Photo Credit: Jason Weingardt

West Kaua’i

Rest Of Today: Breezy. Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs around 83 near the shore to around 71 above 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Partly cloudy. Isolated showers in the evening. Lows around 68 near the shore to around 57 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Wednesday: Sunny. Highs around 83 near the shore to around 71 above 3000 feet. Northeast winds up to 10 mph shifting to the west in the afternoon.

South Kaua’i

Rest Of Today: Breezy. Partly sunny with scattered showers. Highs around 80. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Tonight: Partly cloudy. Breezy. Scattered showers in the evening, then isolated showers after midnight. Lows 64 to 69. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Wednesday: Sunny. Isolated showers in the morning. Highs around 80. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Kaua’i Mountains

Rest Of Today: Mostly cloudy with numerous showers. Highs 70 to 77 in the valleys to around 61 above 4000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 57 to 62 in the valleys to around 50 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Wednesday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 70 to 77 in the valleys to around 61 above 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

North Kaua’i

Rest Of Today: Partly sunny with scattered showers. Highs 73 to 83. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 60 to 68. East winds up to 15 mph. Chance of rain 50 percent.

Wednesday: Mostly sunny with isolated showers. Highs 73 to 83. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

East Kaua’i

Rest Of Today: Partly sunny with scattered showers. Highs 73 to 82. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 57 to 70. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday: Mostly sunny with isolated showers. Highs 73 to 82. Northeast winds around 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A band of enhanced moisture is expected to bring some showery weather to mainly windward areas today, with breezy trade winds prevailing. Drier trade wind weather should move back in tonight and Wednesday, with the trades gradually easing to moderate levels. A shift to a land and sea breeze pattern is expected Thursday, with this pattern lingering into Saturday. Light winds will keep showers near the coast at night and over interior and leeward areas each afternoon. A front will enter the northwest islands late Saturday and shift down the island chain Saturday night through early next week. The front will usher in light to moderate north-northeasterly winds and return the shower focus to windward slopes and coasts.

Discussion

Currently at the surface, a ridge of high pressure is located around 750 miles north of Honolulu, and is driving moderate to locally breezy trade winds across the island chain early this morning. Infrared satellite imagery shows partly to mostly cloudy conditions across the state, with cloud cover most prevalent over windward areas. Radar imagery shows scattered to numerous showers moving into windward locales, and a few showers reaching leeward areas from time to time. Main short term focus revolves around trade wind trends and rain chances.
A ridge of high pressure north of the islands will settle slowly east-southeastward during the next couple days. Breezy trade winds will prevail today, then ease into the moderate range Wednesday as a front begins to approach from the northwest. The trades will become light and variable Thursday into Saturday as the front continues to slowly approach the islands, with sea and land breezes common statewide. The front appears to move into the northwest islands late Saturday, then slide southeast down the island chain Saturday night into early next week. Light to moderate north-northeasterly winds will fill over the western islands late Saturday, with moderate northeast trades expected across the entire state Sunday into early next week.
As for the remaining weather details, a band of enhanced moisture associated with an old front will move through the islands today, bringing some showery weather to windward areas and sending a few more showers into leeward locales. Drier conditions should move back in tonight and Wednesday, with mainly windward showers expected. A land and sea breeze pattern will set up Thursday and continue into Saturday. No significant rainfall is expected during this time, with showers holding mainly near the coast each night and over the island interiors during each afternoon. A return of the trades should focus showers back over windward slopes and coasts Saturday night through early next week.

Aviation

The satellite imagery this morning shows an unstable cumulus cloud band associated with the remnants of an old frontal boundary drifting through the islands. Expect increasing cloud and shower trends through this morning, especially over windward and mountain areas. Leeward areas will see less shower activity.
The high pressure ridge north of the state will weaken and drift closer to the Hawaiian Islands due to a weak cold front approaching the islands from the northwest. Trade winds will weaken into the moderate to locally breezy range today, becoming moderate trades on Wednesday.
AIRMET Sierra remains in effect for mountain obscuration over north through east sections of Kauai, Oahu and Molokai.
AIRMET Tango remains in effect for moderate turbulence below 9,000 feet over and immediately southwest through northwest of mountains. This AIRMET will likely remain in effect through the early morning hours, and then be cancelled later this morning as wind speeds weaken.

Marine

Surface high pressure centered far northeast of the islands is maintaining locally strong easterly trade winds across the state early this morning. A Small Craft Advisory (SCA) remains in effect through early Wednesday morning for the typically windier waters adjacent to the islands of Maui County and the Big Island. The trade winds are expected to begin weakening during the daytime hours on Wednesday as a front sags south toward the islands. The background winds will likely become light and variable in the vicinity the western islands starting Thursday, and over the remainder of the state by Friday. The weakening front may move down close to Kauai this weekend. The arrival of this feature may usher in a period of light to locally moderate northeast winds over the western islands starting Saturday.
A combination of small, long-period south (170-180 degrees) and short-period southeast (130-140 degrees) swells will likely keep modest background surf along south facing shores into this weekend. Looking ahead, a gale low is currently moving across the Tasman Sea. The fetch associated with this feature appears to be aimed toward Hawaii. Based on typical travel times from this source region, a small long-period south-southwest (210-220 degrees) swell could potentially arrive in the islands early next week. The locally strong trade winds will likely keep choppy, moderate surf along east facing shores today. Expect the surf to gradually lower along east facing shores from later tonight through the end of the week as the trade winds weaken.
Surf along north facing shores will likely remain small into mid- week. A moderate, medium-period north-northwest (330-340 degrees) swell arriving Thursday will likely cause surf to increase along exposed north facing shores through early Friday. A reinforcing, medium-period north-northwest (340-350 degrees) swell spreading over the area starting Friday night will cause surf to continue to build heading into next weekend. Surf heights produced by this swell may reach the High Surf Advisory criteria along exposed north facing shores from Saturday into Sunday.

HFO Watches/Warnings/Advisories

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

Data Courtesy of NOAA.gov