Photo Credit: Jason Weingardt

West Kaua’i

Today: Mostly sunny. Isolated showers in the afternoon. Highs around 83 near the shore to around 70 above 3000 feet. Northeast winds around 10 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Isolated showers in the evening. Lows around 68 near the shore to around 57 above 3000 feet. Northeast winds around 10 mph. Chance of rain 20 percent.

Thursday: Sunny with isolated showers. Highs around 82 near the shore to around 70 above 3000 feet. East winds around 10 mph in the morning becoming light. Chance of rain 20 percent.

South Kaua’i

Today: Mostly sunny. Isolated showers in the afternoon. Highs around 82. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 64 to 69. Northeast winds 10 to 15 mph. Chance of rain 30 percent.

Thursday: Mostly sunny with isolated showers. Highs around 81. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Kaua’i Mountains

Today: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 70 to 78 in the valleys to around 64 above 4000 feet. Northeast winds around 10 mph. Chance of rain 40 percent.

Tonight: Partly cloudy with isolated showers. Lows 57 to 62 in the valleys to around 51 above 4000 feet. Northeast winds around 10 mph. Chance of rain 20 percent.

Thursday: Partly sunny with scattered showers. Highs 69 to 77 in the valleys to around 64 above 4000 feet. Northeast winds up to 10 mph. Chance of rain 40 percent.

North Kaua’i

Today: Mostly sunny. Isolated showers in the afternoon. Highs 75 to 82. Southeast winds around 10 mph shifting to the northeast in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 60 to 69. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Thursday: Mostly sunny with isolated showers. Highs 74 to 81. Northeast winds around 10 mph. Chance of rain 20 percent.

East Kaua’i

Today: Mostly sunny. Scattered showers in the afternoon. Highs 74 to 82. Northwest winds around 10 mph shifting to the northeast in the afternoon. Chance of rain 40 percent.

Tonight: Mostly cloudy with scattered showers. Lows 58 to 70. Northeast winds 10 to 15 mph. Chance of rain 30 percent.

Thursday: Mostly sunny with isolated showers. Highs 74 to 81. Northeast winds around 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Light winds and mostly dry weather are expected this morning, with some patchy high clouds. Light to moderate trade winds will return later today, and will then continue into the weekend, bringing just a few windward showers. The exception will be on the Big Island, where lingering moisture will support greater shower coverage the next day or two, and possibly a thunderstorm. High clouds will diminish statewide the next couple of days, but may increase again over the weekend.

Discussion

Light and variable winds have led to the development of land breezes over the islands, which has precluded any overnight rainfall in most areas. The exception is windward Big Island, where radar shows a few showers moving ashore. Radar also has been detecting some returns associated with the ongoing eruption atop Mauna Loa, where some lightning was briefly observed overnight. Morning sounding data show that a moist and relatively unstable air mass persists over the Big Island, with a somewhat drier and more stable air mass over Kauai.
Surface high pressure will build to the distant N of the islands today, while a persistent area of low pressure lingers to the NE of the area. For the islands from Kauai to Maui, NE trade winds will strengthen slightly today and tonight, then remain light to moderate into Thursday before becoming easterly Friday as the low moves further E. Little overall change is expected over the weekend, although wind speeds may increase slightly. The NE trade winds will bring limited moisture as surface dew points lower, with just a few windward showers expected. Winds may be light enough to allow localized afternoon sea breezes to drive some leeward cloud formation, but little rainfall. As for the Big Island (and maybe windward Maui), lingering deep moisture and weak surface convergence associated with the distant low will keep showers a little more active the next couple of days, with a slight chance of thunderstorms over windward waters this morning. Decreasing moisture is expected to lower rain chances by Friday, continuing into the weekend. High clouds are expected to thin over the next couple of days, but may increase again over the weekend.
Forecast confidence is diminished after the weekend as a strongly meridional flow aloft develops. A blocked flow pattern is expected to develop, potentially leading to the development of a closed low along the longitude of the islands. While there is some consensus as to the low's development, guidance has been inconsistent as to its eventual location, which has big implications as to the details of the local forecast. For now, a continuation of trade wind weather is forecast, but changes are likely.
With Mauna Loa's emissions emanating at high elevations (around 10- 13 kft), the forecast does not anticipate vog or other volcanic emissions having a significant impact on lower elevation populated areas of the Big Island, or the other islands. We will continue to monitor this dynamic situation for any potential changes to the forecast philosophy.

Aviation

Other than a few areas over and just east of the Big Island, shower activity is quite minimal early this morning, due in part to the land breezes that developed in the light wind flow overnight. A slow transition back toward trade wind flow is expected through the day today, though some interior and leeward areas may still see brief sea breezes and afternoon clouds. Mainly VFR conditions are expected through the TAF period, with isolated MVFR conditions possible in any showers, most likely around the Big Island. No AIRMETs are currently in effect or expected through tonight.

Marine

A ridge of high pressure slowly building north of the state will bring the return of light to moderate northeast trade winds today. Winds will strengthen slightly on Thursday and veer to a more easterly direction, but will remain at gentle to moderate speeds through the weekend as the ridge becomes further established far north of the state.
The current long-period west-northwest swell (310 degrees) will gradually decline today. Therefore the High Surf Advisory (HSA) has been canceled. A larger, west- northwest (300 degrees) swell is expected to build Thursday into Friday and will produce surf heights well above the advisory threshold and possibly reaching borderline warning thresholds along most north and west facing shores. Due to the westerly angle, this larger swell could see surf heights reach HSA thresholds for west Big Island on Friday.
Surf along east facing shores will remain small through the next several days as winds remain light. A rise is expected over the weekend as a moderate northeast swell fills in. A tiny southwest swell is possible along south facing shores today. Otherwise, only background energy from the south is expected through the rest of the week.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov