Photo Credit: Braden Jarvis

West Kaua’i

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

Tonight: Partly cloudy. Breezy. Isolated showers in the evening, then scattered showers after midnight. Lows around 69 near the shore to around 59 above 3000 feet. Northeast winds up to 20 mph. Chance of rain 50 percent.

Tuesday: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 84 near the shore to around 72 above 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

South Kaua’i

Today: Partly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 81. Northeast winds 15 to 20 mph. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 68. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Tuesday: Breezy. Partly sunny with scattered showers. Highs around 81. Northeast winds 15 to 25 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Breezy. Cloudy with frequent showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 71 to 78 in the valleys to around 62 above 4000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 80 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then frequent showers after midnight. Lows 60 to 65 in the valleys to around 54 above 4000 feet. East winds up to 20 mph. Chance of rain 80 percent.

Tuesday: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 71 to 78 in the valleys to around 62 above 4000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 70 percent.

North Kaua’i

Today: Breezy. Partly sunny with scattered showers. Highs 74 to 84. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 62 to 70. East winds 10 to 15 mph. Chance of rain 70 percent.

Tuesday: Partly sunny with scattered showers. Highs 74 to 84. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

East Kaua’i

Today: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 74 to 84. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 61 to 72. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Tuesday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 74 to 84. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Breezy easterly trade winds will continue through Wednesday, then ease slightly through the latter half of the week as the ridge weakens north of the area and an upper disturbance moves in. Showers will favor windward and mauka locations, especially overnight through the early mornings as pockets of moisture move through. As the upper disturbances moves southward into the region, there is a possibility of increasing shower coverage and intensity later in the week. A more stable trade wind pattern is possible next weekend as the upper disturbances moves away.

Discussion

Short-term guidance remains in good agreement and depicts the breezy easterly trades holding through midweek as the ridge builds to the north. An area of low clouds and enhanced moisture approaching from the east will support better windward shower coverage beginning this morning for the eastern end of the state, then statewide tonight through Tuesday. Stable conditions associated with an upper ridge and plenty of mid-level dry air, however, will limit rainfall amounts through this period. Mostly dry conditions will prevail over the leeward areas of the smaller islands.
Although confidence in the details remains poor due to some inconsistencies in the guidance over the past couple of days, a transition period is possible Thursday as upper heights lower in response to an upper trough digging southward into the area. A weakness within the surface ridge could result and lead to our local trade winds easing slightly. Added instability accompanying the upper trough would be enough to support a few locally heavier showers Thursday through Friday night if this scenario materializes. A more stable trade wind pattern is likely next weekend as the upper trough shifts east of the area.

Aviation

Moderate to locally breezy trade winds will steer bands of light showers off the Pacific towards windward slopes and coasts. Mostly dry conditions will prevail along leeward coasts of the smaller islands. On the Big Island, weak land breezes this morning will give way to light sea breezes in the afternoon. Mostly clear skies along leeward slopes this morning will be replaced by cumulus build-ups in the afternoon. Brief MVFR CIG or VIS are likely in showers, otherwise VFR conditions are expected statewide.
Moderate trade winds combined with a strengthening inversion aloft near summit level are generating areas of moderate low-level turbulence downwind of higher terrain. AIRMET Tango is currently in effect for Big Island, Maui, and Molokai. It may need to be expanded later today to include Oahu and Kauai.

Marine

Trade winds will continue to strengthen today, as a high pressure system builds far northeast, generating widespread fresh to locally strong trade winds as well as near gales for the windier zones around Maui County and the Big Island. The Small Craft Advisory has been expanded to include most waters east of Oahu through 6 AM HST Wednesday due to the combination of strengthening winds and building seas. Trade winds are expected to weaken towards the end of the week as the high weakens.
A small south swell is producing inconsistent pulses near the summer average along south facing shores. This swell should hold through today before tapering off tomorrow. A series of small swells from the southwest, south and southeast directions will keep surf from becoming flat this week. Otherwise, no significant swells are expected for south facing shores through the weekend.
Expect rough and choppy surf along east facing shores to slowly build over the next few days as trades strengthen, then hold into the second half of the week before gradually easing into the weekend. Nearly flat conditions are expected along north facing shores this week.

HFO Watches/Warnings/Advisories

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

Data Courtesy of NOAA.gov