Photo Credit: Tyler Rooke

West Side

Today: Breezy. Mostly sunny with isolated showers. Highs 78 to 88. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 67 to 74. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Monday: Mostly sunny. Isolated showers in the morning. Highs 77 to 87. East winds 10 to 15 mph. Chance of rain 20 percent.

South Side

Today: Sunny. Highs around 90. Northeast winds 10 to 15 mph.

Tonight: Mostly clear. Lows 66 to 75. Northeast winds 10 to 15 mph decreasing to up to 15 mph after midnight.

Monday: Sunny. Highs around 89. North winds 10 to 15 mph.

North Shore

Today: Partly sunny with scattered showers. Highs 78 to 86 near the shore to around 68 near 5000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 70 near the shore to 49 to 55 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Monday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 77 to 85 near the shore to around 67 near 5000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Central Maui

Today: Mostly sunny. Isolated showers in the morning. Highs 83 to 89. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 66 to 72. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Monday: Mostly sunny. Isolated showers in the morning. Highs 82 to 88. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Upcountry

Today: Sunny and breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 63 at the visitor center to around 60 at the summit. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Mostly clear with isolated showers. Lows around 47 at the visitor center to around 45 at the summit. East winds up to 15 mph increasing to 10 to 15 mph after midnight. Chance of rain 20 percent.

Monday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 62 at the visitor center to around 59 at the summit. East winds 10 to 15 mph. Chance of rain 50 percent.

East Maui

Today: Partly sunny with scattered showers. Highs 78 to 86 near the shore to around 68 near 5000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 70 near the shore to 49 to 55 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Monday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 77 to 85 near the shore to around 67 near 5000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Lanai City

Today: Mostly sunny. Breezy. Highs 74 to 83. Northeast winds 10 to 20 mph.

Tonight: Mostly clear. Breezy. Lows 57 to 62. Northeast winds 10 to 20 mph.

Monday: Mostly sunny. Highs 74 to 82. East winds around 10 mph.

Kaunakakai

Today: Breezy. Mostly sunny with isolated showers. Highs 68 to 89. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows 57 to 74. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Monday: Mostly sunny. Scattered showers in the morning. Highs 67 to 88. East winds around 15 mph. Chance of rain 30 percent.

Detailed Forecast

Synopsis

The high pressure ridge north of the state will weaken over the next two days, gradually decreasing the trade wind strength through Tuesday. Expect brief passing showers in this trade wind regime, mainly over windward and mountain areas during the overnight to early morning hours. Lighter winds remain in the forecast starting Tuesday afternoon with land and sea breezes developing over all islands through next weekend. Converging sea breeze winds and surface heating will build clouds over island interior sections during the day with isolated shower activity.

Discussion

Trade winds begin to fade away over the next few days as the high pressure ridge north of the Hawaiian Islands weakens due to passing cold frontal troughs far north of the state. Moderate trade winds will weaken through Tuesday with local scale land and sea breezes developing from Tuesday afternoon through next weekend. A weak cold front will drift into the Hawaii region and stall just north of Kauai on Saturday and Sunday.
On the rainfall side of the forecast we will continue to see brief passing trade wind showers into Tuesday until trade winds finally diminish on Wednesday. Light large scale trade winds will allow local scale land and sea breezes to develop, due to the uneven heating and cooling cycles between the islands and the ocean. Sea breeze winds will converge with light background trade winds on Tuesday producing isolated showers over island interior sections during the day. By Wednesday sea breezes will strengthen and combine with surface heating to build clouds and a few showers over island interior sections, favoring the afternoon hours. Diverging land breezes in the overnight hours will produce more stable conditions and clear out much of the island cloud cover. This land and sea breeze pattern continues into next weekend.
In the extended range forecast for next weekend we see a weak cold front stalling out just north of Kauai. American (GFS) and European (ECMWF) models are showing different solutions for the weekend time period. Increasing shower trends remain a possibility depending on the position and intensity of this weak frontal trough relative to the islands.

Aviation

Breezy trade winds are expected to continue through this evening. Low clouds and showers are being transported into the windward sides of the island chain early this morning, especially on Kauai, Oahu, and the Big Island. These low clouds and showers will likely continue to produce periods of MVFR conditions over some windward sections this morning. AIRMET Sierra remains in effect for mountain obscuration above 2000 feet over windward Kauai, but this AIRMET may be lowered by sunrise. Otherwise, VFR conditions will likely prevail across most of the state this morning.
The forecast guidance shows stable atmospheric conditions will persist today. The guidance also appears to indicate a drying trend later today, so there may be a decrease in the coverage of low clouds even over windward areas from this afternoon into the evening hours. There is still a possibility of brief MVFR conditions over some windward facing slopes.
AIRMET Tango remains in effect for TEMPO moderate turbulence below 8000 feet downwind of the terrain on all islands. These conditions will likely persist into this evening.

Marine

High pressure located north northwest of the region will weaken the next couple of days as it sinks southward toward the islands. Upper ridging will build northwest of the state as this surface high settles in just north of the Hawaiian coastal waters by Tuesday. This will commence a downtrend in these recently moderate to locally strong trade winds. Trades will fall back to just gentle to low end moderate speeds from Tuesday into next weekend. Light to gentle breezes are progged to occur over the western islands of Kauai and Oahu as early as Tuesday…slightly higher gentle to more moderate trades across windward Maui and surrounding Maui County waters including Big Island’s windward and southern coastal waters. A Small Craft Advisory for locally strong trades is in effect for those typically windier waters surrounding Maui County and south of Big Island through early Monday morning.
The current north northwest swell will be reinforced by a couple of small northwest swells today and Tuesday. A moderate size, medium period northwest swell is timed to arrive Friday morning. This swell may peak north facing shore surf close to High Surf Advisory levels Friday and Saturday. Long period background southerly swells will persist through Monday. A slightly larger, long period south swell emanating from a recent gale near New Zealand is being picked up by the American Samoa buoy and is timed to reach the islands Tuesday. The early week arrival of this swell should provide a small bump in south facing shore surf Wednesday. Choppy wind driven surf along many east facing shores will subside through the week in response to weakening trades.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Monday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov