Photo Credit: Jeni Ji Cousins

West Side

Today: Sunny and windy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 80 to 90. East winds 10 to 30 mph shifting to the northeast 25 to 30 mph in the afternoon. Chance of rain 30 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 70 to 77. Northeast winds 10 to 25 mph. Chance of rain 50 percent.

Wednesday: Breezy. Mostly cloudy with scattered showers. Highs 79 to 88. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

South Side

Today: Sunny and breezy. Highs around 90. Northeast winds up to 25 mph increasing to 15 to 25 mph in the afternoon.

Tonight: Breezy. Partly cloudy with isolated showers. Lows 70 to 76. Northeast winds 10 to 25 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny in the morning then becoming mostly cloudy. Breezy. Isolated showers. Highs around 88. Northeast winds 10 to 25 mph. Chance of rain 20 percent.

North Shore

Today: Mostly sunny. Breezy. Showers in the morning, then scattered showers in the afternoon. Highs 78 to 88 near the shore to around 68 near 5000 feet. East winds 10 to 25 mph. Chance of rain 40 percent.

Tonight: Breezy and showers. Lows around 72 near the shore to 51 to 57 near 5000 feet. East winds 10 to 25 mph. Chance of rain near 100 percent.

Wednesday: Breezy and showers. Highs 77 to 87 near the shore to around 67 near 5000 feet. East winds 10 to 20 mph. Chance of rain near 100 percent.

Central Maui

Today: Sunny and breezy. Isolated showers in the morning. Highs 84 to 91. East winds 10 to 25 mph increasing to 20 to 25 mph in the afternoon. Chance of rain 20 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 72. East winds 10 to 20 mph. Chance of rain 50 percent.

Wednesday: Partly sunny in the morning then becoming cloudy. Breezy. Scattered showers. Highs 83 to 89. East winds 10 to 25 mph. Chance of rain 50 percent.

Upcountry

Today: Mostly sunny. Windy. Showers in the morning, then scattered showers in the afternoon. Highs around 62 at the visitor center to around 57 at the summit. East winds 10 to 30 mph. Chance of rain 40 percent.

Tonight: Breezy and showers. Lows around 49 at the visitor center to around 45 at the summit. East winds 10 to 20 mph. Chance of rain near 100 percent.

Wednesday: Becoming cloudy in the afternoon. Breezy and showers. Highs around 61 at the visitor center to around 55 at the summit. East winds 10 to 20 mph. Chance of rain near 100 percent.

East Maui

Today: Mostly sunny. Breezy. Showers in the morning, then scattered showers in the afternoon. Highs 78 to 88 near the shore to around 68 near 5000 feet. East winds 10 to 25 mph. Chance of rain 40 percent.

Tonight: Breezy and showers. Lows around 72 near the shore to 51 to 57 near 5000 feet. East winds 10 to 25 mph. Chance of rain near 100 percent.

Wednesday: Breezy and showers. Highs 77 to 87 near the shore to around 67 near 5000 feet. East winds 10 to 20 mph. Chance of rain near 100 percent.

Lanai City

Today: Sunny and breezy. Highs 75 to 82. Northeast winds 10 to 25 mph.

Tonight: Mostly cloudy. Breezy. Lows around 67. Northeast winds 15 to 25 mph.

Wednesday: Partly sunny. Breezy. Isolated showers in the afternoon. Highs 74 to 81. Northeast winds 15 to 25 mph. Chance of rain 20 percent.

Kaunakakai

Today: Sunny and breezy. Highs 71 to 90. East winds 10 to 25 mph.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 60 to 76. East winds 15 to 25 mph. Chance of rain 50 percent.

Wednesday: Breezy. Mostly cloudy with scattered showers. Highs 71 to 89. Northeast winds 15 to 25 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Trades will become locally strong today into Wednesday as they deliver frequent showers to windward and mauka zones. Showery conditions, mainly for windward areas, will continue through the week as winds decrease and an upper low brings decreased stability during the latter half of the week.

Discussion

With the islands positioned between shower bands, the next poised to arrive later this evening, shower activity and cloud cover has diminished considerably this morning. This brief period of dry advection in the boundary layer is coinciding with the descent of strong 1040mb north Pacific high pressure from around 45N to 40N, and will bring a period of locally strong trades to the area today into Wednesday. No change to overall expectations today with the typical windy locales in Maui County and the Big Island potentially flirting with wind advisory criteria at times. A greater coverage of trade wind showers is then expected tonight through Wednesday night as an organized band of upstream showers works through the islands. This band of showers has shown organization for a couple of days now and originated within a corridor of convergent easterly flow beneath an upper low residing well east of the area. This lends confidence in model depictions of very showery weather over windward and mauka slopes through this time. The increased moisture depth combined with breezy to strong trades will likewise ensure frequent leeward drift of showers, particularly overnight and during the early morning.
Upper troughing then approaches islands from the north Thursday into Friday. Strong consensus exists among the global models that a closed low will develop somewhere in the vicinity of the islands this weekend. The guidance remains touchy with respect to the ultimate location of the closed low, though the overall trend has been for a more progressive initial trough passage followed by closed low development east or northeast of the islands. The initial wave of dynamic forcing associated with the passing trough axis accompanied by steeper lapse rates will be favorable for diurnal thunderstorm development over the Big Island on Thursday and/or Friday. Moved the forecast in this direction for the morning forecast package with the introduction of schc thunder for the Big Island on Thursday afternoon. As the closed low develops near/east of the islands late this week, stability will decrease and moderate trades will focus frequent showers over windward zones for the remainder of the week with occasional waves of showers reaching leeward areas as well.

Aviation

High pressure far northeast of the state will maintain a trade wind weather pattern across the islands through tonight, with trade winds strengthening to locally strong through Wednesday. Scattered showers will remain focused mainly across windward areas, while showers remain limited elsewhere.
Mainly VFR conditions are expected into Wednesday morning. However, MVFR conditions accompanying heavier showers remain possible, generating potential brief periods of tempo mountain obscuration across some windward locations.
AIRMET Tango remains in effect for moderate low-level mechanical turbulence downwind of island terrain toady.

Marine

No significant changes to the forecast this morning. High pressure to the north and northeast of the region will maintain the fresh to locally strong trade winds through tonight, before we see a bit of a decrease. A Small Craft Advisory (SCA) is now in effect for waters near Oahu and to the east. At this time, the SCA is in effect through tonight. Models indicate the winds will weaken some Wednesday, and even further Wednesday night. At this time don't have the best confidence, so going to leave the SCA as it, but likely will need to extend it for some areas.
A recent gale north of the region will be sending a series of northwest to north swells today and tomorrow, which will boost surf north and west- facing shores. Additional northerly swells are possible this weekend into early next week. Generally background, medium period south swell will hold through the week, but a larger and longer period south swell is expected to arrive Friday. This will bump surf along south facing shores for the weekend. As the trades strengthen in the next couple of days, expect more elevated and choppy surf along east- facing shores.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Wednesday for Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov