Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Mostly sunny in the morning, then mostly cloudy with a 20 percent chance of showers in the afternoon. Highs 85 to 91 near the shore to around 76 above 3000 feet. Northeast winds around 10 mph shifting to the southwest in the afternoon.

Tonight: Mostly cloudy with a 20 percent chance of showers early in the evening, then partly cloudy in the late evening and overnight. Lows around 66 near the shore to around 58 above 3000 feet. Northeast winds around 10 mph in the evening becoming light.

Wednesday: Mostly sunny. A 20 percent chance of showers in the late morning and afternoon. Highs 86 to 91 near the shore to around 77 above 3000 feet. Northeast winds around 10 mph shifting to the south in the afternoon.

South Kaua’i

Today: Mostly sunny in the morning, then partly sunny with a 20 percent chance of showers in the afternoon. Highs 82 to 90. North winds around 10 mph shifting to the south in the afternoon.

Tonight: Mostly cloudy. Lows around 68. North winds around 10 mph.

Wednesday: Partly sunny in the morning, then mostly sunny with a 20 percent chance of showers in the afternoon. Highs 81 to 89. North winds around 10 mph shifting to the southeast in the afternoon.

Kaua’i Mountains

Today: Mostly sunny in the morning, then cloudy with a 40 percent chance of showers in the afternoon. Highs 76 to 85 in the valleys to around 67 above 4000 feet. Southwest winds up to 10 mph shifting to the northeast around 10 mph in the afternoon.

Tonight: Mostly cloudy. Chance of showers early in the evening, then slight chance of showers in the late evening and overnight. Lows 59 to 65 in the valleys to around 55 above 4000 feet. South winds around 10 mph in the evening becoming light. Chance of rain 40 percent.

Wednesday: Partly sunny. Slight chance of showers in the morning, then chance of showers in the afternoon. Highs 76 to 86 in the valleys to around 67 above 4000 feet. Light winds. Chance of rain 40 percent.

North Kaua’i

Today: Mostly sunny in the morning, then mostly cloudy with a 20 percent chance of showers in the afternoon. Highs 78 to 88. South winds up to 10 mph shifting to the north around 10 mph in the afternoon.

Tonight: Mostly cloudy with a 20 percent chance of showers. Lows 61 to 68. South winds around 10 mph in the evening becoming light.

Wednesday: Partly sunny in the morning then becoming mostly sunny. A 20 percent chance of showers. Highs 77 to 88. South winds around 10 mph shifting to the northeast in the afternoon.

East Kaua’i

Today: Mostly sunny in the morning, then mostly cloudy with a 20 percent chance of showers in the afternoon. Highs 76 to 87. West winds around 10 mph shifting to the east in the afternoon.

Tonight: Mostly cloudy with a 20 percent chance of showers. Lows 61 to 70. West winds up to 10 mph.

Wednesday: Partly sunny in the morning then becoming mostly sunny. A 20 percent chance of showers. Highs 75 to 87. Northwest winds up to 10 mph shifting to the east around 10 mph in the afternoon.

Detailed Forecast

Synopsis

Light winds and mostly dry weather will prevail for the next couple of days. Strengthening trade winds from Friday into the weekend will bring an increase in showers, some potentially heavy, especially over windward areas.

Discussion

Light winds and mostly dry weather are on tap the next several days. Trade winds will strengthen from Friday into next week, and may bring an increase in showers, especially to windward areas.
Latest satellite imagery shows that there's been a slight diurnal increase in low cloud cover over waters E of the islands, with areas of scattered low clouds punctuating otherwise nearly clear skies. A few small showers are noted over waters E of Maui and the Big Island, moving generally W near 10 mph. An area of showery low clouds that loitered near Kona airport through the night appears to be dissipating. Land-based observations show light winds mostly blowing downslope and offshore, except at exposed windward locations, where light E trade winds are coming it at speeds less than 10 mph. The trade-wind-supporting ridge to the N, and the local pressure gradient, remains weakened by a slow-moving complex low about 1300 miles NW of Kauai. The subtropical jest S of this feature is sending wispy high clouds over the area from the W, while morning soundings indicated a relatively dry air mass, with PWAT near 1.1″.
The slow-moving low to the NW will keep winds light, while a quickly developing low about 1300 miles NE of the islands will also contribute to keep the local pressure gradient loose into Friday. The resultant land and sea breeze weather regime means mostly clear (aside from some high clouds) and cool mornings, with a slight chance of a windward shower. Afternoon clouds over leeward areas will also bring a chance of a shower, especially on the Big Island. A nearby ridge aloft will ensure little to no rainfall accumulation. As mentioned, there will be periods when increased high clouds move over the islands from the W, especially this afternoon and tonight.
Surface high pressure building N of the islands from Friday into early next week will lead to strengthening trade winds that become breezy by Sunday. The ridge aloft will weaken over the weekend as a low aloft moves over the area from the N, but model guidance remains inconsistent as to the timing and location of this low. A slow- moving front will approach the islands from the NE this weekend, and some guidance indicates that this source of increased low- and mid- level moisture will eventually move over the islands with the increasing trade wind flow. The forecast has been indicating the potential for heavy showers (and even snow on the Big Island Summits) this weekend. While this remains in the official forecast for the sake of consistency, it is worth noting that it is not well supported by EPS guidance. Regardless, rainfall would favor windward areas with the trade winds prevailing.

Aviation

A cold front far north of the state will slowly drift south and keep light winds in the forecast through at least Wednesday. Lighter large scale winds will produce more variable wind directions with afternoon sea breezes and overnight land breezes over all islands. A weak ridge aloft will also produce stable conditions across the state with limited clouds and only a few showers possible.
No AIRMETs in effect and none are expected.

Marine

A surface ridge to the north will remain weak for the next several days as broad low pressure meanders well northwest of the state. Expect land and sea breeze conditions near the coasts, with diurnally driven accelerations potentially leading to fresh breezes during the afternoons. A return of fresh to strong easterly trades is possible over the weekend as the ridge strengthens to the north.
Surf along north and east-facing shores will trend up Wednesday through the second half of the week, as a short- to medium- period north-northeast swell arrives from a storm-force low forecast to develop around 1,000 nautical miles to the northeast today through midweek. This will be a long-lived event, as the system slowly evolves and drifts northeastward late in the week. Guidance indicates a reinforcement from this system Friday into Saturday, which may coincide with the peak surf. Heights will near advisory levels for east-facing shores (10 ft faces) from Thursday through Saturday, while north-facing exposures are expected to remain below advisory levels (15 ft faces). For the long-range, guidance shows a gale- to storm-force low tracking eastward from the Bering Sea to the Gulf of Alaska late Wednesday through Friday. If this materializes, a long-period northerly swell could arrive late Sunday into early next week from this feature.
Surf along south facing shores will remain small, with predominantly a mix of short- to medium-period southeast and long- period south to south-southwest swells. A slightly larger south swell is expected this weekend.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov