Photo Credit: Braden Jarvis

West Kaua’i

Today: Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 79 to 84 near the shore to around 73 above 3000 feet. East winds up to 10 mph shifting to the south in the afternoon. Chance of rain 20 percent.

Tonight: Mostly cloudy with isolated showers. Lows 66 to 71 near the shore to around 59 above 3000 feet. Light winds. Chance of rain 20 percent.

Thursday: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 78 to 83 near the shore to around 71 above 3000 feet. Southeast winds around 10 mph. Chance of rain 50 percent.

South Kaua’i

Today: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs around 83. Southwest winds up to 10 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with isolated showers. Lows around 67. Light winds. Chance of rain 20 percent.

Thursday: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 81. Northeast winds around 10 mph shifting to the southeast in the afternoon. Chance of rain 30 percent.

Kaua’i Mountains

Today: Mostly sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 73 to 79 in the valleys to around 67 above 4000 feet. Light winds. Chance of rain 30 percent.

Tonight: Partly cloudy. Lows 59 to 66 in the valleys to around 57 above 4000 feet. Light winds becoming southwest up to 10 mph after midnight.

Thursday: Mostly sunny in the morning, then mostly cloudy with showers likely in the afternoon. Highs 71 to 77 in the valleys to around 65 above 4000 feet. Southeast winds around 10 mph. Chance of rain 60 percent.

North Kaua’i

Today: Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 74 to 82. Light winds. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 61 to 69. Light winds. Chance of rain 20 percent.

Thursday: Mostly sunny with isolated showers in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 73 to 81. Light winds. Chance of rain 50 percent.

East Kaua’i

Today: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 75 to 85. South winds up to 10 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy. Lows 61 to 71. Southwest winds up to 10 mph in the evening becoming light.

Thursday: Partly sunny. Scattered showers in the afternoon. Highs 72 to 82. Light winds. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Land and sea breezes will continue over the smaller islands through Thursday afternoon. The chance for afternoon showers across island interiors will increase each day. Isolated thunderstorms are possible around Kauai as well as across portions of the Big Island Thursday and Friday as an upper trough moves by. Moderate trade winds may return early next week.

Discussion

There is no change in forecast philosophy from last evening. A weak surface trough northwest of the main Hawaiian Islands has put a dent in the subtropical ridge which normally drives trade wind flow across the state. As a result, the pressure gradient across the islands is rather slack and winds are light enough to allow local land and sea breeze development. Our airmass remains rather dry and stable this morning, limiting shower development. Radar shows very little shower activity, with only light isolated showers noted across southeast sections of the Big Island. Satellite loop shows scattered low clouds to clear skies almost everywhere outside showery areas. A large area of broken stable low clouds persists over leeward waters west of the Big Island. Except for a bit more moisture moving in to fuel afternoon cloud cover and showers, expect the current pattern to continue into Thursday.
Models show deepening southwesterly flow aloft Thursday and Friday in response to a shortwave trough advancing through the area. This will push the weak surface trough northwest of the state closer to the islands where it will stall near Kauai. Associated prefrontal moisture will provide fuel for increased shower coverage and intensity. Winds will remain light through Thursday as southeasterlies persist but are blocked by the Big Island. Interior showers should get a boost Thursday afternoon as southwesterly flow aloft and height falls associated with the advancing shortwave trough destabilize our airmass. Thunderstorms are possible across leeward and interior portions of the Big Island Thursday and Friday afternoon, with the better chance being on Friday. Thunderstorms are also possible on and around Kauai, where deeper moisture will reside on Thursday night. Elsewhere, land breezes will maintain quiet conditions overnight Thursday. Models show southerly flow at the surface by late Friday with stability already on the rebound as the upper trough departs. This increased stability will begin to cap shower potential during this time, but increased showers may still occur over leeward portions of Oahu and Kauai Friday night and, for Kauai, Saturday as well. Expect moderate trades to return by Monday, focusing clouds and showers over windward and mauka areas.

Aviation

A weak surface ridge just north of the area will maintain a light southeast wind flow today. Mostly sunny skies (VFR conditions) this morning will transition to sea breezes late morning with low clouds and light showers developing this afternoon over island interiors. Some of these clouds may result in brief mountain obscurations. An area of moisture south of Hawaii will lift northwest and potentially impact the western end of the state this evening and tonight. No AIRMETs are currently in effect.

Marine

No significant changes to the marine forecast with the morning package, and no change in the forecast philosophy. Weak high pressure will remain in place near the islands over the next several days. Meanwhile, a couple weak frontal boundaries will clip the northern offshore waters, before a stronger front approaches the northwest offshore waters Friday, and pushes through the northern offshore waters over the weekend. Some isolated thunderstorms are possible over the northern offshore waters as these boundaries move through. There is a chance for some thunderstorms entering the coastal waters Thursday night and Friday with these initial weaker boundaries. Details still to be determined about the threat for thunderstorms in the coastal waters this weekend.
Ahead of these boundaries the background flow is from the east- southeast. Winds will be light and variable over the waters near Kauai and Oahu, and a touch stronger out of the east-southeast over the waters near Maui County and the Big Island. Little change is expected in the winds until Friday when the winds will increase a bit out of the southeast across the coastal waters. Moderate to fresh southeast to south winds are forecast to develop ahead of an approaching front Friday and Saturday, with light to moderate trades potentially filling back in Sunday into early next week as the front dissipates and a new area of high pressure builds north of the island chain. Winds and seas are forecast to remain below Small Craft Advisory thresholds through at least Saturday.
The current moderate northwest swell will continue to slowly decline today. A couple new reinforcing northwest swells are expected today and tomorrow, which should maintain moderate surf along north facing shores. A larger northwest swell should bring another round of advisory level surf to north and west facing shores on Friday, with a dip below advisory levels forecast for Saturday. A much larger northwest swell is expected Sunday through Monday with surf heights well above warning thresholds and possibly approaching over 40 feet during its peak along north facing exposures of the smaller islands. At this time, surf looks to peak Sunday afternoon through Sunday night and with the combination of the high tides from the new moon, we could see coastal impacts with waves washing across roads near the shorelines during the early morning high tide Sunday night.
Background south swell energy is expected through the weekend. A new small long-period south swell could give south shore surf a minor boost early next week. Surf along east facing shores will remain small due to the lack of trade winds over and upstream of the islands.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov