Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 80 to 85 near the shore to around 72 above 3000 feet. Northeast winds around 10 mph shifting to the southwest in the afternoon. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers. Lows 66 to 71 near the shore to around 59 above 3000 feet. Light winds becoming northeast around 10 mph after midnight. Chance of rain 20 percent.

Saturday: Sunny with isolated showers. Highs 81 to 86 near the shore to around 73 above 3000 feet. East winds 10 to 15 mph decreasing to up to 10 mph in the afternoon. Chance of rain 20 percent.

South Kaua’i

Today: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 79 to 85. Northeast winds around 10 mph shifting to the southeast in the afternoon. Chance of rain 40 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows around 68. Light winds becoming northeast around 10 mph after midnight. Chance of rain 40 percent.

Saturday: Partly sunny with scattered showers. Highs 80 to 85. East winds 10 to 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 73 to 79 in the valleys to around 65 above 4000 feet. Southeast winds around 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 61 to 66 in the valleys to around 57 above 4000 feet. Light winds becoming east around 10 mph after midnight. Chance of rain 50 percent.

Saturday: Partly sunny with scattered showers. Highs 74 to 80 in the valleys to around 66 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

North Kaua’i

Today: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 74 to 82. Southeast winds around 10 mph shifting to the northeast in the afternoon. Chance of rain 50 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 62 to 71. Light winds becoming east around 10 mph after midnight. Chance of rain 40 percent.

Saturday: Mostly sunny with scattered showers. Highs 76 to 84. East winds 10 to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 74 to 83. North winds around 10 mph shifting to the east in the afternoon. Chance of rain 50 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 62 to 73. Light winds becoming east around 10 mph after midnight. Chance of rain 50 percent.

Saturday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 74 to 84. East winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Light winds and humid conditions will prevail today. The light winds will allow afternoon sea breezes to drive the formation of a few showers, some briefly heavy, over the islands this afternoon. Light to moderate trade winds will bring increasingly settled weather tonight into Saturday, with just a few windward showers expected. Winds will veer to the southeast Sunday and Monday, but a mostly dry weather regime will continue. A front is expected to move over the islands Tuesday into Thursday, bringing the potential for southerly winds and increased showers that may persist for several days.

Discussion

Early morning regional satellite imagery shows overcast mid- and high-level clouds over the Big Island, with partly cloudy to mostly clear skies over the remainder of the islands. Strong thunderstorm clusters that were over Hawaiian Offshore waters N and SW of the islands yesterday evening have all but diminished, with a small cell persisting about 175 miles SW of South Point. Radar shows a few showers over near shore waters SW and W of Maui and the Big Island, with light returns associated with the cloud deck over the Big Island. Otherwise, a mostly dry night/morning is ongoing, although a thunderstorm briefly dropped heavy rain over parts of leeward Kohala overnight. Overnight sounding data shows a strengthened subsidence inversion at PHTO based near 5000', while the PHLI sounding showed a strong ground-based inversion due to radiational cooling, but an otherwise somewhat unstable profile. Water vapor imagery continues to highlight cyclonic flow aloft over the area, associated with a trough axis near Kauai that extends well N of the islands.
A weakening surface low about 700 miles N of Oahu had an associated surface trough that extended toward the island chain, but it has dissipated overnight. Light and variable winds persist over most areas, except for light E to SE winds near the Big Island. Trade winds will strengthen from E to W across the chain as a ridge near the islands moves N and strengthens, supported by a strong high centered to the distant NW. However, light winds are expected to persist today. A mostly dry morning will feature some lingering high clouds near the Big Island, with developing sea breezes bringing the potential for cloud and shower formation over island interiors in the afternoon. Lingering moisture and instability will bring the potential for some briefly heavy showers.
Light to moderate trade winds are expected to be strongest on Saturday as the ridge strengthens. On Sunday and Monday, another low and front (now near the Date Line) will slowly approach from the NW, forcing the ridge to move close to Kauai – leading to gradually weakening and veering SE winds that may allow localized land and sea breezes to develop. Weak mid-level ridging is expected to limit shower coverage this weekend as PWAT diminishes and a subsidence inversion strengthens, with windward slopes the most likely recipient of a few brief showers.
On Tuesday and Wednesday, latest guidance indicates the front will move over the islands, bringing the potential for southerly winds and increased shower coverage/intensity. The potential exists for another cut-off low to develop NW of the islands thereafter, which would keep a shower-supporting front and/or a convergence boundary in the vicinity of the islands into the following weekend.

Aviation

A cold front north of the state will continue to generate shower and thunderstorm activity far north of the islands. Isolated showers still remain possible further south, over the forecast area, though not expecting anything widespread.
With light flow in place, land breezes should persist through early this morning. Sea breeze development early this afternoon will likely lead to showers over the islands interior and higher terrain.
No AIRMETs are currently in effect.

Marine

Surface ridging will build north of the state today and tonight, allowing trade winds to return from east to west across the island chain. The trades will reach moderate levels across the entire marine area by daybreak Saturday, then become locally strong over the weekend as the ridge lifts a bit further north. The windier zones around Maui and the Big Island will likely reach Small Craft Advisory (SCA) thresholds during this time. The trades will be on the decrease by Sunday night as a front approaches from the west, with light to moderate southeasterly winds, strongest over the eastern islands, expected for the first half of next week.
A mix of small, medium period northwest swells will keep some small surf rolling into north and west facing shores through Saturday. A small longer period northwest swell will build on Sunday, giving a more noticeable boost to north shore surf Sunday night and Monday. This swell will then lower Tuesday with only small surf expected Wednesday. A new medium period northwest swell could give a slight boost to north and west shore surf late next week.
Surf along east facing shores will hold steady today and tonight, with a slight boost expected over the weekend as trades strengthen over and upstream of the islands. East shore surf will then change little through the middle of next week, remaining at below normal levels. A long period northeast swell could give east shore surf a more noticeable boost late next week.
Only background south swell energy is expected through late next week.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov