Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 87 near the shore to around 74 above 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening, then scattered showers after midnight. Lows 69 to 74 near the shore to around 60 above 3000 feet. East winds up to 20 mph. Chance of rain 40 percent.

Monday: Mostly sunny with isolated showers. Highs 84 to 89 near the shore to around 74 above 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

South Kaua’i

Today: Partly sunny. Breezy. Numerous showers in the morning, then isolated showers in the afternoon. Highs 82 to 89. Northeast winds 15 to 25 mph. Chance of rain 60 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 70. Northeast winds 15 to 20 mph. Chance of rain 40 percent.

Monday: Breezy. Partly sunny with scattered showers. Highs 81 to 89. East winds 15 to 20 mph. Chance of rain 40 percent.

Kaua’i Mountains

Today: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 72 to 80 in the valleys to around 65 above 4000 feet. East winds up to 25 mph. Chance of rain 60 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 62 to 68 in the valleys to around 58 above 4000 feet. East winds up to 25 mph increasing to 10 to 25 mph after midnight. Chance of rain 50 percent.

Monday: Breezy. Mostly cloudy with scattered showers. Highs 72 to 79 in the valleys to around 64 above 4000 feet. East winds 10 to 20 mph. Chance of rain 40 percent.

North Kaua’i

Today: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 75 to 86. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 64 to 73. East winds up to 20 mph. Chance of rain 50 percent.

Monday: Partly sunny with scattered showers. Highs 75 to 85. East winds 10 to 15 mph. Chance of rain 40 percent.

East Kaua’i

Today: Partly sunny. Breezy. Numerous showers in the morning, then isolated showers in the afternoon. Highs 72 to 84. Northeast winds 10 to 20 mph. Chance of rain 60 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 63 to 74. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Monday: Mostly cloudy with scattered showers. Highs 72 to 83. East winds around 15 mph. Chance of rain 40 percent.

Detailed Forecast

Synopsis

Strengthening trades will generate locally strong winds and gusty conditions into Monday. Trades will focus showers mainly over windward and mauka zones through the beginning of the week. A few showers over windward Big Island and Maui, will be locally heavy this morning. Breezy conditions and a period of showery weather are likely on Thanksgiving Day as a cold front advances the area.

Discussion

The upper trough which has been slowly exiting eastward of the state, will remain anchored about 300 miles east of the Big Island today, while an upper ridge builds over the western end of the state, and a surface ridge strengthens north of the region.
Radar trends this morning show showers remained scattered across mainly windward areas, as high pressure north of the islands reinforces trade wind flow. Radar precipitation rate estimates this morning, show mainly light rainfall, however radar does still indicate a few cells with rainfall rates nearing one inch per hour this morning. These higher rainfall rates are mainly confined to locations between Maui and the Big Island.
Overall expect showers to remain scattered across windward areas today, as a narrowing band of enhanced moisture (satellite based PW values around 1.50″) continues to flow into the region from the east. Satellite data and forecast modeled moisture depths, suggest deeper layered moisture and greatest concentration of showers, will remain over the central smaller islands and Big Island today. However, diminishing modeled stability index values and drying PW values will reduce the chance for enhanced rainfall today through tonight.
Otherwise, the mid level gradient will sharpen over the state today as the 500mb ridge builds west of the region while the mid- level trough lingers southeast of the Big Island. This pattern will cause northeasterly winds to strengthen considerably at summit level, therefore a wind advisory has been issued for for the Big Island Summits. These Winds will remain strong likely into Monday also. Similarly, at the surface, trade winds will increase, with windy trades accelerating through the typical windier zones of Maui County and the Big Island. Therefore, a wind advisory has also been issued for these zones today, with forecast trends suggesting these gusty conditions may persist through Monday.
Otherwise, high pressure well established north of the islands through early this week, will maintain a typical trade wind pattern across the state. Model data shows relatively dry low and mid level moisture streaming into the region through the period, with forecast PW values under 1.30 inches, while moisture depths linger under 9k ft. This will generate a typical trade wind weather pattern across the islands, with showers focusing mainly along windward areas. The greatest concentration of showers will be during the overnight and early morning hours.
Medium range forecast shows the potential for increasing winds Thanksgiving Day. A progressive pattern over the north Pacific will force strong surface high to cross the Dateline late Tuesday. Global models show a surface low rapidly strengthens and moves quickly eastward north of the state. The trailing cold front associated with this system will eventually advance through the islands bringing a period of rain and breezy conditions, followed by a noticeably cooler and drier airmass filling in its wake. While confidence is reasonably high that a period of showery and breezy conditions is in store for Thanksgiving Day, the magnitude of wind within and behind the cold front will be dependent on the mid-latitude trough as it develops northeast of the islands. This continues to be the primary source of spread among the various model solutions and will make the difference between breezy northeast winds and the potential for wind headlines on Thursday.

Aviation

A high pressure ridge will continue to build north of the Hawaiian Islands with breezy to windy trade winds in the forecast through Monday. Brief passing showers will favor windward and mountain areas from the overnight to early morning hours.
AIRMET Sierra in effect for mountain obscurations above 020 for north through east sections of Kauai, Oahu, Molokai, Maui, and the Big Island. This AIRMET will likely diminish a few hours after sunrise.
AIRMET Tango remains in effect for moderate low level mechanical turbulence over and to the lee of island mountains. This AIRMET will likely continue at least through Monday.

Marine

As the high north of the state strengthens, trade winds will further increase and become strong across all Hawaiian waters today. A Gale Warning is in effect for Pailolo and Alenuihaha channel through tonight. A Small Craft Advisory (SCA) is also in effect for all Hawaiian waters through tonight. A vigorous cold front could impact the Hawaiian waters around Thanksgiving, which may produce Gale force winds and high seas.
A new long-period west-northwest swell (310 degrees), has begun to show a slight rise on the offshore buoys. It will fill in throughout the day today and peak late tonight into Monday. At the peak of the swell, it may produce surf heights near the advisory level for north facing shores. A much larger north- northwest to north swell is expected late Wednesday into Thanksgiving Day. The peak of this swell could reach warning levels and it could coincide with the spring high tide during the early morning hours. Also, if you add on the potential for gale force north east winds during this time, we could see significant overwash issues and large wave run up along north- facing shorelines early Thanksgiving and Friday mornings. Latest wave run up forecast from PACIOOS is indicating wave run-up heights exceeding 8 feet and approaching 10 feet. Above 8 feet, overtopping of lower roadways closer to the shore should be expected.
Surf along east facing shores will see a steady rise during the next few days as the trades strengthen. Areas exposed to north swells should see a significant rise during the second half of next week as a very large north-northwest to north swell fills in. Other than some wind swell wrap, south facing shores will see minimal energy for the foreseeable future.

HFO Watches/Warnings/Advisories

Wind Advisory until 6 AM HST Monday for Lanai Mauka, Kahoolawe, Maui Windward West, Maui Leeward West, Kohala, Big Island Interior, Molokai North, Molokai West, Molokai Leeward South, Lanai Windward, Lanai Leeward, Lanai South, Maui Central Valley South, Windward Haleakala, South Maui/Upcountry, South Haleakala, Big Island South, Big Island Southeast, Big Island North.
Wind Advisory until 6 PM HST Monday for Big Island Summits.
Small Craft Advisory until 6 AM HST Monday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Maalaea Bay, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.
Gale Warning until 6 AM HST Monday for Pailolo Channel, Alenuihaha Channel.

Data Courtesy of NOAA.gov