Photo Credit: Braden Jarvis

West Kaua’i

Today: Sunny. A 20 percent chance of showers in the afternoon. Highs 81 to 86 near the shore to around 72 above 3000 feet. Light winds.

Tonight: Partly cloudy with a 20 percent chance of showers. Lows 62 to 67 near the shore to around 54 above 3000 feet. Light winds.

Tuesday: Mostly sunny with a 20 percent chance of showers. Highs around 82 near the shore to around 70 above 3000 feet. Light winds becoming south up to 10 mph in the afternoon.

South Kaua’i

Today: Mostly sunny. A 20 percent chance of showers in the afternoon. Highs 80 to 86. Northeast winds around 10 mph in the morning becoming light.

Tonight: Partly cloudy with a 20 percent chance of showers. Lows around 64. Light winds becoming north up to 10 mph after midnight.

Tuesday: Sunny. Highs 78 to 85. Northeast winds up to 15 mph.

Kaua’i Mountains

Today: Mostly sunny with isolated showers in the morning, then partly sunny with chance of showers in the afternoon. Highs 72 to 79 in the valleys to around 64 above 4000 feet. Light winds. Chance of rain 40 percent.

Tonight: Mostly cloudy with a 40 percent chance of showers. Lows 56 to 61 in the valleys to around 52 above 4000 feet. Light winds.

Tuesday: Mostly sunny with a 40 percent chance of showers. Highs 70 to 77 in the valleys to around 62 above 4000 feet. Light winds becoming northeast up to 15 mph in the afternoon.

North Kaua’i

Today: Mostly sunny. Isolated showers in the morning, then chance of showers in the afternoon. Highs 74 to 83. Light winds. Chance of rain 30 percent.

Tonight: Mostly cloudy with a 40 percent chance of showers. Lows 57 to 65. Light winds becoming southwest up to 10 mph after midnight.

Tuesday: Mostly sunny with a 20 percent chance of showers. Highs 72 to 81. Southeast winds up to 10 mph shifting to the northeast in the afternoon.

East Kaua’i

Today: Mostly sunny with isolated showers. Highs 73 to 83. Light winds. Chance of rain 20 percent.

Tonight: Partly cloudy with a 20 percent chance of showers. Lows 57 to 67. Light winds becoming northwest up to 10 mph after midnight.

Tuesday: Mostly sunny with a 20 percent chance of showers. Highs 71 to 81. North winds around 10 mph.

Detailed Forecast

Synopsis

Light to moderate trade winds will continue around Maui County and the Big Island into Tuesday, with light winds across the remaining islands. A stable airmass overhead will limit shower chances until a weak front moves in from the northwest midweek.

Discussion

While many aspects of the forecast were modified with the morning package, the overall forecast philosophy remains the same. Most changes were to ensure consistency between the forecast parameters. Winds were dropped a notch for midweek in keeping with the trend in the forecast, but will still be stronger than what we have been experiencing as of late.
A ridge to the north of the islands and ridging aloft will maintain an overall dry weather pattern over the islands today and into Tuesday. The global models are in good agreement with a low forming north of the islands tonight and moving to the northeast. the tail end of moisture associated with this front will move down the island chain Tuesday night through early Thursday. A high pressure system at the same time will spread northerly winds across the islands, turning to the northeast by Thursday.
Being at the tail end of the moisture band, and with the north to northeast winds overspreading the islands, most of the showers will be focused over the more typical windward and mauka areas. The current inversion remains low, which is helping to limit rainfall. As this moisture band reaches the islands, we expect the inversion to be a little higher, helping showers to produce a few more showers.
The high will stick around to the northeast, keeping a stable trade wind pattern over the islands for the end of the week.

Aviation

Light to moderate east to southeast low-level flow will allow overnight/early morning land breezes and daytime sea breezes to develop for most areas through Tuesday. Although a brief period with MVFR VSBYS/CIGS can't be ruled out in and around any showers, VFR conditions will prevail with the dry and stable conditions in place. The best chance for these showers will favor windward coastal areas overnight through the mornings, then over interior/leeward sections through the afternoon hours. AIRMETs are not anticipated.

Marine

A very large, long-period northwest swell (310-320 degrees) continues to spread down across the coastal waters early this morning. Buoy observations are showing significant wave heights of 10 feet or greater mainly due to this swell. Therefore, a Small Craft Advisory (SCA) remains in effect through early Tuesday morning for waters exposed to this large northwest swell.
The western end of a weak surface ridge appears to be about 100 nm north of Kauai early this morning. As a result, the background flow remains light near the western islands, while light to locally moderate east to east-southeast winds are across the rest of the state. The winds will weaken slightly over most areas by tonight as a cold front moves rapidly down from the north- northwest toward the region. Expect moderate northeast winds to eventually spread down over the state Tuesday as the front approaches, and high pressure builds in far northwest of the region. The front will likely weaken as it moves down across the state from late Tuesday through Wednesday, but it may bring a narrow band of low clouds and showers during its passage. The northeast to east winds will also strengthen along and behind the front. We do not currently have SCA winds in the forecast for any waters during mid-week, but the winds could approach SCA speeds in some of the typically windier waters adjacent to the islands of Maui County and the Big Island later this week.
The northwest swell, which is producing elevated seas in the vicinity of the islands, appears to be at least 2 feet above the model guidance based on observations from the buoys. This swell will produce dangerously large breaking waves along exposed north and west facing shores. As a result, a High Surf Warning remains in effect through early Tuesday morning for most north and west facing shores of the smaller islands. A High Surf Advisory has also been issued starting at noon HST today for west facing shores of the Big Island that are exposed to this swell. This swell is expected to gradually lower on Tuesday, and then shift from a more northerly direction by mid-week. The forecast guidance continues to indicate a small south-southwest swell (200 degrees) may arrive late tonight and Tuesday, and then linger for a day or two. Surf along east facing shores will remain small early this week due to the lack of strong trades locally and upstream of the state. As the current northwest swell becomes northerly around mid-week, it may cause a slight increase in surf along some east facing shores with a northerly exposure. Otherwise, minimal surf is expected along east and south facing shores this week.

HFO Watches/Warnings/Advisories

High Surf Warning until 6 AM HST Tuesday for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kauai North, Koolau Windward, Molokai Windward, Molokai North, Molokai West, Windward Haleakala.
High Surf Advisory from noon today to 6 AM HST Tuesday for Kona, Kohala.
Small Craft Advisory until 6 AM HST Tuesday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Alenuihaha Channel, Big Island Windward Waters.

Data Courtesy of NOAA.gov