Photo Credit: Braden Jarvis

West Kaua’i

Today: Mostly sunny with isolated showers. Highs around 85 near the shore to around 73 above 3000 feet. Northeast winds up to 15 mph shifting to the southwest in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 68 to 73 near the shore to around 59 above 3000 feet. East winds around 10 mph. Chance of rain 50 percent.

Friday: Mostly sunny with isolated showers. Highs around 85 near the shore to around 73 above 3000 feet. East winds around 10 mph. Chance of rain 20 percent.

South Kaua’i

Today: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 82. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows 66 to 72. East winds 10 to 15 mph. Chance of rain 50 percent.

Friday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 82. East winds 10 to 15 mph. Chance of rain 70 percent.

Kaua’i Mountains

Today: Mostly cloudy. Showers in the morning, then numerous showers in the afternoon. Highs 72 to 79 in the valleys to around 63 above 4000 feet. East winds up to 15 mph. Chance of rain 80 percent.

Tonight: Mostly cloudy. Breezy. Numerous showers in the evening, then showers after midnight. Lows 59 to 64 in the valleys to around 54 above 4000 feet. East winds 10 to 20 mph. Chance of rain 80 percent.

Friday: Partly sunny. Frequent showers in the morning, then scattered showers in the afternoon. Highs 72 to 79 in the valleys to around 63 above 4000 feet. East winds 10 to 15 mph. Chance of rain 80 percent.

North Kaua’i

Today: Partly sunny with scattered showers. Highs 75 to 84. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 62 to 72. East winds 10 to 15 mph. Chance of rain 70 percent.

Friday: Partly sunny with scattered showers. Highs 75 to 84. East winds 10 to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 75 to 83. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with numerous showers. Lows 60 to 73. East winds 10 to 15 mph. Chance of rain 70 percent.

Friday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 75 to 83. East winds 10 to 15 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Moderate to breezy easterly trade winds will continue through early next week, with clouds and showers favoring windward and mauka locations. An upper level low will linger over the state through early next week, which will allow for some locally heavy showers over windward areas at times as occasional increases in low-level moisture embedded within the trades move into the islands.

Discussion

Surface high pressure remains about 1500 miles northeast of the island chain early this morning, which is driving moderate to breezy easterly trade winds across the islands. Minor fluctuations in trade wind speeds are to be expected for the next several days, as models depict the surface high weakening slightly through early Friday and then strengthening again slightly Friday through Saturday. Overall, however, the moderate to locally breezy trade wind flow will persist throughout the next few days.
Latest satellite imagery early this morning shows scattered showers are moving in on the trade wind flow, favoring windward and mauka areas. Upstream of the islands, a cluster of enhanced showers is located roughly 50 miles offshore and could further increase shower activity later this morning as it approaches closer to the state. Meanwhile, water vapor imagery shows a low aloft lingering near the islands. This upper low has been over the islands for the last several days but produced minimal impacts on island weather. However, as this feature continues to meander overhead, models suggest that it could deepen and move a bit further west over the next several days. This could also provide support for some enhanced trade wind showers through the rest of this week, though it will largely depend on occasional increases in low-level moisture moving in from the east. Also with the added moisture and instability, an isolated thunderstorm or two cannot be ruled out over the Big Island slopes Thursday afternoon.
For the weekend, the upper level low is expected to be centered near the western end of the state, which could produce unstable conditions into early next week. Details still remain uncertain, but some locally heavy showers will be possible for windward areas around the Sunday-Monday time frame.

Aviation

Moderate to breezy easterly trade winds will continue through the 24-Hr forecast period, with clouds and showers favoring windward and mauka locations as pockets of moisture move through. Expect some showers to carry over into leeward areas periodically due to a weak upper disturbance in the area, especially overnight through the morning hours. MVFR CIGS/VSBYS are possible in and around any showers that move through, and AIRMET Sierra can't be ruled out later this morning as a band of broken low clouds lurking upstream move in.
AIRMET Tango remains in effect for moderate low-level turbulence over and downwind of terrain of the eastern end of the state. This AIRMET will likely remain in place today.

Marine

Surface high pressure anchored roughly 1500 nm northeast of the islands will maintain moderate to strong easterly trade winds through the most of the coming week. A Small Craft Advisory (SCA) is in effect for the typically windier waters around Maui County and the Big Island through Friday night. The forecast keeps SCA conditions in these same waters into next week.
A pulse of south-southwest swell is producing surf near June average through tonight before slowly declining Thursday. A series of overlapping pulses of small, long- period south and south- southwest (170-220 degrees) swells will produce mainly background level surf along southern shores Friday through the middle of next week. Choppy, moderate surf will persist along east facing shores due to the trade winds locally, and upstream of the islands. An out-of- season, 3 to 5 foot medium period northwest swell generated by former Northwest Pacific Typhoon Guchol, which has transitioned into an extratropical storm is forecast to arrive this weekend. This swell will provide a boost to north and west shore surf well above June normal peaking Sunday and Monday, before declining Tuesday.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Saturday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov