Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 82 near the shore to around 68 above 3000 feet. East winds up to 15 mph. Chance of rain 40 percent.

Tonight: Partly cloudy. Isolated showers after midnight. Lows around 67 near the shore to around 56 above 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Thursday: Partly sunny with isolated showers in the morning, then mostly sunny in the afternoon. Highs around 80 near the shore to around 68 above 3000 feet. East winds around 10 mph. Chance of rain 20 percent.

South Kaua’i

Today: Breezy. Partly sunny with scattered showers. Highs around 79. East winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 63 to 68. East winds 10 to 15 mph. Chance of rain 40 percent.

Thursday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 79. East winds 10 to 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Partly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 71 to 77 in the valleys to around 61 above 4000 feet. East winds up to 20 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows 56 to 61 in the valleys to around 50 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Thursday: Partly sunny with scattered showers. Highs 67 to 75 in the valleys to around 62 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

North Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 73 to 81. Southeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 59 to 68. East winds 10 to 15 mph. Chance of rain 40 percent.

Thursday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 72 to 79. East winds around 10 mph. Chance of rain 50 percent.

East Kaua’i

Today: Partly sunny with scattered showers. Highs 72 to 80. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 57 to 69. East 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 72 to 79. East winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Breezy to locally windy easterly trade winds will continue through tonight and then ease Thursday in the gentle to local breezy range. Trade wind showers will primarily focus over more windward and mauka slopes with an occasional showers passing into leeward areas. A front will approach the state from the far northwest Friday through the weekend further easing winds to light to gentle range and veering winds out of a more southeasterly direction. Showers will focus over exposed windward and mauka areas and along interior areas as sea breezes develop each afternoon, and clear overnight and early morning with land breezes.

Discussion

A 1032 mb surface high 1050 miles northwest of Kauai is producing breezy to locally windy easterly trades. Stable conditions are evident in satellite imagery as a broad field of scattered shallow stratocumulus blankets the Hawaiian Islands along the southwestern periphery of the surface high. Morning soundings show an inversion heights around 5 kft for Lihue and 7 kft for Hilo with precipitable water vapor measurements near to slightly below normal. Radar imagery shows scattered light to moderate showers embedded in the trade wind flow mainly focusing over windward and mauka areas with an occasional shower spilling over to leeward zones. Modest rainfall totals were recorded overnight with 12 hour totals ranging from 0.01 – 0.5 inches.
The surface high will drift southeastward along its general eastern trek and weaken over the next couple of days, resulting in a slowly weakening pressure gradient. This will ease regional winds to more gentle speeds, with locally breezy conditions Thursday. Shower activity will primarily follow typical tradewind shower pattern with showers favoring windward and mauka areas with and occasional shower spilling over into leeward areas at times, especially during the overnight and early morning hours. Shower frequency may increase slightly tonight and Thursday night as upper level troughing and slightly higher available moisture upstream of the state invigorates some trade showers that will advect over the state. In addition, model guidance shows the inversion gradually eroding Thursday through the weekend which could allow for deeper clouds to form with slightly higher rain rates. However total rainfall amounts will remain modest.
Late Friday and over the weekend trades will ease to light to gentle range and shift out of the southeast as a front approaches the state from the distant northwest. During this transition, some showers will focus on exposed windward areas, in addition, onshore sea breezes for the more sheltered regions will allow for interior and mauka clouds and showers to develop each afternoon and clear overnight and early morning as land breezes take over. Dewpoints will climb to near to slightly above normal as more moisture is advected over the state with the southeasterly flow. A weak frontal boundary will push over the state early next week which may also increase cloud and shower activity slightly ahead of the front. Light northerly winds will briefly fill in behind the front. Another, stronger, front is forecast to move across the state middle to late next week.

Aviation

Breezy to locally windy easterly trades will continue through the TAF period with low clouds and isolated to scattered showers favoring windward and mauka areas. Cloud and shower coverage will be greatest through the early morning hours, with some light showers spilling over into leeward areas of the smaller islands. Expect mainly VFR conditions with brief MVFR possible under passing showers.
AIRMET Tango for moderate lee turbulence below 8,000 ft remains in effect for areas over and downwind of all island terrain through at least tonight, with winds starting to slowly weaken over the next several days.

Marine

High pressure far northeast of the state continues to produce strong easterly trade winds across the coastal waters this morning. These strong trades, their resulting large wind waves, and slowly declining northwest and northeast swells are all contributing to rough seas and Small Craft Advisory (SCA) conditions across most coastal waters. Models show a combination of elevated seas and strong winds will likely continue throughout this afternoon. Therefore, the SCA remains in effect through 6 PM HST this evening for all waters except for Kauai and Oahu leeward waters. Strong trade winds will gradually weaken tonight through the rest of the week as the high pressure weakens and eventually shifts east-southeast.
Large easterly wind waves and a diminishing northeast (040 deg) swell continue to produce advisory level surf along east facing shores this morning. Although the northeast swell will gradually ease over the next 24 hours and wind waves will also slowly decrease as wind speeds ease, advisory level surf will linger through this afternoon for east facing shores. Therefore, the High Surf Advisory (HSA) remains in effect until 6pm HST this evening. Surf is expected to drop below HSA threshold by tonight. Small to moderate surf along north and west facing shores will continue to slowly decline as a northwest (310 deg) swell continues to diminish.
Models show that another significant northwest swell will move into the region Friday into the weekend. Surf could approach near advisory levels for exposed north and west facing shores on Friday.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST this evening for east facing shores of Kauai Oahu Molokai Maui and the Big Island.
Small Craft Advisory until 6 PM HST this evening for Kauai Northwest Waters, Kauai Windward Waters, Kauai Channel, Oahu Windward Waters, Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov