Photo Credit: Braden Jarvis

West Kaua’i

Today: Breezy. Cloudy with numerous showers. Highs around 81 near the shore to around 69 above 3000 feet. Southwest winds 10 to 20 mph. Chance of rain 70 percent.

Tonight: Cloudy. Numerous showers in the evening, then showers after midnight. Lows around 67 near the shore to around 58 above 3000 feet. Southwest winds 10 to 15 mph. Chance of rain 80 percent.

Thursday: Mostly cloudy with scattered showers. Highs around 81 near the shore to around 70 above 3000 feet. Southwest winds 10 to 15 mph. Chance of rain 50 percent.

South Kaua’i

Today: Cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 80. Southwest winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows around 67. West winds around 10 mph. Chance of rain 70 percent.

Thursday: Mostly cloudy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 81. Southwest winds around 15 mph. Chance of rain 30 percent.

Kaua’i Mountains

Today: Cloudy and breezy. Numerous showers in the morning, then showers in the afternoon. Highs 70 to 77 in the valleys to around 63 above 4000 feet. Southwest winds 10 to 25 mph. Chance of rain 90 percent.

Tonight: Breezy. Cloudy with numerous showers. Lows around 61 in the valleys to around 54 above 4000 feet. Southwest winds 10 to 25 mph. Chance of rain 70 percent.

Thursday: Breezy. Cloudy with scattered showers. Highs 70 to 77 in the valleys to around 64 above 4000 feet. Southwest winds 10 to 20 mph. Chance of rain 50 percent.

North Kaua’i

Today: Cloudy. Scattered showers in the morning, then numerous showers in the afternoon. Highs 73 to 80. West winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Cloudy with scattered showers. Lows 60 to 69. Southwest winds 10 to 15 mph shifting to the south after midnight. Chance of rain 50 percent.

Thursday: Mostly cloudy with scattered showers. Highs 74 to 81. Southwest winds up to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Cloudy with scattered showers. Highs 72 to 81. Southwest winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows 60 to 70. Southwest winds 10 to 15 mph. Chance of rain 70 percent.

Thursday: Mostly cloudy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 73 to 81. Southwest winds 10 to 15 mph. Chance of rain 40 percent.

Detailed Forecast

Synopsis

Light to moderate south to southwest winds will continue across the state as a front meanders north of the area. These winds will continue to carry clouds and showers over Kauai and Oahu through early Thursday, while mostly dry conditions will persist across Maui County and the Big Island. Later this week, the southerly winds will focus low clouds and showers mainly over south through west sections of the western islands, with a relatively dry weather pattern elsewhere. A developing upper-level trough moving in from the northwest late this weekend could send another front with enhanced showers towards Kauai early next week.

Discussion

A weak surface low is centered about 550 miles north-northeast of Honolulu early this morning, while a second weak surface low appears to be about 435 miles northwest of Lihue. These features, which are moving toward the east-northeast at about 20 mph, are connected by a meandering frontal boundary. Elsewhere, a weak east-northeast to west-southwest oriented surface ridge remains in the vicinity of the southern Big Island. Since the islands are sandwiched between there features, expect light to moderate south to southwest winds to persist for the next few days.
The deep southerly flow is transporting abundant moisture over the western islands. Loops of satellite imagery and radar reflectivity data show low clouds and scattered showers near Kauai. In addition to the low clouds, there are widespread high clouds moving rapidly from west to east, which are associated with a jet stream north of the area. Winds on the highest elevations of the Big Island have been strong overnight, so a Wind Advisory has been issued for the Big Island Summits through this afternoon. The winds are expected to weaken there by this evening.
The forecast guidance indicates that strong zonal flow in the upper levels will help keep the meandering frontal boundary with transient weak low-pressure systems north and northwest of the islands through mid-week. This will maintain the moist flow moving up from the south and southwest over Kauai and Oahu through tonight, while most of Maui County and the Big Island will remain relatively dry. From Thursday through Friday, somewhat drier conditions are expected to be over the western islands, with some low clouds and brief showers moving over the south through west sections and mountains of Kauai, and possibly Oahu. Drier conditions are expected elsewhere, but the relatively light winds may allow local sea breezes to produce a few afternoon showers over some areas, such as the leeward Big Island.
Later this weekend, the forecast models continue to show an upper-level trough northwest of the islands will begin to dig down towards the region. A deepening surface low associated with the trough aloft will likely stay northwest or north of the islands. However, this low and the approaching upper-level may push a cold front towards Kauai early next week. Assuming this scenario unfolds, there may an increase in the coverage of clouds and showers starting Sunday night or Monday. However, there is still some uncertainty about the details of these weather features, so we will continue to monitor future runs of the models to determine if the long-term forecast needs to be adjusted.

Aviation

Moderate south to southwesterly winds will focus moisture over leeward zones through the forecast period. For now, deeper moisture has lifted out of the area leaving behind shallow low clouds and isolated showers along with a partial canopy of high clouds. Kauai will remain on the periphery of deeper moisture through today which will be sufficient for an increase in showers and attendant MVFR over leeward zones as southwesterlies slightly strengthen today. Shower coverage quickly decrease with southeast extent. Prevailing VFR is anticipated from Oahu through the Big Island, though pockets of low MVFR cigs will drift onshore in most places from time to time. Showers will further increase in coverage over Kauai tonight as deeper moisture gradually nudges toward the island.
AIRMET Sierra remains in effect for Leeward Kauai.

Marine

A ridge will continue to meander over and south of the islands through the rest of the week as a series of lows move through from west to east along a frontal boundary positioned north of the area. This pattern will support periods of gentle to moderate south to southwest winds. Expect the strongest of these winds and choppier seas over the Kauai and Oahu waters, closer to the lows passing to the north. The eastern end of the state will remain near the ridge axis, which will translate to land and sea breeze conditions near the coasts with a background southerly flow prevailing.
Seas will remain on the small side this week for all Hawaiian waters with minimal swell energy expected. This quiet period will persist until the blocking pattern that has setup over the far northwest Pacific shunting the jet stream northward breaks down. Long-range guidance does, however, depict a short-to medium-period north swell arriving early next week, which could drive the seas up toward the 10 ft advisory level if it materializes.
Limited swell translates to small surf prevailing for all shores with mainly a mix of background north and south swell energy moving through. For the long range, decent sized area of 30 kt winds and 20 foot seas southeast of New Zealand was observed with latest ascat and altimeter pass. This fetch is forecast to nose northward keeping the winds focused at the islands down the 190 degree directional band over the next day or two. This pulse should reach Pago Pago this weekend according to WW3, then our southern shores next week from Tuesday through midweek.

HFO Watches/Warnings/Advisories

Wind Advisory until 6 PM HST this evening for the Big Island Summits.

Data Courtesy of NOAA.gov