Weather Forecast

Hawaii County Weather Forecast for August 05, 2021

August 5, 2021, 7:16 AM HST
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Hilo

Today: Occasional showers, mainly before 1pm. High near 80. Light and variable wind becoming east 5 to 10 mph in the afternoon. Chance of precipitation is 80%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Occasional showers, mainly after 7pm. Low around 69. East northeast wind 5 to 10 mph. Chance of precipitation is 80%. New precipitation amounts of less than a tenth of an inch possible.

Friday: Occasional showers, mainly before 1pm. High near 82. Northeast wind 5 to 9 mph. Chance of precipitation is 80%. New precipitation amounts of less than a tenth of an inch possible.

Kona

Today: Isolated showers after noon. Increasing clouds, with a high near 81. West wind around 6 mph. Chance of precipitation is 20%.

Tonight: Scattered showers, mainly before 11pm. Mostly cloudy, with a low around 69. South southwest wind around 5 mph becoming north after midnight. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

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Friday: Scattered showers, mainly after noon. Mostly sunny, with a high near 81. West wind around 5 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Waimea

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Today: Showers likely, mainly before noon. Partly sunny, with a high near 72. Breezy, with an east northeast wind around 15 mph, with gusts as high as 21 mph. Chance of precipitation is 60%. New precipitation amounts between a tenth and quarter of an inch possible.

Tonight: Scattered showers. Mostly cloudy, with a low around 61. East wind around 14 mph, with gusts as high as 18 mph. Chance of precipitation is 40%. New precipitation amounts between a tenth and quarter of an inch possible.

Friday: Scattered showers, mainly before noon. Mostly sunny, with a high near 74. East northeast wind around 13 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Kohala

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Today: Showers likely. Mostly cloudy, with a high near 67. Breezy, with an east wind around 16 mph, with gusts as high as 22 mph. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Occasional showers. Low around 59. Breezy, with an east wind around 17 mph, with gusts as high as 24 mph. Chance of precipitation is 80%. New precipitation amounts of less than a tenth of an inch possible.

Friday: Showers likely, mainly before noon. Mostly cloudy, with a high near 69. Breezy, with an east wind 16 to 18 mph, with gusts as high as 25 mph. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

South Big Island

Today: Mostly sunny, with a high near 84. Windy, with an east wind 26 to 28 mph, with gusts as high as 36 mph.

Tonight: Isolated showers. Partly cloudy, with a low around 75. Windy, with an east northeast wind 24 to 26 mph, with gusts as high as 34 mph. Chance of precipitation is 20%.

Friday: Isolated showers before noon. Mostly sunny, with a high near 85. Windy, with an east wind around 24 mph, with gusts as high as 31 mph. Chance of precipitation is 20%.

Puna

Today: Occasional showers, mainly before noon. High near 76. Breezy, with an east northeast wind 10 to 15 mph, with gusts as high as 21 mph. Chance of precipitation is 80%. New precipitation amounts between a tenth and quarter of an inch possible.

Tonight: Occasional showers. Low around 66. Northeast wind around 11 mph. Chance of precipitation is 80%. New precipitation amounts between a tenth and quarter of an inch possible.

Friday: Occasional showers, mainly before noon. High near 77. Breezy, with a north northeast wind 11 to 15 mph, with gusts as high as 21 mph. Chance of precipitation is 80%. New precipitation amounts between a tenth and quarter of an inch possible.

Waikoloa

Today: Sunny, with a high near 84. North northeast wind around 8 mph.

Tonight: Mostly clear, with a low around 69. East northeast wind around 5 mph.

Friday: Sunny, with a high near 85. North wind around 6 mph.

Detailed Forecast

Synopsis

High pressure to the north will keep breezy trade winds over the islands through most of the weekend, with a decrease in wind speed possible early next week. Low clouds will deliver a few showers, mainly to windward areas and especially during nights and mornings, with a few brief showers spreading to leeward areas.

Discussion

Surface high pressure far NNE of the islands will drive breezy trade winds into the weekend, with the high expected to remain nearly stationary through Saturday with a central pressure hovering near 1030 mb. On Sunday into Tuesday, the center of the high is expected to drift toward the NE, while a low-level trough (remnants of former tropical cyclones Hilda and Jimena – see official forecasts issued by the National Hurricane Center) may approach and pass near or N of the islands. This would lead to some reduction in trade wind speeds, but confidence in this outcome remains low.
Model guidance does not highlight any significant moisture sources to bring enhanced rainfall to the islands into early next week. However, stable and showery low clouds will continue to stream toward the islands from the E. While a nearby mid-level ridge will keep a subsidence inversion in place, the base of the inversion will likely waiver between 8000 and 10000 feet. This is sufficiently high to allow showers to develop within the incoming cumuli, while also allowing orographic lift to drive some shower formation. Most of the light to moderate rainfall will remain over and just downwind of the windward mountains, and will be most likely during nights and mornings. Any light rain that occasionally falls over windward coastal areas, or that spreads to leeward communities, will do little to override the drying effects of the breezy trades and strong solar insolation. The exception will be the Kona slopes of the Big Island, where the typical afternoon and evening showers will continue to deliver beneficial rainfall.
Depending on the eventual trajectory of the increased low-level moisture associated with the aforementioned dissipated tropical cyclones, we could see some increase in showers around the middle of next week, but we could just as easily end up seeing the bulk of the moisture passing N of the islands.

Aviation

High pressure far northeast of the region will maintain moderate to locally strong trade winds today, although some weakening is expected. This weakening will likely result in widespread moderate wind speeds across the region. AIRMET Tango remains in place for low level mechanical turbulence downstream of the mountains. Even as winds decrease a bit, expect this AIRMET to remain in place.
VFR conditions are expected to prevail, however brief MVFR conditions are possible with passing clouds and showers. Most likely place for these MVFR conditions to occur will be over east sides of the Big Island and Kauai. At this time, not expecting any conditions that would warrant AIRMETs for mountain obscuration.

Marine

Locally strong trade winds persist across the islands early this morning due to a strong surface high pressure system located far north of the region. This feature is expected to drift slowly north during the next few days, which may cause a slight weakening of the trades as we head into the weekend. A Small Craft Advisory (SCA) remains in effect today for the Kaiwi Channel, as well as the typically windier waters adjacent to the islands of Maui County and the Big Island. The strongest winds are expected to be only in the typical windy zones by tonight, so the SCA has been extended for these zones through Saturday. The latest forecast indicates trade wind speeds may gradually decrease from Sunday into early next week.
The latest nearshore PacIOOS buoys continue to show trade wind swell around 7 feet with a period of about 8 seconds. This is producing rough, slightly elevated surf along east facing shores. The forecast guidance shows the surf along east facing shores dropping to near the summertime average as we head into the weekend due to the slight weakening of the trades. Expect a further decrease in surf heights along east facing shores early next week, due to additional weakening of the trades. Small south and southeast swells will keep small background surf along most south facing shores through early Friday. A new small southwest swell is expected to spread across the area from late Friday into this weekend, followed by the potential for a slightly larger, long-period south swell reaching the state early next week. If this swell does arrive, it may cause surf heights along south facing shores to reach, or possibly exceed, the seasonal average starting next Monday night or Tuesday. Expect nearly flat conditions along most north facing shores into early next week.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Saturday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.
Small Craft Advisory until 6 PM HST this evening for Kaiwi Channel.

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Data Courtesy of NOAA.gov

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