Photo Credit: Braden Jarvis

West Kaua’i

Today: Sunny and breezy. Isolated showers in the morning. Highs around 84 near the shore to around 73 above 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Tonight: Mostly clear with isolated showers. Lows 66 to 72 near the shore to around 59 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Thursday: Sunny. Isolated showers in the morning. Highs around 84 near the shore to around 73 above 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

South Kaua’i

Today: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 77 to 85. Northeast winds 15 to 20 mph. Chance of rain 40 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 71. Northeast winds 15 to 20 mph. Chance of rain 40 percent.

Thursday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 77 to 85. Northeast winds 15 to 20 mph. Chance of rain 40 percent.

Kaua’i Mountains

Today: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs 71 to 80 in the valleys to around 63 above 4000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 61 to 69 in the valleys to around 57 above 4000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Thursday: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs 71 to 80 in the valleys to around 63 above 4000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

North Kaua’i

Today: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 73 to 85. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 40 percent.

Tonight: Partly cloudy with scattered showers. Lows 62 to 72. East winds 10 to 15 mph. Chance of rain 40 percent.

Thursday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 73 to 84. East winds 10 to 15 mph. Chance of rain 40 percent.

East Kaua’i

Today: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 70 to 83. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 64 to 74. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Thursday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 71 to 83. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Strong trades will focus showers over windward and mauka areas through tomorrow, particularly for the eastern end of the state. Trades then ease for the weekend and into next week with limited shower activity.

Discussion

Current radar and satellite imagery show isolated to scattered showers moving into windward and mauka areas across the island chain this morning, with a focus on windward Big Island. Temperature inversion heights as seen on this morning's upper air soundings are high enough to allow for some showers to spill over to leeward areas at times. Looking upstream, this shower activity should continue through the morning hours with the focus remaining on the eastern end of the state.
The main focus for this forecast remains on the strengthening trade winds in response to the high pressure ridge building to our north and a mid to upper level low southeast of the islands deepening and migrating westward, remaining south of the islands through the end of the week. Guidance still points to winds peaking today into tonight at breezy to strong levels across the state when the pressure gradient is expected to be at its strongest, particularly for the eastern half of the state. A Wind Advisory is in effect for the typical windier areas of the Big Island and portions of Maui County and has been extended through tonight based on the latest model guidance. This Wind Advisory may need to be expanded to include portions of Oahu today, but confidence is low on those zones reaching criteria, so have chosen to not include them at this time. A High Wind Warning for the Big Island Summits remains in effect through 6 PM HST today, but elevated winds will likely continue into tonight, so it may need to be extended or a Wind Advisory may be needed to cover the overnight hours.
Otherwise, a fairly dry and stable trade wind pattern will persist for the western end of the state with temperature inversion heights measured around 6000 feet at Lihue this morning and little moisture upstream of Kauai and Oahu. For the rest of the state, greater trade wind shower activity can be expected over the next couple of days. This will be due to a combination of the proximity of the upper level low moving westward to our south, and deeper moisture edging up from the south into the eastern end of the state. As such, this will raise the inversion locally and enhance shower activity, particularly tonight through Friday.
Then heading into the weekend and early next week, trade winds will be on the decline as the low south of the island dissipates and a series of fronts passing to our north weaken the surface ridge. In addition, drier air will filter across the region, putting a damper on trade wind shower activity.

Aviation

AIRMET Tango remains in effect for both low-level turbulence to the lee of the mountains across the state, and for strong surface winds east of Molokai. Both of these are expected to remain in effect into Thursday due to the high pressure north of the islands. Models show an area of upper level turbulence to the east of the island early this morning. Ellrod guidance suggests the turbulence is decreasing, and will be monitoring the situation over the next few hours to determine if an upper level AIRMET is needed.
Clouds and showers riding in on the trades will continue to focus showers over the windward sides of the islands, with isolated MVFR conditions. At this time no widespread mountain obscuration is expected.

Marine

Strong high pressure over the Central North Pacific will hold through Thursday then gradually weaken. Easterly trade winds will be at their strongest through Thursday morning then gradually decline Thursday night and Friday. The Gale Warning for Maalea Bay, the Pailolo and Alenuihaha Channels, and waters south of the Big Island will remain in effect through tomorrow afternoon. A Small Craft Advisory remains in effect for the remaining waters where winds will still be fresh to strong and seas are expected to hover near the 10 foot mark.
Surf along north and west-facing shores has begun to subside. The High Surf Advisory (HSA) for north and west facing shores of Niihau, Kauai, Oahu, and Molokai, and north facing shores of Maui, has been cancelled. North and west shore surf will remain elevated through Friday then decline over the weekend.
Surf along south-facing shores will return to seasonal normals today. A small southeast bump in surf is possible later today through tomorrow for windward Big Island due to a small southeast reinforcement, but this will have little effect elsewhere.
Surf along east-facing shores will rise through Thursday in response to the strong trade winds. Lower surf is expected for the weekend.

Fire weather

Gusty trades will be accompanied by slightly drier conditions today and tomorrow compared to yesterday. Afternoon relative humidity (RH) values may briefly dip below 50%, but the probability of reaching the fire weather threshold of 45% appears low. No fire weather headlines anticipated at this time.

HFO Watches/Warnings/Advisories

Wind Advisory until 6 AM HST Thursday for Lanai Mauka, Kahoolawe, Maui Windward West, Maui Leeward West, Kohala, Big Island Interior, Lanai Windward, Lanai Leeward, Lanai South, Maui Central Valley North, Maui Central Valley South, South Haleakala, Big Island South, Big Island Southeast, Big Island North.
High Wind Warning until 6 PM HST this evening for Big Island Summits.
Small Craft Advisory until 6 PM HST Thursday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Big Island Windward Waters.
Gale Warning until 6 PM HST Thursday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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