Photo Credit: James Grenz

Hilo

Today: Showers likely, mainly before noon. Mostly cloudy, with a high near 83. 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.

Tonight: Frequent showers. Low around 71. East northeast wind around 5 mph becoming calm in the evening. Chance of precipitation is 80%. New precipitation amounts of less than a tenth of an inch possible.

Thursday: Frequent showers, mainly before noon. High near 83. Light and variable wind becoming east northeast 5 to 10 mph. Chance of precipitation is 80%. New precipitation amounts of less than a tenth of an inch possible.

Kona

Today: Scattered showers and thunderstorms after noon. Partly sunny, with a high near 81. Calm wind becoming west southwest 5 to 7 mph. Chance of precipitation is 50%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Tonight: Isolated showers before 11pm. Mostly cloudy, with a low around 71. Light and variable wind. Chance of precipitation is 20%.

Thursday: Scattered showers after noon. Partly sunny, with a high near 81. Calm wind becoming west 5 to 9 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Waimea

Today: Scattered showers, mainly before noon. Mostly cloudy, with a high near 76. Breezy, with a northeast wind 15 to 20 mph, with gusts as high as 28 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 58. Breezy, with a northeast wind 10 to 18 mph, with gusts as high as 25 mph. Chance of precipitation is 40%. New precipitation amounts between a tenth and quarter of an inch possible.

Thursday: Scattered showers, mainly before noon. Mostly cloudy, with a high near 76. Windy, with a northeast wind 15 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.

Kohala

Today: Showers likely, mainly before noon. Cloudy, with a high near 67. Breezy, with an east wind 15 to 22 mph, with gusts as high as 31 mph. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Showers likely. Mostly cloudy, with a low around 53. Windy, with an east wind 16 to 24 mph, with gusts as high as 34 mph. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

Thursday: Showers likely, mainly before noon. Mostly cloudy, with a high near 67. Breezy, with an east wind 16 to 21 mph, with gusts as high as 29 mph. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

South Big Island

Today: Mostly sunny, with a high near 83. Windy, with an east wind 21 to 25 mph, with gusts as high as 32 mph.

Tonight: Partly cloudy, with a low around 74. Windy, with an east wind 23 to 29 mph, with gusts as high as 37 mph.

Thursday: Mostly sunny, with a high near 83. Windy, with an east northeast wind 23 to 26 mph, with gusts as high as 33 mph.

Puna

Today: Showers likely, mainly before noon. Cloudy, with a high near 80. North northwest wind 5 to 13 mph becoming northeast in the afternoon. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Frequent showers. Low around 69. Northeast wind 3 to 8 mph. Chance of precipitation is 90%. New precipitation amounts between a tenth and quarter of an inch possible.

Thursday: Frequent showers, mainly before noon. High near 80. Breezy, with a northeast wind 5 to 15 mph, with gusts as high as 21 mph. Chance of precipitation is 90%. New precipitation amounts between a tenth and quarter of an inch possible.

Waikoloa

Today: Mostly sunny, with a high near 85. Breezy, with a north northeast wind 9 to 18 mph, with gusts as high as 25 mph.

Tonight: Mostly clear, with a low around 70. East northeast wind 6 to 11 mph becoming light east after midnight.

Thursday: Mostly sunny, with a high near 85. Breezy, with a light and variable wind becoming east northeast 17 to 22 mph. Winds could gust as high as 31 mph.

Detailed Forecast

Update

The forecast has been updated to reflect the possibility of heavy rainfall in the areas with isolated thunderstorms, both over and near Kauai this morning, and over some of the Big Island slopes this afternoon. That area this morning is over and near Kauai where a line of showers is currently impacted the area. The PoPs in that area have been increased to better represent what we are seeing on radar. Will be taking a closer look at the possibility of thunder and locally heavy rainfall over other parts of the islands through the day.

Synopsis

Showers and the possibility of isolated thunderstorms this morning over Kauai are in response to increased low level moisture and an upper trough near the islands. A thunderstorm or two over the Big Islands slopes this afternoon is also possible. Otherwise, expect moderate to breezy easterly trade winds into Thursday, with strengthening afterwards. Clouds and showers will favor windward and mauka locations, especially overnight through the morning periods. A return of drier trade wind conditions is anticipated late Thursday through the weekend.

Aviation

The moderate to locally strong trade winds held, and even had a minor surge before the 1000z package issuance, thus keeping AIRMET Tango for low level turb another round. There is a good chance that Tango for low level turb be drop with the 16z package.
AIRMET Sierra for windward Big Island has been lowered as conditions have improved there. The entire stretch of east facing Big Island, including the Kau district, is likely to be affected by the moisture of a former tropical disturbance late this afternoon leading to the potential issuance of AIRMET Sierra for extensive mountain obscuration. This moisture may spread to east Maui later tonight.
An upper level low northwest of Kauai has provided an unstable air mass over the islands that will particularly affect Kauai County mainly this morning and the Kona coast and slopes this afternoon. These two areas can expect spotty heavy showers and a slight chance of a thunderstorm, which may also warrant an AIRMET Sierra for mountain obscuration.
A surge of mid and high level moisture across Kauai County has resulted in the potential light rime icing between FL150 and FL220. These clouds are expected to thin out as the morning progresses.

Marine

A high pressure system slowly building north to northeast of the region will keep fresh to strong trade winds in the forecast through Thursday with wind speeds strengthening from Friday into the weekend. A Small Craft Advisory remains in effect for the typically windier waters and channels near Maui County and the Big Island through Thursday and may expand in coverage on Thursday and Friday.
Moderate choppy surf along east facing shores will remain on the small side through Thursday due to a surface ridge decreasing the fetch length of the trades upstream of the islands. A slight increasing trend in the trade wind swell and surf along east facing shores will develop from Friday into the weekend.
A mix of south and southeast swells will keep small surf heights along exposed south shores into the first half of next week.
A small west-northwest swell, from tropical cyclone activity in the NW Pacific, may produce a minor bump in surf heights along some exposed north and west facing shores of Kauai and Oahu on Thursday and Friday.

Prev discussion

/ISSUED 313 AM HST Wed Jul 28 2021/
Water vapor imagery depicted an amplified upper pattern over the region, characterized by an upper trough extending southwest from an upper low centered within a few hundred miles northwest of Kauai. Decent southwest flow to its east, a shortwave trough rotating through its base, and a sufficient amount of tropical moisture will support locally heavy showers, and even a few thunderstorms today. The best chance for this activity will be over the western end of the state around Kauai, where the better instability and deeper moisture resides. The high-resolution WRF guidance reflects this with a large area of heavy showers forming this morning over the Kauai waters. For the Kona slopes, another round of localized heavy showers/thunderstorms can’t be ruled out this afternoon during the peak heating hours. Later tonight through early Thursday, a large area of tropical moisture lurking east of the Big Island will move over the eastern end of the state, keeping the rainfall chances up.
Guidance remains in good agreement and depicts the subtropical ridge strengthening to the north later in the week and into the weekend. This combined with rising upper heights as the aforementioned upper trough lifts out and drier air will support a more stable trade wind pattern. Easterly trades will respond and become strong by Friday.
AVIATION… The moderate to locally strong trade winds held, and even had a minor surge before the 1000z package issuance, thus keeping AIRMET Tango for low level turb another round. There is a good chance that Tango for low level turb be drop with the 16z package.
AIRMET Sierra for windward Big Island has been lowered as conditions have improved there. The entire stretch of east facing Big Island, including the Kau district, is likely to be affected by the moisture of a former tropical disturbance late this afternoon leading to the potential issuance of AIRMET Sierra for extensive mountain obscuration. This moisture may spread to east Maui later tonight.
An upper level low northwest of Kauai has provided an unstable air mass over the islands that will particularly affect Kauai County mainly this morning and the Kona coast and slopes this afternoon. These two areas can expect spotty heavy showers and a slight chance of a thunderstorm, which may also warrant an AIRMET Sierra for mountain obscuration.
A surge of mid and high level moisture across Kauai County has resulted in the potential light rime icing between FL150 and FL220. These clouds are expected to thin out as the morning progresses.
MARINE… A high pressure system slowly building north to northeast of the region will keep fresh to strong trade winds in the forecast through Thursday with wind speeds strengthening from Friday into the weekend. A Small Craft Advisory remains in effect for the typically windier waters and channels near Maui County and the Big Island through Thursday and may expand in coverage on Thursday and Friday.
Moderate choppy surf along east facing shores will remain on the small side through Thursday due to a surface ridge decreasing the fetch length of the trades upstream of the islands. A slight increasing trend in the trade wind swell and surf along east facing shores will develop from Friday into the weekend.
A mix of south and southeast swells will keep small surf heights along exposed south shores into the first half of next week.
A small west-northwest swell, from tropical cyclone activity in the NW Pacific, may produce a minor bump in surf heights along some exposed north and west facing shores of Kauai and Oahu on Thursday and Friday.

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.

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Data Courtesy of NOAA.gov