Hilo

Today: Scattered showers, mainly before noon. Mostly sunny, with a high near 76. Light and variable wind becoming northeast 5 to 7 mph in the afternoon. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Occasional showers, mainly after midnight. Low around 60. North northeast wind around 5 mph becoming west southwest in the evening. Chance of precipitation is 80%. New precipitation amounts of less than a tenth of an inch possible.

Thursday: Scattered showers. Mostly cloudy, with a high near 75. West southwest wind 5 to 8 mph becoming northeast in the morning. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Kona

Today: Isolated showers after noon. Mostly sunny, with a high near 78. Calm wind becoming west 5 to 7 mph in the afternoon. Chance of precipitation is 20%.

Tonight: Scattered showers, mainly before midnight. Partly cloudy, with a low around 58. South southwest wind 5 to 7 mph becoming light and variable after midnight. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Thursday: Scattered showers after noon. Mostly cloudy, with a high near 77. Southwest wind 5 to 8 mph becoming calm in the afternoon. 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 sunny, with a high near 73. Breezy, with a northeast wind 17 to 20 mph, with gusts as high as 29 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers. Partly cloudy, with a low around 49. Breezy, with a northeast wind 13 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.

Thursday: Scattered showers. Mostly cloudy, with a high near 72. Breezy, with a northeast 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: Scattered showers. Mostly sunny, with a high near 69. Windy, with an east northeast wind 21 to 26 mph, with gusts as high as 38 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Showers likely, mainly after midnight. Partly cloudy, with a low around 42. Windy, with an east wind 18 to 23 mph, with gusts as high as 33 mph. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

Thursday: Scattered showers. Mostly cloudy, with a high near 68. Breezy, with an east northeast wind 11 to 20 mph, with gusts as high as 26 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

South Big Island

Today: Sunny, with a high near 78. Windy, with an east wind 22 to 25 mph, with gusts as high as 32 mph.

Tonight: Isolated showers. Partly cloudy, with a low around 66. Windy, with an east wind 18 to 24 mph, with gusts as high as 31 mph. Chance of precipitation is 20%.

Thursday: Isolated showers after noon. Mostly cloudy, with a high near 77. Windy, with an east northeast wind 17 to 23 mph, with gusts as high as 29 mph. Chance of precipitation is 20%.

Puna

Today: Showers likely, mainly before noon. Mostly sunny, with a high near 75. Northwest wind 8 to 10 mph becoming north northeast in the morning. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Occasional showers, mainly after midnight. Low around 58. North northeast wind 6 to 9 mph becoming west northwest in the evening. Chance of precipitation is 80%. New precipitation amounts between a tenth and quarter of an inch possible.

Thursday: Scattered showers. Mostly cloudy, with a high near 74. West northwest wind 7 to 9 mph becoming north northeast in the afternoon. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Waikoloa

Today: Sunny, with a high near 79. Windy, with a northeast wind 18 to 23 mph, with gusts as high as 33 mph.

Tonight: Isolated showers between 7pm and 1am. Partly cloudy, with a low around 58. Breezy, with a northeast wind 11 to 20 mph, with gusts as high as 26 mph. Chance of precipitation is 20%.

Thursday: Isolated showers after 1pm. Increasing clouds, with a high near 78. Breezy, with an east wind 9 to 17 mph becoming north northwest in the afternoon. Winds could gust as high as 24 mph. Chance of precipitation is 20%.

Detailed Forecast

Synopsis

Breezy trades will persist today, then lower to moderate levels Thursday and Friday. Fairly typical trade wind weather will persist through Thursday, with showers favoring windward and mauka areas, particularly at night and into the early morning hours. A surface trough will develop in the vicinity of the islands Thursday night, then slowly shift westward Friday and Friday night. This will bring wet trade wind conditions particularly to windward sections of the smaller islands. As the trough shifts westward, a more typical but slightly wetter than normal trade wind pattern will return over the weekend, with trades increasing back to breezy levels. The trades will strengthen to windy levels early next week, with the wetter than normal trade wind conditions persisting.

Discussion

Currently at the surface, a 1042 mb high is centered around 1700 miles northwest of Honolulu, and is driving moderate to breezy trades across the island chain early this morning. Infrared satellite imagery shows a band of clouds moving through the region resulting in mostly cloudy conditions across much of the state, although some decrease in cloud cover is already evident over much of Maui County behind the cloud band. Radar imagery shows scattered to numerous showers moving through Kauai and Oahu, as well as windward sections of the Big Island, with only a few showers with the trades blowing a few showers into leeward sections affecting windward sections of Maui. Main short term concerns revolve around trade wind trends and rain chances during the next couple days.
High pressure northwest of the islands will gradually weaken as it settles southeastward during the next few days. Breezy trades are expected today, with the trades then diminishing to moderate levels Thursday through Friday. A weak surface trough will develop in the vicinity of the islands on Friday, then shift westward Friday night as a new strong 1040+ mb high builds north of the state. This strong high will slowly settle southeastward through early next week, with breezy conditions expected over the weekend, and windy conditions developing for the first half of the next week.
As for the remaining weather details, fairly typical trade wind weather will prevail through Thursday, with showers favoring windward and mauka areas, particularly at night and through the early morning hours. We should see things dry out nicely behind the band of clouds and showers early this morning, paving the way for a really nice day with only a few windward showers. Another band of clouds and showers which can be seen in satellite imagery further upstream to the northeast of the state, appears on track to move through the islands tonight bringing another increase in shower coverage. Expect conditions to dry out similarly on Thursday, although quite a bit of high cloud cover will be overspreading the islands as an upper level trough digs to the northwest of the state.
A weak surface trough will develop in the vicinity of the islands Thursday night along the tail end of an old front. This surface trough will then slide slowly westward Friday and Friday night. Moisture from the surface trough combined with added instability from the trough aloft will lead to an increase in shower coverage and intensity across the islands during this time, with the potential for some locally heavy rainfall over windward areas. At the moment, the deepest moisture appears to target the smaller islands, particularly Kauai and Oahu. Once the surface trough shifts west of the state, we should see a fairly typical but slightly wetter than normal trade wind pattern develop for the weekend, which will continue into early next week.

Aviation

Early this morning, a band of clouds and showers has been moving across the state. This has resulted in brief periods of moderate to heavy rain and MVFR level clouds for Oahu and Kauai. As a result, AIRMET Sierra was issued to account for tempo mountain obscuration for Oahu and Kauai this morning, though clouds and showers are expected to begin breaking up over the next few hours.
A surface high to the northwest of the state will continue to support breezy to locally strong easterly trade winds today, but speeds will gradually wane. AIRMET Tango remains in effect for moderate to severe low-level turbulence near and downwind of mountains, as well as moderate mid-level turbulence between FL220 and FL300. With winds expected to east throughout the day, AIRMET Tango for surface winds greater than 30kts for Maui and the Big Island will likely be allowed to expire later this morning.

Marine

The Gale Warning for Alenuihaha and Pailolo channels, Maalaea Bay and for waters south of the Big Island has been downgraded to a Small Craft Advisory (SCA). This SCA, along with the SCA in effect for all other waters, will remain in effect through this afternoon due to a combination of strong trade winds and elevated seas. The SCA may be scaled back briefly to typically windy waters around Big Island and Maui County tonight. Building high pressure to the northwest of the state will boost trades first over waters west of Kauai, then across remaining waters Thursday into the weekend. This may warrant an expansion and continuation of the SCA.
Large trade wind-driven seas will maintain east shoreline surf at or above the 8 foot High Surf Advisory (HSA) threshold through this afternoon. As trade winds over and upstream of the islands weaken, surf along east facing shores will decrease, becoming small by Thursday. Increasing trade wind swell and an arriving northerly swell at the end of this week and into the weekend will provide a bump in east shoreline surf.
A northwest swell will begin arriving this afternoon and evening, peaking surf along north and west-facing shores late Thursday into Friday. The secondary north swell will arrive Friday and, in addition to the returning trade wind swell wrap, may boost surf heights to, or slightly above, HSA heights from the end of this week into the weekend.
Surf along south-facing shores continues to pull in some trade wind swell wrap, with an expected decline today with the easing trades. A southwest swell will fill in late today through Thursday before slowly declining through the weekend, which will keep south shore surf from going flat.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST this evening for Kauai Windward, Oahu Koolau, Olomana, Molokai Windward, Maui Windward West, Windward Haleakala, South Big Island, Big Island North and East.
Small Craft Advisory until 6 PM HST this evening for all Hawaiian waters,

Data Courtesy of NOAA.gov