Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Partly sunny with scattered showers in the morning, then cloudy with showers likely in the afternoon. Highs around 81 near the shore to around 71 above 3000 feet. East winds up to 10 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with showers likely. Lows 64 to 69 near the shore to around 55 above 3000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

Friday: Mostly cloudy with showers likely. Highs around 87 near the shore to around 75 above 3000 feet. Southeast winds 10 to 15 mph. Chance of rain 70 percent.

South Kaua’i

Today: Partly sunny in the morning then becoming cloudy. Scattered showers. Highs around 80. Northeast winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with showers likely. Lows 64 to 70. Northeast winds up to 10 mph. Chance of rain 70 percent.

Friday: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs around 84. East winds up to 10 mph shifting to the south in the afternoon. Chance of rain 60 percent.

Kaua’i Mountains

Today: Mostly cloudy with showers likely. Highs 69 to 75 in the valleys to around 64 above 4000 feet. North winds up to 10 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with showers likely. Lows around 59 in the valleys to around 51 above 4000 feet. Southeast winds around 10 mph becoming up to 15 mph after midnight. Chance of rain 70 percent.

Friday: Mostly cloudy with showers likely. Highs 74 to 81 in the valleys to around 65 above 4000 feet. South winds up to 15 mph. Chance of rain 70 percent.

North Kaua’i

Today: Mostly cloudy with scattered showers. Highs 71 to 80. North winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then showers likely after midnight. Lows 59 to 67. Southeast winds up to 10 mph. Chance of rain 70 percent.

Friday: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs 77 to 86. Southeast winds up to 15 mph. Chance of rain 70 percent.

East Kaua’i

Today: Mostly cloudy with scattered showers. Highs 71 to 81. North winds around 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then showers likely after midnight. Lows 57 to 69. Northwest winds up to 10 mph shifting to the southwest after midnight. Chance of rain 70 percent.

Friday: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs 77 to 85. Southwest winds up to 10 mph shifting to the south in the afternoon. Chance of rain 70 percent.

Detailed Forecast

Synopsis

A stalled front near Molokai is expected to weaken, and become a surface trough later this morning. Moderate northeast winds persist west of the front, while light and variable winds are over the eastern islands. Once it develops, the surface trough will move back toward the western end of the island chain from later today through Friday. This will likely keep a wet weather pattern across portions of the state, especially on Oahu and Kauai, during the next couple of days. Once this surface feature moves west of the islands, expect a more typical trade wind weather pattern to return to the state from this weekend into the middle of next week.

Discussion

Based on satellite imagery, radar reflectivity data, and surface observations, a weakening front appears to have stalled over Maui County near Molokai early this morning. An area of locally heavy rainfall developed over portions of Molokai late Wednesday evening. Some showers linger along the northeast coastal section of Molokai, but most of these showers have now moved over the coastal waters just north of eastern Molokai. A diffuse band of broken to locally overcast low clouds with embedded light showers remains draped across Oahu and Kauai to the west of the front. Moderate northeast winds also continue to the west of the front, while light and variable winds persist elsewhere. As a result, local nighttime land breezes, which become established last evening, dominate the flow over most of the Big Island and Maui. The showers west of the front will continue to favor north through northeast facing slopes of Oahu and Kauai through this morning.
There is an upper-level low centered near 33N 158W with an upper- level trough extending down over Oahu. This trough aloft will keep the atmosphere unstable over the western islands during the next few days as it tracks slowly westward. At the same time, the nearly stationary front will transform into a surface trough later this morning. The forecast guidance is in good agreement that the surface trough will begin to shift back slowly west toward Oahu by this afternoon. This will cause the winds to become lighter, and gradually shift out of the southeast across much of the area later today and tonight. The atmospheric instability due to the upper-level trough will persist over the western islands. This combined with the slightly enhanced moisture that will accompany the westward moving surface trough will produce passing showers as it moves over Oahu tonight, and then over Kauai on Friday. At the moment, we do not anticipate significant flooding due to widespread heavy rainfall in the forecast guidance. However, some locally heavy downpours cannot be ruled later today and/or Friday.
By Saturday, the surface trough will be departing to the west of Kauai. Surface high pressure will build to our north, which will allow moderate trade winds to gradually fill back in over the state this weekend. The trade winds are expected to persist into the middle of next week. Low clouds and showers transported by the trades into the islands will tend to favor windward and mauka areas, but the trade winds may transport light showers over to leeward sections of some of the smaller islands. A weak inverted upper-level trough is forecast to set up just east of the islands early next week, which may enhance some of the low clouds and showers as they arrive into the state. However, rainfall totals on any given day or night will be highly dependent on incoming moisture availability.

Aviation

A stationary front, currently situated near Molokai, will transition into a trough later today and retrograde westward across the state. This feature will bring layers of clouds and scattered to numerous showers to mainly interior portions of Oahu and Kauai. MVFR conditions may accompany this activity, see AIRMET SIERRA below. Elsewhere, isolated showers will prevail.
Light flow will allow for seabreeze development by late this morning and into the afternoon, especially along the more sheltered leeward coastal locations.
AIRMET SIERRA remains in effect above 2500 feet for north thru east sections of Kauai, Oahu, and Molokai for tempo mountain obscuration due to clouds and showers.

Marine

A front will stall and weaken to a trough around Maui County today. Southeast winds will develop over the eastern end of the state later today and usher the boundary west into tomorrow. A high will build far northeast of the state allowing strong to moderate trades to return to all waters by Saturday and hold into early next week.
A storm low located roughly 700 nm north of Kauai will continue to send a large, short period north swell towards the state through today. The High Surf Advisory has been extended for north facing shores of Kauai, Oahu and Maui County through tonight and may need to be extended for some zones later this afternoon. In addition, a Small Craft Advisory now in effect for most forecast waters due to continued elevated seas. Swell produce from this low will peak today, hold into tonight before steadily declining tomorrow into the weekend.
A series of moderate, long-period south swells will keep south facing shore surf elevated tonight through Saturday. With no significant trade wind flow over and upwind of the state, most surf along east facing shores will be from north swell wrap through the week. Moderate, choppy east shore surf will likely return over the weekend and persist into early next week as the trade winds return.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 AM HST Friday for north facing shores of Kauai, Niihau, Oahu, Molokai and Maui
Small Craft Advisory until 6 PM HST this evening for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Alenuihaha Channel, Big Island Windward Waters.

Data Courtesy of NOAA.gov