Photo Credit: Jeni Ji Cousins

West Side

Today: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 81 to 87. Northeast winds up to 15 mph. Chance of rain 40 percent.

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 70 to 77. East winds up to 15 mph. Chance of rain 40 percent.

Tuesday: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs 81 to 87. East winds up to 10 mph. Chance of rain 40 percent.

South Side

Today: Sunny. Isolated showers in the afternoon. Highs 85 to 90. North winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Gusts up to 35 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Isolated showers in the evening. Lows around 69. North winds up to 10 mph shifting to the southwest after midnight. Chance of rain 20 percent.

Tuesday: Mostly sunny. Isolated showers in the afternoon. Highs 85 to 90. Light winds. Chance of rain 20 percent.

North Shore

Today: Partly sunny with scattered showers. Highs around 81 near the shore to 64 to 69 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with showers likely. Lows 68 to 75 near the shore to around 54 near 5000 feet. East winds 10 to 15 mph shifting to the southeast after midnight. Chance of rain 70 percent.

Tuesday: Partly sunny with scattered showers. Highs around 81 near the shore to 64 to 69 near 5000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Central Maui

Today: Breezy. Mostly sunny with isolated showers. Highs 84 to 90. Northeast winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy with scattered showers. Lows 67 to 74. East winds up to 15 mph. Chance of rain 50 percent.

Tuesday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 84 to 90. East winds up to 10 mph. Chance of rain 30 percent.

Upcountry

Today: Breezy. Mostly sunny with isolated showers. Highs 56 to 69. East winds up to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with scattered showers. Lows around 49 at the visitor center to around 46 at the summit. East winds up to 15 mph. Chance of rain 50 percent.

Tuesday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs around 57 at the visitor center to around 55 at the summit. East winds up to 15 mph. Chance of rain 50 percent.

East Maui

Today: Partly sunny with scattered showers. Highs around 81 near the shore to 64 to 69 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with showers likely. Lows 68 to 75 near the shore to around 54 near 5000 feet. East winds 10 to 15 mph shifting to the southeast after midnight. Chance of rain 70 percent.

Tuesday: Partly sunny with scattered showers. Highs around 81 near the shore to 64 to 69 near 5000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Lanai City

Today: Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 75 to 82. Northeast winds 10 to 15 mph. Chance of rain 30 percent.

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows around 68. Northeast winds up to 10 mph in the evening becoming light. Chance of rain 30 percent.

Tuesday: Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 75 to 82. Light winds. Chance of rain 40 percent.

Kaunakakai

Today: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 74 to 88. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 62 to 73. East winds 10 to 15 mph. Chance of rain 50 percent.

Tuesday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 74 to 88. East winds 10 to 15 mph decreasing to up to 10 mph in the afternoon. Chance of rain 40 percent.

Detailed Forecast

Synopsis

Trade winds will ease today as an area of moisture increases showers over mainly windward Big Island and Maui. Weak trade winds will allow localized land and sea breezes to take over Tuesday into Thursday, and humid conditions will bring an uptick in windward showers along with spotty afternoon rainfall across leeward areas. Trade winds will rebuild Thursday and Friday and may become breezy during the weekend.

Discussion

Stable moderate trade winds will begin a gradual decline today as an area of moisture brings an increase in rainfall to mainly windward portions of the Big Island and Maui. Trades will be on a decline as a surface ridge currently sitting almost 350 miles north of Kauai is pushed southward and weakened. A drier air mass with precipitable water of 1 to 1.2 inches now over the islands will start to be displaced by increased moisture surrounding a weak surface trough now just east of the Big Island. Expect the initial increase in rainfall to affect windward Big Island and Maui today, while modest rainfall persists over windward Oahu and Kauai.
Trade winds will drop to gentle to locally moderate strength tonight through Wednesday as the weak surface trough and its associated moisture spreads across the island chain. Humidity will rise as dew points climb into the lower 70s, and windward portions of all islands will experience an uptick in rainfall. Daytime sea breezes will overpower the trades, leading to afternoon clouds and a scattered leeward and interior showers. Conditions aloft should remain somewhat stable, lowering chances for heavy rainfall.
Trade winds will likely remain suppressed into Thursday, though a drier air mass moving in from the east should lower humidity and lead to a decrease in showers. Trade winds will rebuild late Thursday and Friday and may become breezy next weekend.

Aviation

Surface high pressure north of the state will maintain moderate trade wind flow through this evening. This winds should further weaken tonight into Tuesday as a mid-level trough approaches the island from the east. This feature will bring enhanced low level moisture to the region and an uptick of shower coverage along the windward portions of the islands. There may be brief periods of MVFR conditions associated with this activity, though not expecting anything widespread.
There are currently no AIRMETs in effect.

Marine

A high pressure ridge north of the islands will weaken today with trade winds in the moderate to locally fresh range through Thursday. The Small Craft Advisory (SCA) is cancelled with the morning forecast package and no SCA conditions are in the forecast through at least Thursday. Trade winds begin to strengthen again from Friday onward.
The current long period south swell has peaked and will slowly decrease later today. The latest buoy observations this morning are already showing these gradual downward trends. The High Surf Advisory (HSA) will remain in effect through the day for all south facing shores. Surf along west facing shores will remain elevated due to the long period south swell wrapping along the western sides of each island. The south swell energy will drop below HSA thresholds later tonight, and the HSA will be dropped as the south swell continues to decline through Wednesday.
Short period trade wind swell will decline with lower trade wind speeds forecast through the week. A northwest swell is building into the region today producing fun sized surf through Thursday along north facing shores.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST this evening for south facing shores of all islands.

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Data Courtesy of NOAA.gov