Photo Credit: Brendan Stephen

West Kaua’i

Today: Mostly sunny. Highs around 88 near the shore to around 76 above 3000 feet. East winds up to 15 mph.

Tonight: Partly cloudy. Lows 69 to 74 near the shore to around 60 above 3000 feet. Northeast winds up to 15 mph.

Wednesday: Mostly sunny. Highs around 88 near the shore to around 76 above 3000 feet. East winds up to 15 mph.

South Kaua’i

Today: Partly sunny. Breezy. Isolated showers in the morning. Highs around 85. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Breezy. Mostly cloudy with isolated showers. Lows 67 to 73. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Wednesday: Partly sunny. Breezy. Isolated showers in the morning. Highs around 85. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Kaua’i Mountains

Today: Mostly cloudy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 75 to 82 in the valleys to around 66 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 60 to 65 in the valleys to around 55 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday: Mostly cloudy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 75 to 82 in the valleys to around 66 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

North Kaua’i

Today: Partly sunny with isolated showers. Highs 78 to 87. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with isolated showers. Lows 63 to 73. East winds up to 15 mph shifting to the southeast after midnight. Chance of rain 20 percent.

Wednesday: Partly sunny with isolated showers. Highs 78 to 87. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

East Kaua’i

Today: Partly sunny with isolated showers. Highs 78 to 86. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with isolated showers. Lows 61 to 75. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Wednesday: Partly sunny with isolated showers. Highs 78 to 86. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Detailed Forecast

Update

The forecast has been updated to include a Wind Advisory for the Big Island Summits through 6 PM HST this evening.

Synopsis

Breezy trade winds will continue through midweek, then ease from Thursday into the weekend as the surface ridge weakens to the north. A dry airmass will limit rainfall chances through much of the week, with the best chances remaining over windward and mauka locations overnight through the morning periods. A slight increase in moisture associated with a mid- to upper-level disturbance could lead to better shower coverage later in the week and into the upcoming weekend.

Discussion

Short-term guidance shows dry trade wind conditions prevailing through midweek as a deep layer ridge remains in place. The overnight upper air soundings reflect this pattern, showing strong subsidence inversions around 5,000 to 6,000 ft with limited moisture available. Any brief showers that form will favor the typical windward and mauka locations, primarily during the overnight and early morning periods.
The mid- to upper-level ridge will begin to weaken during the second half of the week and into the upcoming weekend as a weak upper low settles north of Kauai and a mid-level trough approaches from the east. The surface ridge will respond by weakening, resulting in the trades easing to light to moderate levels. Upper-level height falls combined with increasing low-level moisture could lead to better windward shower coverage, especially over the weekend as the mid-level trough moves through from east to west. Additionally, a few showers could form over dry leeward areas during the afternoon where localized sea breezes develop.

Aviation

Moderate to locally breezy trades are expected through Wednesday. Mostly VFR conditions will prevail with brief periods of MVFR possible in the overnight to early morning hours along windward and mountain slopes.
AIRMET Sierra remains in effect for tempo mountain obscuration over north and east sections of Maui and the Big Island.
AIRMET Tango remains in effect for moderate turbulence over and immediately south through west of all island mountains due to the breezy trade winds.

Marine

A surface ridge north of the state will support moderate to locally strong trade winds through midweek. The ridge may weaken somewhat thereafter, with trade wind speeds slowly diminishing in response. A Small Craft Advisory (SCA) is posted for the typical windy waters around Maui and the Big Island through Wednesday. As the trades ease during the second half of the week, seas will also subside, and the SCA will go away.
The medium-period S swell of the past several days will trend lower today. Surf should return to background levels by Thursday along south facing shores. A small, longer period SSW swell should fill in on Friday and peak over the weekend with surf heights near or slightly above the summer average.
A small, short-period NNW swell will decline tonight into Tuesday night. Another small, short-period NNW swell may arrive around Thursday. Short-period wind waves will support small to moderate surf along E facing shores through Wednesday. Small, long-period E swells from increased E Pacific tropical cyclone activity may arrive (low confidence) from Wednesday onward, leading to a subtle increase in surf heights.

HFO Watches/Warnings/Advisories

Wind Advisory until 6 PM HST this evening for Big Island Summits.
Small Craft Advisory until 6 PM HST Wednesday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov