Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Breezy. Mostly sunny with isolated showers. Highs around 84 near the shore to around 74 above 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening, then scattered showers after midnight. Lows 67 to 72 near the shore to around 58 above 3000 feet. Northeast winds up to 20 mph. Chance of rain 50 percent.

Thursday: Breezy. Mostly sunny with isolated showers. Highs around 85 near the shore to around 75 above 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

South Kaua’i

Today: Partly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 82. Northeast winds 10 to 25 mph increasing to 20 to 25 mph in the afternoon. Chance of rain 60 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 65 to 71. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Thursday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 83. Northeast winds 15 to 25 mph. Chance of rain 40 percent.

Kaua’i Mountains

Today: Partly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 77 in the valleys to around 66 above 4000 feet. East winds 10 to 20 mph. Chance of rain 60 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows around 61 in the valleys to around 53 above 4000 feet. East winds up to 20 mph. Chance of rain 60 percent.

Thursday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 78 in the valleys to around 67 above 4000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 40 percent.

North Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs 77 to 83. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 61 to 70. East winds up to 15 mph. Chance of rain 60 percent.

Thursday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 78 to 84. East winds up to 20 mph. Chance of rain 40 percent.

East Kaua’i

Today: Mostly cloudy with numerous showers in the morning, then mostly sunny with scattered showers in the afternoon. Highs 75 to 81. Northeast winds 10 to 15 mph. Chance of rain 60 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 59 to 72. Northeast winds 10 to 15 mph. Chance of rain 60 percent.

Thursday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 76 to 82. Northeast winds 10 to 20 mph. Chance of rain 40 percent.

Detailed Forecast

Synopsis

An unstable upper low southwest of Kauai will continue to drift away from the state. Stable trade wind weather has returned under an upper level ridge building over the state. Shower trends will increase just a bit this weekend, as another weak upper low forms just northeast of the Hawaiian Islands. Trade winds will continue to blow across the region through much of next week with periods of passing showers.

Discussion

Satellite imagery this morning shows the upper low southwest of Kauai drifting farther away from the islands. Radar imagery shows scattered to numerous showers developing across the local area. Shower intensities are in the light to moderate range as more stable conditions have returned to the region due to a building ridge aloft. A subtropical jet stream shown on the satellite water vapor channel outlines this upper ridge and is producing extensive high clouds across the region.
The current weather forecast remains on track with more stable trade winds expected across the state through Friday under the upper level ridge. Trade wind temperature inversion heights are around 7,000 feet elevation as shown by the 2 AM HST Lihue upper air balloon sounding. Model cross sections over the region show this inversion height will range from 5,000 to 7,000 feet limiting cloud heights and shower activity. Brief passing showers are possible mainly over windward and mountain areas with the highest shower coverage forecast from the overnight to early morning hours. Easterly trade winds will become locally breezy in wind favored areas through Thursday.
A subtle change in the more typical trade wind weather pattern will start this weekend as yet another weak upper low develops along a narrow upper trough just northeast of the Hawaiian Islands on Saturday. Instability from this low will lift the trade wind inversion heights by 1,000 to 2,000 feet, just enough to slightly increase shower coverage across the region. These showers will also favor windward and mountain areas and increase over most locations during the overnight to early morning hours.
In the extended outlook, easterly trade winds will continue at least through the first half of next week in typical trade wind weather pattern for this time of year.

Aviation

High pressure northeast of the state will keep moderate to breezy trade winds in place during the next 24+ hours. A drier more stable airmass will keep showers limited primarily to windward slopes and coasts. Lingering mid-level instability could allow for the development of a thunderstorm or two over the Big Island slopes this afternoon however.
AIRMET Sierra remains in effect for windward sections of Kauai. This AIRMET will likely remain in place through mid to late morning before being canceled. AIRMET Tango remains in effect for moderate upper level turbulence over the entire state, and will likely remain in place through the night. See SIGMET Papa series for severe turbulence area. AIRMET Tango may also be needed for moderate low level turbulence over and downwind of the terrain later this morning.

Marine

Trade winds have returned due to high pressure building far northeast of the state, and should hold through the weekend. Small Craft Advisory (SCA) level winds (25 kt) will persist over the windier waters from Oahu to the Big Island through at least Thursday.
Surf along east facing shores will remain up due to the trades locally and upstream of the state. Guidance shows this holding each day through the rest of the week.
The quiet conditions across the northern Pacific continue this week with minimal swell and nearly flat surf anticipated for north and west facing shores, with the exception of some trade wind energy wrapping into north shores. For the extended, there is a potential for a short/medium-period northerly swell that would arrive locally early next week and linger through midweek.
For south facing shores, guidance supports the small conditions continuing for the foreseeable future, with mainly background energy moving through.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Thursday for Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov