Weather Forecast

Maui Weather Forecast for October 21, 2021

October 21, 2021, 7:15 AM HST
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Photo Credit: Tyler Rooke

West Side

Today: Sunny. Isolated showers in the morning. Highs 76 to 87. Light winds becoming east up to 15 mph in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 67 to 73. Northeast winds up to 15 mph. Gusts up to 35 mph after midnight. Chance of rain 20 percent.

Friday: Breezy. Sunny with isolated showers. Highs 77 to 88. East winds up to 15 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 20 percent.

South Side

Today: Sunny. Highs around 88. North winds up to 10 mph increasing to 10 to 15 mph in the afternoon.

Tonight: Mostly clear. Lows 67 to 75. East winds up to 15 mph.

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Friday: Sunny and breezy. Highs around 89. North winds 10 to 20 mph.

North Shore

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Today: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 76 to 84 near the shore to around 65 near 5000 feet. East winds up to 15 mph. Chance of rain 40 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 70 near the shore to 48 to 54 near 5000 feet. Southeast winds up to 20 mph increasing to 10 to 20 mph after midnight. Chance of rain 50 percent.

Friday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 76 to 84 near the shore to around 65 near 5000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Central Maui

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Today: Sunny. Isolated showers in the morning. Highs 81 to 87. Northeast winds up to 10 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 67 to 72. East winds around 10 mph. Chance of rain 20 percent.

Friday: Sunny and breezy. Isolated showers in the morning. Highs 81 to 88. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Upcountry

Today: Sunny with isolated showers. Highs around 61 at the visitor center to around 57 at the summit. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with scattered showers. Lows around 45 at the visitor center to around 42 at the summit. East winds 15 to 25 mph. Chance of rain 50 percent.

Friday: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 61 at the visitor center to around 57 at the summit. East winds 15 to 25 mph. Chance of rain 40 percent.

East Maui

Today: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 76 to 84 near the shore to around 65 near 5000 feet. East winds up to 15 mph. Chance of rain 40 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 70 near the shore to 48 to 54 near 5000 feet. Southeast winds up to 20 mph increasing to 10 to 20 mph after midnight. Chance of rain 50 percent.

Friday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 76 to 84 near the shore to around 65 near 5000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Lanai City

Today: Sunny. Highs 72 to 82. Light winds becoming northeast up to 15 mph in the afternoon.

Tonight: Partly cloudy with isolated showers. Lows 62 to 67. Northeast winds up to 10 mph. Chance of rain 20 percent.

Friday: Sunny and breezy. Highs 72 to 82. Northeast winds 10 to 20 mph.

Kaunakakai

Today: Mostly sunny. Isolated showers in the afternoon. Highs 66 to 88. Northeast winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 58 to 74. Northeast winds up to 15 mph. Chance of rain 20 percent.

Friday: Mostly sunny. Breezy. Isolated showers in the morning. Highs 67 to 89. East winds 10 to 20 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

An area of low clouds and light showers is pushing down across most of the smaller islands early this morning. Easterly trade winds will gradually strengthen later today and tonight, which will likely transport additional low clouds and showers into the windward sides of the islands, especially Kauai and Oahu, from tonight through Friday. Expect breezy trade winds from Friday through this weekend. In addition, drier conditions will also return across most of the smaller islands starting Saturday, but showers may increase over the windward Big Island early this weekend. The trade winds are expected to gradually weaken early next week.

Discussion

An area of broken low clouds and light showers continues to push down across portions of the smaller islands early this morning. This is the remnant moisture from a dissipated frontal boundary. There are much fewer clouds and showers to the north of this area of moisture, so it appears that there will be a break in precipitation over many areas some time after sunrise this morning.
The leading edge of a band of broken low clouds and scattered showers associated with a weakening frontal boundary is less than 300 miles north of Lihue. Elsewhere, a 1027 mb surface high pressure system centered near 37N 158W, or about 1100 miles north of Honolulu, is moving toward the south-southeast at 15 to 20 mph. This feature is pushing the frontal boundary down toward the state. The close proximity of the weakening front between the islands and the high to the north continues to produce light background northeasterly flow across most of the state early this morning.
The forecast guidance shows the trade winds will gradually become more easterly and strengthen later today and tonight. These trade winds will likely transport low clouds and showers over windward and mauka sections of the islands, especially Kauai and Oahu, through tonight. A few showers may also reach some leeward sections of the western islands. By Friday, the trade winds will be locally breezy. The models still indicate the relatively wet trade wind weather pattern may continue across windward and mauka areas of the western islands through Friday as the remnant moisture lingers and a weak upper-level trough moves into the vicinity of the state.
The trade winds will likely remain breezy this weekend. At the same time, mid-level ridging builds in, which will eventually strengthen the low-level trade wind inversion. The area of low clouds and showers over the western islands is expected to push west of Kauai. An area of low-level moisture may be transported toward the Big Island from the east by the trades Saturday. The models show this moisture passing south of the rest of the state, so any low clouds and showers within this area would mainly impact the windward and southeastern Big Island. The surface high pressure system to the north may eventually weaken early next week, which could lead to a weakening trend in trade wind speeds by next Tuesday.

Aviation

The overall wind flow remains weak across the state, with land breezes over the more sheltered leeward areas. The remnants of a couple of old fronts remain evident in satellite imagery early this morning, the first of which has reached Kauai and Oahu, providing a slight increase in shower activity and cloud cover. The moisture associated with the second batch will become more diffuse as it nears the islands later today, but should still be enough to increase clouds and showers over windward areas this evening and tonight. Trades will restrengthen later today as well, helping to push a few showers to leeward areas at times.
No AIRMETs are currently in effect, but TEMPO MVFR conditions with mountain obscuration are possible along windward slopes, especially for the western half of the state. Trades will increase further tonight through Friday, which could warrant an AIRMET Tango for moderate low-level turbulence.

Marine

No major changes to the coastal marine forecast this morning, with things pretty much on track. The remnants of a front will bring some clouds and showers mainly to the windward waters, but the organization of this feature is quickly falling apart. Some evidence of this boundary is expected to remain near the islands over the next 24 hours or so.
Behind the front, a new high will will build north of the islands. As the high builds in, expect a gradual increase in northeast trade winds late today/tonight, shifting to the east at moderate to locally strong speeds by Friday. As the winds increase, a Small Craft Advisory (SCA) will be required for the typical windier waters near Maui and the Big Island. It could be as early as tonight, but more likely tomorrow as winds reach SCA levels, with winds expected to remain nearly steady then into next week.
Nearshore buoy observations are generally on track with the current forecast. The current north-northwest swell may still boost surf along exposed shores over the next few hours, but will then diminish into Friday, as a new north swell is expected to build. This next swell is being generated by a powerful low moving into the Gulf of Alaska. While this swell has the potential to bring surf to near advisory levels, confidence remains not so high given the relatively small window for the swell generation. Due to the size and direction of the swell, this has the potential to produce moderate harbor surges in the Kahului and Hilo harbors. A low near the Aleutian Islands will generate a small to moderate northwest swell for Sunday/Monday. A slight increase in long- period south swell is expected today/tonight. As the trades increase over the weekend, expect a slight boost in short-period wind waves along east facing shores.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov

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