Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Windy. Partly sunny with scattered showers in the morning, then mostly sunny in the afternoon. Highs around 82 near the shore to around 69 above 3000 feet. Northeast winds 10 to 30 mph. Chance of rain 40 percent.

Tonight: Windy. Partly cloudy with isolated showers. Lows around 63 near the shore to around 51 above 3000 feet. Northeast winds 10 to 30 mph. Chance of rain 20 percent.

Friday: Breezy. Mostly sunny with isolated showers. Highs around 82 near the shore to around 69 above 3000 feet. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

South Kaua’i

Today: Windy. Partly sunny with scattered showers in the morning, then mostly sunny in the afternoon. Highs around 79. Northeast winds 30 to 35 mph. Chance of rain 30 percent.

Tonight: Windy. Partly cloudy with isolated showers. Lows 60 to 66. Northeast winds 20 to 30 mph with gusts to 50 mph. Chance of rain 20 percent.

Friday: Breezy. Mostly sunny with isolated showers. Highs around 79. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Kaua’i Mountains

Today: Windy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 73 in the valleys to around 62 above 4000 feet. Northeast winds 10 to 30 mph with gusts to 50 mph. Chance of rain 50 percent.

Tonight: Windy. Mostly cloudy with scattered showers. Lows around 55 in the valleys to around 47 above 4000 feet. Northeast winds 10 to 30 mph with gusts to 50 mph. Chance of rain 50 percent.

Friday: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs around 73 in the valleys to around 62 above 4000 feet. Northeast winds 10 to 25 mph decreasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

North Kaua’i

Today: Windy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 71 to 80. Northeast winds 15 to 30 mph with gusts to 50 mph. Chance of rain 50 percent.

Tonight: Breezy. Partly cloudy with scattered showers. Lows 55 to 65. East winds 10 to 25 mph with gusts to 45 mph. Chance of rain 30 percent.

Friday: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 71 to 80. Northeast winds 10 to 20 mph. Chance of rain 30 percent.

East Kaua’i

Today: Windy. Partly sunny with scattered showers in the morning, then mostly sunny in the afternoon. Highs 72 to 79. Northeast winds 15 to 30 mph. Chance of rain 40 percent.

Tonight: Windy. Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 53 to 67. Northeast winds 10 to 30 mph. Chance of rain 30 percent.

Friday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 72 to 79. Northeast winds 10 to 20 mph. Chance of rain 40 percent.

Detailed Forecast

Synopsis

A cold front currently moving into Kauai and Oahu from the northwest is producing very strong and gusty winds and showers over both islands this morning. These strong winds and showers will spread into Maui and Hawaii Counties later today. Trade winds will weaken on Friday, and then becoming light and variable through the weekend. Drying trends are forecast to develop behind the front and last through the weekend. A band of tropical moisture lifting northward into the islands on Monday may enhance clouds and showers across the region in a southeasterly wind pattern through the middle of next week.

Discussion

The satellite imagery this morning shows an extensive cold frontal cloud band moving into Niihau, Kauai and Oahu as of 4 AM HST this morning. This front will move into Molokai and Lanai later this morning, and reaching Maui by noon HST and the Big Island in the afternoon hours. Strong and gusty winds are forecast right behind the front as it passes through each island with cooler conditions and drying trends as more stable air moves in behind the front.
Very strong and gusty winds are the main weather story with this frontal passage. Wind advisories remain in effect for all islands lasting through early Friday morning. Only the highest peaks on Maui and the Big Island will remain out of the wind advisory with this event.
On Friday, a high pressure ridge will build over the islands causing northeasterly trade wind speeds to weaken through Friday, and then diminish statewide over the weekend as the ridge weakens and lifts north. As large scale winds diminish, local scale land and sea breezes will form over each island this weekend. A passing upper level trough north of the region will draw up deeper tropical moisture into the islands and produce a southeasterly wind pattern across the state by early next week.
Weatherwise, most areas of each island will see up to 6 hours of good rainfall as the main frontal cloud band passes quickly through the state. Rainfall intensity should remain moderate for most areas and the threat for flash flooding is low at this time due to the relatively fast moving front and shower bands. Showers that develop behind the front will favor windward and mountain areas. Gradual drying trends are forecast after the front passes each island with decreasing precipitation trends statewide from tonight into the weekend. Medium range forecast guidance for Sunday and Monday shows a passing upper level trough north of the region that will draw up deeper tropical moisture northward into the state, possibly increasing rainfall trends again from Monday through Wednesday. However, in this southeasterly wind pattern most islands will fall into the rain shadow of the Big Island mountains, yielding less rainfall over the smaller islands. However, areas along the southeast slopes of the Big Island, the Pahala and Volcano areas, will see increasing rainfall trends over the same time period.
Our confidence remains high in these strong and gusty winds blowing across Hawaii through most of the Thanksgiving Day. Be careful if you are traveling around the state today and tonight as driving conditions will be more difficult in this wet and windy weather pattern. Also be prepared for possible power outages. Please consider moving any planned outdoor Thanksgiving events indoors, and postpone hanging outdoor holiday decorations as they may become damaged or airborne with these strong winds. Stay safe and have a happy Thanksgiving.

Aviation

A forceful cold front will spread wind and rain from one end of the state to the other today. The front moved into Kauai from the north northwest shortly after midnight and is expected to pass over Oahu and Molokai later this morning then the remainder of the smaller islands this afternoon. The front will then weaken and stall over Windward Big Island this evening. This fast moving front is expected to bring short periods of IFR or MVFR in moderate showers as well as several hours worth of east to northeast winds in excess of 30 kt to each island.
An AIRMET for mountain obscuration is currently in effect for Kauai. Conditions will likely spread to windward portions of Oahu, Molokai, and Maui by midday. Improvement from west is expected in the afternoon as the front pushes steadily eastward.
An AIRMET for low level mechanical turbulence is currently in effect for portions of Kauai downstream of higher terrain. Conditions are expected to spread across Oahu and Molokai by and the remainder of the state by late afternoon.
An AIRMET for strong surface winds is currently in effect for Kauai and adjacent waters. Conditions are expected to spread across the remaining smaller islands by late afternoon and portions of the Big Island this evening.

Marine

At 0300 HST, a vigorous cold front is passing across the central local waters and will be adversely impacting the state through the holiday. Strong to gale force northeast winds will occur in the wake of the front as it travels southeast across the island chain, reaching the Big Island waters by mid day and then slowing and dissipating over the eastern waters Friday. A Gale Warning (GLW) is in effect for the waters surrounding Kauai as well as the leeward waters of Maui County and Big Island to account for channeling winds through the Pailolo and Alenuihaha Channels. These winds will generate rough seas across areawide coastal waters through Friday. Elevated sea heights will be exacerbated by a large, medium period north swell that will coincide with these strong northeasterlies. Winds will begin to taper off Friday as a cut-off low develops along the front far northeast of the islands. This low will disrupt the local pressure gradient and result in dramatically weakening winds this weekend.
A large north swell is building in today. The peak of this swell will increase surf heights to High Surf Warning (HSW) levels along the north-facing shores of Niihau, Kauai, Oahu, Molokai and Maui. Thus, a HSW is in effect through 0600 HST Friday for all north-facing shores except for Big Island. This HSW may need to be extended in time with the addition of Big Island. This north swell is coming in during a early morning high spring tide both to day and Friday. This increases the probability of significant overwash issues and large wave run up along many north-facing shores through Friday morning. There is a good chance that 8 feet of wave run-up will cause the lower roadways closest to the shore to be overcome by nearshore wash. Areas exposed to north swells on other shorelines will also see a significant rise in surf as the north swell moves in, especially the west-facing shores of more western islands. A High Surf Advisory (HSA) remains in effect for the western shores of Kauai, Oahu and Molokai…along with the north-facing shores of Big island…through 0600 HST Friday.
Storm force winds early Friday around the backside of the cut-off low northeast of the islands mentioned above will send a second large, medium period north northeast swell into the windward waters Friday night and early Saturday. This swell will keep at least HSA level surf in place along north-facing shores through Saturday and result in a greater impact along Maui and Big Island's north and east-facing shores whereas Big Island's north shore may need to be upgraded to a HSW during this time period. There is a potential for harbor surges in both Kahului and Hilo from today through the weekend in association with both the north and then the north northeast swell. Surf along east-facing shores will become more choppy and rough as these strong northeasterlies impact the state into Friday, but should stay below HSA levels given the more northerly direction of the winds. South-facing shores will experience minimal energy for the foreseeable future.

HFO Watches/Warnings/Advisories

High Surf Warning until 6 AM HST Friday for north facing shores of Niihau, Kauai, Oahu and Molokai.
High Surf Advisory until 6 AM HST Friday for west facing shores of Kauai Oahu Molokai and north facing shores of the Big Island.
Gale Warning until 6 AM HST Friday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Maui County Leeward Waters, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters.
Small Craft Advisory until 6 AM HST Friday for Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Big Island Windward Waters, Big Island Southeast Waters.
Wind Advisory until 6 AM HST Friday for all islands except the summits of Haleakala on Maui, and the summits of Mauna Kea and Mauna Loa on the Big Island.

Data Courtesy of NOAA.gov