Photo Credit: Brendan Stephen

West Kaua’i

Today: Breezy. Mostly sunny with isolated showers. Highs around 86 near the shore to around 74 above 3000 feet. East winds 15 to 25 mph with gusts to 50 mph. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows around 69 near the shore to around 59 above 3000 feet. East winds 15 to 25 mph with gusts to 50 mph. Chance of rain 50 percent.

Friday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 85 near the shore to around 71 above 3000 feet. East winds 15 to 20 mph with gusts to 45 mph. Chance of rain 50 percent.

South Kaua’i

Today: Windy. Partly sunny with scattered showers. Highs 79 to 86. East winds 20 to 30 mph with gusts to 50 mph. Chance of rain 50 percent.

Tonight: Windy. Mostly cloudy with scattered showers. Lows around 69. East winds 20 to 30 mph. Chance of rain 50 percent.

Friday: Partly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 78 to 84. East winds 20 to 25 mph with gusts to 45 mph. Chance of rain 70 percent.

Kaua’i Mountains

Today: Windy. Partly sunny with scattered showers. Highs 72 to 80 in the valleys to around 63 above 4000 feet. East winds 20 to 30 mph with gusts to 50 mph. Chance of rain 50 percent.

Tonight: Windy. Mostly cloudy with numerous showers. Lows around 65 in the valleys to around 57 above 4000 feet. East winds 20 to 30 mph. Chance of rain 70 percent.

Friday: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 70 to 78 in the valleys to around 62 above 4000 feet. East winds 20 to 25 mph with gusts to 45 mph. Chance of rain 70 percent.

North Kaua’i

Today: Breezy. Partly sunny with scattered showers. Highs 74 to 86. East winds 15 to 25 mph with gusts to 50 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows 63 to 72. East winds 15 to 25 mph with gusts to 45 mph. Chance of rain 70 percent.

Friday: Partly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 73 to 85. East winds 15 to 25 mph. Chance of rain 70 percent.

East Kaua’i

Today: Breezy. Partly sunny with scattered showers. Highs 71 to 83. East winds 20 to 25 mph with gusts to 50 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows 63 to 72. East winds 15 to 25 mph with gusts to 45 mph. Chance of rain 70 percent.

Friday: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 69 to 81. East winds 20 to 25 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

A very strong high pressure system north of the state will maintain strong and gusty trade winds through Friday. Periods of showers will favor typical windward and mountain areas, with a few showers drifting into leeward areas at times. Trade wind speeds will decrease into the moderate to breezy range this weekend. A slight drying trend remains in the forecast through the first half of next week.

Discussion

In the larger synoptic scale weather pattern, a very strong high pressure system around 1050 mb remains north of the Hawaiian Islands producing windy and gusty trade winds through Friday. A cutoff low lingers around 900 miles northwest of Kauai this evening with little impacts to island weather. Small bands of unstable looking cumulus clouds are drifting into the windward mountain slopes of each island producing passing showers over these areas. Shower activity will favor the overnight to early morning hours, with some of the stronger showers drifting into leeward areas at times. This windy and fairly wet trade wind weather pattern will continue into Friday. Wind speeds are strong enough to keep a Wind Advisory in effect for the windier areas of each island. This advisory currently runs through later this afternoon. However, these stronger trade winds may linger into Friday for some of the windier zones and the current Wind Advisory may need to be extended in time to cover these areas.
The high center will weaken and drift south over the weekend. Trade wind speeds will weaken this weekend, becoming moderate to breezy trade winds by Sunday. A cold front approaching the islands from the north early next week will break down the high pressure ridge north of the island chain, weakening the wind speeds for next week Monday and Tuesday.
Current long range model solutions show this weakening cold frontal cloud band sweeping into the islands from the north by the middle of next week. This passing front should bring another round of enhanced showers to all islands by the middle to end of next week. Trade winds will increase yet again after the frontal band passes through each island.

Aviation

Robust high pressure north of the state will continue to drive breezy to windy trades during the next couple days. MVFR cigs/vsbys will affect windward slopes and coasts at times, with a few decaying showers reaching leeward areas where VFR conditions should prevail.
AIRMET Sierra remains in effect for mountain obscuration over windward Kauai, Oahu, Molokai, Maui and Big Island. Conditions should improve on the smaller islands later this morning, but may linger through much of the day on the Big Island.
AIRMET Tango remains in effect for low level turbulence over and downwind of the terrain of all islands. This AIRMET is expected to continue for at least the next couple days.

Marine

Strong to gale-force easterly trade winds will prevail for the next couple days as an exceptionally strong 1052 mb high, currently about 1200 nm north of the islands, drifts south and gradually weakens. The Gale Warning for the windier areas around Maui and the Big Island has been extended through Friday afternoon, with a Small Craft Advisory (SCA) in effect elsewhere. As the high weakens further, trades will decline during the weekend, though SCA conditions should persist for all waters through at least Saturday. Winds will continue to decline early next week, and the SCA could be dropped entirely.
Large, trade wind generated seas will dominate for the next several days, contributing to the need for a SCA. Measurements at the NOAA and PacIOOS buoys have been holding between 11 and 14 ft overnight, and these seas continue to be dominated by trade wind swell of 10 to 13 feet at 10 seconds, and is expected to hold around here for the next couple of days. A High Surf Advisory remains in effect for east facing shores of most islands through Friday, though the elevated surf could linger into Saturday. As trade winds ease this weekend, the rough east shore surf will gradually decline, and the trade wind swell will fall to around April average Monday or Tuesday. A 4 foot, medium- period north- northeast swell mixed in with the trade wind swell seems to be on track with peaking early this morning then trending down late morning and afternoon. For southern shores, small pulses of medium- period south- southeast swell and long- period southwest swell may arrive this weekend.

Fire weather

Long-term conditions over leeward areas are drier than normal for this time of year. Though the Keetch-Byram Drought Index, measured in Honolulu, will remain well below the critical 600 mark this week, the strong and gusty trade winds will elevate the fire danger over the drier leeward areas through Friday.

HFO Watches/Warnings/Advisories

Wind Advisory until 6 PM HST this evening for windier areas of each island.
High Surf Advisory until 6 PM HST Friday for exposed east facing shores.
Small Craft Advisory until 6 AM HST Saturday for all Hawaiian Coastal Waters outside of the Gale Warning areas.
Gale Warning until 6 PM HST Friday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov