Weather Forecast

Hawaii County Weather Forecast for August 11, 2021

August 11, 2021, 7:15 AM HST
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Hilo

Rest Of Today: Showers in the morning, then partly sunny with scattered showers in the afternoon. Locally heavy rainfall possible in the morning. Highs around 82 near the shore to 67 to 73 at 4000 feet. East winds up to 10 mph. Chance of rain near 100 percent.

Tonight: Mostly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 69 near the shore to around 55 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 40 percent.

Thursday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 84 near the shore to 69 to 74 at 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 30 percent.

Kona

Rest Of Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 82 to 88 near the shore to around 69 near 5000 feet. Light winds becoming west up to 10 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 70 to 75 near the shore to around 56 near 5000 feet. Light winds. Chance of rain 40 percent.

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Thursday: Sunny in the morning, then mostly cloudy with isolated showers in the afternoon. Highs 82 to 87 near the shore to around 69 near 5000 feet. Light winds. Chance of rain 20 percent.

Waimea

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Rest Of Today: Mostly cloudy with showers in the morning, then mostly sunny with scattered showers in the afternoon. Locally heavy rainfall possible in the morning. Highs around 82 near the shore to 70 to 80 near 3000 feet. East winds up to 15 mph. Chance of rain 90 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows around 69 near the shore to 57 to 63 near 3000 feet. East winds up to 15 mph increasing to 10 to 15 mph after midnight. Chance of rain 30 percent.

Thursday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 82 near the shore to 69 to 79 near 3000 feet. East winds 10 to 15 mph. Chance of rain 30 percent.

Kohala

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Rest Of Today: Mostly cloudy with showers in the morning, then mostly sunny with scattered showers in the afternoon. Locally heavy rainfall possible in the morning. Highs around 82 near the shore to 70 to 80 near 3000 feet. East winds up to 15 mph. Chance of rain 90 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows around 69 near the shore to 57 to 63 near 3000 feet. East winds up to 15 mph increasing to 10 to 15 mph after midnight. Chance of rain 30 percent.

Thursday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 82 near the shore to 69 to 79 near 3000 feet. East winds 10 to 15 mph. Chance of rain 30 percent.

South Big Island

Rest Of Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Locally heavy rainfall possible in the afternoon. Highs around 85 near the shore to around 69 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows around 71 near the shore to around 54 near 5000 feet. East winds up to 15 mph increasing to 10 to 15 mph after midnight. Chance of rain 40 percent.

Thursday: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 86 near the shore to around 73 near 5000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Puna

Rest Of Today: Showers in the morning, then partly sunny with scattered showers in the afternoon. Locally heavy rainfall possible in the morning. Highs around 82 near the shore to 67 to 73 at 4000 feet. East winds up to 10 mph. Chance of rain near 100 percent.

Tonight: Mostly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 69 near the shore to around 55 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 40 percent.

Thursday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 84 near the shore to 69 to 74 at 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 30 percent.

Waikoloa

Rest Of Today: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Locally heavy rainfall possible in the afternoon. Highs around 87 near the shore to 68 to 74 above 4000 feet. Northwest winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy. Isolated showers in the evening. Lows around 73 near the shore to 52 to 59 above 4000 feet. Northeast winds up to 10 mph. Chance of rain 20 percent.

Thursday: Mostly sunny. Isolated showers in the afternoon. Highs around 87 near the shore to 70 to 76 above 4000 feet. North winds up to 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A surface high pressure system centered northeast of the islands will maintain trade winds across the area through early next week. Trades are currently light to moderate, but a boost will come this Friday to locally strong, and continue through Saturday night as the high shifts closer to the islands. A gradual softening of the trades will then follow through Monday as a surface trough approaches the islands from the east. An upper level disturbance accompanying the low level feature will help enhance some of the showers on Monday.

Discussion

The main Hawaiian Islands is under a light to moderate trade wind regime this morning. The 1032 mb surface high is centered well over 1500 miles northeast of the islands which at this distance is accounting for the weakness in the trades. But this high will be shifting closer to the islands during the next 48 hours where we expect a boost in the trades to locally strong by Friday, lasting through Saturday. A gradual weakening of the trades follow into Monday as a surface trough cuts through the islands. The surface trough will have the aid of an upper level disturbance that will enhance some of the showers.
A tropical air mass currently lies over the islands, but an area of clouds and showers is located just off Cape Kumukahi Big Island. It looks like this area of enhanced moisture will affect the Big Island with spill over to windward Maui and possibly windward Molokai later this morning. There is a mention of the possibility that a few of these showers will be heavy for the Big Island. Some thinning and dissipating of this moisture field is expected for the northern part of the Big Island starting sometime this afternoon.
Weakness in the trades will lead to a mix of trades and sea breezes, with sea breezes developing after sunrise over the west and lee side of the islands west of Maui. The addition of daytime heating will result in some local afternoon clouds and showers.
This tropical air mass will be replaced by a drier and stable airmass by Thursday, lasting into the weekend. More or less we are expecting the continuation of a trade wind shower pattern, although on the drier than normal side of the spectrum.
On Monday, a low level trough accompany by an upper level disturbance may be making its way over the islands from the east. The low level trough will weaken the trades, while the upper level disturbance will help enhance the showers.

Aviation

Light to moderate easterly trade winds will continue through the period with clouds and showers favoring windward and mauka locations. A batch of low clouds associated with a weak trough moving in from the east will support periods of MVFR CIGS/VSBYS through the morning hours today (eastern end of the island chain). As a result, AIRMET Sierra for mountain obscuration will likely continue this morning from Molokai to the Big Island.

Marine

A surface high pressure system located far north-northeast of the state will maintain moderate trades through Thursday. A new surface high pressure system is expected to build north of the islands as we head into the weekend. The latest forecast indicates locally strong trade winds could return starting Friday, with Small Craft Advisory (SCA) conditions likely developing across the typically windier waters adjacent to the islands of Maui County and the Big Island. The SCA may be required for these windier areas through Saturday, followed by weaker trades starting Sunday.
The recent observations from the nearshore PacIOOS buoys are reporting a swell height of 3 to 4 feet with a period of around 15 seconds due to the current south-southwest swell. This swell, which is maintaining slightly elevated surf along south facing shores, is expected to peak later today, and then gradually lower from tonight through Thursday. A small, reinforcing south- southwest swell is expected to arrive Friday, followed by a larger swell from the same direction starting Sunday. The latter swell will likely be long-lived, with a peak in the Tuesday through Wednesday time period next week.
Active tropical cyclone activity in the northwest Pacific has been sending small, back-to-back west-northwest swell energy toward the region. The PacIOOS buoy at Hanalei shows a small west- northwest swell of around 2 feet with a period of about 14 seconds early this morning. This will cause surf to trend up along exposed north and west facing shores today. This swell may lower by Thursday morning, with another small, reinforcing west- northwest swell reaching Kauai late Thursday. A slightly larger west-northwest swell may arrive this weekend.
Surf along east facing shores will continue to lower due to the lighter trade winds locally and upstream of the islands. A tiny, short-period northeast swell may arrive this weekend, but surf will likely remain small along east facing shores into early next week.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov

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