Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Mostly sunny. Breezy. Isolated showers in the morning. Highs around 91 near the shore to around 79 above 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers after midnight. Lows around 73 near the shore to around 62 above 3000 feet. East winds 10 to 15 mph decreasing to up to 15 mph after midnight. Chance of rain 20 percent.

Thursday: Mostly sunny with isolated showers. Highs around 91 near the shore to around 79 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

South Kaua’i

Today: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 83 to 90. East winds 10 to 25 mph. Chance of rain 50 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows around 74. Northeast winds around 15 mph. Chance of rain 50 percent.

Thursday: Mostly cloudy with numerous showers in the morning, then mostly sunny with scattered showers in the afternoon. Highs 82 to 90. Northeast winds around 15 mph. Chance of rain 70 percent.

Kaua’i Mountains

Today: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs 76 to 89 in the valleys to around 68 above 4000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 65 to 73 in the valleys to around 60 above 4000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Thursday: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 75 to 89 in the valleys to around 67 above 4000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

North Kaua’i

Today: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 78 to 92. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 67 to 75. East winds 10 to 15 mph. Chance of rain 50 percent.

Thursday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 78 to 91. East winds 10 to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 75 to 87. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 66 to 78. East winds 10 to 15 mph. Chance of rain 50 percent.

Thursday: Partly sunny with scattered showers. Highs 75 to 87. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Breezy trade winds will deliver limited and brief showers the next couple of days, mainly to windward areas. From late Friday through the weekend, island weather will be highly dependent on the track and intensity of a tropical cyclone that is expected to develop far east-southeast of the islands.

Discussion

A stable and breezy summertime trade wind weather pattern will prevail through Friday as deep-layer high pressure prevails over the central N Pacific. Brief showers will favor windward areas, mainly during nights and mornings.
From late Friday through the weekend, confidence in forecast details remains on the lower end of the spectrum, but models are coming to an increased consensus on some of the larger scale features. A tropical cyclone (TC) is likely to form about 1350 miles ESE of the islands today, and head generally westward while intensifying the next couple of days, potentially passing dangerously close to the islands over the weekend.
It is too early for forecast specifics with respect to potential impacts in the islands, but the triple threat that a TC could bring includes strong and damaging winds, heavy and potentially flooding rainfall, as well as high surf and storm surge.
If a TC does form, note that public and marine forecasts from WFO Honolulu will be updated on a modified schedule, in conjunction with the latest TC forecast issued at 5 am/pm and 11 am/pm HST. As a reminder, the Central Pacific Hurricane Center in Honolulu has forecast responsibility for TCs after they move W of 140W. This potential tropical cyclone, regardless of development level, will likely cross 140W late tonight or Thursday morning. Throughout the life cycle of any TC near Hawaii, forecast information can be found on the web at hurricanes.gov.
It is the peak of hurricane season here in Hawaii, and now is a good time to make sure that you and your family are prepared. For more information, visit weather.gov/safety/hurricane-plan.

Aviation

Moderate to locally breezy trades will increase slightly today. Low cigs and SHRA should be focused mainly over windward and mauka areas. Brief MVFR conds will be possible with any SHRA, but VFR conds should prevail.
No AIRMETs are currently in effect.
AIRMET Tango may be needed later this morning to account for moderate low level turb downwind of the terrain of all islands.

Marine

Trades will strengthen to more areawide fresh to locally strong magnitudes beginning today and will persist at these speeds through the remainder of the week. This is in response to a large area of high pressure anchored far north of the islands that is producing a tight pressure gradient back toward the islands. The Small Craft Advisory (SCA) remains in effect for the typical windier waters surrounding Maui County and Big Island until early Thursday morning. The SCA will likely be expanded in areal coverage to account for these stronger trades. There is a high probability that a tropical depression or tropical cyclone will develop near the delineation between the East Pacific and Central Pacific basins (i.e.,140W longitude) in the next 24 hours. If a tropical depression or tropical storm does develop, it is forecast to track westward toward the islands during the remainder of the week, possibly reaching the local southeastern waters this weekend. In such a scenario, offshore conditions will become quite windy with the development of gales likely occurring within eastern island bays and channels. Seas will also significantly increase in both wind wave and in easterly swell originating from the captured fetch. This week's marine forecasts will be highly dependent upon the potential evolution, development and track of a potential tropical cyclone.
Very small size, long period forerunners outracing the northwest (310 degrees) swell from once Typhoon Ampil are showing up at both the Hanalei and Waimea Bays early this morning. The lower period swell energy will fill in around Kauai's shores near sunrise. This swell will quickly lift surf to near head high within larger sets along Kauai's north and west-facing exposures this morning. Better blocked Oahu should experience this lifted surf by the afternoon. The recent south (190 degree) swell that peaked early Tuesday morning has leveled out and will hold small through the day before fading Thursday. Wind wave eastern chop will increase in the next day or so as a result of strengthening trades over and upstream of the island chain.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Thursday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov