Weather Forecast

Hawaii County Weather Forecast for May 12, 2021

May 12, 2021, 7:16 AM HST
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Photo Credit: James Grenz

Hilo

Today: Scattered showers. Partly sunny, with a high near 82. North northeast wind around 10 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Showers likely, mainly after midnight. Mostly cloudy, with a low around 66. East northeast wind around 5 mph becoming calm after midnight. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

Thursday: Scattered showers. Partly sunny, with a high near 82. Northeast wind 3 to 8 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Kona

Today: Scattered showers after noon. Mostly sunny, with a high near 79. Southeast wind around 6 mph becoming southwest in the afternoon. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers, mainly before midnight. Partly cloudy, with a low around 66. Calm wind. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

ARTICLE CONTINUES BELOW AD

Thursday: Scattered showers after noon. Mostly sunny, with a high near 79. Light north northwest wind. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Waimea

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Today: Scattered showers. Partly sunny, with a high near 73. Windy, with a northeast wind around 23 mph, with gusts as high as 32 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 56. East wind 8 to 10 mph. Chance of precipitation is 40%. New precipitation amounts between a quarter and half of an inch possible.

Thursday: Scattered showers. Partly sunny, with a high near 73. East northeast wind 10 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.

Kohala

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Today: Scattered showers. Mostly cloudy, with a high near 67. Breezy, with an east northeast wind around 22 mph, with gusts as high as 31 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Showers likely. Mostly cloudy, with a low around 55. Breezy, with an east wind around 18 mph, with gusts as high as 25 mph. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

Thursday: Scattered showers. Partly sunny, with a high near 67. Breezy, with an east northeast wind 14 to 21 mph, with gusts as high as 29 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

South Big Island

Today: Isolated showers. Mostly sunny, with a high near 80. Windy, with an east wind 24 to 26 mph, with gusts as high as 34 mph. Chance of precipitation is 20%.

Tonight: Isolated showers. Partly cloudy, with a low around 72. Breezy, with an east northeast wind 20 to 22 mph, with gusts as high as 28 mph. Chance of precipitation is 20%.

Thursday: Isolated showers. Mostly sunny, with a high near 80. Breezy, with an east wind around 21 mph, with gusts as high as 26 mph. Chance of precipitation is 20%.

Puna

Today: Scattered showers. Partly sunny, with a high near 79. Northeast wind around 14 mph, with gusts as high as 18 mph. Chance of precipitation is 50%. New precipitation amounts between a tenth and quarter of an inch possible.

Tonight: Showers likely, mainly after midnight. Mostly cloudy, with a low around 63. North wind 6 to 9 mph. Chance of precipitation is 60%. New precipitation amounts between a tenth and quarter of an inch possible.

Thursday: Showers likely, mainly before noon. Partly sunny, with a high near 79. North northeast wind 10 to 14 mph, with gusts as high as 18 mph. Chance of precipitation is 60%. New precipitation amounts between a tenth and quarter of an inch possible.

Waikoloa

Today: Isolated showers after noon. Mostly sunny, with a high near 82. Windy, with an east northeast wind around 24 mph, with gusts as high as 34 mph. Chance of precipitation is 20%.

Tonight: Isolated showers before midnight. Partly cloudy, with a low around 67. East northeast wind 3 to 5 mph. Chance of precipitation is 20%.

Thursday: Isolated showers after noon. Sunny, with a high near 82. North wind 5 to 7 mph. Chance of precipitation is 20%.

Detailed Forecast

Synopsis

A broad surface ridge far north of the island chain will maintain moderate to locally breezy trade winds into this weekend. Low clouds and passing trade showers will continue to favor windward and mauka areas, while brief showers are possible over some leeward sections.

Discussion

A northeast to southwest oriented surface ridge is evident far north of the main Hawaiian Islands early this morning. This feature is producing a tight pressure gradient across the region, which is driving moderate to locally breezy trade winds in the vicinity of the island chain. Aloft, an upper-level trough is evident in water vapor imagery north of the islands. This feature is digging toward the south-southeast. In the meantime, the atmosphere is currently relatively stable across the state. The low-level trade wind flow is transporting scattered to locally broken low clouds with embedded scattered showers into the islands based on satellite imagery and radar reflectivity data. These low clouds and showers will continue to move over windward facing slopes and coastlines. In addition, the trades are strong enough to transport a few brief showers over to the leeward sections of some of the smaller islands.
The forecast guidance shows surface high pressure will remain in place far north of the state through this weekend. As a result, expect the moderate to locally breezy trade winds to persist. The forecast models also continue to indicate the upper-level trough, which was mentioned above, will propagate down toward the area just northeast of the state through Thursday. In addition, the models show a short wave trough moving down above the islands later today and tonight. This may cause an increase in cloud cover and trade showers from late this afternoon through tonight.
Once it arrives, the forecast models show the upper-level trough appears to stall just to the northeast of the state from Thursday night through this weekend. The feature will eventually lift out away from the region early next week. In the meantime, the relatively close proximity of this trough aloft may provide some enhancement to low clouds and trade showers from Thursday into the weekend. However, the models are showing a decrease in the low-level moisture sources upstream of the state. If so, this would potentially limit the actual cloud cover and precipitation as we head into the weekend. The current forecast keeps a typical trade wind weather pattern later this week until we see evidence that there may be an enhancement in clouds and showers.

Aviation

High pressure northeast of the state will keep moderate to breezy trades in place through tonight. Passing showers may bring brief MVFR cigs/vsbys to windward areas, mainly during the early morning and overnight hours. Otherwise VFR conditions should prevail statewide.
No AIRMETs are currently in effect.

Marine

A Small Craft Advisory (SCA) remains in effect for the windier waters around Maui County and the Big Island through late tonight, thanks to persistent high pressure to our north. Surf will remain up along south facing shores as a series of overlapping small, long period swells from the southern hemisphere pass by. Eastern shores will experience rough and choppy wind wave conditions due to persistent moderate to fresh trades. Surf along north facing shores will trend down through the middle of the week in response to a diminishing northwest swell.

HFO Watches/Warnings/Advisories

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

Data Courtesy of NOAA.gov

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