Photo Credit: Brendan Stephen

West Kaua’i

Today: Mostly sunny with isolated showers. Highs around 87 near the shore to around 75 above 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows around 71 near the shore to around 61 above 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Wednesday: Breezy. Mostly sunny with isolated showers. Highs around 87 near the shore to around 75 above 3000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

South Kaua’i

Today: Mostly sunny. Breezy. Isolated showers in the morning, then scattered showers in the afternoon. Highs 79 to 87. East winds 15 to 20 mph. Chance of rain 30 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 73. Northeast winds 15 to 20 mph. Chance of rain 40 percent.

Wednesday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 79 to 87. Northeast winds 15 to 20 mph. Chance of rain 40 percent.

Kaua’i Mountains

Today: Breezy. Partly sunny with scattered showers. Highs 73 to 84 in the valleys to around 64 above 4000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 63 to 70 in the valleys to around 59 above 4000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Wednesday: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs 72 to 82 in the valleys to around 64 above 4000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

North Kaua’i

Today: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs 75 to 88. East winds 10 to 15 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy with scattered showers. Lows 65 to 73. East winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 75 to 88. East winds 10 to 20 mph. Chance of rain 50 percent.

East Kaua’i

Today: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs 72 to 85. East winds 10 to 15 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy with scattered showers. Lows 65 to 76. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 71 to 85. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Breezy trade winds will be with us through the remainder of the week. Higher terrain may experience areas of windy trades from Wednesday into this weekend. Showers will focus along windward mauka exposures.

Discussion

The North Pacific synoptic picture is characterized by two broad gyres of ridging split by a progressively moving trough to the east northeast. The 1032 mb surface high backing the surface cold front will merge with the 1029 mb high currently centered 1,300 miles northeast of Oahu. The latter cell is creating a tight pressure gradient aimed directly toward the islands. This will result in continued statewide breezy easterly trade winds. This morning's soundings are consistent in delivering the message of a stable and drier environment; a slightly lower near 6-7k foot trade inversion and lowering precipitable waters of about .20-.30 inches from 12 hours ago. This strong trade inversion is contributing to many exposed windward sites reporting overnight breezy near 20 knot easterlies with gusts to 30 mph. Lower level drier air is filtering in behind last night's westward-passing shallow moisture band that produced scattered offshore showers in the island's leeward eddies. The advection of drier air will trend overall rain chances down into low end to moderate chance categories (25-40%) with the highest rain chances of near 50% being confined to upper, windward-facing slopes. Occasional light showers will make it over into leeward communities under this healthy trade regime. While the state will experience breezy to windy trades, numerical weather prediction guidance indicates that lower layer moisture or near surface humidities will remain high enough (lower elevation leeward afternoon %RHs falling into the 50s as surface temperatures approach the mid 80s) to maintain a somewhat low fire weather threat the next several days.
A strong low moving across the northern Pacific, and its associated aforementioned cold front extending from roughly 45N145W southwestward to just east of the date line, will quickly advance east into the U.S. mainland Pacific Northwest Wednesday. As this occurs and surface high pressure builds in behind this boundary north of the islands, the further tightening of a taut upstream pressure gradient will boost already breezy easterly trades to near windy speeds. Island-wide high end breezy to localized windy, gusty trades may reach Wind Advisory criteria (equal to or greater than 30 mph) as early as Wednesday morning …especially through higher elevation gaps and over ridgelines. The southern tail of the front will settle south and reach our area in backdoor fashion from the north northeast Friday or Saturday. Other than providing a quick amplification to already robust winds, moisture pooling along the boundary may enhance late week shower activity.

Aviation

Breezy easterly trades will continue today, with clouds and showers favoring windward and mauka locations. Brief periods with MVFR CIGS/VSBYS are possible in passing showers. Otherwise, VFR conditions will prevail. The trades will become strong and gusty starting Wednesday.
AIRMET Tango for moderate low-level turbulence will persist over and downwind of all island terrain.

Marine

A broad ridge of high pressure remains established north of the islands generating fresh to locally strong trades. The broad ridge will strengthen through the rest of the week translating to strong to near gale force trades developing Wednesday into Thursday and possibly reaching gale force Friday into the weekend. The existing Small Craft Advisory remains in effect and will eventually require an expansion in coverage as trades strengthen and seas become elevated.
Existing medium to long period northwest (320 degrees) swell will hold steady through the morning hours. A larger, long period northwest (320) swell will fill in later tonight keeping surf elevated. This swell is forecast to peak above the High Surf Advisory threshold for north (15 feet) and west (12 feet) facing shores Wednesday and may near High Surf Warning thresholds late Wednesday (25 feet north shores and 20 feet west shores) before fading Thursday. This swell will mix with a small, long period north-northwest (340-350) swell that will also peak tonight into Wednesday.
Rough and choppy surf along east facing shores will gradually become more elevated during the second half of the week as strong trades further develop locally and upstream. Surf along east facing shores is expected to build to the HSA thresholds (10 feet) Thursday into Friday and hold into the weekend.
Surf along south facing shores remains small through the period except which a small bump expected Wednesday.
Peak monthly tides are forecast during the Nov 14th to Nov 18th period. This along with elevated seas due to strong trades and fading large northwest swell will exacerbate coastal inundation impacts, particularly for vulnerable locations during early morning high tides.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Wednesday for Oahu Leeward Waters, 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