Weather Forecast

Hawaii County Weather Forecast for May 15, 2021

May 15, 2021, 7:16 AM HST
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Hilo

Today: Showers likely, mainly before 1pm. Partly sunny, with a high near 78. West southwest wind 5 to 14 mph becoming north northeast in the afternoon. Winds could gust as high as 18 mph. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Showers likely, mainly after 1am. Mostly cloudy, with a low around 65. North northwest wind 8 to 14 mph, with gusts as high as 18 mph. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

Sunday: Showers likely, mainly before 1pm. Mostly cloudy, with a high near 79. North wind around 8 mph. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

Kona

Today: Scattered showers after noon. Mostly sunny, with a high near 78. East wind around 5 mph becoming west northwest in the afternoon. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers before midnight. Partly cloudy, with a low around 64. East wind 3 to 5 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

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Sunday: Isolated showers after noon. Mostly sunny, with a high near 78. Light and variable wind. Chance of precipitation is 20%.

Waimea

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Today: Scattered showers. Partly sunny, with a high near 71. Breezy, with an east northeast wind 14 to 20 mph, with gusts as high as 28 mph. Chance of precipitation is 40%. New precipitation amounts between a tenth and quarter of an inch possible.

Tonight: Scattered showers. Mostly cloudy, with a low around 54. East wind 11 to 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.

Sunday: Scattered showers, mainly before noon. Mostly sunny, with a high near 72. East northeast wind 11 to 14 mph, with gusts as high as 18 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Kohala

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Today: Showers likely, mainly after noon. Partly sunny, with a high near 64. Windy, with an east northeast wind 16 to 23 mph, with gusts as high as 32 mph. Chance of precipitation is 60%. 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 northeast wind 16 to 20 mph, with gusts as high as 28 mph. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

Sunday: Showers likely, mainly before noon. Partly sunny, with a high near 65. Breezy, with an east northeast wind 17 to 22 mph, with gusts as high as 31 mph. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

South Big Island

Today: Sunny, with a high near 81. Windy, with an east wind 22 to 24 mph, with gusts as high as 31 mph.

Tonight: Isolated showers after midnight. Partly cloudy, with a low around 70. Breezy, with an east northeast wind 15 to 17 mph, with gusts as high as 22 mph. Chance of precipitation is 20%.

Sunday: Isolated showers before noon. Mostly sunny, with a high near 81. Breezy, with an east wind around 18 mph, with gusts as high as 23 mph. Chance of precipitation is 20%.

Puna

Today: Showers likely, mainly before noon. Partly sunny, with a high near 74. Breezy, with a north northeast wind 8 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.

Tonight: Occasional showers, mainly after midnight. Low around 61. Breezy, with a north wind around 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.

Sunday: Occasional showers, mainly before noon. High near 74. Breezy, with a north wind around 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: Isolated showers after noon. Sunny, with a high near 81. Breezy, with a north northeast wind 9 to 17 mph, with gusts as high as 24 mph. Chance of precipitation is 20%.

Tonight: Mostly clear, with a low around 62. East wind 7 to 9 mph.

Sunday: Sunny, with a high near 81. North northeast wind 5 to 7 mph.

Detailed Forecast

Synopsis

Breezy northeast trade winds will shift to a more easterly direction Monday, and then continue into the middle of the week. Showers will favor windward and mountain locations, especially through the overnight and early morning periods.

Discussion

Overall the forecast remains on track. Have lowered the PoPs over the Big Island for this morning based on satellite data showing fewer clouds than originally anticipated there. Have also knocked PoPs back a little state wide for Sunday and Sunday night. Originally the PoPs had been boosted for the shortwave expected to move through, however subsequent model runs have continued to show a relatively dry airmass remaining overhead which will help to limit shower activity.
High pressure to the northeast remains our dominant weather feature, bringing breezy northeast trades to the islands. A front far north of the islands will push to the east and help to nudge the high southward during the first part of the new work week. This will help shift the trades to a little more of an easterly direction. Longer range, the models show the associated ridge will sink closer to the islands towards the end of the new week, which could weaken winds. In the meantime, expect moderate to locally breezy trades to continue.
An upper level low to the northeast of the islands continues to remain nearly stationary, but is expected to start to start lifting to the northeast tomorrow. Meanwhile the models do still suggest a weak shortwave swinging through the islands from the north. However as the more recent model runs have shown, with the upper low moving away from the islands at that time, combined with the drier airmass in place over the islands, it doesn’t look like there will be much impact from the shortwave.

Aviation

Breezy northeast trade winds are expected to remain in place across the state this weekend. This will allow showers and periods of MVFR ceilings and visibilities to favor north through east sections of the islands, especially during the overnight and early morning hours. Early this morning, improving conditions for windward Big Island allowed for the cancellation of AIRMET Sierra, but mountain obscuration could become an issue again later this morning. Otherwise, VFR conditions are expected to prevail throughout the forecast period.
AIRMET Tango remains in effect for mechanical low-level turbulence downwind of mountainous terrain of all islands, and this AIRMET will likely be needed through at least tonight as the breezy trade winds continue.

Marine

High pressure north of the area will maintain locally strong trade winds through the coming week. A Small Craft Advisory (SCA) remains in effect for the windy waters around Maui county and the Big Island through Sunday afternoon. The SCA will likely be extended.
Surf will remain below the High Surf Advisory Thresholds along all shores through the coming week. Surf along south facing shores will remain elevated through today, subside Sunday and Monday, then remain small through the rest of the week.
Surf will remain quite small along north facing shores through the weekend. A small north northwest swell arriving Sunday night will peak Monday, then subside through Tuesday. A small west northwest swell will peak Wednesday, then subside through Thursday.
The trade winds will produce choppy surf along east facing shores through the coming week. Wave heights may build a bit early next week as the trade-wind fetch lengthens.

HFO Watches/Warnings/Advisories

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

Data Courtesy of NOAA.gov

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