Weather Forecast

Hawaii County Weather Forecast for June 18, 2021

June 18, 2021, 7:16 AM HST
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Photo Credit: James Grenz

Hilo

Today: Scattered showers. Mostly cloudy, with a high near 83. Northeast wind 5 to 7 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers. Mostly cloudy, with a low around 68. Light north northeast wind. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Saturday: Scattered showers. Mostly cloudy, with a high near 84. Northeast wind around 6 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Kona

Today: Scattered showers after noon. Increasing clouds, with a high near 79. Light and variable wind becoming west around 5 mph in the morning. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers before midnight. Mostly cloudy, with a low around 65. Calm wind. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

ARTICLE CONTINUES BELOW AD

Saturday: Scattered showers after noon. Mostly cloudy, with a high near 79. Southwest wind 3 to 5 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Waimea

ARTICLE CONTINUES BELOW AD

Today: Scattered showers. Partly sunny, with a high near 76. Northeast wind 5 to 11 mph. Chance of precipitation is 30%. New precipitation amounts between a tenth and quarter of an inch possible.

Tonight: Isolated showers after midnight. Mostly cloudy, with a low around 58. East northeast wind around 7 mph. Chance of precipitation is 20%.

Saturday: Scattered showers. Partly sunny, with a high near 76. Northeast wind 7 to 9 mph. Chance of precipitation is 30%. 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. East wind 5 to 9 mph becoming calm in the afternoon. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers after midnight. Partly cloudy, with a low around 54. East wind around 6 mph. Chance of precipitation is 30%.

Saturday: Showers likely, mainly after noon. Mostly cloudy, with a high near 65. East wind 5 to 10 mph becoming light in the afternoon. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

South Big Island

Today: Mostly sunny, with a high near 80. Breezy, with an east wind 17 to 21 mph, with gusts as high as 25 mph.

Tonight: Isolated showers. Partly cloudy, with a low around 72. Breezy, with an east northeast wind 15 to 17 mph, with gusts as high as 22 mph. Chance of precipitation is 20%.

Saturday: Scattered showers, mainly before noon. Partly sunny, with a high near 80. Breezy, with an east wind around 17 mph, with gusts as high as 22 mph. Chance of precipitation is 30%.

Puna

Today: Scattered showers. Mostly cloudy, with a high near 82. Northeast wind 9 to 13 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers, mainly after midnight. Mostly cloudy, with a low around 66. North northeast wind around 7 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Saturday: Showers likely, mainly before noon. Mostly cloudy, with a high near 83. North northeast wind around 8 mph. Chance of precipitation is 60%. New precipitation amounts between a tenth and quarter of an inch possible.

Waikoloa

Today: Isolated showers after noon. Increasing clouds, with a high near 84. East wind around 6 mph becoming light and variable. Chance of precipitation is 20%.

Tonight: Partly cloudy, with a low around 66. Calm wind becoming east around 5 mph after midnight.

Saturday: Scattered showers after noon. Partly sunny, with a high near 84. Northeast wind 5 to 7 mph becoming northwest in the afternoon. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Detailed Forecast

Synopsis

Moderate trade winds are expected to hold through early next week as a broad area of high pressure centered far northeast of the islands stays nearly stationary. Showers riding in with the trade winds will favor the windward and mountain areas of the larger islands. Lee areas will continue dry. This is despite the presence of a disturbance aloft that will produce a few briefly heavy showers.

Discussion

A broad 1028 mb surface high is forecast to remain nearly stationary some 14 hundred miles northeast of the main Hawaiian Islands through the weekend, thus maintaining the moderate trades. The softening of the trades to light to moderate speeds may occur on Tuesday as the high shifts southeastward and weakens. This weakening of the trades is due to the ridge associated with the surface high being moved closer to the islands by a front pressing in from the north.
An upper level disturbance is currently located 150 miles north of Kauai. It has set off a thunderstorm or two over our offshore waters west and far northwest of Kauai. Brief spurts of moderate to heavy showers have also been noted over interior and windward Kauai since Thursday afternoon. Elsewhere has been quiet with very minor showers, favoring the windward and mountain areas.
Looking ahead, the disturbance is forecast to move east, across our windward waters, reaching just north of Maui Saturday afternoon. The disturbance then heads north Saturday night and Sunday. Given this path of the disturbance, the associated instability, that is temperature related of around minus 10 to 12 degrees C, will spread from Kauai to Oahu this morning, then Maui County Saturday, before heading north and clearing the islands. The minus 10 degree C may clip northern Big Island Saturday, warranting just an outside and slight chance of an afternoon thunderstorm for the higher elevations and summits.
Currently, there isn’t much low level moisture. A pocket of moisture continues to clear Kauai, while a pool of dry air is advancing toward Oahu and Kauai. This dry pool is followed by some scattered low clouds that is now approaching Maui. Once this moisture gets to a more favorable environment, that is Oahu later today, do expect some moderate to heavy showers to show up. For Kauai, despite the dryness heading there, it won’t take much moisture for the instability to set off a heavy shower or two. Terrain will also the enhancement of these showers.
Models are pointing to an area of low level moisture slated to arrive around sunrise Saturday that will impact most islands. This added moisture combined with sufficient instability may lead to an active and wet Saturday.
Satellite imagery also show a thin layer of cirrus clouds cutting across Maui and Big Island counties. A more threatening area is the dense layered clouds southeast through south of the Big Island. It is forecast to move north and clip the Big Island this afternoon and tonight, then clear out by Saturday afternoon.
A further decrease in trade winds is possible around Tuesday as the surface ridge to the north is eroded. The upper level trough will be replaced by mid level ridging, leading to stable conditions and limited rainfall under a weak trade wind flow with afternoon sea breezes.

Aviation

Beneath a high cloud canopy, prevailing VFR is entrenched areawide this morning. Instances of MVFR will remain possible as moderate trades focus limited cloud and shower activity over windward slopes, but better moisture remains well upstream. Tall showers with tops up to about 18kft were observed over interior Big Island on Thursday. A similar evolution is possible today, although high clouds may suppress inland convection.
No AIRMETs in effect.

Marine

A surface high pressure system remains far northeast of the islands early this morning. A surface ridge extends west- southwest from this high through a point slightly less than 600 nm north of Kauai. These features are maintaining moderate to fresh trade winds across the island chain. The surface ridge is expected to drift slowly southward starting later today, which will cause the trade wind speeds to gradually weaken through this weekend. A front moving down from the northwest toward the region next week will cause the ridge to move even closer to the state, so expect the weaker background flow pattern to persist into the middle of next week. As a result, no Small Craft Advisory conditions are expected during the next 5 days.
A series of long-period south swells will spread up across the area into next week, which will keep surf near or above the summertime average along south facing shores. The latest guidance indicates that surf along south facing shores should gradually increase into early next week, and surf heights will likely peak near the High Surf Advisory threshold along south facing shores from late Saturday into Monday. Surf is then expected to gradually lower along along south facing shores from late Monday into the middle of next week. Surf along north facing shores will remain very small through this weekend. A series of small northwest swells will likely provide a small boost to surf heights along most north and west facing shores from Sunday night through the middle of next week. Finally, the weaker trade wind regime will cause surf heights to remain slightly below seasonal values along east facing shores through the middle of next week.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov

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