Photo Credit: Jason Weingardt

West Kaua’i

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 85 near the shore to around 73 above 3000 feet. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly clear with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 68 to 73 near the shore to around 60 above 3000 feet. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Saturday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 85 near the shore to around 74 above 3000 feet. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

South Kaua’i

Today: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 81 to 86. Northeast winds around 15 mph. Chance of rain 70 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows around 70. Northeast winds around 15 mph. Chance of rain 50 percent.

Saturday: Partly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 81 to 86. Northeast winds 15 to 20 mph. Chance of rain 70 percent.

Kaua’i Mountains

Today: Mostly cloudy. Frequent showers in the morning, then scattered showers in the afternoon. Highs 72 to 79 in the valleys to around 65 above 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 90 percent.

Tonight: Mostly cloudy. Numerous showers in the evening, then frequent showers after midnight. Lows 61 to 66 in the valleys to around 57 above 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 90 percent.

Saturday: Mostly cloudy. Breezy. Frequent showers in the morning, then scattered showers in the afternoon. Highs 72 to 79 in the valleys to around 65 above 4000 feet. Northeast winds 10 to 20 mph. Chance of rain 90 percent.

North Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 75 to 84. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 63 to 72. East winds 10 to 15 mph. Chance of rain 70 percent.

Saturday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 75 to 84. East winds 10 to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Mostly cloudy with numerous showers in the morning, then mostly sunny with scattered showers in the afternoon. Highs 72 to 83. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with numerous showers. Lows 63 to 73. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Saturday: Breezy. Mostly cloudy with numerous showers in the morning, then mostly sunny with scattered showers in the afternoon. Highs 73 to 83. Northeast winds 15 to 20 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Instability will persist today as a passing upper trough enhances showers and triggers isolated thunderstorms across windward waters. Thunderstorms are possible across leeward Big Island areas this afternoon. Winds will become strong this weekend as the upper trough exits and high pressure redevelops northeast of the islands.

Discussion

After diminishing significantly before midnight, heavy showers and thunderstorms have once again developed across Oahu and Maui County windward waters this morning as an upper trough passes by. A surface trough weakened winds over the local area yesterday, which will allow low clouds and showers to spread leeward through the day today.
Expect enhanced showers today as the upper trough passes by and surface winds remain weakened. Models show that as the upper trough exits the area to the east, a surface trough to our north washes out, allowing trade winds to begin returning by this afternoon. The weak surface ridge to the north of the area will restrengthen into a high to the northeast this weekend, causing trades to become strong over the state through early next week. During this time, building mid-level ridging and below normal PW values will result in a drier than average trade shower pattern. Models hint at a front approaching Hawaii from the northwest beginning Wednesday night. As we head into Thanksgiving Day, a band of showers and large area of strong northeast winds behind the front could move into the island chain. Quite a bit of variance exists in the models this far out, so the forecast for that period is a blend of the current forecast with the latest deterministic models and their respective ensembles.

Aviation

A surface trough just north of the islands, will maintain the weak background trade wind flow across most of the state this morning. In addition, an upper-level short wave trough will continue to move east above the islands, which will keep some instability over the area today. There is still a slight chance of thunderstorms over the coastal waters north and northeast of the central and eastern islands today. There are also low clouds with embedded locally heavy showers lingering near some of the islands. These enhanced clouds and showers will continue to move over the windward sections of some of the islands and the adjacent coastal waters this morning. This will likely produce periods of MVFR ceilings and visibilities mainly along some windward facing slopes and coastlines. Otherwise, VFR conditions are expected to prevail across most leeward areas this morning.
AIRMET Sierra remains in effect for mountain obscuration above 2500 feet along windward sections of Maui. Conditions are expected to gradually improve on Maui, so we may be able to cancel this AIRMET later this morning. Also, there is the potential for light icing to develop in some of the mid- and upper-level clouds in the layer between FL180 and FL280 this morning.
By this afternoon, a more typical trade wind flow is expected to redevelop as the surface trough weakens, and a surface ridge builds north of the state. Low clouds and brief trade showers will tend to favor windward sections of the islands as a more typical trade wind weather pattern becomes established from this afternoon through this evening. Note that there is a slight chance of thunderstorms over the leeward Big Island this afternoon.

Marine

A surface ridge a couple of hundred miles northwest to north of Kauai is supporting light to moderate trade winds. A surface trough north of Maui and Oahu that has interrupted early morning trade flow has also been the impetus for overnight (primarily windward water) scattered showers and thunderstorms. As high pressure builds to the northwest of the islands, the trough will weaken and move north through the day. Weekend trades will strengthen statewide as the high expands northeast of the islands. These stronger trades will drive heightened seas, thus a Small Craft Advisory is anticipated for the winder zones this weekend. Gradual weakening of the northern surface ridge will likely result in diminishing winds and lowering seas early next week.
North swell (360 degrees) energy has been slow to fall along many north-facing shores and has remained steady through the early morning hours. Thus, the High Surf Advisory (HSA) for all islands (except Lanai and Kahoolawe) has been extended through Noon today to account for this slowly declining swell. A similar size, slightly longer period northwest swell will begin building in late Saturday into Sunday morning. This will lift surf to near or slightly over HSA levels as it peaks out late Sunday going into Monday. Another much larger north northwest swell associated with a cold front is timed to reach the islands around Thanksgiving and increase surf along north and west-facing shores to possible High Surf Warning thresholds. East- facing shore surf will remain small through the day but will be on the rise over the weekend and into early next week per strengthening trades. The recent south swell will be fading from tonight through Saturday morning.

HFO Watches/Warnings/Advisories

High Surf Advisory until noon HST today for Niihau, Oahu North Shore, Olomana, Maui Windward West, Kauai North, Koolau Windward, Molokai Windward, Molokai North, Maui Central Valley North, Windward Haleakala, Big Island East, Big Island North.

Data Courtesy of NOAA.gov