Photo Credit: Brendan Stephen

West Kaua’i

Today: Windy. Sunny with isolated showers. Highs around 76 near the shore to around 64 above 3000 feet. Northeast winds 10 to 30 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Windy. Lows around 65 near the shore to around 54 above 3000 feet. Northeast winds 10 to 30 mph.

Friday: Mostly sunny. Highs around 77 near the shore to around 65 above 3000 feet. Northeast winds 10 to 15 mph decreasing to up to 15 mph in the afternoon.

South Kaua’i

Today: Windy. Mostly sunny with isolated showers. Highs around 75. Northeast winds 20 to 30 mph. Chance of rain 20 percent.

Tonight: Windy. Partly cloudy with isolated showers. Lows 61 to 66. Northeast winds 25 to 30 mph decreasing to 15 to 25 mph after midnight. Chance of rain 20 percent.

Friday: Mostly sunny. Breezy. Isolated showers in the morning. Highs around 76. Northeast winds 15 to 20 mph. Chance of rain 20 percent.

Kaua’i Mountains

Today: Windy. Partly sunny with scattered showers. Highs 63 to 71 in the valleys to around 58 above 4000 feet. Northeast winds 10 to 30 mph. Chance of rain 50 percent.

Tonight: Windy. Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 54 to 59 in the valleys to around 48 above 4000 feet. Northeast winds 25 to 35 mph decreasing to 15 to 30 mph after midnight. Chance of rain 50 percent.

Friday: Partly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 65 to 73 in the valleys to around 59 above 4000 feet. Northeast winds 15 to 20 mph. Chance of rain 40 percent.

North Kaua’i

Today: Windy. Mostly sunny with scattered showers. Highs 68 to 75. Northeast winds 10 to 30 mph. Chance of rain 40 percent.

Tonight: Windy. Mostly cloudy with isolated showers. Lows 57 to 66. East winds 10 to 30 mph. Chance of rain 20 percent.

Friday: Mostly sunny in the morning then becoming partly sunny. Breezy. Isolated showers. Highs 70 to 77. East winds 10 to 20 mph. Chance of rain 20 percent.

East Kaua’i

Today: Windy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 68 to 75. Northeast winds 15 to 20 mph increasing to 15 to 30 mph in the afternoon. Chance of rain 40 percent.

Tonight: Windy. Mostly cloudy with isolated showers. Lows 55 to 67. Northeast winds 25 to 30 mph decreasing to 15 to 25 mph after midnight. Chance of rain 20 percent.

Friday: Partly sunny in the morning then becoming mostly sunny. Breezy. Isolated showers. Highs 69 to 77. Northeast winds 15 to 20 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A cold front will push across Big Island this morning. Rather wet conditions can be expected along and immediately behind the front as it moves through, particularly along windward slopes and coasts. Behind the front, windier, drier, and cooler conditions will overspread the state. A more typical trade wind pattern will briefly return Friday through the weekend as winds ease to breezy level and moisture gradually increases. Locally windy trades may return early next week.

Discussion

A band of showers and low clouds associated with a passing cold front, is now moving over the Big Island. Some showers continue to produce rainfall rates up to 0.5 inches an hour but the majority of the showers are producing lesser amounts mainly focused along windward and mauka areas. Windy to very windy conditions have been observed overnight behind the front and expected to continue through today.
The forecast is on track showing the robust high far north- northwest of the state drifting eastward. In addition, a surface low far north of the state continues to sag southward. This will tighten the pressure gradient over the state again today, resulting in a secondary, brief, increase in wind speeds. The strongest winds are expected over and downwind of mountains, through valleys and channels. A High Wind Warning has been issued for Lanai and windier areas of the Big Island through tonight. A wind advisory remains in effect for all remaining lower elevations through tonight.
A cooler and much drier airmass is filling in over the state behind the front. Dewpoints have already dipped down into the 50s over Kauai and Oahu. Dewpoints will continue to drop in the 50s for the rest of the state by this afternoon. Below normal dewpoints and ambient high temperatures struggling to reach 80 degrees will make for seemingly cooler than normal temperatures today into the weekend. Chances of showers will be limited due below normal moisture availability, however low clouds will still ride in with the trades and focus over windward and mauka areas.
As the strong high north of the islands settles southward closer to the state Friday, winds will shift out of the east- northeast. The high will also begin to gradually weaken through weekend allowing wind speeds ease to locally breezy Saturday. The airmass will moisten up some late Sunday into early next week, allowing for more normal trade wind weather to return. The high north of the islands is forecast to strengthen again early next week, that may boost trade wind speeds to locally windy levels.

Aviation

The cold front will continue to gradually move across the Big Island this morning bringing widespread clouds and showers to mainly windward areas. This will result in periods of MVFR in SHRA. Post-frontal conditions over Maui County and areas west will continue to improve through the morning as a dry air mass settles over the region. Given improving conditions will likely be able to drop AIRMET Sierra for mountain obscuration over most of the smaller islands. However, will also need to issue AIRMET Sierra for windward Big Island later this morning as conditions start to deteriorate.
Windy trades will continue to impact all islands through today, with gusts greater than 30 kt possible at times. The strong winds will continue to lead to low-level turbulence downwind of island terrain so AIRMET Tango remains in effect through today.

Marine

A cold front will exit the Big Island and push south of the coastal waters this morning, while high pressure builds north of the state. Strong to Gale force northeast trade winds are expected across the marine area through tonight, with the strongest winds expected over the windier areas around Maui and the Big Island. The trades should ease into the fresh to strong range for the weekend as the high to the north weakens. The high will then restrengthen early next week, with the trades responding and ramping up to strong and near Gale force levels.
The Gale Warning for the windier zones around Maui County and the Big Island has been extended through 6 am Friday, and it is possible it may need to be extended through Friday. The Gale Warning for the remaining waters has been cancelled and replaced with a Small Craft Advisory. This SCA now covers all waters not in the Gale Warning, through 6 am Saturday. The SCA will likely need to be extended for portions of the marine area through early next week.
The High Surf Advisory has been cancelled as surf has dropped below advisory thresholds. A new long period northerly swell will then fill in tonight, likely sending north shore surf back up to advisory levels through Friday. North shore surf will then show a slow decline over the weekend. A small long period northwest swell will move through Monday through the middle of next week.
A building northeast swell is expected to fill in late Sunday and Sunday night, with surf likely building to advisory levels along east facing shores for Monday, potentially holding above the advisory threshold through the middle of next week. Some wrap into north facing shores will likely occur with this swell as well. South shore surf will remain tiny through the weekend, with a small boost possible Monday through the middle of next week as a small long period south-southwest swell moves through.

HFO Watches/Warnings/Advisories

High Wind Warning until 6 AM HST Friday for Lanai South, Big Island Southeast, Big Island North.
Wind Advisory until 6 AM HST Friday for all remaining lower elevations not in the High Wind Warning.
Gale Warning until 6 AM HST Friday for Maui County Leeward Waters, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.
Small Craft Advisory until 6 AM HST Saturday for all remaining waters not in the Gale Warning.

Data Courtesy of NOAA.gov