Photo Credit: Tyler Rooke

West Side

Today: Partly sunny. Highs 76 to 85. East winds 10 to 15 mph.

Tonight: Mostly cloudy. Isolated showers after midnight. Lows 66 to 73. East winds 10 to 15 mph. Chance of rain 20 percent.

Thursday: Cloudy with scattered showers. Highs 75 to 84. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 40 percent.

South Side

Today: Mostly sunny in the morning then becoming partly sunny. Breezy. Highs around 86. Northeast winds 10 to 20 mph.

Tonight: Mostly cloudy. Breezy. Isolated showers after midnight. Lows 64 to 71. East winds 10 to 20 mph. Chance of rain 20 percent.

Thursday: Cloudy. Isolated showers in the afternoon. Highs around 85. East winds 10 to 15 mph. Chance of rain 20 percent.

North Shore

Today: Partly sunny. Scattered showers in the morning. Highs 75 to 82 near the shore to around 64 near 5000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 68 near the shore to 47 to 53 near 5000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Thursday: Cloudy with numerous showers. Locally heavy rainfall possible in the morning. Highs 76 to 82 near the shore to around 65 near 5000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

Central Maui

Today: Partly sunny. Breezy. Highs 81 to 86. East winds 10 to 20 mph.

Tonight: Mostly cloudy. Isolated showers after midnight. Lows 64 to 69. East winds 10 to 15 mph. Chance of rain 20 percent.

Thursday: Cloudy with isolated showers. Highs 80 to 86. East winds 10 to 15 mph. Chance of rain 20 percent.

Upcountry

Today: Mostly cloudy. Isolated showers in the morning. Highs around 59 at the visitor center to around 54 at the summit. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy. Isolated showers after midnight. Lows around 46 at the visitor center to around 42 at the summit. East winds 10 to 15 mph. Chance of rain 20 percent.

Thursday: Cloudy with numerous showers. Locally heavy rainfall possible in the morning. Highs around 59 at the visitor center to around 54 at the summit. Southeast winds 10 to 15 mph. Gusts up to 35 mph in the afternoon. Chance of rain 70 percent.

East Maui

Today: Partly sunny. Scattered showers in the morning. Highs 75 to 82 near the shore to around 64 near 5000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 68 near the shore to 47 to 53 near 5000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Thursday: Cloudy with numerous showers. Locally heavy rainfall possible in the morning. Highs 76 to 82 near the shore to around 65 near 5000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

Lanai City

Today: Partly sunny. Highs 70 to 78. East winds 10 to 15 mph.

Tonight: Mostly cloudy. Scattered showers after midnight. Lows around 63. Northeast winds 10 to 15 mph. Chance of rain 30 percent.

Thursday: Cloudy with scattered showers. Highs 70 to 76. East winds 10 to 15 mph. Chance of rain 50 percent.

Kaunakakai

Today: Mostly sunny in the morning then becoming partly sunny. Highs 66 to 85. East winds 10 to 15 mph.

Tonight: Mostly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 56 to 71. East winds 10 to 15 mph. Chance of rain 40 percent.

Thursday: Cloudy with scattered showers. Highs 65 to 83. East winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Light to moderate trades will focus showers over windward zones. Interior showers may develop over sheltered and leeward areas this afternoon. Expect bouts of heavy rainfall over Kauai and possibly Oahu Thursday through Friday. Isolated thunderstorms are also possible. Moderate trade flow will return from Sunday onward.

Discussion

Low pressure far northeast of the main Hawaiian Islands continues to put a big dent in the subtropical ridge which normally drives trade wind flow across the islands. The result is weaker flow like what we saw overnight. Light to moderate trades will allow development of a hybrid land and sea breeze pattern today and tonight. Aloft, the subtropical jet is pushing an area of thick high clouds across the Big Island and the islands of Maui County this morning. Broken to overcast low clouds linger across mauka sections of Kauai and Oahu, with the view of low clouds obscured by thick high clouds farther to the east.
Models show an upper trough northwest of the islands will dig southeastward over the next few days, developing into an upper low which will move across Kauai late Friday before filling. Light to moderate southeasterly flow and weak surface troughing beneath the upper low will enhance rainfall across the western islands Thursday through Friday. Isolated thunderstorms may also occur. As a result, a Flood Watch remains in effect for the islands of Niihau, Kauai and Oahu Thursday through Friday.
By Sunday, a rapidly weakening upper low will have moved east of the islands and surface ridging will have rebounded with the lifting of low pressure northeast of the islands farther northward. Moderate trade flow will build westward across the islands from Sunday into next week. Weak ridging aloft will stabilize our airmass, limiting total rainfall from Sunday onward.

Aviation

Light to moderate easterly trades will continue, with clouds and showers favoring the typical windward and mauka locations. The exception will be over sheltered leeward locations where sea breezes develop this afternoon. Expect brief periods of MVFR CIGS/VSBYS in and around showers, and AIRMET Sierra can't be ruled out through the early morning hours for N thru E sections of each island.

Marine

Gentle to locally fresh trade winds are being driven by a surface ridge 200 nm northeast of the state. Winds will begin to veer southeasterly tonight as the ridge erodes and a surface trough develops several hundred miles west of Kauai. Gentle to moderate southeasterly winds will prevail late tonight through Friday and bring chances for thunderstorms, mainly around Kauai and Oahu. The surface trough will dissipate on Saturday, leading to a return of the trade winds and Small Craft Advisory conditions around the Big Island and Maui.
A small, medium-period north swell will decline through today, followed by a small, short-period reinforcing swell late tonight and Thursday. Some of this swell will wrap into exposed eastern shores, but otherwise, east shore surf will be below May average as the nearby trade wind flow will be weaker than normal into Saturday. A small northwest swell is possible early next week, while returning trade winds will increase east shore surf.
Generally background swell from the southwest and southeast will maintain surf below May average through the next few days. Little source for southerly swell is seen beyond the weekend.

HFO Watches/Warnings/Advisories

Flood Watch from Thursday morning through Friday afternoon for Niihau, Kauai Leeward, Kauai Mountains, Waianae Coast, Oahu North Shore, Olomana, Central Oahu, Waianae Mountains, Kauai North, Kauai East, Kauai South, East Honolulu, Honolulu Metro, Ewa Plain, Koolau Windward, Koolau Leeward.
Wind Advisory until 6 AM HST Friday for Big Island Summits.

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Data Courtesy of NOAA.gov