Photo Credit: Brendan Stephen

West Kaua’i

Today: Mostly sunny in the morning then becoming partly sunny. Highs around 79 near the shore to around 69 above 3000 feet. East winds up to 15 mph shifting to the southeast in the afternoon.

Tonight: Partly cloudy. Lows around 68 near the shore to around 62 above 3000 feet. Northeast winds up to 15 mph.

Wednesday: Mostly sunny in the morning then becoming partly sunny. Highs around 80 near the shore to around 70 above 3000 feet. East winds up to 15 mph shifting to the southeast in the afternoon.

South Kaua’i

Today: Partly sunny. Isolated showers in the morning. Highs around 77. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with isolated showers. Lows around 68. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Wednesday: Partly sunny. Isolated showers in the morning. Highs around 78. East winds 10 to 15 mph. Chance of rain 20 percent.

Kaua’i Mountains

Today: Mostly cloudy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 68 to 73 in the valleys to around 60 above 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 61 to 66 in the valleys to around 59 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Wednesday: Mostly cloudy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 69 to 74 in the valleys to around 61 above 4000 feet. Southeast winds up to 15 mph. Chance of rain 50 percent.

North Kaua’i

Today: Partly sunny with isolated showers. Highs 70 to 79. Southeast winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with isolated showers. Lows 63 to 69. Southeast winds up to 15 mph. Chance of rain 20 percent.

Wednesday: Partly sunny with isolated showers. Highs 71 to 80. Southeast winds up to 15 mph. Chance of rain 20 percent.

East Kaua’i

Today: Mostly cloudy with isolated showers. Highs 69 to 78. Northeast winds up to 10 mph shifting to the east in the afternoon. Chance of rain 20 percent.

Tonight: Mostly cloudy with isolated showers. Lows 59 to 70. East winds up to 15 mph. Chance of rain 20 percent.

Wednesday: Mostly cloudy with isolated showers. Highs 70 to 79. East winds up to 15 mph shifting to the southeast in the afternoon. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Moderate east to southeast trades will continue through midweek, with the best rainfall chances remaining over windward and mauka locations through the overnight and early morning periods. Increasing moisture and a return of breezy easterly trades will support better windward shower coverage later in the week through the weekend.

Discussion

Guidance remains in good agreement and shows surface high pressure to the north weakening and shifting to an area northeast of the state today through Wednesday as a front passes far to the north and deep low pressure begins to set up to the west. The low-level flow will respond and veer out of the east-southeast while holding at moderate levels. The dry and stable conditions associated with deep layer ridging over the state will limit windward shower coverage, with the best chances overnight through the morning hours. Increasing cloud coverage along with a few afternoon showers can't be ruled out over leeward areas where localized sea breezes form.
Although forecast confidence lowers Thursday through the weekend due to persistent differences shown within the guidance, all generally depict a moistening trend as deep low pressure evolves to the west and drifts eastward toward the islands. The tightening pressure gradient between this feature and strong high pressure building to the north will lead to breezy easterly trades returning. This moistening trend combined with a band of low-level moisture associated with an old front moving in from the northeast over the weekend will support increasing rainfall chances across windward and mauka locations, with some showers spilling over into leeward sections of the smaller islands.

Aviation

High pressure northeast of the state will maintain light to moderate easterly trade winds during the next 24 hours, with some localized land and sea breezes possible in the more sheltered areas. Rather dry conditions will prevail, with a few light showers affecting windward and mauka areas at times. Predominantly VFR conditions are expected to prevail.
No AIRMETs are in effect and none are expected today.

Marine

Surface high pressure north of the state will slowly weaken and move eastward today. East to southeast winds will slowly decline but remain fresh to locally strong. The Small Craft Advisory (SCA) is in effect for the typical windy waters around the Big Island and Maui through Wednesday. The combination of another high building far north of the islands and low pressure developing far to the west will likely bring increasing east to east-southeast trade winds by late Wednesday and Thursday. Stronger winds are possible this weekend.
A small to moderate long period northwest swell (320 to 330 degrees) will build down the island chain today. Long period forerunners is already underway at the nearshore PacIOOS 51201. This swell is expected to have continued reinforcements through Friday although all below High Surf Advisory (HSA) levels. A medium period north (360 to 010 degrees) swell will continue to decline through Wednesday. This declining swell is still producing moderate surf along most north and exposed east facing shores.
A similarly sized northwest swell and a small north-northeast swell are possible this upcoming weekend. East shores will experience some wrapping north swell through Tuesday, followed by moderate, short period wind swell through Friday and potentially higher seas this weekend. South shores will remain seasonably small.

HFO Watches/Warnings/Advisories

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

Data Courtesy of NOAA.gov