Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Cloudy with numerous showers and slight chance of thunderstorms. Highs around 82 near the shore to around 72 above 3000 feet. Light winds. Chance of rain 70 percent.

Tonight: Cloudy. Scattered showers and slight chance of thunderstorms in the evening, then numerous showers and slight chance of thunderstorms after midnight. Lows 64 to 69 near the shore to around 55 above 3000 feet. Light winds. Chance of rain 60 percent.

Sunday: Cloudy with numerous showers and slight chance of thunderstorms. Highs around 83 near the shore to around 73 above 3000 feet. East winds up to 15 mph. Chance of rain 70 percent.

South Kaua’i

Today: Cloudy with numerous showers and slight chance of thunderstorms. Highs around 80. East winds up to 10 mph. Chance of rain 70 percent.

Tonight: Cloudy. Scattered showers and slight chance of thunderstorms in the evening, then numerous showers and slight chance of thunderstorms after midnight. Lows 62 to 68. Light winds. Chance of rain 60 percent.

Sunday: Breezy. Cloudy with numerous showers and slight chance of thunderstorms. Highs around 81. East winds 10 to 20 mph. Chance of rain 70 percent.

Kaua’i Mountains

Today: Cloudy with numerous showers and slight chance of thunderstorms. Highs around 75 in the valleys to around 64 above 4000 feet. Light winds. Chance of rain 70 percent.

Tonight: Cloudy with numerous showers and slight chance of thunderstorms. Lows around 58 in the valleys to around 50 above 4000 feet. Light winds. Chance of rain 60 percent.

Sunday: Cloudy with numerous showers and slight chance of thunderstorms. Highs around 76 in the valleys to around 65 above 4000 feet. East winds up to 15 mph. Chance of rain 70 percent.

North Kaua’i

Today: Cloudy with numerous showers and slight chance of thunderstorms. Highs 75 to 81. East winds up to 10 mph. Chance of rain 70 percent.

Tonight: Cloudy. Scattered showers and slight chance of thunderstorms in the evening, then numerous showers and slight chance of thunderstorms after midnight. Lows 58 to 67. Southeast winds up to 10 mph in the evening becoming light. Chance of rain 60 percent.

Sunday: Cloudy with numerous showers and slight chance of thunderstorms. Highs 76 to 82. East winds up to 15 mph. Chance of rain 70 percent.

East Kaua’i

Today: Cloudy with numerous showers and slight chance of thunderstorms. Highs 73 to 79. East winds up to 10 mph. Chance of rain 70 percent.

Tonight: Cloudy with numerous showers and slight chance of thunderstorms. Lows 56 to 69. Light winds becoming northeast up to 10 mph after midnight. Chance of rain 60 percent.

Sunday: Cloudy with numerous showers and slight chance of thunderstorms. Highs 74 to 80. East winds 10 to 15 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Considerable high cloud cover will keep skies mostly cloudy through the weekend. Rather dry weather will continue over the eastern end of the state today and tonight, while scattered showers continue and a few thunderstorms remain possible over the western islands. An afternoon thunderstorm may develop on the Big Island as well. A disturbance aloft will develop over the state on Sunday, increasing showers and bringing the potential for a few thunderstorms to the entire island chain. Moderate to breezy trade winds and more typical trade wind weather will then return Monday and linger through late next week.

Discussion

Currently at the surface, a trough of low pressure is located 175 miles northwest of Kauai, while a 1027 mb high is centered around 1500 miles north-northeast of Honolulu. Light winds prevail over the western islands, while moderate trades persist over the eastern end of the state. Infrared satellite imagery shows mostly cloudy skies across the state. Radar imagery shows scattered showers over Kauai, a few showers showers affecting the Big Island, and very little if any shower activity over Oahu and Maui County at the moment. Main short term focus revolves around trade wind trends and thunder chances during the next couple days.
The trough of low pressure will remain nearly stationary northwest of Kauai today and tonight, with little change to the winds expected. The trough will then slowly shift west and further away from the islands Sunday and Sunday night as high pressure builds to the distant northeast, allowing moderate to locally breezy trade winds to build back across the entire island chain. A ridge of high pressure will then settle in several hundred miles to the north and northeast of the state next week, keeping moderate to breezy trade winds in place across the island chain.
As for the remaining weather details, little change in the overall weather pattern is expected through tonight, with shower coverage remaining the highest over Kauai. Shower coverage will be less over Oahu during this time, but not as dry as over Maui County and the Big Island where fairly dry weather will continue. The airmass will remain unstable over the western end of the state, so a slight chance of thunderstorms will need to be included in the forecast from Oahu westward. A thunderstorm or two could pop over the Big Island slopes this afternoon as well. A disturbance aloft will develop over the state Sunday, bringing the potential for some heavier showers and even a few thunderstorms to the entire island chain. Considerable cloudiness will continue statewide through the weekend. The most unstable airmass appears to slide south of the state by daybreak Monday, allowing a more typical trade wind pattern featuring mainly windward and mauka showers to settle in and linger through the end of the work week.

Aviation

The active pattern with showers and the potential for isolated thunderstorms will continue this weekend due to an upper disturbance and surface trough lingering to the northwest. Low- level flow will remain out of the east-southeast, which will translate to the localized land/sea breeze regime holding for Oahu and Kauai. Although the bulk of the shower activity will remain focused over the western end of the state this morning, much of the state could get into the mix later today through the end of the weekend as deep moisture pools northward ahead of the upper trough.
AIRMET Sierra remains in effect for mountain obscuration for Kauai and Oahu due to low clouds and showers. This may be lifted for Oahu later this morning if conditions continue to improve.
AIRMET Tango remains in effect for tempo moderate turbulence in the layer FL200-FL400.

Marine

Weak ridging over the state, with a stationary trough west of Kauai, is resulting in generally moderate areawide southeasterlies that are veering more southerly around Kauai. The trough is forecast to remain nearly stationary through the day before it drifts slowly westward into early next week. This will allow trades to return over the near and offshore waters through the remainder of the week. Winds across the eastern end of the state will remain strong enough to continue a Small Craft Advisory (SCA) for the windier areas around Big Island. Upper level troughing northwest of the area, along with convergence ahead of the surface trough, will create enough instability to support thunderstorm activity over the coastal waters from Oahu westward through the weekend. Thunderstorm activity may expand into more eastern waters Sunday as a new low aloft develops over the state.
The ongoing small northwest (320 degree) swell will slowly decline through Saturday. A small northeast swell will fill in tonight, peak Saturday and then level out through early next week. There are no other significant North Pacific swells that will affect the islands through late next week. Moderate to fresh trades upstream of the state will continue to produce choppy surf conditions along eastern exposures through next week. Small background energy from different southerly directions will continue to hold small surf in along south-facing shores for the foreseeable future.

HFO Watches/Warnings/Advisories

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

Data Courtesy of NOAA.gov