Weather Forecast

Hawaii County Weather Forecast for July 31, 2021

July 31, 2021, 7:16 AM HST
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Photo Credit: James Grenz

Hilo

Today: Scattered showers, mainly before noon. Partly sunny, with a high near 83. Calm wind becoming east northeast 5 to 9 mph in the morning. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers, mainly after 10pm. Mostly cloudy, with a low around 71. Northwest wind 3 to 5 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Sunday: Scattered showers, mainly before noon. Partly sunny, with a high near 83. North wind 6 to 10 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Kona

Today: Isolated showers after noon. Partly sunny, with a high near 82. West wind 5 to 8 mph becoming calm in the afternoon. Chance of precipitation is 20%.

Tonight: Partly cloudy, with a low around 71. East southeast wind around 6 mph.

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Sunday: Isolated showers after noon. Mostly sunny, with a high near 82. Calm wind becoming south southeast around 6 mph in the afternoon. Chance of precipitation is 20%.

Waimea

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Today: Isolated showers. Mostly sunny, with a high near 77. Windy, with an east northeast wind 20 to 29 mph, with gusts as high as 45 mph. Chance of precipitation is 20%.

Tonight: Isolated showers. Partly cloudy, with a low around 58. Windy, with a northeast wind around 29 mph, with gusts as high as 41 mph. Chance of precipitation is 20%.

Sunday: Isolated showers. Mostly sunny, with a high near 77. Very windy, with a northeast wind 29 to 31 mph, with gusts as high as 45 mph. Chance of precipitation is 20%.

Kohala

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Today: Scattered showers, mainly before noon. Partly sunny, with a high near 70. Windy, with an east northeast wind 25 to 29 mph, with gusts as high as 55 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers, mainly after 10pm. Mostly cloudy, with a low around 52. Windy, with an east northeast wind around 29 mph, with gusts as high as 41 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Sunday: Scattered showers, mainly before noon. Mostly sunny, with a high near 70. Very windy, with an east northeast wind 30 to 32 mph, with gusts as high as 47 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

South Big Island

Today: Mostly sunny, with a high near 82. Windy, with an east wind 28 to 30 mph, with gusts as high as 39 mph.

Tonight: Partly cloudy, with a low around 75. Windy, with an east wind around 29 mph, with gusts as high as 37 mph.

Sunday: Mostly sunny, with a high near 82. Very windy, with an east wind around 31 mph, with gusts as high as 40 mph.

Puna

Today: Scattered showers, mainly before noon. Partly sunny, with a high near 81. Breezy, with a northeast wind 8 to 15 mph, with gusts as high as 21 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers. Mostly cloudy, with a low around 70. North northwest wind 9 to 13 mph. Chance of precipitation is 50%. New precipitation amounts between a tenth and quarter of an inch possible.

Sunday: Scattered showers, mainly before noon. Partly sunny, with a high near 81. Breezy, with a north wind 13 to 16 mph, with gusts as high as 22 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Waikoloa

Today: Mostly sunny, with a high near 85. Windy, with an east northeast wind 17 to 26 mph, with gusts as high as 38 mph.

Tonight: Mostly clear, with a low around 70. Breezy, with an east wind 14 to 20 mph, with gusts as high as 28 mph.

Sunday: Sunny, with a high near 85. Very windy, with an east northeast wind 20 to 25 mph increasing to 26 to 31 mph in the afternoon. Winds could gust as high as 45 mph.

Detailed Forecast

Synopsis

A strong high pressure system building far northeast of the Hawaiian Islands will produce strong trade winds through the weekend. Trade wind speeds will decrease to more moderate levels from late Monday onward. A strong high pressure ridge over the islands will limit shower activity over the region through Monday. A passing low level trough will increase rainfall coverage trends from Tuesday to Thursday favoring windward and mountain areas.

Discussion

Satellite and radar imagery are showing fairly stable clouds with isolated to scattered showers drifting into windward and mountain areas on the easterly trade winds. Infra-red satellite imagery shows a wildfire in the Kohala area producing smoke over portions of the Kohala and Kona districts.
A strong high pressure system building far northeast of the region will produce strong trade winds this weekend. Increasing trade winds will approach and possibly exceed wind advisory levels for wind favored terrain areas of the Big Island and Maui County on Saturday and Sunday. A low trade wind inversion height may help to funnel these stronger winds over these wind favored areas and a Wind Advisory may be needed for Sunday. The high pressure system north of the islands weakens from late Monday onward, moderating trade wind speeds back to more normal levels for this time of year.
A stable high pressure ridge aloft will keep trade wind inversion heights in the 5000 to 7000 foot range this weekend, limiting showers to isolated to scattered coverage mainly over windward and mountain areas in the overnight to early morning hours. This pattern may change a bit on Tuesday when a low level trough in the easterlies drifts through the islands. Trade wind temperature inversion heights lift into the 8000 to 10000 foot elevation range allowing for scattered to numerous showers along windward and mountain slopes with isolated showers possible over leeward areas

Aviation

The stratus that developed last evening has either dissipated or transitioned to a lower coverage of stratocu. AIRMET Sierra for mountain obscuration has therefore been cancelled for all locations, although isolated instances of MVFR will remain possible. Breezy trades will further strengthen today, aided by the strengthening inversion, and will become strong in some locations. Showers will be light and mainly confined to windward locales. AIRMET Tango for lee turbulence below 8kft will remain in effect through the period.

Marine

Fresh to locally strong trade winds will increase into Sunday as high pressure strengthens north of the state. A Small Craft Advisory (SCA) has been expanded to cover all Hawaiian waters, and a Gale Watch has been issued for the typically windy waters around the Big Island and Maui on Sunday. The SCA will likely be needed for most, if not all, waters on Monday and for the typically windy waters around the Big Island and Maui through most of next week.
A belt of trade winds across the region is generating seas around seasonal average of 6 ft at 7 to 8 seconds. Rough east shore surf will build a notch with the trade winds tonight and Sunday, then fall back to seasonal average early next week.
South shore surf will remain rather small for this time of year, with a small pulse of south swell occurring today and Sunday. Nearly flat conditions will continue for north facing shores this week, while tiny swell energy from the west will be possible during the next couple of days.

Fire weather

Dry minimum humidity levels and stable weather will combine with strong and gusty trade winds this weekend. Breezy trade winds on Saturday will strengthen on Sunday. Weather conditions this weekend are expected to approach critical fire weather thresholds over some windier leeward areas mainly in the late morning to afternoon hours through Sunday.

HFO Watches/Warnings/Advisories

Gale Watch from Sunday morning through Sunday afternoon for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.
Small Craft Advisory until 6 AM HST Sunday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.
Small Craft Advisory until 6 PM HST Sunday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Big Island Windward Waters.

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Data Courtesy of NOAA.gov

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