Photo Credit: Braden Jarvis

West Kaua’i

Rest Of Today: Partly sunny with scattered showers. Highs around 85 near the shore to around 73 above 3000 feet. South winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 68 to 73 near the shore to around 59 above 3000 feet. Southeast winds up to 15 mph. Chance of rain 50 percent.

Monday: Breezy. Mostly cloudy with scattered showers. Highs around 85 near the shore to around 73 above 3000 feet. Southeast winds 10 to 20 mph. Chance of rain 50 percent.

South Kaua’i

Rest Of Today: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 82. South winds around 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 66 to 72. South winds up to 10 mph. Chance of rain 50 percent.

Monday: Mostly cloudy with scattered showers. Highs around 82. South winds around 10 mph. Chance of rain 50 percent.

Kaua’i Mountains

Rest Of Today: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 72 to 79 in the valleys to around 63 above 4000 feet. South winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 59 to 65 in the valleys to around 53 above 4000 feet. South winds up to 10 mph. Chance of rain 50 percent.

Monday: Mostly cloudy. Scattered showers in the morning, then numerous showers in the afternoon. Highs 72 to 79 in the valleys to around 63 above 4000 feet. South winds up to 10 mph. Chance of rain 70 percent.

North Kaua’i

Rest Of Today: Mostly sunny with isolated showers. Highs 75 to 85. South winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 63 to 72. South winds up to 15 mph. Chance of rain 50 percent.

Monday: Mostly cloudy with scattered showers. Highs 75 to 85. South winds up to 15 mph. Chance of rain 50 percent.

East Kaua’i

Rest Of Today: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 75 to 84. South winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 60 to 73. Southwest winds around 10 mph. Chance of rain 50 percent.

Monday: Mostly cloudy with scattered showers. Highs 75 to 84. South winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

A surface ridge over the Hawaiian Islands and a weakening stationary front northwest to north of the state will keep a stable light southerly wind pattern over the region through Monday. A surface low develops along the dissipated frontal trough northwest of the islands on Monday. This deepening surface low will increase east to southeast winds over the region from Monday through Wednesday. Shower trends will gradually increase from Tuesday through Friday in moderate to locally breezy east to southeast wind flow.

Discussion

The large scale weather pattern remains unchanged this morning with a surface ridge over the islands and a weakening stationary front northwest to north of the state. Light southerly winds will continue with dry weather conditions under a high pressure ridge aloft. Trade wind temperature inversion heights remain in the 5,000 to 7,000 foot range as reported by the 2 AM HST upper air balloon soundings at Lihue and Hilo. These low trade wind inversion heights will limit vertical cloud development and shower activity. Expect continued light winds with afternoon sea breezes lasting into Monday with only isolated showers possible over most islands. A subtropical jet stream northwest of the island chain will continue to advect periods of high level cirrus clouds over all islands through next week, likely enhancing sunrise and sunset colors across the region.
On Monday this stable light wind pattern begins to change. A strong upper level trough approaching the Hawaii region from the northwest stalls out and forms a cold core upper low. Divergence aloft ahead of this cut off low will cause a surface low to form along the remnants of the old stationary front northwest of Kauai. This surface low will deepen and initially drift northwest, away from the islands and towards the upper low center. The development of this surface low will initiate a weather pattern shift, from light southerly winds to moderate east to southeast winds by Tuesday.
By Tuesday, the ridge over the islands will weaken as the surface low deepens and drifts slowly north. Increasing east to southeast wind flow allowing brief periods of showers to return to the islands from Tuesday through Friday. Increasing shower trends will start over the windward and southeast slopes of the Big Island, East Maui and Kauai, then spread to windward sections of all islands later in the week.
By Wednesday long range global model solutions show the trough northwest of the islands begins to approach Kauai at the western end of the state, possibly producing a few convergent shower bands near Kauai and Oahu for the Wednesday to Thursday time periods. Scattered showers will spread to windward areas statewide by Friday as winds strengthen to a more easterly trade wind direction lasting into next weekend.

Aviation

Light to moderate southerly to southeasterly flow will continue across the islands today as a frontal boundary lingers to the north and a surface ridge meanders over the eastern end of the state. Expect cloud buildups during the afternoon and evening with mostly dry conditions. Scattered high clouds will pass over the islands from time to time due to the front's proximity to the north. VFR conditions will dominate statewide, but AIRMET Sierra may be needed from time to time for mountain obscuration.

Marine

A weakening surface ridge extends over the smaller islands from a surface high to the east of the state. Elsewhere, a frontal boundary continues to meander north and northwest of the state. A surface low has developed along this front about 550 nm west- southwest of Kauai. The close proximity of all of these features is maintaining light to moderate south to southeast winds across the smaller islands, with moderate southeast winds in the vicinity of the Big Island. The forecast guidance continues to show the low pressure system will deepen as it moves slowly toward the north-northeast. At the same time, a new surface high is expected to build far north of the area from Monday through mid-week. These features are expected to produce light to moderate south to southeast winds near Kauai, while moderate east to southeast winds will likely be elsewhere. In addition, combined seas are expected to approach the Small Craft Advisory threshold over the waters north and northwest of Kauai starting late tonight or early Monday due to a building north swell.
A north-northwest (340-350 deg) swell has arrived in the islands early this morning. The National Data Buoy Center buoys northwest of Kauai are showing the swell height is currently around 6 ft with a period of near 11 sec. This swell will likely continue to build today and tonight, before peaking early Monday. This is expected to produce small to moderate surf along most north facing shores from later today and tonight through Monday night. This swell will gradually lower, and swing around from a north- northeast (020-030 deg) direction by Tuesday. A mix of small north-northwest (340-350 deg) and northwest (320 deg) swells filling in starting Wednesday may maintain modest surf along exposed north and west facing shores from Wednesday through Friday.
The north swell may cause a slight increase in surf along some east facing shores with a northerly exposure from Monday into early Tuesday. As the trade winds strengthen near and upstream of the islands from late Tuesday through mid-week, expect choppy surf to increase along most east facing shores. Finally, a small, long-period south (190 deg) swell arriving Monday will build through Tuesday. This will likely produce small to moderate surf along most south facing shores starting Tuesday. This south swell will gradually lower from Wednesday into Thursday.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov