Photo Credit: Jason Weingardt

West Kaua’i

Today: Mostly sunny with isolated showers. Highs around 84 near the shore to around 72 above 3000 feet. East winds around 10 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Lows around 68 near the shore to around 57 above 3000 feet. East winds 10 to 15 mph.

Monday: Mostly sunny with isolated showers. Highs around 83 near the shore to around 71 above 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

South Kaua’i

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 81. East winds 10 to 15 mph. Chance of rain 40 percent.

Tonight: Partly cloudy. Isolated showers after midnight. Lows 64 to 69. East winds around 15 mph. Chance of rain 20 percent.

Monday: Breezy. Partly sunny with scattered showers. Highs around 80. East winds 15 to 20 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Partly sunny with scattered showers. Highs 71 to 78 in the valleys to around 62 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Breezy. Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 57 to 62 in the valleys to around 50 above 4000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Monday: Breezy. Partly sunny with scattered showers. Highs 70 to 77 in the valleys to around 61 above 4000 feet. East winds 15 to 20 mph. Chance of rain 50 percent.

North Kaua’i

Today: Mostly sunny with isolated showers. Highs 74 to 84. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Scattered showers after midnight. Lows 60 to 68. East winds 10 to 15 mph. Chance of rain 30 percent.

Monday: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs 73 to 83. East winds 10 to 20 mph. Chance of rain 50 percent.

East Kaua’i

Today: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 74 to 83. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 57 to 73. East winds 10 to 15 mph. Chance of rain 50 percent.

Monday: Partly sunny with scattered showers. Highs 73 to 83. East winds around 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Breezy trade winds will continue to spread across the state today as a more stable airmass settles over the islands. This trade wind pattern is expected to persist through at least mid-week, with showers favoring windward and mountain locations. By the end of the week, a front approaching the islands from the northwest will likely weaken winds as they shift to become more southeasterly. Early indications are that an overall wetter pattern could return next weekend.

Discussion

Early this morning, a surface ridge axis extends from the North Pacific High that is centered nearly 1700 miles northeast of Kauai to just north of the Garden Isle. Additionally, latest satellite imagery shows some mid to high clouds over the western end of the state ahead of a diminishing surface trough west of Kauai. Scattered showers have generally favored windward and mountain areas overnight, though as stability has increased across the region, showers have been light with most rain gauges reporting very little or no accumulation across the islands.
During the day today, trade winds will continue to spread across the state and reach breezy levels, where they will remain through at least the middle of the week. Meanwhile, relatively stable air will persist overhead, with only isolated to scattered showers favoring manly windward and mountain locations. A few transient bands of increased moisture could move into the islands from the east on the trade winds from time to time (particularly Monday night and early Wednesday), but in general, expect isolated to scattered showers to favor windward and mountain locations with greatest coverage during the overnight and early morning hours.
Models continue to show a front far northwest of the islands on Wednesday extending from a closed low pressure system centered over 1000 miles north of Kauai. Both the GFS and ECMWF then depict the front approaching closer to the islands from the northwest during the second half of the week as the low pressure system sinks southward. In this scenario, winds would weaken by Friday as they shift more southeasterly. The weaker winds and breakdown of background trade flow would likely result in sea breezes developing on Friday afternoon, and these changes have been reflected in the forecast with this morning's updates.
There is considerable uncertainty in the forecast beyond Friday, as the overall pattern will be dictated by the track of the surface low, front, and associated trough aloft. Although there is potential for a wetter pattern to develop across the islands by next weekend, some significant model differences remain. It is too early to determine specifics at this time, so future model runs will be monitored in hopes for better consensus in the extended range.

Aviation

A building ridge, both surface and aloft, will lead to strengthening trade winds into tonight, while also leading to increased stability. VFR conditions will prevail, with only brief MVFR VIS/CIG in SHRA anticipated, mainly over windward areas, and over leeward Big Island slopes in the afternoon. The strengthening trade winds may require AIRMET Tango later today/tonight due to moderate low-level turbulence to the lee of the terrain.

Marine

Moderate to fresh easterly trades winds will expand across all waters tonight into the first half of the week as an area of high pressure builds northeast of the state. Locally strong trades around Maui County and the Big island will gradually strengthen to near gale by Monday and hold through Tuesday. The Small Craft Advisory has been extended for waters around the Big Island and Maui County through 6 AM HST Wednesday, and expanded to include Maalaea Bay. Trade winds are expected to ease during the second half of the week as the high weakens.
Surf will be mainly background level with some peaks near average along all shores. Inconsistent pulses of south- southwest and south- southeast swell will produce near average sized surf for the next few days. A tiny pulse of northwest swell is possible today and tomorrow. Expect rough and choppy surf along east facing shores to build today and tomorrow, as trades build, then hold into the second half of the week before gradually easing into next weekend.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Wednesday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov