Photo Credit: Braden Jarvis

West Kaua’i

Rest Of Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs around 83 near the shore to around 73 above 3000 feet. Northwest winds up to 10 mph shifting to the east around 10 mph in the afternoon. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers. Lows 62 to 67 near the shore to around 53 above 3000 feet. Northeast winds around 10 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 83 near the shore to around 73 above 3000 feet. Northeast winds around 10 mph. Chance of rain 50 percent.

South Kaua’i

Rest Of Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs around 81. Light winds becoming east around 10 mph in the afternoon. Chance of rain 40 percent.

Tonight: Mostly cloudy with isolated showers. Lows 60 to 66. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Tuesday: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 81. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Kaua’i Mountains

Rest Of Today: Mostly sunny with isolated showers in the morning, then mostly cloudy with numerous showers in the afternoon. Highs around 76 in the valleys to around 65 above 4000 feet. North winds up to 10 mph. Chance of rain 60 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 56 in the valleys to around 48 above 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 30 percent.

Tuesday: Mostly cloudy. Scattered showers in the morning, then numerous showers in the afternoon. Highs around 76 in the valleys to around 65 above 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

North Kaua’i

Rest Of Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 76 to 82. North winds up to 10 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 56 to 65. Northeast winds 10 to 15 mph. Chance of rain 30 percent.

Tuesday: Partly sunny with scattered showers. Highs 76 to 82. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

East Kaua’i

Rest Of Today: Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 74 to 80. Light winds becoming northeast around 10 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 54 to 67. North winds around 10 mph. Chance of rain 30 percent.

Tuesday: Partly sunny with scattered showers. Highs 74 to 80. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

A front will reach Kauai tonight, then move eastward down the island chain before stalling near Maui on Wednesday. Remnant moisture will linger across the central islands through the end of the week as the front dissipates. Light winds will shift to northeasterlies after frontal passage. The highest potential for rainfall will occur during frontal passage, but light winds will trigger increased clouds and showers across mauka areas each afternoon, especially across sheltered areas.

Discussion

Persistent troughing to our north has put a dent in the subtropical ridge, keeping the pressure gradient slack and winds rather light across the main Hawaiian Islands this morning. Local land breezes dominated overnight, clearing skies across the islands. Expect increased cloud and shower coverage across mauka areas this afternoon with the onset of sea breezes. Satellite loop shows scattered low clouds to clear skies across the smaller islands, with scattered to patchy broken low clouds lingering across southeast Big Island slopes. Radar shows scant shower coverage, with the bulk of this noted within cloud cover around the Big Island and across waters around Kauai.
Models show a front northwest of Kauai will reach that island tonight, then move slowly eastward down the island chain before stalling near Maui on Wednesday. Residual associated moisture will linger across the central islands through the rest of the forecast period as the front dissipates. Expect increased frontal showers on Kauai late today, around Oahu on Tuesday, then across Maui County and/or the Big Island during the latter half of the week. A short-lived period of light north northeast trades will build in behind the front on Tuesday, mainly over Kauai and Oahu. Away from the front, light winds will allow development of sea breezes, triggering increases in cloud and shower coverage across mauka areas during afternoon and early evening hours. Land breezes will bring clearing each night away from the front. Light to moderate east northeast trade flow will gradually reach the islands as the front dissipates toward next weekend.

Aviation

A weak cold front just west of Kauai early this morning, will slowly push across the western islands through tonight. This pattern will eventually increase northeast flow across Kauai and vicinity later today and tonight, while maintaining light and variable winds over the central smaller islands, with light east to southeast winds continuing over the eastern end of the state.
Showers will increase in areal coverage across the western end of the state today in advance of the approaching boundary. Otherwise, the weak pressure gradient in place will generate sea breezes and interior clouds/showers across the central smaller islands again this afternoon.
Mainly VFR conditions are expected across TAF locations through today. However, MVFR cigs and vsby are possible later today, continuing the potential need of AIRMET Sierra for tempo mountain obscuration across some locations.

Marine

A northeast to southwest oriented surface ridge extends from a surface high pressure system centered far northeast of state down to near Maui County early this morning. Elsewhere, the leading edge of a band of broken low clouds with embedded towering cumulus clouds and scattered heavy showers associated with a weak front is just northwest of Kauai. The close proximity of this frontal boundary, which is moving slowly toward the southeast, and the surface ridge near the central islands continues to disrupt the pressure gradient across the area. As a result, light and variable winds prevail over the waters adjacent to Kauai and Oahu, while light southeast winds are over most of the waters in the vicinity of Maui County and Big Island.
The forecast guidance shows the surface ridge will linger just northeast or east-northeast of Maui and the Big Island into mid- week. The weak front will eventually push down over the western islands from later today and tonight through Tuesday, as a new surface high builds in far northwest of the state. The arrival of the weak frontal boundary will likely result in light to moderate northeast winds developing from this afternoon into Wednesday for most of the waters adjacent to Kauai and Oahu. However, the surface ridge will keep the winds relatively weak near Maui County and the Big Island into mid-week. The frontal boundary will eventually dissipate when it stalls near the central islands by late Wednesday. The surface high is also expected to dissipate far north of the area by Thursday, which will cause the winds to weaken across all Hawaiian waters that day. By Friday, the forecast models indicate a new surface high pressure system will build far north of the area, which will likely result in strengthening trade winds heading into next weekend.
A medium-period northwest (320 degrees) swell has arrived in the islands early this morning. Forerunners from this swell initially arrived at the National Data Buoy Center buoys northwest of Kauai late Sunday afternoon. This swell, which appears to be 1 to 2 feet above the wave model guidance, will spread down across the state today. This will likely produce somewhat elevated surf along most exposed north and west facing shores later today when it peaks. This northwest swell will gradually lower from Tuesday into mid- week. A small northwest (310 degrees) swell may arrive around Thursday / Friday, while a small north-northwest (330-340 degrees) swell may spread over the area next weekend.
The current small, medium-period south (190 degrees) swell will gradually subside through Tuesday. The wave model guidance suggests there may be a small, reinforcing south (180-190 degrees) swell around mid-week. Elsewhere, the lack of significant trade winds in the vicinity of, or upstream of, the smaller islands will keep minimal surf along most east facing shores this week. However, moderate surf may persist into early Tuesday along east facing shores of the Big Island due to an upstream fetch of light to locally moderate east-southeast winds.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov