Weather Forecast

Hawaii County Weather Forecast for July 12, 2021

July 12, 2021, 7:15 AM HST
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Photo Credit: James Grenz

Hilo

Today: Showers likely, mainly before noon. Mostly cloudy, with a high near 83. East southeast wind around 9 mph. Chance of precipitation is 70%. New precipitation amounts between a tenth and quarter of an inch possible.

Tonight: Scattered showers. Mostly cloudy, with a low around 66. Light east wind. Chance of precipitation is 50%. New precipitation amounts between a tenth and quarter of an inch possible.

Tuesday: Showers likely, mainly before noon. Partly sunny, with a high near 83. Light northeast wind increasing to 5 to 10 mph in the afternoon. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

Kona

Today: Isolated showers after noon. Sunny, with a high near 79. West wind around 9 mph. Chance of precipitation is 20%.

Tonight: Isolated showers before midnight. Partly cloudy, with a low around 65. North wind 5 to 7 mph becoming calm after midnight. Chance of precipitation is 20%.

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Tuesday: Scattered showers after noon. Mostly sunny, with a high near 79. Calm wind becoming west northwest around 6 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Waimea

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Today: Isolated showers. Mostly sunny, with a high near 78. Windy, with a northeast wind 21 to 26 mph, with gusts as high as 38 mph. Chance of precipitation is 20%.

Tonight: Scattered showers, mainly after 7pm. Mostly cloudy, with a low around 58. Breezy, with an east wind 11 to 21 mph, with gusts as high as 29 mph. Chance of precipitation is 40%. New precipitation amounts between a tenth and quarter of an inch possible.

Tuesday: Scattered showers. Partly sunny, with a high near 78. East northeast wind around 13 mph. Chance of precipitation is 40%. New precipitation amounts between a tenth and quarter of an inch possible.

Kohala

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Today: Scattered showers. Partly sunny, with a high near 64. Windy, with an east wind around 23 mph, with gusts as high as 32 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Showers likely. Mostly cloudy, with a low around 53. Breezy, with an east wind 15 to 20 mph, with gusts as high as 28 mph. Chance of precipitation is 60%. New precipitation amounts between a tenth and quarter of an inch possible.

Tuesday: Showers likely. Mostly cloudy, with a high near 64. Windy, with an east northeast wind 18 to 24 mph, with gusts as high as 34 mph. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

South Big Island

Today: Scattered showers, mainly after noon. Mostly sunny, with a high near 84. Windy, with an east wind around 26 mph, with gusts as high as 34 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Isolated showers. Partly cloudy, with a low around 74. Breezy, with an east northeast wind 17 to 21 mph, with gusts as high as 26 mph. Chance of precipitation is 20%.

Tuesday: Isolated showers. Mostly sunny, with a high near 84. Breezy, with an east wind 17 to 21 mph, with gusts as high as 26 mph. Chance of precipitation is 20%.

Puna

Today: Showers, mainly before noon. High near 82. East wind 9 to 11 mph. Chance of precipitation is 80%. New precipitation amounts between a tenth and quarter of an inch possible.

Tonight: Showers likely, mainly before midnight. Mostly cloudy, with a low around 64. North northeast wind 8 to 10 mph. Chance of precipitation is 60%. New precipitation amounts between a tenth and quarter of an inch possible.

Tuesday: Showers likely, mainly before noon. Mostly cloudy, with a high near 82. Breezy, with a northeast wind 10 to 16 mph, with gusts as high as 22 mph. Chance of precipitation is 60%. New precipitation amounts between a tenth and quarter of an inch possible.

Waikoloa

Today: Sunny, with a high near 84. Breezy, with a north wind 8 to 18 mph, with gusts as high as 25 mph.

Tonight: Isolated showers before midnight. Mostly clear, with a low around 66. Northeast wind around 6 mph. Chance of precipitation is 20%.

Tuesday: Isolated showers after noon. Sunny, with a high near 84. North wind 6 to 8 mph. Chance of precipitation is 20%.

Detailed Forecast

Synopsis

A high pressure ridge north of the islands will remain in place into the weekend producing moderate to breezy trade winds across the state. A narrow upper trough and passing low level disturbances will produce periods of showers favoring the windward and mountain areas in the overnight to early morning time periods. Showery trade wind weather will likely hold into Friday. Long range models are suggesting slight drying trends by this weekend.

Discussion

The satellite imagery this morning continues to show a narrow upper trough in place just north of the Hawaiian Islands. A subtropical jet stream south of this upper trough will continue to produce periods of high level cirrus clouds over the islands through the week. These upper level features will continue to weaken the trade wind inversion heights above the 8000 foot level, allowing deeper cloud heights, and above normal rainfall coverage for this time of year. Cirrus clouds will continue to enhance sunrise and sunset colors across the state.
In the lower atmosphere, a weak trough shown on satellite imagery and 700 mb streamlines, is currently located over the eastern Hawaiian Islands. This system will continue to drift slowly westward across the state into Tuesday. The low level convergence associated with this trough will enhance shower activity across the eastern islands today. A lesser increase in shower activity is forecast for the western islands through tonight. Another low level disturbance will drift from east to west across the Hawaiian Islands on Wednesday and Thursday producing another round of enhanced showers across the state.
The wind pattern remains the same with a fairly strong high pressure ridge locked in place north of the state. This ridge will produce moderate to breezy winds across the region. Periods of showers are expected favoring the windward and mountain areas, trending higher in the overnight to early morning hours. Expect some of the stronger showers to spread into leeward areas of each island. This enhanced shower regime will likely hold into Friday. Long range models are suggesting slight drying trends by this weekend.

Aviation

Locally strong trade winds will persist as surface high pressure to the N maintains a tight low-level pressure gradient over the area. AIRMET Tango for low-level turbulence over and downstream of the terrain will remain posted for all islands.
Modest instability associated with a nearby upper-level trough will combine with low-level moisture moving in from the E to fuel windward showers. While VFR conditions are expected to prevail at the terminals and over most leeward areas, periods of MVFR VIS/CIG in SHRA are expected over windward areas, potentially requiring an AIRMET for mountain obscuration. AIRMET SIERRA is currently posted for windward slopes of Oahu.

Marine

High pressure centered north of the state in a zonal orientation across 40N latitude will be the dominating weather feature this week. This high, in relation to lower equatorial pressure, will keep the north to northeast pressure gradient tight across the area. This will continue to support fresh easterly trade winds over both the nearshore and offshore Hawaiian waters. Locally strong trades has a Small Craft Advisory (SCA) in effect for the waters east of and including the Kaiwi Channel through this afternoon. The SCA continues through Tuesday afternoon for the typical windier zones surrounding Maui County and Big Island. There is a high likelihood that this SCA will need to be extended through mid week.
Background southerly swell will maintain very small surf along south facing shorelines. Fresh easterly trades will hold short period, slightly elevated wind waves along many eastern exposures. Recent gales traveling around New Zealand are sending swells northward toward Hawaii. These long period, small south swells are timed to arrive late in the week and provide a minor bump to south coast surf.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Tuesday for all eastern channels and coastal waters.
Small Craft Advisory until 6 PM HST this evening for 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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