Weather Forecast

Hawaii County Weather Forecast for February 18, 2021

February 18, 2021, 7:15 AM HST
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Photo Credit: James Grenz

Hilo

Today: Occasional showers and possibly a thunderstorm. High near 79. East southeast wind 3 to 7 mph. Chance of precipitation is 80%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Tonight: Occasional showers and possibly a thunderstorm. Low around 63. Southeast wind around 5 mph. Chance of precipitation is 80%. New precipitation amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Friday: Occasional showers. High near 78. Southeast wind 6 to 9 mph. Chance of precipitation is 80%. New precipitation amounts of less than a tenth of an inch possible.

Kona

Today: Scattered showers and thunderstorms, mainly after 1pm. Widespread haze. Mostly cloudy, with a high near 81. Calm wind becoming northwest 5 to 8 mph in the afternoon. Chance of precipitation is 50%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Tonight: Scattered showers and thunderstorms before 1am, then isolated showers. Widespread haze. Mostly cloudy, with a low around 61. Light and variable wind becoming north 5 to 8 mph after midnight. Chance of precipitation is 50%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

ARTICLE CONTINUES BELOW AD

Friday: Isolated showers, then scattered showers and thunderstorms after 1pm. Widespread haze. Mostly cloudy, with a high near 80. North wind around 6 mph becoming west southwest in the morning. Chance of precipitation is 50%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Waimea

ARTICLE CONTINUES BELOW AD

Today: Scattered showers and thunderstorms, then showers likely and possibly a thunderstorm after 1pm. Mostly cloudy, with a high near 75. East wind 8 to 14 mph, with gusts as high as 18 mph. Chance of precipitation is 60%. New rainfall amounts between a quarter and half of an inch possible.

Tonight: Showers likely and possibly a thunderstorm. Mostly cloudy, with a low around 52. East wind 7 to 11 mph. Chance of precipitation is 60%. New precipitation amounts between a half and three quarters of an inch possible.

Friday: Showers likely, mainly after 1pm. Mostly cloudy, with a high near 74. East southeast wind 6 to 8 mph. Chance of precipitation is 60%. New precipitation amounts between a half and three quarters of an inch possible.

Kohala

ARTICLE CONTINUES BELOW AD

Today: Occasional showers and possibly a thunderstorm. High near 71. Breezy, with an east wind 13 to 22 mph, with gusts as high as 31 mph. Chance of precipitation is 80%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Tonight: Occasional showers. Low around 45. Breezy, with an east southeast wind 10 to 17 mph, with gusts as high as 24 mph. Chance of precipitation is 90%. New precipitation amounts of less than a tenth of an inch possible.

Friday: Occasional showers. High near 70. Breezy, with an east southeast wind 9 to 16 mph, with gusts as high as 22 mph. Chance of precipitation is 80%. New precipitation amounts of less than a tenth of an inch possible.

South Big Island

Today: Scattered showers and thunderstorms, mainly after noon. Widespread haze. Mostly cloudy, with a high near 81. Windy, with an east wind 21 to 24 mph, with gusts as high as 31 mph. Chance of precipitation is 30%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Tonight: Scattered showers. Widespread haze. Mostly cloudy, with a low around 69. Windy, with an east wind 21 to 23 mph, with gusts as high as 30 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Friday: Scattered showers. Widespread haze. Mostly cloudy, with a high near 80. Windy, with an east wind 21 to 24 mph, with gusts as high as 31 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Puna

Today: Occasional showers and possibly a thunderstorm. High near 78. East wind 3 to 8 mph. Chance of precipitation is 80%. New rainfall amounts between a quarter and half of an inch possible.

Tonight: Occasional showers. Low around 61. East northeast wind 5 to 7 mph becoming calm. Chance of precipitation is 90%. New precipitation amounts between a quarter and half of an inch possible.

Friday: Occasional showers. High near 77. East wind 5 to 9 mph. Chance of precipitation is 80%. New precipitation amounts between a quarter and half of an inch possible.

Waikoloa

Today: Scattered showers and thunderstorms after noon. Mostly cloudy, with a high near 82. East wind 5 to 8 mph becoming north northwest in the morning. Chance of precipitation is 30%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Tonight: Isolated showers before midnight. Mostly cloudy, with a low around 61. East northeast wind 5 to 7 mph becoming light and variable. Chance of precipitation is 20%.

Friday: A 20 percent chance of showers and thunderstorms after noon. Mostly cloudy, with a high near 81. Southeast wind around 5 mph becoming calm in the afternoon.

Detailed Forecast

Synopsis

A lingering upper trough near the state will produce a cloudy and somewhat wet trade wind weather pattern through Friday. A gradual drying trend is expected for the weekend, with easterly trade winds continuing early next week.

Discussion

A ragged band of layered clouds, marking a front, extends northeast to southwest across waters west of Kauai, with the ill- defined leading edge of the cloud band just across Kauai this morning. Brief heavy showers and isolated thunderstorms formed within this cloud band overnight but have decreased over the past few hours. However, the threat of redevelopment is serious enough to keep a Flash Flood Watch up through Thursday afternoon.
Unstable trade wind weather is in store through Friday. High pressure far north and northeast of the state will drive moderate to breezy trade winds. The front will weaken and drift to the north and west of Kauai today, leaving residual moisture in the trade wind flow. The upper trough will develop into a low to the southwest of the state and there may be sufficient instability for development of heavy showers and thunderstorms state-wide. Windward areas will experience the greatest amount of rainfall, though some showers will periodically carry over to leeward areas. Periods of snow and ice may occur on the high summits of the Big Island.
A gradual drying trend is expected this weekend. The nearly stationary upper low will weaken into a trough again, and temperatures aloft will slowly warm. While some instability will linger, especially on Saturday, the threat for heavy showers and thunderstorms will diminish. High pressure to our north will generate easterly trade winds, which will keep windward areas wetter. High clouds will linger across most of the region on Saturday and diminish Sunday. Models suggest a more stable easterly trade wind flow early next week, with pockets of moisture affecting mainly windward slopes.

Aviation

A front stalled near Kauai, along with a nearby upper air disturbance, will keep a chance of heavy downpours and isolated thunderstorms today, mainly over Kauai, Niihau, and adjacent waters. The other islands will see scattered windward and mauka showers. Winds will return to a trade regime through the day, in the moderate to locally breezy range, as the front gradually dissipates and high pressure builds north of the islands.
An AIRMET is posted for mountain obscuration over windward portions of the Big Island as an area of low clouds and showers moves in from the east.

Marine

A stationary front just west of Kauai will dissipate today. An upper level trough will continue to linger over the western waters and will produce unstable conditions through Friday. A strong high building far north of the state has brought the return of fresh to strong trades across area waters and is expected to hold through next week. A Small Craft Advisory (SCA) is now in effect for the typical windier waters around Maui and the Big Island and also for waters west of Kauai due to the strong northeasterly winds from the frontal boundary. The winds associated with the front should be on the decrease today.
The current northwest swell will be on a gradual decline over the next few days. A series of small west-northwest swells are expected through the first half of next week. The first swell is expected to slowly fill in late Saturday and peak Sunday into Monday followed by another small swell Tuesday into Wednesday. Surf heights from these west-northwest swells should remain below High Surf Advisory (HSA) levels through the period.
Surf along east facing shores will gradually increase during the weekend into early next week as a large fetch of strong trades develop upstream of the state. Surf could reach advisory thresholds by early next week. Small, mainly background southerly swells will continue throughout the forecast period.

HFO Watches/Warnings/Advisories

Flash Flood Watch through this afternoon for Niihau, Kauai.
Small Craft Advisory until 6 PM HST Saturday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.
Small Craft Advisory until 6 PM HST this evening for Kauai Northwest Waters, Kauai Leeward Waters.

Data Courtesy of NOAA.gov

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