Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Cloudy and windy. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 86 near the shore to around 73 above 3000 feet. East winds 20 to 30 mph with gusts to 50 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Windy. Isolated showers. Lows around 70 near the shore to around 60 above 3000 feet. East winds 15 to 30 mph with gusts to 50 mph. Chance of rain 20 percent.

Thursday: Breezy. Mostly sunny with isolated showers. Highs around 86 near the shore to around 74 above 3000 feet. East winds 15 to 25 mph with gusts to 45 mph. Chance of rain 20 percent.

South Kaua’i

Today: Windy. Cloudy with scattered showers. Highs 78 to 85. East winds 25 to 30 mph with gusts to 50 mph. Chance of rain 50 percent.

Tonight: Windy. Mostly cloudy with scattered showers. Lows around 70. Northeast winds 20 to 30 mph. Chance of rain 50 percent.

Thursday: Windy. Partly sunny with scattered showers. Highs 79 to 86. East winds 20 to 30 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Windy. Cloudy with numerous showers. Highs 71 to 80 in the valleys to around 63 above 4000 feet. East winds 20 to 30 mph with gusts to 50 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Windy. Scattered showers in the evening, then numerous showers after midnight. Lows 63 to 68 in the valleys to around 57 above 4000 feet. East winds 15 to 30 mph with gusts to 50 mph. Chance of rain 70 percent.

Thursday: Windy. Partly sunny with scattered showers. Highs 72 to 80 in the valleys to around 63 above 4000 feet. East winds 20 to 30 mph with gusts to 50 mph. Chance of rain 50 percent.

North Kaua’i

Today: Windy. Cloudy with scattered showers. Highs 74 to 86. East winds 10 to 30 mph increasing to 20 to 30 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows 63 to 72. East winds 15 to 25 mph with gusts to 50 mph. Chance of rain 70 percent.

Thursday: Breezy. Partly sunny with scattered showers. Highs 74 to 86. East winds 15 to 25 mph with gusts to 45 mph. Chance of rain 50 percent.

East Kaua’i

Today: Cloudy and breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 71 to 82. East winds 15 to 25 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows 64 to 73. East winds 15 to 25 mph. Chance of rain 70 percent.

Thursday: Breezy. Partly sunny with scattered showers. Highs 71 to 83. East winds 20 to 25 mph with gusts to 45 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

A very strong high pressure system will set up north of the state today, leading to windy and gusty trade winds lasting into Friday. Periods of showers will favor typical windward and mountain areas. The stronger of these showers will briefly drift into drier leeward areas at times. Trade wind speeds will decrease to breezy levels by this weekend. A disturbance aloft will send high clouds over the islands today.

Discussion

A very strong high pressure system continues to build far north of the Hawaiian Islands today. This high center will weaken as it drifts south from Thursday through Sunday. Meanwhile a cutoff low continues to linger roughly 600 miles northwest of Kauai. A band of thunderstorms is forming this along the southeastern flank of the cutoff low. High level cirrus clouds will continue to drift over all islands through the evening hours, enhancing sunrise and sunset colors. Morning upper air balloon soundings at Lihue on the island of Kauai show temperature inversion heights in the 6,000 to 7,000 foot range. This inversion height along with the stronger trade winds should keep scattered to numerous showers over all windward areas through this evening. More isolated shower coverage remains in the forecast today for leeward areas.
Wet trade wind weather will continue into the weekend with higher shower coverage in the overnight to early morning hours. The upper level cutoff low northwest of the state will tend to add some instability into the mix over the western islands. Trade winds will blow across all islands at windy levels through Thursday. Wind advisories remain in effect for the windier zones of each island until Thursday evening. Some of these wind advisory areas may need to be extended into Friday. Maui and Big Island summits wind speeds will be lighter and remain below wind advisory thresholds during this event.
Trade winds will slowly ease over the weekend with breezy conditions. Mostly windward showers will favor the overnight to early morning hours. Slight drying trends will develop during the first half of next week as the low level ridge drifts over the islands ahead of a cold front farther to the north dives towards the island chain. Clouds and enhanced showers may briefly develop over all islands by the middle of next week as this weakening cold front moves quickly from north to south through the state.

Aviation

Breezy to windy easterly trade winds will persist, with clouds and showers favoring windward slopes and coasts. Expect periods with MVFR CIGs/VSBYs in showers, particularly overnight through the early morning hours as areas of moisture move through. Some showers will spill over into leeward areas of the smaller islands periodically.
AIRMET Sierra for mountain obscuration remains in effect for N through E sections of Oahu, Molokai, Maui, and the Big Island.
AIRMET Tango for moderate low-level turbulence over and southwest through northwest of mountains remains in effect for all islands.

Marine

The central pressure of a strong, slow-moving surface high far N of the islands will peak near 1052 mb today, driving strong to gale-force E trade winds. The high will drift S and gradually weaken from Thursday into Sunday, but wind speeds will be slow to diminish until later this weekend. A Gale Warning is posted for windier areas around Maui and the Big Island, and a Small Craft Advisory is in effect elsewhere. The Marine Weather Message (MWWHFO) contains the details.
A small to moderate, short-period (~10 seconds) N swell will peak today, then gradually diminish. The strong trade winds near and upstream of the islands are driving increasing short-period (8-10 seconds) wind waves toward the islands from the ENE, and latest near shore PacIOOS buoy observations indicate combined seas have increased to 10-12 feet. A High Surf Advisory has been issued for E facing shores of islands exposed to this trade wind swell, with details in the Coastal Hazard Message (CFWHFO). Elsewhere, a small, medium-period SSE swell is possible over the weekend.

Fire weather

Long-term conditions over leeward areas are drier than normal for this time of year. Though the Keetch-Byram Drought Index measured in Honolulu will remain well below the critical 600 mark this week, the strong and gusty trade winds will elevate the fire danger over the drier leeward areas through Friday.

HFO Watches/Warnings/Advisories

Wind Advisory until 6 PM HST Thursday for windier areas of most Hawaiian Islands.
High Surf Advisory until 6 PM HST Friday for east facing shores.
Small Craft Advisory until 6 AM HST Saturday for all Hawaiian Waters outside of the Gale Warning areas.
Gale Warning until 6 AM HST Friday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov