West Kaua’i

Today: Sunny and breezy. Highs 87 to 93 near the shore to around 80 above 3000 feet. East winds up to 20 mph.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Lows 71 to 77 near the shore to around 64 above 3000 feet. East winds up to 15 mph.

Thursday: Partly sunny. Highs 86 to 93 near the shore to around 80 above 3000 feet. East winds 10 to 15 mph.

South Kaua’i

Today: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 83 to 90. East winds 10 to 20 mph. Chance of rain 40 percent.

Tonight: Breezy. Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows around 75. East winds 10 to 20 mph. Chance of rain 30 percent.

Thursday: Partly sunny. Breezy. Scattered showers in the morning. Highs 83 to 91. East winds 10 to 20 mph. Chance of rain 30 percent.

Kaua’i Mountains

Today: Mostly sunny with scattered showers. Highs 77 to 87 in the valleys to around 68 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Scattered showers. Lows 67 to 72 in the valleys to around 61 above 4000 feet. East winds up to 20 mph increasing to 10 to 25 mph after midnight. Chance of rain 40 percent.

Thursday: Partly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 76 to 87 in the valleys to around 69 above 4000 feet. East winds 10 to 25 mph. Chance of rain 40 percent.

North Kaua’i

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 79 to 89. Southeast winds up to 15 mph. Chance of rain 30 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Isolated showers. Lows 67 to 75. East winds up to 15 mph. Chance of rain 20 percent.

Thursday: Partly sunny. Isolated showers in the morning. Highs 79 to 89. East winds 10 to 15 mph. Chance of rain 20 percent.

East Kaua’i

Today: Partly sunny with scattered showers. Highs 75 to 88. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 67 to 78. East winds 10 to 15 mph. Chance of rain 40 percent.

Thursday: Mostly cloudy. Scattered showers in the morning. Highs 75 to 87. East winds 10 to 15 mph. Chance of rain 40 percent.

Detailed Forecast

Synopsis

Moderate to locally breezy trades will continue to gradually strengthen today as a high north of the state drifts south. Clouds and light showers will focus along windward and mauka areas, particularly overnight and during the early morning as a rather dry and stable airmass settles over the state and persists into the weekend.

Discussion

Surface high far north of the state is driving moderate to locally breezy trade winds. Radar and satellite imagery show mostly scattered, light showers focusing mainly along windward and mauka regions. The surface pressure gradient will strengthen over the next few days as the high sinks south and tropical cyclones pass far south of Hawaii, maintaining moderate to locally breezy conditions with minor fluctuations in strength into the weekend. A typical summertime trade wind pattern will hold through the week with stable, light to moderate showers focusing mainly along windward and mauka areas, particularly during the overnight and mornning hours with a few showers spilling over leeward overnight.

Aviation

Trade winds will increase over the next few days with prevailing VFR conditions. Brief periods of MVFR conditions are possible with low clouds and showers favoring windward and mountain areas in the overnight to early morning hours.
AIRMET Sierra remains in effect for Mountain Obscuration over Kauai, Oahu, Molokai, and Lanai. This AIRMET will diminish in coverage later this morning.
AIRMET Tango in effect for low level Moderate Turbulence over and immediately S and W of island mountains. This AIRMET will likely continue for the next several days.

Marine

Trade winds will maintain at moderate to strong speeds as high pressure to the far north-northwest drifts southeastward and Hurricane Iona and Tropical Storm Kali passes several hundred miles south of the state. The Small Craft Advisory (SCA) remains in effect for the typical windier waters and channels around Maui County and the Big Island and has been expanded in coverage to include the Kauai waters through tonight as trade winds strengthen. This SCA will likely be expanded to most local waters by the weekend.
The two current Tropical cyclones in the Central Pacific are forecast to pass several hundred miles south of Hawaii over the next couple of days, more information on Hurricane Iona can be found at WMO header WTPA21 PHFO and AWIPS header HFOTCMCP1, and information on Tropical Storm Keli can be found at WMO header WTPA22 PHFO and AWIPS header HFOTCMCP2. Additional Tropical Cyclone development could be expected far southeast of Hawaii in the next few days. Isolated thunderstorms along the northern periphery of these systems may effect the far southern portion of the offshore waters, and while some short- period southeast swells may reach southern and southeastern shores of Hawaii, a much larger and unrelated south swell will dominate.
A multi-day buildup of surf for south facing shores is expected starting today as long period swells fill in. The first swell has started to show long period forerunners early this morning and will build through the afternoon. By this evening, forerunners from the next much larger swell will start to fill in and peak late Thursday well over advisory levels and may near warning levels near its peak, then hold through Friday. The swell will gradually decline over the weekend and will be followed by another long period south swell early next week.
East shore surf will trend up over the next few days as strengthening trade winds generate larger wind waves. Surf along east facing shores will rise to seasonal average late this evening or Thursday and hold into the weekend, followed by a possible decline early next week.
Flat summer conditions along north facing shores may be interrupted this weekend by a small long period northwest swell from Typhoon Krosa, currently in the western Pacific.

Fire weather

Humidity and wind speeds will be near critical conditions today into the weekend as breezy conditions develop. Some uncertainty remains in the wind speeds later this week and will continue to monitor for possibility of any headlines.

HFO Watches/Warnings/Advisories

Tsunami Advisory until noon HST today for all Hawaii islands,
Tsunami Advisory until noon HST today for all Hawaiian waters,
Small Craft Advisory until 6 AM HST Thursday for Kauai Northwest Waters, Kauai Leeward Waters.
Small Craft Advisory until 6 AM HST Thursday for Kaiwi Channel, Maui County Windward Waters, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.