Photo Credit: James Grenz

Hilo

Today: Showers likely, mainly before noon. Mostly cloudy, with a high near 84. South wind 5 to 10 mph becoming east in the afternoon. 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 66. Light and variable wind becoming west around 5 mph in the evening. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

Friday: Showers likely, mainly before noon. Mostly cloudy, with a high near 83. East northeast wind 5 to 9 mph. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

Kona

Today: Isolated showers after noon. Mostly sunny, with a high near 79. Southwest wind 3 to 7 mph. Chance of precipitation is 20%.

Tonight: Scattered showers, mainly before midnight. Partly cloudy, with a low around 65. North northwest wind 5 to 9 mph becoming light and variable after midnight. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Friday: Isolated showers after noon. Partly sunny, with a high near 79. Light and variable wind becoming southwest around 6 mph. Chance of precipitation is 20%.

Waimea

Today: Scattered showers. Partly sunny, with a high near 76. Windy, with a northeast wind 14 to 24 mph, with gusts as high as 34 mph. Chance of precipitation is 50%. New precipitation amounts between a quarter and half of an inch possible.

Tonight: Scattered showers. Mostly cloudy, with a low around 58. Windy, with a northeast wind 18 to 23 mph decreasing to 11 to 16 mph after midnight. Winds could gust as high as 32 mph. Chance of precipitation is 50%. New precipitation amounts between a tenth and quarter of an inch possible.

Friday: Scattered showers, mainly after 1pm. Partly sunny, with a high near 76. Breezy, with an east wind 10 to 15 mph, with gusts as high as 21 mph. Chance of precipitation is 40%. New precipitation amounts between a tenth and quarter of an inch possible.

Kohala

Today: Occasional showers. High near 65. Windy, with an east wind 20 to 24 mph, with gusts as high as 34 mph. Chance of precipitation is 80%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Occasional showers. Low around 53. Windy, with an east wind 19 to 24 mph decreasing to 10 to 15 mph after midnight. Winds could gust as high as 34 mph. Chance of precipitation is 80%. New precipitation amounts of less than a tenth of an inch possible.

Friday: Showers likely. Mostly cloudy, with a high near 64. East 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.

South Big Island

Today: Isolated showers. 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 73. Breezy, with an east wind 16 to 21 mph, with gusts as high as 26 mph. Chance of precipitation is 20%.

Friday: Mostly sunny, with a high near 80. Breezy, with an east wind 20 to 22 mph, with gusts as high as 28 mph.

Puna

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Waikoloa

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Detailed Forecast

Synopsis

Moderate to locally breezy trade winds will continue into Friday, followed by slightly weaker trades this weekend. The trades will continue to transport low clouds and brief showers into windward facing sections of the state, especially during nights and mornings. The background flow is forecast to become even lighter next week. which will likely allow afternoon sea breezes and nighttime land breezes to develop.

Discussion

The tight pressure gradient south of a nearly stationary east- northeast to west-southwest oriented surface ridge located slightly less than 750 miles north of Honolulu is maintaining moderate to locally breezy trade winds across the state early this morning. Aloft, loops of water vapor satellite imagery show a slow-moving cold core upper-level low centered near 26N 161W, or about 270 miles north-northwest of Lihue. The relatively close proximity of this feature appears to be causing some destabilization of the atmosphere, especially near Kauai. The upper-level low will likely continue to drift down closer to the western end of the island chain. Since the colder temperatures assoicated with this low may cause additional instability, this poses a forecast challenge in the near term. Satellite imagery and radar reflectivity data currently show broken low clouds with embedded scattered showers in the vicinity of the windward sides of most islands.
The forecast guidance keeps the moderate to locally breezy trade wind speeds in place into Friday. After that, expect a slow weakening of the trades from late Friday through this weekend as a front pushes down toward the area from the northwest, and causes the surface ridge to weaken. We anticipate a fairly typical trade wind weather pattern during the next few days. Therefore, expect low clouds and brief showers along windward facing slopes and coasts, with the greatest coverage during nights and mornings. In addition, with the upper-level low lingering near the area through Saturday, a brief heavy downpour cannot be ruled out over Kauai and Oahu, as well as possibly along the upslope sections of the Big Island during the next day or two. Note that high clouds that are associated with the low aloft and its accompanying subtropical jet may move over portions of the state later today or tonight. The latest guidance indicates even thicker high cloud cover may spread over portions of the Big Island on Friday.
Looking ahead to next week, another slightly stronger front appears to push down closer to the islands from the northwest. This will likely cause the surface ridge to move down close to Kauai, which will result in lighter background winds next Tuesday and Wednesday. The weaker winds will likely allow local afternoon sea breezes and nighttime land breezes to form over each of the individual islands. Also, expect the atmosphere to become more stable after the upper-level low departs the region. This will mean that even though clouds may form over leeward and interior sections of the islands each afternoon when the sea breezes develop, there will likely be only a few brief showers. Therefore, the light wind regime will likely result in an extended period of abundant sunshine and very warm temperatures next week.

Aviation

Moderate wind out of the E-ESE sector will continue to funnel occasional clouds and showers over windward areas through the forecast period. Latest satellite imagery reveals an abundance of moisture embedded within prevailing flow streaming onshore over Windward Big Island and Maui where MVFR observations have been common during the last several hours. Increasing clouds and showers have also been observed over windward slopes of the remaining smaller islands as this band of moisture is stretched over the west section of the island chain. For now, MVFR is forecast to remain isolated in nature for Molokai through Kauai.
AIRMET Sierra for mountain obscuration remains in effect for Windward Maui and Big Island.

Marine

High pressure northeast of the islands will keep moderate to locally strong trade winds in place through tonight. A Small Craft Advisory remains in effect through 6 PM this evening for the windier waters around Maui and the Big Island, and this may need to be extended into tonight. Trade winds are expected to begin easing on Friday, then lower into the light to moderate range this weekend through early next week, as a couple of fronts approach and stall out well to the northwest of the island chain.
Surf along south facing shores will remain near or above the summertime average during the next 7 days, as a series of long- period south swells move through the island chain. South shore surf will slowly build during the next several days, peak Saturday night through Monday near High Surf Advisory levels, then gradually lower into the middle of next week. Surf along north facing shores will remain very small through the weekend. A couple back to back small northwest swells could give north shore surf a boost Sunday night through the middle of next week. Surf along east facing shores will hold fairly steady at slightly below seasonal levels through the middle of next week.

HFO Watches/Warnings/Advisories

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

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Data Courtesy of NOAA.gov