West Kaua’i

Rest Of Tonight: Mostly clear with isolated showers. Lows around 76 near the shore to around 66 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Monday: Breezy. Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 88 to 93 near the shore to around 79 above 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Monday Night: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 74 to 82 near the shore to around 65 above 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

South Kaua’i

Rest Of Tonight: Breezy. Mostly cloudy with scattered showers. Lows 73 to 78. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Monday: Breezy. Partly sunny with scattered showers. Highs 81 to 91. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Monday Night: Breezy. Mostly cloudy with scattered showers. Lows 73 to 81. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Kaua’i Mountains

Rest Of Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 71 in the valleys to around 64 above 4000 feet. East winds 10 to 20 mph decreasing to up to 20 mph after midnight. Chance of rain 50 percent.

Monday: Mostly cloudy with numerous showers. Highs 75 to 83 in the valleys to around 69 above 4000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Monday Night: Mostly cloudy with scattered showers. Lows around 69 in the valleys to around 61 above 4000 feet. East winds up to 15 mph increasing to 10 to 15 mph after midnight. Chance of rain 50 percent.

North Kaua’i

Rest Of Tonight: Mostly cloudy with scattered showers. Lows 67 to 76. East winds up to 15 mph. Chance of rain 50 percent.

Monday: Partly sunny with scattered showers. Highs 72 to 88. East winds up to 15 mph. Chance of rain 50 percent.

Monday Night: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 65 to 76. East winds up to 15 mph. Chance of rain 40 percent.

East Kaua’i

Rest Of Tonight: Mostly cloudy with scattered showers. Lows 69 to 78. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Monday: Mostly cloudy with scattered showers. Highs 79 to 87. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Monday Night: Mostly cloudy with scattered showers. Lows 68 to 79. East winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Locally strong and gusty trade winds will ease slightly on Monday as Tropical Storm Moke passes several hundred miles south of the islands. Moisture along the northern periphery of Moke will bring wet conditions and a risk of flash flooding on the Big Island, while less rainfall is expected to impact windward sections from Maui to Kauai over the next couple of days. Trade winds will drop to moderate strength on Tuesday as Moke moves westward away from the area, with drier trade wind weather returning for the remainder of the week.

Discussion

Locally strong and gusty trades winds continue statewide, and wet conditions prevail on windward Big Island as moisture along the northern periphery of Tropical Storm Moke brushes the southern end of the island chain. The exposed low level center marking the center of Moke is currently centered over 300 miles south- southwest of Kailua-Kona, while deep moisture being sheared to the north of the system is largely skirting just south of Big Island. This has kept rainfall on windward Big Island at light to moderate intensity today, limiting rainfall to less than one inch during the past 12 hours and less than a half of an inch in Kau and much of windward Maui. While the wind field surrounding Moke is well south of the islands, the tropical storm is helping to produce a rather tight pressure gradient over the state. The resulting breezy trades are enhanced over and just south of terrain, especially on portions of Big Island and Maui County where gusts of around 50 mph are supporting a Wind Advisory.
A flood threat will continue for the Big Island through Monday, and winds will remain elevated through this evening. As Moke continues to move westward, low- to mid-level flow on the Big Island will shift out of the east to east-southeast, which could optimize orographic lift and increase rainfall on windward and southeast slopes. The guidance continues to show large variation in potential total precipitation, meaning that confidence is lower than normal, but the main window for flooding will be through early Monday morning on windward areas, with a chance for spotty afternoon showers to produce localized flooding across the Kona Districts. A Flood Watch is posted for Big Island through Monday afternoon. Elsewhere in the state, expect somewhat wet conditions windward, with passing showers leeward on gusty trades. The Wind Advisory for portions of Big Island and Maui County has been extended through midnight to account for lingering strong winds this evening. Later tonight and Monday, trades will gradually lower as departing Moke allows the local pressure gradient to slowly relax.
Drier conditions will develop on Tuesday as trades fall to moderate strength. Expect much of the coming week to feature typical trade wind weather, with showers favoring windward slopes.

Aviation

Tropical Storm Moke was centered nearly 300 hundred miles south of the Big Island and continued on its westward track. Rain bands from the tropical storm will impact windward Big Island through tonight, which will bring MVFR and periods of IFR conditions to the area.
Trade winds are expected to be moderate to locally strong statewide. Outside of windward Big Island, showers embedded within the trade wind flow will primarily impact windward and mountain areas, bringing periods of MVFR conditions. Otherwise, VFR will prevail.
AIRMET Tango is in effect for low level turbulence downwind of terrain due to the strengthened trade winds. AIRMET Sierra is in effect for mountain obscurations over windward portion of the islands. An AIRMET for IFR conditions over portions of windward Big Island is also a possibility tonight.
TC SIGMET series XRAY covers Tropical Storm Moke and its convection.

Marine

Fresh to locally strong winds will hold across all waters through tonight as Tropical Storm Moke passes far south of the island chain and a broad high pressure remains north of the state. A Tropical Storm Warning is in effect for the offshore waters. Intense convection associated with this storm will remain over the southern portion of the offshore waters as this system tracks west and exits the region by Monday. A Small Craft Advisory (SCA) for all waters has been extended through 6 AM HST Monday. Some areas of the coastal waters should drop out of the SCA Monday as TS Moke shifts west of state easing the pressure gradient across the state. Moderate to locally strong trades should return by Monday night or Tuesday.
Higher winds and short period wind wave swell generated by TS Moke appears to have peaked over the eastern half of the state. Surf along east and east-southeast facing shores should trend down a notch by Monday as TS Moke tracks west of the state but will still be elevated and choppy and strong trades hold.
Surf along most south-facing shores will be slightly below summer norms but still remain somewhat elevated due to a lingering small, long period south southwest swell. A three to four foot, medium to long period south swell is expected to arrive Monday and Tuesday which will maintain these near summertime heights.
Small, medium to long period west to north swell originating from Hurricane Lala is passing around north and west-facing coasts has peaked and should trend down Monday.

Fire weather

Locally strong and gusty trades will ease later tonight and Monday, while humidity remains higher than normal due to moisture on the northern periphery of Tropical Storm Moke brushing the state. Heavy rain is expected on windward and southeast slopes of the Big Island, while lower rainfall totals are expected over other windward areas. The inversion will be weak to non-existent into Monday. A typical summertime trade wind pattern will return by Tuesday.

HFO Watches/Warnings/Advisories

Wind Advisory until midnight HST tonight for Lanai Mauka, Kahoolawe, Maui Leeward West, Kohala, Big Island Interior, Molokai Southeast, Molokai North, Molokai West, Molokai Leeward South, Lanai Windward, Lanai Leeward, Maui Central Valley North, Maui Central Valley South, Windward Haleakala, South Haleakala, Big Island South, Big Island Southeast, Big Island North.
Flood Watch through Monday afternoon for Big Island,
Small Craft Advisory until 6 AM HST Monday for all Hawaiian waters,

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Data Courtesy of NOAA.gov