Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Mostly sunny with isolated showers. Highs around 87 near the shore to around 75 above 3000 feet. Northeast winds up to 10 mph shifting to the southwest in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows around 69 near the shore to around 58 above 3000 feet. East winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Monday: Mostly sunny. Isolated showers in the afternoon. Highs around 87 near the shore to around 75 above 3000 feet. Light winds. Chance of rain 20 percent.

South Kaua’i

Today: Mostly sunny with isolated showers. Highs 83 to 88. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 67. Northeast winds around 10 mph. Chance of rain 30 percent.

Monday: Mostly sunny with isolated showers. Highs 83 to 88. Light winds. Chance of rain 20 percent.

Kaua’i Mountains

Today: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs 74 to 81 in the valleys to around 65 above 4000 feet. Northeast winds around 10 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy with scattered showers. Lows 58 to 64 in the valleys to around 54 above 4000 feet. East winds around 10 mph. Chance of rain 50 percent.

Monday: Mostly sunny with isolated showers. Highs 75 to 82 in the valleys to around 66 above 4000 feet. Light winds becoming northeast around 10 mph in the afternoon. Chance of rain 20 percent.

North Kaua’i

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 78 to 86. Northeast winds around 10 mph. Chance of rain 30 percent.

Tonight: Partly cloudy with scattered showers. Lows 61 to 70. Southeast winds around 10 mph. Chance of rain 30 percent.

Monday: Mostly sunny with isolated showers. Highs 78 to 86. Northeast winds around 10 mph. Chance of rain 20 percent.

East Kaua’i

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 76 to 85. East winds around 10 mph. Chance of rain 30 percent.

Tonight: Mostly cloudy with scattered showers. Lows 59 to 71. Northeast winds around 10 mph shifting to the northwest after midnight. Chance of rain 40 percent.

Monday: Mostly sunny with isolated showers. Highs 77 to 86. East winds around 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Trade winds will weaken over the next two days as a low pressure system approaches the region from the north breaking down the high pressure ridge. Light to moderate trade winds are forecast today, becoming a land and sea breeze weather pattern with mountain and island interior clouds developing in the afternoon hours on Monday and Tuesday. The weather pattern shifts towards the wet side from Wednesday onward as a cold front drifts into the islands from the north. The timing of these showers will vary from day to day for each island and the highest rainfall amounts are expected to develop along the frontal cloud band. Gusty north to northeast winds will develop after the front passes and then slowly dissipates over the islands on Thursday.

Discussion

Fairly stable conditions persist over the region with just a few pop up showers drifting in on the moderate trade winds. Stable stratocumulus clouds are shown upstream of the Hawaiian Islands on satellite. A low pressure system currently moving into the Central Pacific will eventually bring wet weather to the region by Wednesday.
The short term weather forecast remains unchanged with light to moderate trade winds continuing today in a stable air mass limiting shower activity. The approaching low pressure system will weaken the subtropical ridge north of the islands producing light and variable winds on Monday and Tuesday. Local scale land and sea breezes will develop over each island in the absence of large scale trade winds. Onshore sea breezes and surface heating of the land will build clouds over mountains and island interior sections each day. Due to the stable conditions aloft our trade wind inversion heights will range from around 5,000 to 7,000 feet through Tuesday, allowing for more isolated shower activity over each island, favoring the afternoon to early evening hours.
Weather conditions trend wet and unsettled from Wednesday onward as a low pressure system forms just north of the region. This system will become cut off from the polar jet stream and drive a weakening cold frontal shower band into the islands on Wednesday. This low will then drift westward causing the forward motion of the front to stall out over the islands on Thursday. Clouds and showers will become more numerous along the frontal band as it stalls and weakens into a trough over the state. There are stark differences in our forecast guidance on where this stalled front lands, which means rainfall impacts for each island are less certain at this point in time. The northwestern islands of Kauai and Oahu show the highest potential for wet weather conditions, however Maui and Hawaii Counties are not out of the mix yet as previous model runs have shown these wet weather trends reaching as far southeast as the Big Island by Thursday and Friday.
These cut off lows are very challenging for long range model solutions to predict in the four to six day forecast window. Much of these wet weather impacts will depend on the final track of this cut off low. These run to run weather model differences are not unusual and are minimized by using a model blend approach. However, this also means we may see large changes in our island by island weather impacts for this time period. Stay tuned for changes to our extended range forecast over the next few days as the weather prediction time line grows shorter and our confidence improves.

Aviation

Moderate trades will gradually veer from northeasterly to a more easterly direction during the next 24 hours while focusing showers over windward and mauka zones. Limited moisture and prevailing high stability throughout this time will limit shower intensity and any instances of MVFR are expected to be brief.
No AIRMETs in effect.

Marine

No significant changes to the forecast with the morning package. High pressure to the northwest is moving to the east, and is expected to be far northeast of the state by Monday. The high will maintain light to locally moderate trade winds into tonight. A cold front approaching from the northwest on Monday will bring lighter winds out ahead of the front. The front may reach Kauai and possibly Oahu Wednesday. Stronger north to northeast winds are looking to return to the area behind the front, with winds possibly reaching Small Craft Advisory (SCA) levels. As the front weakens and drifts westward Friday, winds will become lighter across the area.
The current north swell will continue to to decline today. A new, moderate sized northwest swell (320-340 degrees) is expected to fill in later today, peaking at low end advisory levels tonight/early Monday, and then lower through Tuesday. As the swell hasn't yet hit the buoys to the northwest of the state, holding off on issuing the advisory at the moment, but anticipate it will likely be issued later today. A larger, but short period, north swell (360 degrees) is expected to arrive on Wednesday, around the same time as the above mentioned cold front arrives. This swell may bring low end advisory level surf to north facing shores Wednesday night and early Thursday, before lowering late Thursday through Saturday. It will also likely bring SCA level seas to exposed waters. Small background south swells (180 degrees) are expected through Tuesday, with a series of slightly larger long period south swells expected Wednesday through Saturday. With no significant trade wind flow over and upwind of the state, most surf along east facing shores will be from north swell wrap.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov