Photo Credit: Brendan Stephen

West Kaua’i

Today: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny in the afternoon. Highs around 87 near the shore to around 77 above 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Partly cloudy. Breezy. Lows 70 to 75 near the shore to around 61 above 3000 feet. East winds up to 20 mph.

Wednesday: Mostly sunny. Breezy. Highs around 87 near the shore to around 77 above 3000 feet. East winds up to 20 mph.

South Kaua’i

Today: Partly sunny. Breezy. Numerous showers in the morning. Highs around 86. East winds 10 to 20 mph. Chance of rain 70 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Scattered showers. Lows 68 to 74. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Wednesday: Breezy. Mostly cloudy with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 86. Northeast winds 15 to 25 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Mostly cloudy. Breezy. Frequent showers early in the morning, then scattered showers in the late morning and afternoon. Highs 73 to 81 in the valleys to around 70 above 4000 feet. East winds 10 to 20 mph. Chance of rain 80 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then showers likely after midnight. Lows 61 to 66 in the valleys to around 56 above 4000 feet. East winds up to 25 mph. Chance of rain 70 percent.

Wednesday: Breezy. Partly sunny with scattered showers. Highs 73 to 81 in the valleys to around 70 above 4000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

North Kaua’i

Today: Mostly cloudy with scattered showers. Highs 76 to 86. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 64 to 74. East winds 10 to 15 mph shifting to the southeast after midnight. Chance of rain 50 percent.

Wednesday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 76 to 86. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

East Kaua’i

Today: Mostly cloudy. Numerous showers early in the morning, then scattered showers late in the morning. Isolated showers in the afternoon. Highs 75 to 86. East winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows 62 to 75. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday: Mostly cloudy in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs 75 to 86. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Moderate trade winds will steadily increase later today through the rest of the week as a weak trough near Kauai moves away and the surface ridge strengthens to the north. Showers will favor windward and mauka locations, particularly through the overnight and early morning hours as areas of moisture move through. Although dry conditions will persist over our leeward areas, an occasional brief shower may hold together.

Discussion

Guidance remains in decent agreement and shows a return of strong and gusty trades beginning later today into Wednesday, in the wake of a weak surface trough moving through the western end of the state this morning. A decent-sized area of moisture and low clouds (precipitable water values up around 1.4 inches) accompanying this trough supports scattered showers, mostly over windward and mauka locations. Accumulations from these showers should remain light, with only a few brief showers reaching our dry leeward areas. Drier air has already begun to reach the Big Island this morning and will continue spreading westward as the trough moves away from the area today.
A weak mid- to upper-level trough approaching on Wednesday will move through from east to west late Wednesday night through early Friday. This, combined with the gusty trades, could lead to another period of enhanced windward and mauka shower coverage. For the extended period, the surface ridge will remain strong to the north, which supports the gusty trades holding through early next week.

Aviation

Locally breezy trade winds will strengthen to moderate to strong by this evening. AIRMET Tango for lee side turbulence will be needed later today.
Bands of showers off the Pacific passing over the islands will impact mainly the western half of of the state this morning. Drier conditions expected in the afternoon and evening, but showery weather should return to windward slopes and coasts early Wednesday.

Marine

The Pailolo Channel and Maui windward waters were added to the Small Craft Advisory (SCA) this morning due to the latest high resolution model data. Otherwise, little change to the forecast.
A broad ridge remains north of the state and is expected to strengthen over the next several days. Expect winds to increase to moderate to locally strong levels over the next couple of days, and then remain elevated into the weekend. The SCA is in effect for the typical windier areas around Maui and the Big Island, along with the Pailolo Channel and Maui windward waters. Additional areas may need to be added Wednesday as the ridge continues to strengthen.
The current small south-southeast swell will slowly decline this week, while a small, long period south-southwest swell fills in early Tuesday. This will maintain small surf along the south facing shores for much of the week. A storm-force low pressure system southeast of New Zealand will send a decent run of south swells beginning this weekend. Resultant surf heights may reach advisory thresholds of 10 feet along south facing shores during its peak Sunday into Monday. Rough, choppy surf along east facing shores will steadily increase during the middle to second half of the week in response to the building trade winds upstream of the state. Surf along north and west facing shores will remain nearly flat.

HFO Watches/Warnings/Advisories

Wind Advisory until 6 AM HST Wednesday for Big Island Summits.
Small Craft Advisory until 6 AM HST Thursday for Kaiwi Channel, Maui County Windward Waters, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov