Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Mostly sunny. Highs around 78 near the shore to around 67 above 3000 feet. North winds up to 10 mph shifting to the southwest in the afternoon.

Tonight: Partly cloudy. Lows 62 to 69 near the shore to around 52 above 3000 feet. Light winds becoming northeast up to 10 mph after midnight.

Tuesday: Mostly sunny. Isolated showers in the afternoon. Highs around 78 near the shore to around 67 above 3000 feet. Northwest winds up to 10 mph. Chance of rain 20 percent.

South Kaua’i

Today: Partly sunny. Isolated showers in the morning. Highs around 75. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with isolated showers. Lows 59 to 68. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Tuesday: Partly sunny. Breezy. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 76. Northeast winds 10 to 20 mph. Chance of rain 40 percent.

Kaua’i Mountains

Today: Mostly cloudy with isolated showers. Highs 66 to 72 in the valleys to around 58 above 4000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with scattered showers. Lows 51 to 59 in the valleys to around 47 above 4000 feet. Light winds becoming east up to 10 mph after midnight. Chance of rain 50 percent.

Tuesday: Mostly cloudy with scattered showers. Highs 66 to 71 in the valleys to around 59 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

North Kaua’i

Today: Partly sunny with isolated showers. Highs 68 to 78. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with isolated showers. Lows 56 to 67. Southeast winds up to 10 mph. Chance of rain 20 percent.

Tuesday: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 69 to 77. East winds up to 15 mph. Chance of rain 40 percent.

East Kaua’i

Today: Partly sunny with isolated showers. Highs 67 to 77. East winds around 10 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with isolated showers. Lows 52 to 70. Northeast winds up to 10 mph. Chance of rain 20 percent.

Tuesday: Mostly cloudy. Isolated showers in the morning, then scattered showers in the afternoon. Highs 67 to 77. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Moderate easterly trades will continue through the first half of the week, with clouds and light showers favoring windward and mauka locations overnight through the mornings. A return of breezy easterly trades and increasing rainfall chances is possible through the second half of the week as an upper disturbance moves into the area.

Discussion

Guidance remains in good agreement, indicating dry and stable conditions continuing through the first half of the week as upper heights rise over the region. This will create a more suppressed environment with precipitable water values remaining around an inch or less and a strong subsidence inversion hovering around 5-6 kft. The best chances for a few, mostly light, showers will be over typical windward and mauka locations overnight through the early mornings with moderate easterly trades continuing. Any leeward showers are more likely to occur in the afternoons, where localized sea breezes form. Accumulations will be minimal with the stable conditions in place.
A gradual strengthening and destabilization of the trade wind flow is possible through the second half of the week. There is higher confidence that trades will likely increase as a deeper surface high sets up far north of the state, potentially resulting in breezy conditions by Friday. An upper-level trough will slowly pass over the region during this time, bringing 500 mb temperatures as low as -15C Wednesday through Friday. While there could be some increase in shower coverage in response to the added instability, a mid-level ridge may be able to maintain stability and lower the chances of locally heavy rainfall. Guidance shows a pulse of upper-level energy dipping southward on the backside of this upper trough Friday through Saturday, potentially closing off an upper low over the eastern end of the state. If this were to materialize, these conditions anticipated through the second half of the week could linger through next weekend.

Aviation

Light to moderate east-northeast trade winds will persist through midweek. As such, clouds and showers will favor windward and mauka areas, especially during the late night and morning hours. A strongly stable air mass will limit shower development and intensity. Low level moisture will remain trapped beneath the strong inversion aloft: low clouds will lift slightly after sunrise, but are not likely to dissipate.
AIRMET Sierra is currently in effect for northeast facing slopes of the Big Island. Conditions are expected to improve later this morning, but may redevelop after sunset. Otherwise and elsewhere, VFR conditions will prevail.

Marine

After a brief pick up in early morning northeast to east trade winds, primarily focused through the notoriously windier areas around Maui County and Big Island, today's trades will ease back to more moderate magnitudes as a result of high pressure settling in north of the coastal waters. Little change is expected through Wednesday when another high develops farther north of the region. This high will build in Thursday and Friday and tighten the regional pressure gradient enough to strengthen trades back to fresh to locally strong levels into the weekend.
Several overlapping northwest swells are scheduled to arrive this week. The latest moderate size, long period northwest (310-320 degree) swell peaked surf to near or slightly under High Surf Advisory (HSA) thresholds along most north and west-facing Kauai-to-Maui shores last night into early morning. This swell will decline through the afternoon and into Tuesday to then be followed by a slightly larger northwest (310-330 degree) swell building in Tuesday night. As a result, the arrival of this high end moderate size, long period swell will likely produce mid week advisory level north and west-facing shore surf. North and west shore surf will fall below HSA heights Thursday. A moderate size northwest (310 degree) swell is due next weekend. A weak pulse of early season, south southwest (200 degree) swell has been passing through the past day or so. Expect this inconsistent swell to peak south-facing shore surf at slightly above March averages today, then surf will gradually decline with the fading swell through Wednesday. East shore surf will remain small through the middle of the week. There will be a slight pick up in chop later this week in response to strengthened trades.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov