Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Mostly sunny. Breezy. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 79 near the shore to around 67 above 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers and isolated thunderstorms. Locally heavy rainfall possible. Lows around 66 near the shore to around 55 above 3000 feet. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Thursday: Partly sunny. Breezy. Isolated showers in the morning. Highs around 79 near the shore to around 67 above 3000 feet. Northeast winds 15 to 20 mph. Chance of rain 20 percent.

South Kaua’i

Today: Breezy. Partly sunny with scattered showers. Highs around 78. Northeast winds 15 to 25 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Occasional showers and isolated thunderstorms in the evening, then numerous showers and isolated thunderstorms after midnight. Locally heavy rainfall possible. Lows 62 to 67. Northeast winds 20 to 25 mph. Chance of rain 80 percent.

Thursday: Partly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 78. Northeast winds 20 to 25 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Breezy. Mostly cloudy with numerous showers. Highs 66 to 74 in the valleys to around 61 above 4000 feet. Northeast winds 10 to 25 mph. Chance of rain 70 percent.

Tonight: Windy. Occasional showers and isolated thunderstorms. Locally heavy rainfall possible. Lows 55 to 60 in the valleys to around 49 above 4000 feet. Northeast winds 10 to 30 mph. Chance of rain near 100 percent.

Thursday: Windy. Partly sunny with scattered showers. Highs 66 to 74 in the valleys to around 61 above 4000 feet. Northeast winds 15 to 30 mph. Chance of rain 50 percent.

North Kaua’i

Today: Partly sunny. Breezy. Scattered showers in the morning, then numerous showers in the afternoon. Highs 71 to 78. East winds 10 to 20 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Breezy. Occasional showers and isolated thunderstorms in the evening, then numerous showers and isolated thunderstorms after midnight. Locally heavy rainfall possible. Lows 58 to 67. East winds 10 to 20 mph. Chance of rain 90 percent.

Thursday: Breezy. Partly sunny with scattered showers. Highs 71 to 78. Northeast winds 15 to 25 mph. Chance of rain 50 percent.

East Kaua’i

Today: Breezy. Partly sunny with scattered showers. Highs 71 to 78. Northeast winds 10 to 25 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Occasional showers and isolated thunderstorms in the evening, then numerous showers and isolated thunderstorms after midnight. Locally heavy rainfall possible. Lows 56 to 68. Northeast winds 15 to 20 mph. Chance of rain 90 percent.

Thursday: Partly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 71 to 78. Northeast winds 15 to 25 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

A wet trade wind pattern with isolated thunderstorms and locally heavy rain, especially over windward areas, will prevail through Wednesday night. Breezy to locally windy trade winds are expected over the next several days.

Discussion

Have made a few changes to the forecast with the morning package. The Winter Storm Warning for the Big Island summits has been cancelled, but a Winter Weather Advisory has been posted. A Wind Advisory for the lower elevations of Maui County and the Big Island has been issued for today.
Satellite shows a decrease in clouds over and immediately upstream of the Big Island this morning, but additional clouds are found about 50 miles to the east. Meanwhile a few more showers have been observed over the windward sides of Maui County and Oahu over the last few hours. PoP and associated grids have been adjusted accordingly.
Webcams on the Mauna Kea on the Big Island show clear skies overhead. While the day is expected to start clear, temperatures remain below freezing and are only expected to get a few degrees above freezing today. As the above mentioned moisture moves in later this morning/early afternoon, there remains a possibility for additional freezing rain, and even for some snow. Not expecting significant amounts, but enough to exercise caution. As a result, the Winter Storm Warning was cancelled, and a Winter Weather Advisory was issued through tomorrow afternoon.
Winds over the lower elevations are expected to once again reach Wind Advisory criteria today over portions of the lower elevations of Maui County and the Big Island. As such, have issued a Wind Advisory that will be in effect from 8am this morning, and persist through the evening hours. The areas most likely to experience the advisory levels winds will over passes, through gaps, and downslopes of mountains.
Synoptically not much has changed. Strengthening high pressure to the north will help to boost trade winds today. maintain the locally windy trade winds today. A new high moving in from the west will replace the existing high tomorrow, and as a result, trades will continue, but should be back to moderate levels. Those trades will continue into next week.
The upper levels continue to be driving the wetter pattern. The upper level trough axis remains oriented northeast to southwest near Kauai, with its associated broad mid level trough over the main Hawaiian islands. There is good model agreement with another area of moisture riding in on the trades later today. As this moisture encounters colder than normal 500 mb temperatures (near -15 C near Kauai and near -12 C the Big Island) there will be another chance for thunderstorms. This area of moisture is expected to move through tonight for another round of wetter weather. Previously felt the focus for this would Maui County and the Big Island, however the latest guidance shows the moisture making its way northward to Oahu as well.
Heading into tomorrow, the large scale pattern undergoes little in the way of change, but deeper troughing west of the islands will pump up heights locally which should help bring an end to the current wet trade wind pattern. A more typical breezy to locally strong trade wind pattern then prevails heading into the weekend.

Aviation

A strong high pressure system north of the islands will keep moderate to locally windy trade wind weather pattern. An upper level trough will produce windward and mountain showers with periods of MVFR conditions. Stronger showers may drift into leeward areas mainly in the overnight to early morning hours. Isolated thunderstorms remain in the forecast through Thursday.
AIRMET Sierra remains in effect for Tempo Mountain Obscurations along north though east slopes of Oahu, Molokai, Maui and the Big Island. This AIRMET will likely decrease in coverage later this morning.
AIRMET Tango remains in effect for moderate mountain wave turbulence over all islands due to breezy to locally windy trade winds. This AIRMET will likely continue through much of this week.

Marine

A large area of high pressure centered approximately 800 nautical miles north of Oahu will slowly move east the next couple of days. This will continue to support a tight enough pressure gradient down across the state to result in strong to near gale force trade winds over the majority of the Hawaiian nearshore waters through the remainder of the week. Late week high pressure moving in from the west will build in the wake of the current high and establish itself north of the islands by Friday. This will maintain persistent strong trades through the weekend. The ongoing all-water Small Craft Advisory will be in effect the next several days. An upper level trough positioned over the state will keep the regional atmosphere unstable the next couple of days. There is a decent probability for brief periods of heavy showers and isolated thunderstorms, especially in windward waters, that may produce strong wind gusts and lower visibilities. The threat for more active weather will diminish Friday in response to a weakening trough.
Persistent fresh to strong trades will continue to generate rough, choppy surf along east-facing shores through the week. Despite these very rough conditions, east surf is expected to remain under High Surf Advisory heights. A small, medium period northwest (310 degree) swell will quickly pass around the island chain today. A bit larger, slightly longer period northwest (320-330 degree) swell is scheduled to arrive late Friday into Saturday. This swell will likely peak north-facing shore surf to double overhead.

HFO Watches/Warnings/Advisories

Wind Advisory from 8 AM this morning to 8 PM HST this evening for Lanai Mauka, Kahoolawe, Maui Windward West, Maui Leeward West, Kohala, Big Island Interior, Molokai, Lanai Windward, Lanai Leeward, Lanai South, Maui Central Valley North, Maui Central Valley South, Windward Haleakala, Kipahulu, South Maui/Upcountry, South Haleakala, Big Island South, Big Island Southeast, Big Island North.
Winter Weather Advisory until 6 PM HST Thursday for Big Island Summits.
Small Craft Advisory until 6 AM HST Friday for all Hawaiian waters,

Data Courtesy of NOAA.gov