Photo Credit: Braden Jarvis

West Kaua’i

Today: Sunny. Highs around 82 near the shore to around 70 above 3000 feet. Light winds.

Tonight: Mostly clear. Lows around 68 near the shore to around 57 above 3000 feet. Light winds.

Friday: Sunny. Highs around 81 near the shore to around 69 above 3000 feet. Light winds.

South Kaua’i

Today: Mostly sunny with isolated showers. Highs around 81. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 64 to 69. Northeast winds around 10 mph. Chance of rain 40 percent.

Friday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 80. East winds around 10 mph. Chance of rain 30 percent.

Kaua’i Mountains

Today: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 69 to 77 in the valleys to around 64 above 4000 feet. Northeast winds around 10 mph in the morning becoming light. Chance of rain 40 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 57 to 62 in the valleys to around 51 above 4000 feet. Light winds. Chance of rain 40 percent.

Friday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 68 to 76 in the valleys to around 63 above 4000 feet. Light winds. Chance of rain 40 percent.

North Kaua’i

Today: Mostly sunny with scattered showers. Highs 74 to 81. Northeast winds around 10 mph. Chance of rain 40 percent.

Tonight: Partly cloudy with scattered showers. Lows 60 to 69. Light winds. Chance of rain 40 percent.

Friday: Mostly sunny with scattered showers. Highs 73 to 80. Light winds. Chance of rain 40 percent.

East Kaua’i

Today: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 74 to 81. Northeast winds around 10 mph. Chance of rain 40 percent.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 58 to 70. Northeast winds around 10 mph in the evening becoming light. Chance of rain 40 percent.

Friday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 73 to 80. Light winds. Chance of rain 40 percent.

Detailed Forecast

Synopsis

Light to moderate trade winds will strengthen somewhat over the weekend, bringing a few brief windward showers. Increasing moisture and strengthening southeast winds may bring more showers next week.

Discussion

High pressure passing far N of the islands will settle far NE of the area this weekend, supporting gentle to moderate NE winds today that will become E on Friday. Some strengthening of the trade wind flow is expected over the weekend as persistent low pressure to the distant ENE dissipates. With a mid-level ridge prevailing overhead and near-normal PWAT expected, rainfall will be limited, and most likely over windward slopes and coasts. One exception will be over the upper slopes of Mauna Loa ans surrounding areas, where the lava- induced extreme heating of the atmosphere may lead to the occasional development of pyrocumulonimbus clouds.
Early next weeek, a strong ridge aloft well W of the area will allow for the downstream development of a large cutoff low, roughly along the longitude of the islands. Latest guidance indicates the low will develop just W of the islands, then drift W. This would lead to a strengthening of the ridge aloft over the islands, and a relatively strong surface high pressure cell to the NE that will support locally strong E-SE trade winds. Depending on the eventual location of the low, associated convergence bands could bring increased showers to the W end of the island chain by the middle of next week.

Aviation

A high pressure system building in from the north will slowly increase trade wind speeds into the moderate range through Friday. Afternoon sea breezes will still hang on along terrain sheltered slopes of all islands. Brief passing showers are possible over windward airfields of the smaller islands with more numerous showers expected along the windward Big Island slopes over the next 24 hours.
No AIRMETs in effect with possible MVFR conditions along the windward Big Island slopes due to clouds and SHRA.

Marine

Large surface high pressure north of the islands will maintain moderate trade winds through late today. Combined seas may near Small Craft Advisory thresholds today as a large northwest swell fills in through the day. As this high sinks southeastward, moderate trades will veer more easterly Friday and persist well into next week. An approaching cold front from the northwest may hang up just west of the state early next week and veer winds more south of east.
A large, long period west northwest (300-310 degree) swell will build in today, peak tonight and Friday morning and then gradually fall Friday night into the weekend. Long period forerunners have been arriving at the Hanalei nearshore buoy this morning with the northwest offshore buoys observing a steady rise in the 16-18 second bands. This swell is expected to be large enough to increase north and west-facing shore surf, due to the more westerly swell direction, to High Surf Advisory (HSA) levels on the main islands (except Big Island) today. This swell may push north and west surf heights up to near High Surf Warning (HSW) thresholds at its peak tonight through Friday morning. This west northwest swell may sneak into Big Island's western waters Friday and increase the odds for placing their west-facing shores within a HSA. A northeast swell moving into our nearshore windward waters Saturday may also lift north and east-facing shore surf across many islands to near HSA levels over the weekend.

HFO Watches/Warnings/Advisories

High Surf Advisory for North and West facing shores of Niihau Kauai Oahu and Molokai and for North facing shores of Maui until 6 pm HST Friday.

Data Courtesy of NOAA.gov