Weather Forecast

Hawaii County Weather Forecast for July 19, 2021

July 19, 2021, 7:16 AM HST
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Hilo

Today: Frequent showers, mainly before 11am. High near 82. West wind around 8 mph becoming northeast in the afternoon. Chance of precipitation is 80%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Showers likely, mainly after 1am. Cloudy, with a low around 68. Northeast wind 3 to 8 mph. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

Tuesday: Showers likely, mainly before 1pm. Mostly cloudy, with a high near 81. Calm wind becoming east northeast 5 to 8 mph in the morning. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

Kona

Today: Scattered showers after 10am. Mostly cloudy, with a high near 82. West 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, mainly before midnight. Cloudy, then gradually becoming partly cloudy, with a low around 68. West northwest wind around 6 mph becoming calm in the evening. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

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Tuesday: Isolated showers. Mostly sunny, with a high near 80. Calm wind becoming west northwest around 6 mph. Chance of precipitation is 20%.

Waimea

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Today: Scattered showers, mainly before 10am. Partly sunny, with a high near 76. Windy, with a northeast wind 21 to 24 mph, with gusts as high as 34 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers. Mostly cloudy, with a low around 59. Windy, with a northeast wind 16 to 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.

Tuesday: Scattered showers. Partly sunny, with a high near 75. Breezy, with an east northeast wind 15 to 17 mph, with gusts as high as 24 mph. Chance of precipitation is 40%. New precipitation amounts between a tenth and quarter of an inch possible.

Kohala

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Today: Showers likely, mainly before 10am. Mostly cloudy, with a high near 69. Windy, with an east wind 26 to 28 mph, with gusts as high as 40 mph. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Showers likely, mainly after midnight. Mostly cloudy, with a low around 58. Windy, with an east wind 24 to 26 mph, with gusts as high as 38 mph. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

Tuesday: Showers likely, mainly before noon. Mostly cloudy, with a high near 69. Windy, with an east wind 22 to 25 mph, with gusts as high as 36 mph. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

South Big Island

Today: Scattered showers before 10am. Partly sunny, with a high near 86. Windy, with an east wind 26 to 28 mph, with gusts as high as 36 mph. Chance of precipitation is 30%.

Tonight: Isolated showers after midnight. Cloudy, then gradually becoming partly cloudy, with a low around 74. Windy, with an east northeast wind 23 to 28 mph, with gusts as high as 36 mph. Chance of precipitation is 20%.

Tuesday: Isolated showers before noon. Mostly sunny, with a high near 84. Windy, with an east wind 21 to 25 mph, with gusts as high as 32 mph. Chance of precipitation is 20%.

Puna

Today: Frequent showers, mainly before 10am. High near 78. Northwest wind 11 to 14 mph becoming northeast in the afternoon. Winds could gust as high as 18 mph. Chance of precipitation is 80%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Showers likely, mainly after midnight. Cloudy, with a low around 66. Northeast wind 9 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.

Tuesday: Showers likely, mainly before noon. Mostly cloudy, with a high near 78. Northeast wind 9 to 13 mph. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

Waikoloa

Today: Mostly sunny, with a high near 84. Windy, with an east northeast wind 17 to 24 mph, with gusts as high as 34 mph.

Tonight: Cloudy during the early evening, then gradual clearing, with a low around 68. Windy, with an east northeast wind 19 to 24 mph decreasing to 10 to 15 mph after midnight. Winds could gust as high as 34 mph.

Tuesday: Sunny, with a high near 83. Northeast wind 6 to 13 mph.

Detailed Forecast

Synopsis

Trade winds will persist through the rest of the new work week as an area of surface high pressure remains north of the islands. The trade winds will strengthen today to locally very windy, then weaken slightly to moderate to strong after Tuesday. Showers will be favoring the windward and mauka areas, especially during the nights and early morning hours. Light rainfall amounts is expected through the week.

Discussion

The area of drier air that descended down on the islands last evening is being replaced by a band of clouds and embedded showers. Expect a somewhat showery kind of morning up to around 8 am HST before the frequency of these showers become less. Scattered windward and mauka showers, mainly light, is expected for the rest of the day, as the band dissipates. But this is expected to be the norm for the rest of the week, that is showers favoring the windward and mountain areas, especially nights and mornings.
The trade winds will continue to blow across the area the rest of this week. In the short term, this cloud band about to cross the islands is expected to usher in a bump up in the trades, resulting in some localized very strong trades. A Wind Advisory has been posted for the lee side of the Kohala Mountains and the saddle area of the Big Island, which is good through tonight. The satellite derive winds indicated pockets of 20 to 25 knot winds behind or to the north of this cloud band. Much though was given for this Wind Advisory to cover central Maui and Lanai, but the trades may have too much of a east component. Never-the- less, we will be monitoring the situation closely, and if needed, a Wind Advisory will be issued. The high center drifts off to the west Tuesday, allowing a slight slackening of the trades.
Forecast models suggest that the low level inversion is to set up shop over the islands this morning as a mid level ridge eases in. Expect this inversion to hover between 5k and 7k feet through Tuesday before rising to 8 to 9k feet Tuesday night. So through Tuesday, expect the showers to be light and or light drizzle, and confined to the windward and mountain areas.
About Friday through Saturday time frame, the islands may get another boost in the trades as the remnants of Felicia passes far south of the islands. Then about 24 to 36 hours later, Sunday through Monday,the trades will soften to light to moderate speed as the remnants of Tropical Cyclone Guillermo reaches the islands. Beside the easing the trades, the remnants of Guillermo may give the islands a boost trade showers. There is much uncertainty of this forecast at this time. It depend on the track of Guillermo.

Aviation

Trade winds will increase today, becoming quite gusty this afternoon, then remain locally windy through Tuesday as high pressure builds far N of the state. A loosely organized band of showery low clouds will move across all islands this morning, bringing periods of MVFR VIS/CIG in SHRA to windward areas. Coverage may become sufficiently widespread to warrant AIRMET Sierra for mountain obscuration. AIRMET Tango for moderate turbulence over and S through W of island terrain will remain in effect for the foreseeable future.
A weak low aloft moving NW away from the islands will bring some high clouds to the Big Island and Maui County into tonight.

Marine

A strong high pressure ridge north of the Hawaiian Islands will continue to produce strong trade winds and elevated rough seas through the week. These strong winds and rough seas will trend down slightly by Wednesday, and trend higher again by Friday. The Small Craft Advisory (SCA) was expanded to include all coastal waters through Tuesday.
The current south swell will gradually trend lower through Tuesday, with smaller size surf for south facing shores lasting into the weekend. Besides some localized wrap of trade wind swell, surf along most north facing shores will remain essentially flat through mid-week. Tropical Cyclone Felicia, currently in the Eastern Pacific, will not produce large surf due to limited fetch. However, Felicia could bring in some small to moderate mid period surf mainly along the east facing shores of the Big Island later this week.

HFO Watches/Warnings/Advisories

Wind Advisory until 6 AM HST Tuesday for Kohala.
Small Craft Advisory until 6 AM HST Tuesday for all Hawaiian waters.

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Data Courtesy of NOAA.gov

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