Weather Forecast

Hawaii County Weather Forecast for May 19, 2021

May 19, 2021, 7:16 AM HST
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Hilo

Today: Showers likely, mainly before 1pm. Partly sunny, with a high near 80. East wind 6 to 8 mph. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Occasional showers, mainly after 7pm. Low around 67. East wind around 5 mph. Chance of precipitation is 80%. New precipitation amounts of less than a tenth of an inch possible.

Thursday: Occasional showers, mainly before 1pm. High near 79. East wind around 9 mph. Chance of precipitation is 80%. New precipitation amounts of less than a tenth of an inch possible.

Kona

Today: Isolated showers after noon. Increasing clouds, with a high near 79. Light and variable wind becoming northwest 5 to 7 mph. Chance of precipitation is 20%.

Tonight: Scattered showers, mainly before midnight. Mostly cloudy, with a low around 65. Light north northwest wind. Chance of precipitation is 30%. New precipitation amounts between a tenth and quarter of an inch possible.

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Thursday: Scattered showers after noon. Increasing clouds, with a high near 80. 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: Scattered showers. Partly sunny, with a high near 73. East northeast wind 11 to 14 mph, with gusts as high as 18 mph. Chance of precipitation is 40%. New precipitation amounts between a quarter and half of an inch possible.

Tonight: Scattered showers. Mostly cloudy, with a low around 57. East wind around 11 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 74. East northeast wind 9 to 11 mph. Chance of precipitation is 50%. New precipitation amounts between a quarter and half of an inch possible.

Kohala

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Today: Showers likely, mainly after noon. Mostly cloudy, with a high near 65. Breezy, with an east wind 11 to 16 mph, with gusts as high as 22 mph. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Occasional showers. Low around 55. East southeast wind around 11 mph. Chance of precipitation is 80%. New precipitation amounts of less than a tenth of an inch possible.

Thursday: Showers likely, mainly before noon. Mostly cloudy, with a high near 66. East wind 8 to 11 mph. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

South Big Island

Today: Isolated showers before noon. Mostly sunny, with a high near 81. Windy, with an east wind 21 to 23 mph, with gusts as high as 30 mph. Chance of precipitation is 20%.

Tonight: Isolated showers. Partly cloudy, with a low around 71. Breezy, with an east northeast wind around 21 mph, with gusts as high as 26 mph. Chance of precipitation is 20%.

Thursday: Isolated showers. Mostly sunny, with a high near 81. Breezy, with an east wind around 22 mph, with gusts as high as 28 mph. Chance of precipitation is 20%.

Puna

Today: Showers likely, mainly before noon. Mostly cloudy, with a high near 75. Northeast wind 10 to 13 mph. Chance of precipitation is 70%. New precipitation amounts between a quarter and half of an inch possible.

Tonight: Occasional showers. Low around 64. East northeast wind 9 to 13 mph. Chance of precipitation is 80%. New precipitation amounts between a quarter and half of an inch possible.

Thursday: Showers likely, mainly before noon. Mostly cloudy, with a high near 74. East northeast wind 10 to 14 mph, with gusts as high as 18 mph. Chance of precipitation is 70%. New precipitation amounts between a tenth and quarter of an inch possible.

Waikoloa

Today: Sunny, with a high near 81. North wind around 6 mph.

Tonight: Mostly clear, with a low around 65. East wind around 6 mph.

Thursday: Isolated showers after noon. Sunny, with a high near 83. Northeast wind around 6 mph becoming north northwest in the morning. Chance of precipitation is 20%.

Detailed Forecast

Synopsis

Breezy trade winds will continue into the weekend. Low clouds and showers will favor windward and mountain areas, with minimal rainfall over most leeward locations. Lighter winds are expected over the weekend, bringing increased humidity and a slight increase in showers.

Discussion

Relatively benign and somewhat breezy trade wind weather will prevail into the weekend, with lighter winds potentially leading to a few more showers over the weekend and early next week.
A seasonable trade wind weather regime will remain firmly entrenched over the islands this week, with a strong subsidence inversion between 8 and 10 thousand feet capping the randomly distributed pockets of moisture embedded in the trade wind flow. This moisture will deliver brief showers to windward portions of the islands, and maybe a sprinkle to leeward areas, although daytime heating will support more significant clouds and showers over leeward Big Island each afternoon and evening.
The locally breezy trade winds are being supported by a 1031 mb surface high centered about 1500 miles NE of the islands. The high will change little as it drifts SE over the next several days, resulting in little change in wind speed over the area.
Guidance indicates that a sharp trough aloft will develop over the islands over the weekend, potentially inducing the formation of a surface trough, while a front to the NW weakens the ridge. The combined effects will lead to decreased winds that are veered to the SE which will likely bring increased moisture over the islands. Atmospheric instability associated with the trough appears minimal, so only a subtle increase in clouds and showers is anticipated, although afternoon sea breezes could potentially bring some leeward showers to the smaller islands. The trough may linger early next week as the front stalls NW and N of the islands, keeping winds on the lighter side.

Aviation

High pressure northeast of the state will continue to generate moderate to breezy trades through the forecast period. Thus, areas of tempo moderate turbulence will likely be present in the lee of island terrain. Scattered shower activity will favor windward areas with isolated showers elsewhere. Expect a slight increase in shower coverage through this morning along the windward coasts and slopes. Brief periods of MVFR ceilings and visibility may occur with some of the passing showers.
AIRMET Tango remains in effect below 8000 feet over and south through west of all mountains due to tempo moderate turbulence.

Marine

A 1030 mb surface high located far northeast of the islands will drift southeast evening. It is expected to drift southeast through Thursday before stalling through the weekend. Moderate to locally strong trade winds will hold through Friday. A Small Craft Advisory (SCA) is in effect for selected nearshore waters of Maui County and the waters south of the Big Island through early Thursday afternoon. The SCA will likely be extended.
A front, northwest of Kauai, is forecast to move toward the islands from the northwest over the weekend and early next week, while a ridge far to the north of the islands and east of the front will drop south. This will cause the trade winds to ease up a notch to moderate speed over the weekend. The ridge weakens early next week as the front continues to press eastward. This will cause further weakening of the trade winds and the winds to become southeast over Kauai.
Surf will remain well below advisory thresholds along all shores through next week. A small to moderate northwest swell will peak today, followed by a slow decline through Thursday night. Another small to moderate north- northwest pulse arrives Saturday night, peak Sunday and Sunday night, followed by gradual decline through Monday. A series of small northwest swell comes in on Tuesday and Thursday night.
A series of long period swell from the south will prevent the surf from going flat along the south facing shores into next week. The largest pulse is set for next Tuesday, followed by a gradual decline through Wednesday. The locally strong trade winds will maintain small to moderate short- period surf along east facing shores for the rest of the week, then slowly decline through early next week, in tandem with the diminishing trades.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM 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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