West Kaua’i

Tonight: Mostly clear. Haze. Lows around 67 near the shore to around 58 above 3000 feet. Light winds.

Thursday: Sunny and haze. Highs 80 to 87 near the shore to around 74 above 3000 feet. Southeast winds up to 10 mph.

Thursday Night: Mostly clear. Isolated showers in the evening. Haze through the night. Lows around 68 near the shore to around 59 above 3000 feet. Light winds. Chance of rain 20 percent.

South Kaua’i

Tonight: Partly cloudy with isolated showers. Haze. Lows around 68. Light winds. Chance of rain 20 percent.

Thursday: Sunny. Isolated showers in the morning. Haze through the day. Highs 81 to 87. East winds up to 10 mph. Chance of rain 20 percent.

Thursday Night: Mostly clear. Haze. Lows around 68. Light winds.

Kaua’i Mountains

Tonight: Partly cloudy with isolated showers. Haze. Lows 58 to 67 in the valleys to around 56 above 4000 feet. Light winds. Chance of rain 20 percent.

Thursday: Mostly sunny with isolated showers. Haze. Highs 76 to 82 in the valleys to around 66 above 4000 feet. Southeast winds up to 10 mph. Chance of rain 20 percent.

Thursday Night: Partly cloudy with isolated showers. Haze. Lows 59 to 68 in the valleys to around 57 above 4000 feet. Light winds. Chance of rain 20 percent.

North Kaua’i

Tonight: Partly cloudy. Isolated showers in the evening. Haze through the night. Lows 61 to 69. Light winds. Chance of rain 20 percent.

Thursday: Sunny. Haze through the day. Isolated showers in the afternoon. Highs 75 to 83. Southeast winds up to 10 mph. Chance of rain 20 percent.

Thursday Night: Partly cloudy with isolated showers. Haze. Lows 62 to 69. Light winds. Chance of rain 20 percent.

East Kaua’i

Tonight: Partly cloudy with isolated showers. Haze. Lows 61 to 71. Southwest winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Thursday: Sunny. Isolated showers in the morning. Haze through the day. Highs 74 to 86. Southeast winds up to 10 mph. Chance of rain 20 percent.

Thursday Night: Partly cloudy with isolated showers. Haze. Lows 62 to 72. Light winds. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Light to occasionally moderate east to southeasterly winds are expected to persist through the remainder of the week and into the weekend. Light showers will focus across windward areas during the overnight hours and leeward and interior areas during the afternoon hours. A deep upper-level low is progged to approach the islands early next week, potentially enhancing southerly winds to the area. However, confidence remains low in the forecast for next week at this time.

Discussion

This afternoon, mostly dry conditions are observed across the island chain. At the surface, a frontal boundary lies outside of the offshore waters to the north and northeast, while a ridge axis near the islands is supporting stable conditions across Hawaii. Afternoon surface observations and a late morning advanced scatterometer (ASCAT) pass show light to moderate east- southeasterly background flow prevailing. Due to the relatively light background winds, sea-breeze induced clouds have developed over interior and leeward sections of the islands this afternoon, though rainfall amounts have been scarce, and where a few showers have occurred, amounts have been very light. Afternoon upper air soundings from Lihue and Hilo show stable, mostly dry profiles with inversions around 7,000 feet.
This evening and tonight, the light southeasterly background winds will continue, prompting overnight land breezes similar to those that occurred last night. This will clear the islands of most clouds and shower activity, though a few showers will remain possible along east and southeast slopes and coasts.
For the rest of this week and into the weekend, a hybrid land/sea breeze pattern, with moderate trade winds at times, will continue as the next front moves toward the island chain and broad upper- level ridging prevails east of the state. Background winds will remain light to occasionally moderate from the southeast for the remainder of the week, keeping most of the smaller islands relatively dry since they will be largely shadowed by the Big Island. While some showers will still be carried into windward areas of the smaller islands on the east to southeast winds, the lighter flow will allow sea breezes to increase clouds and support a few light showers for leeward and interior areas each afternoon. Land breezes will then clear clouds and showers over these leeward and interior areas each night.
By next week, model guidance suggests a deep, upper-level low will develop northwest of the islands. However, there are significant differences amongst model guidance regarding the strength, positioning, and timing of this feature, creating a lot of uncertainty for the forecast beyond this weekend. For example, the ECMWF introduces a more progressive solution, with this feature quickly moving off to the northeast on Monday and then lingering far north of the islands with a front approaching the northern end of the state Tuesday into Wednesday. However, the GFS keeps the feature stalled northwest of the islands through the middle of next week. These differences would have significant impacts on moisture availability and the prevailing wind speed and direction over the main Hawaiian Islands. Some changes were made to the forecast in the long term to trend towards the latest guidance, though have continued with the general theme of relatively dry conditions for most islands, and Kauai having the highest shower chances by the middle of next week.

Aviation

Light to moderate southeasterly winds will produce land/sea breezes over all islands. A few leeward SHRA and some isol MVFR conds can be expected today with land breezes tonight. VFR should generally prevail.
No AIRMETs are currently in effect.

Marine

A weak ridge of high pressure oriented northwest to southeast over the islands will gradually strengthen over the next few days. This will result in several days of generally light to gentle easterlies, with the exception of slightly higher winds over the windward Maui and Big Island surrounding waters. Near shore, localized sea breezes will likely predominate during the day and light offshore winds at night. Early next week, a strong cold front will approach from the west causing causing winds to veer to the south or southwest over the western half of the state.
The current north northwest (330-350 degree) swell will continue to fade even as a new medium period swell out of the north northeast (010-030) builds in. This will provide a slight boost in north- facing shore surf with many sets coming in waist to head high Friday and Saturday. For the coming week, a series of multiple small north and northwest swells will keep surf along along north and west facing shores near seasonal norms.
South-facing shores should remain small with some background long period south southwest swell expected to arrive Thursday or Friday. East-facing shore chop will also remain small due to the absence of any significant trade fetch. However, select east-facing exposures may see a small bump in surf due to wrap from the north- northeast swells tomorrow and Friday.

HFO Watches/Warnings/Advisories

None.

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