Photo Credit: Brendan Stephen

West Kaua’i

Today: Breezy. Mostly cloudy with scattered showers. Highs around 81 near the shore to around 69 above 3000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows around 66 near the shore to around 55 above 3000 feet. East winds 10 to 15 mph. Chance of rain 40 percent.

Sunday: Mostly sunny. Isolated showers in the morning. Highs around 80 near the shore to around 67 above 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

South Kaua’i

Today: Mostly cloudy. Breezy. Occasional showers in the morning, then numerous showers in the afternoon. Highs 76 to 81. East winds 15 to 20 mph. Chance of rain 90 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 66. East winds 15 to 20 mph. Chance of rain 50 percent.

Sunday: Partly sunny. Breezy. Scattered showers in the morning. Highs 75 to 80. East winds 15 to 25 mph. Chance of rain 40 percent.

Kaua’i Mountains

Today: Breezy. Occasional showers in the morning, then numerous showers in the afternoon. Highs 68 to 76 in the valleys to around 59 above 4000 feet. East winds 10 to 25 mph. Chance of rain near 100 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 58 to 63 in the valleys to around 53 above 4000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Sunday: Partly sunny. Breezy. Scattered showers in the morning. Highs 69 to 75 in the valleys to around 59 above 4000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

North Kaua’i

Today: Mostly cloudy. Breezy. Occasional showers in the morning, then numerous showers in the afternoon. Highs 71 to 82. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 90 percent.

Tonight: Mostly cloudy with scattered showers. Lows 59 to 67. East winds 10 to 15 mph. Chance of rain 50 percent.

Sunday: Partly sunny. Breezy. Scattered showers in the morning. Highs 70 to 81. East winds 10 to 20 mph. Chance of rain 40 percent.

East Kaua’i

Today: Breezy. Occasional showers in the morning, then numerous showers in the afternoon. Highs 68 to 79. East winds 10 to 20 mph. Chance of rain near 100 percent.

Tonight: Mostly cloudy with scattered showers. Lows 59 to 70. East winds 10 to 15 mph. Chance of rain 50 percent.

Sunday: Partly sunny. Breezy. Scattered showers in the morning. Highs 68 to 78. East winds 10 to 20 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

High pressure to our north will keep trade winds blowing across local waters through the forecast period. Wind speeds will strengthen later today as the pressure gradient steepens, remaining breezy to windy through much of the new week. Clouds and showers will favor windward and mauka areas.

Discussion

Troughing to the west of the main Hawaiian Islands, combined with a high to our north, is driving breezy east southeasterly trade winds across local waters this morning. Satellite loop shows thick middle and high clouds just north of the islands, marking the northern flank of the subtropical jetstream. Scattered to patchy broken low clouds are noted across windward and mauka sections of the smaller islands, with scattered low clouds to clear skies noted across the Big Island. Radar shows scattered moderate showers associated with this low cloud cover. Overnight soundings show a stable airmass, with positive lifted index values.
Overall, expect a trade wind distribution of clouds and showers through the forecast period, with minor variations defendant on airmass stability and pressure gradient steepness. Models show that winds should turn to a more easterly direction statewide later today as the troughing to our west retreats westward and the high to our north becomes the main flow driver. Latest high- resolution models show winds may reach Wind Advisory threshold across higher terrain immediately adjacent to traditionally windier channels across the eastern half of the state. A Wind Advisory will go into effect at noon today for the Kohala Mountains on the Big Island, as well as for Molokai, Kahoolawe and portions of Lanai and Maui. While this advisory will continue through Sunday afternoon, it may need to be extended.
Showers embedded within trade flow will focus rainfall across windward areas. The almost zonal subtropical jetstream across the islands may enhance these showers at times. Expect a somewhat drier airmass to fill in after today. Total rainfall will be light. Breezy trade winds will push some showers to leeward areas.
By late next week, models show an upper trough will move over the islands from the northwest, introducing a pool of destabilizing cold air aloft. At the surface, high pressure will remain north of the state and trade winds will persist at the surface. However, associated trade showers may be heavier and more widespread as the upper trough moves in.

Aviation

Breezy easterly trade winds will remain in place through the next few days and will focus showers primarily over windward and mountain areas. An increase in shower coverage and intensity is expected this morning as a band of clouds and showers associated with an old front moves into the islands from east to west within the trade wind flow. Although VFR conditions are prevailing statewide early this morning, latest satellite imagery shows this band of clouds and showers just east of the state. MVFR conditions can be expected within these passing showers. Windward shower coverage will then gradually decline this afternoon and tonight.
There are currently no AIRMETs in effect. AIRMET Sierra for mountain obscuration may be needed later this morning for portions of the state as windward showers and cloud cover increase. Additionally, AIRMET Tango will be issued later this morning as well to account for moderate low-level turbulence as wind speeds increase.

Marine

Fresh to strong trade winds expected through the middle of next week. The Small Craft Advisory (SCA) has been expanded to all Hawaiian coastal waters through tonight due to a combination of winds and swell. The SCA will likely extend into next week for some waters as winds remain strong.
An upward trend in surf along north and west facing shores is expected this weekend as a long-period north-northwest swell builds down the island chain. This swell will peak this afternoon through tonight. A High Surf Advisory is posted through tonight for exposed north and west facing shores from Kauai to Maui County based on upstream buoy observations. A slow downward trend is expected by late Sunday.
Surf along exposed north and east facing shores will trend up early next week as a medium-period north-northeast swell arrives. Surf heights will likely reach the advisory levels (potentially near the warning level for east facing shores) as this swell peaks Monday through Tuesday. Otherwise, short-period/rough surf is anticipated along exposed eastern shores due to the strong trades locally and upstream.
Surf along south facing shores will potentially trend up late next week due to the arrival of a long-period south swell.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 AM HST Sunday for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kauai North, Molokai Windward, Molokai North, Molokai West, Maui Central Valley North, Windward Haleakala.
Wind Advisory from noon today to 6 PM HST Sunday for Kahoolawe, Maui Windward West, Kohala, Molokai, Lanai Windward, Lanai Leeward, Maui Central Valley North, Maui Central Valley South, Kipahulu, Big Island North.
Small Craft Advisory until 6 AM HST Sunday for all Hawaiian waters,

Data Courtesy of NOAA.gov