Photo Credit: Brendan Stephen

West Kaua’i

Today: Breezy. Mostly sunny with isolated showers. Highs around 87 near the shore to around 77 above 3000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening, then scattered showers after midnight. Lows 72 to 77 near the shore to around 63 above 3000 feet. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Friday: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 87 near the shore to around 77 above 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

South Kaua’i

Today: Partly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 86. Northeast winds 15 to 20 mph. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 70 to 76. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Friday: Partly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 86. Northeast winds 15 to 20 mph. Chance of rain 70 percent.

Kaua’i Mountains

Today: Mostly cloudy. Breezy. Frequent showers in the morning, then scattered showers in the afternoon. Highs 73 to 81 in the valleys to around 70 above 4000 feet. East winds 10 to 20 mph. Chance of rain 80 percent.

Tonight: Mostly cloudy. Numerous showers in the evening, then frequent showers after midnight. Lows 63 to 68 in the valleys to around 58 above 4000 feet. East winds 10 to 15 mph. Chance of rain 80 percent.

Friday: Mostly cloudy. Breezy. Frequent showers in the morning, then scattered showers in the afternoon. Highs 73 to 81 in the valleys to around 70 above 4000 feet. East winds 10 to 20 mph. Chance of rain 90 percent.

North Kaua’i

Today: Partly sunny with scattered showers. Highs 76 to 86. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 66 to 76. East winds 10 to 15 mph. Chance of rain 70 percent.

Friday: Mostly cloudy with scattered showers. Highs 76 to 86. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

East Kaua’i

Today: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 75 to 86. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 64 to 77. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Friday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 75 to 86. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Breezy trade wind conditions will persist through Friday, with showers favoring windward and mauka locations. The Central Pacific Hurricane Center is closely monitoring newly formed Tropical Depression One far east-southeast of the state tracking westward. While it is too early to determine the exact impacts, a transition to a wet and windy period is likely over the weekend through early next week as this tropical cyclone approaches and moves into the area. For updates on the system's development, refer to the latest advisories issued by the Central Pacific Hurricane Center.

Discussion

Short-term guidance remains consistent, showing breezy trade wind conditions continuing through Friday due to strong high pressure well north of the state. Showers will predominantly affect windward and mauka areas, with some reaching leeward sections. A mid-level trough moving from east to west today, combined with increasing low-level moisture, will likely enhance shower coverage later today through Friday. This trough may also weaken or lift the strong subsidence inversion, increasing rainfall chances over leeward areas, particularly during the overnight and early morning hours.
For the extended period (Friday night through early next week), guidance shows Tropical Depression One becoming a Hurricane over the weekend as it passes south of the Big Island. Forecast confidence is increasing that the system will impact our local weather conditions, regardless of its exact development and track over the next several days. A wet and windy period is expected, potentially beginning as early as Friday night into Saturday over the eastern part of the state, then statewide later Saturday through early next week.
Given the potential for prolonged heavy rainfall, localized flash flooding could occur if the rain becomes concentrated. Depending on the system's development, watches for the potential tropical cyclone may be issued later today or tonight for parts of the state. For further details on this system's development, refer to the Tropical Weather Outlook issued by the Central Pacific Hurricane Center.

Aviation

Breezy to locally windy trades will remain through the forecast period. Low cigs and SHRA should mainly be focused over windward and mauka locations, with isolated spillover to leeward sides. Brief MVFR conds will be possible in any SHRA, but generally VFR conds should prevail.
AIRMET Tango is in effect for mod low level turb downwind of the terrain of all islands.

Marine

Fresh to strong trades will prevail during the next couple days, then ramp up to strong to Gale force levels this weekend. A Small Craft Advisory (SCA) remains in effect for the typically windy waters east of Oahu through early Saturday. In fact, winds could get even stronger this weekend as Tropical Cyclone One nears the islands from the east. The marine forecast this weekend into early next week will be highly dependent upon the track and degree of development of this system, and watches may be needed for portions of the waters later today or tonight.
A small long-period northwest swell will peak today, then slowly decline on Friday. Surf will return to typical summertime flat levels over the weekend through the middle of next week aside from some trade wind swell wrap.
Surf along south facing shores will remain small and below the summertime average through early next week. A new long-period south swell arriving Tuesday and Wednesday next week, could build surf back up close to the summertime average.
Surf along east facing shores will remain near seasonal levels through Friday, then rise above normal over the weekend into early next week as the winds strengthen over and upstream of the islands. Depending on the track and degree of development of a tropical system approaching from the east, surf could potentially reach advisory levels over some east facing shores over the weekend into early next week.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Saturday for Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov