Photo Credit: Jeni Ji Cousins

West Side

Today: Mostly sunny. Breezy. Isolated showers in the morning. Highs 79 to 86. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Lows 68 to 75. East winds 10 to 20 mph decreasing to up to 15 mph after midnight.

Columbus Day: Partly sunny with isolated showers. Highs 80 to 87. East winds up to 15 mph. Chance of rain 20 percent.

South Side

Today: Sunny and breezy. Highs around 88. North winds up to 20 mph shifting to the northeast 10 to 20 mph in the afternoon.

Tonight: Partly cloudy. Lows 67 to 76. North winds up to 15 mph.

Columbus Day: Mostly sunny. Highs around 89. North winds up to 15 mph.

North Shore

Today: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 79 to 84 near the shore to around 66 near 5000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with isolated showers. Lows around 71 near the shore to around 52 near 5000 feet. Southeast winds up to 15 mph. Chance of rain 20 percent.

Columbus Day: Mostly cloudy. Breezy. Showers in the morning, then scattered showers in the afternoon. Highs 80 to 85 near the shore to around 69 near 5000 feet. East winds up to 20 mph. Chance of rain 80 percent.

Central Maui

Today: Mostly sunny. Breezy. Highs 81 to 88. Northeast winds up to 20 mph increasing to 10 to 20 mph in the afternoon.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Lows 68 to 73. East winds 10 to 20 mph decreasing to up to 15 mph after midnight.

Columbus Day: Partly sunny with isolated showers in the morning, then mostly sunny in the afternoon. Highs 83 to 90. East winds up to 15 mph. Chance of rain 20 percent.

Upcountry

Today: Mostly sunny. Highs around 63 at the visitor center to around 70 at the summit. East winds up to 15 mph.

Tonight: Partly cloudy. Breezy. Isolated showers after midnight. Lows around 49 at the visitor center to around 46 at the summit. East winds up to 20 mph increasing to 10 to 25 mph after midnight. Chance of rain 20 percent.

Columbus Day: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs around 65 at the visitor center to around 68 at the summit. East winds up to 25 mph. Chance of rain 50 percent.

East Maui

Today: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 79 to 84 near the shore to around 66 near 5000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with isolated showers. Lows around 71 near the shore to around 52 near 5000 feet. Southeast winds up to 15 mph. Chance of rain 20 percent.

Columbus Day: Mostly cloudy. Breezy. Showers in the morning, then scattered showers in the afternoon. Highs 80 to 85 near the shore to around 69 near 5000 feet. East winds up to 20 mph. Chance of rain 80 percent.

Lanai City

Today: Mostly sunny. Breezy. Highs 73 to 82. Northeast winds up to 20 mph increasing to 10 to 20 mph in the afternoon.

Tonight: Mostly cloudy with isolated showers in the evening, then partly cloudy after midnight. Lows 63 to 68. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Columbus Day: Mostly sunny in the morning, then mostly cloudy with isolated showers in the afternoon. Highs 74 to 82. East winds up to 10 mph in the morning becoming light. Chance of rain 20 percent.

Kaunakakai

Today: Mostly sunny. Highs 71 to 90. Northeast winds 10 to 15 mph.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Lows 59 to 75. Northeast winds 10 to 15 mph.

Columbus Day: Partly sunny. Isolated showers in the morning. Highs 71 to 91. East winds up to 10 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Expect moderate trade winds to continue through Monday, then strengthen into the moderate to locally breezy range from Monday night onward as the subtropical ridge north of the island strengthens. Shower activity will increase from tonight into Monday as a weak trough moves westward across the state. Another brief increase in showers will develop from Thursday into Saturday as another weak disturbance moves down the island chain.

Discussion

The satellite picture this morning shows some enhanced low level clouds forming along an easterly wave roughly 250 miles east of Hilo, riding in on the trade winds. Expect an increase in shower activity steading over the eastern islands later tonight, then into the western islands by Monday morning. The highest coverage for shower activity will develop over windward and mountain slopes in the overnight to early morning hours. A few bands of high level cirrus clouds are also passing over the state today.
The latest model guidance continues to show a weak subtropical ridge north of the Hawaiian Islands producing moderate trade winds across the region through early Monday. A hybrid trade wind and sea breeze pattern will continue for the next two days, sea breeze areas will develop along the western terrain sheltered slopes of each island.
By Monday night the ridge north of the state strengthens slightly, producing moderate to locally breezy trade winds across the Hawaii region through Thursday. Clouds and showers will tend to favor windward and mountain areas through the week, mainly over the overnight to early morning hours. Another trough in the easterly trade winds and a weak upper level low may bring another brief increase in shower activity from Thursday morning near the Big Island, then spreading slowly to the western islands from Friday to Saturday.

Aviation

Light to moderate trades expected for the few days. ISOL SHRA should favor windward and mauka locations. Sea breezes could bring a few ISOL SHRA to leeward areas, with land breezes at night. Brief MVFR conds can be expected in any SHRA but VFR should generally prevail.
No AIRMETs are in effect.

Marine

A cold front north of the islands will produce a weaker upstream pressure gradient and this will result in continued gentle to moderate trade winds through early Monday. As the front passes northeast of the state the next couple of days, high pressure will reestablish itself over the East Pacific. Trades will respond by strengthening back to more areawide moderate to locally strong magnitudes by early Tuesday. A Small Craft Advisory may be required for the notoriously windy eastern island bays and channels by early Tuesday. Trades will drop off a touch late in the week as the next cold front pushes the high northeast of the state closer to the islands and weakens the pressure gradient.
A small reinforcing medium period north (350 degree) swell that moved through yesterday will hold chest to head high surf in across north shores through the day. The arrival of a larger, medium to long period north (350 degree) swell tonight into early Monday morning will produce advisory level surf along north-facing shores. This swell and resulting surf will peak Monday evening and then slowly decline through the middle of the week. The most recent small, long period south (180 degree) swell will begin to fade through the day as will near waist high south shore surf. Surf along west-facing shores will remain elevated and increase through tomorrow due to the influence of the north swell wrap. East-facing shore wind waves will remain relatively small under this recent weaker trade regime. East chop will pick back up through Tuesday in response to strengthening trades.

HFO Watches/Warnings/Advisories

High Surf Advisory from 6 AM Monday to 6 PM HST Tuesday for north facing shores of Niihau, Kauai, Oahu, Molokai, Maui and the Big Island.

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Data Courtesy of NOAA.gov