morning, then scattered showers in the late morning and afternoon. Highs 66 to 86. Northeast winds up to 15 mph. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy in the evening then becoming partly cloudy. Breezy. Isolated showers. Lows 65 to 73 near the shore to 57 to 64 near 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

South Big Island

Tonight: Partly cloudy. Lows around 75 near the shore to around 57 near 5000 feet. Northeast winds up to 15 mph.

Wednesday: Mostly sunny early in the morning, then partly sunny with scattered showers in the late morning and afternoon. Highs 83 to 88 near the shore to around 70 near 5000 feet. South winds up to 10 mph. Chance of rain 50 percent.

Wednesday Night: Partly cloudy. Breezy. Lows around 76 near the shore to around 57 near 5000 feet. East winds up to 20 mph.

Puna

Tonight: Partly cloudy. Isolated showers in the evening. Lows 65 to 73 near the shore to 54 to 60 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny early in the morning, then partly sunny with scattered showers in the late morning and afternoon. Highs 81 to 88 near the shore to 68 to 74 at 4000 feet. North winds up to 10 mph shifting to the east in the afternoon. Chance of rain 50 percent.

Wednesday Night: Partly cloudy with isolated showers. Lows 67 to 72 near the shore to 55 to 60 at 4000 feet. East winds up to 10 mph shifting to the south after midnight. Chance of rain 20 percent.

Waikoloa

Tonight: Partly cloudy. Lows around 74 near the shore to 52 to 57 above 4000 feet. Northeast winds up to 15 mph shifting to the southeast after midnight.

Wednesday: Partly sunny. Scattered showers in the late morning and afternoon. Highs 85 to 90 near the shore to 67 to 75 above 4000 feet. North winds up to 15 mph. Chance of rain 50 percent.

Wednesday Night: Partly cloudy. Lows around 75 near the shore to around 55 above 4000 feet. North winds up to 15 mph in the evening becoming light.

Detailed Forecast

Synopsis

Trade winds will weaken to land and sea breezes by Wednesday as remnant of former Tropical Cyclone Gil passes just north of the state through Wednesday night. Humidity, cloud cover and showers will increase through Thursday, and will repeat Sunday through Monday as Henriette passes to the north.

Discussion

Former Tropical Cyclone Gil, currently centered 430 miles northeast of Hilo, will open to a trough as it passes north of state on Wednesday. Winds will weaken this evening to where nighttime land breezes and daytime sea breezes dominate through the following 24 hours.
Gil remnants will bring cloud cover and very humid air mass across the state. While most of the trough of what is left of Gil will pass to the north, moisture along the southern fringes will get caught in Wednesday's sea breeze flow and allow for interior clouds with scattered showers to set up for all islands in the afternoon. Some showers could become briefly moderate-heavy intensity. The trough will move west of the area Wednesday night with some lingering clouds and showers expected around the area Thursday.
Drier conditions return briefly with moderate trade winds on Friday and Saturday. Long range global models currently show another weakening tropical system, currently Tropical Storm Henriette in the East Pacific, will pass north of the islands from Sunday through Monday, once again disrupting trade winds with land and sea breezes, along with warm and very humid conditions.

Aviation

Light to moderate trade winds today will diminish further tonight into tomorrow morning as a trough drifts just north of the area. Land and sea breezes can be expected tomorrow and an influx of moisture from the trough could allow for increased cloud and shower coverage. Due to the nature of the sea breezes, the highest cloud and shower chances look to come tomorrow afternoon for interior and leeward areas as well as the slopes of the Big Island. VFR conditions will be most prevalent with MVFR conditions in the showers.
No AIRMETs in effect and none are expected until tomorrow where AIRMET Sierra for mountain obscurations will be possible.

Marine

Moderate to fresh northeasterly trade winds will weaken tonight and Wednesday as a surface trough passes north of the islands. Trade winds will strengthen and become more easterly on Thursday as the trough moves northwest of Kauai, and a Small Craft Advisory (SCA) will likely be needed for the typically windy waters near Maui County and the Big Island Thursday and Friday. High pressure far northeast of the state will drift to the north over the weekend as Tropical Storm Henriette nears the region from the east, and local winds are expected to decline below SCA strength by Saturday. Henriette will be near or north of the islands by Sunday.
An extended run of south swell will continue this week. During its peak last night and this morning, the current swell produced surf at the High Surf Advisory (HSA) threshold, and this swell will continue to slowly decline through Wednesday. Long-period forerunners from the next south-southwest swell will build late Wednesday, and during the Thursday peak of the swell, south shore surf should remain below the HSA threshold. A larger south swell will build Friday through Saturday, generating surf well above the HSA threshold, and possibly near the High Surf Warning level, into Sunday. This swell will gradually decline early next week.
Even as wind wave energy declines with the easing trades, east shore surf will be elevated through Wednesday due to east swell produced by former Tropical Cyclone Gil. Windward PacIOOS buoys have been registering swell of around 3 feet at 13 seconds today, and guidance suggests that the swell may rise as high as 5 or 6 feet tonight as the period drops to 11 or 12 seconds. This may be enough energy to produce HSA level surf along east facing shores into Wednesday morning. Due to a lack of confidence in the rising swell, we have opted to hold off on issuing a HSA for now but will monitor the buoys tonight. The swell will decline rapidly late Wednesday and Thursday as strengthening trades generate near seasonal average wind waves. As waves decline over the weekend, east swell from East Pacific Tropical Storm Henriette may arrive.
A very small northwest swell originating from a former West Pacific typhoon is producing tiny surf along north shores. Another tiny northwest swell is scheduled to arrive late Wednesday into Thursday, preventing north shore surf from going completely flat.

Fire weather

Trades will diminish tonight while humidity levels increase as a tide of tropical moisture sweeps into the islands as the remnants of former Tropical Cyclone Gil drifts westward and passes just north of the Hawaiian Islands on Wednesday. Another round of deep tropical moisture will sweep through the islands from Sunday into Monday as Henriette follows a similar path.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov