Photo Credit: Braden Jarvis

West Kaua’i

Today: Mostly sunny with scattered showers. Highs around 83 near the shore to around 71 above 3000 feet. East winds up to 10 mph shifting to the southeast in the afternoon. Chance of rain 50 percent.

Tonight: Partly cloudy with scattered showers. Lows around 69 near the shore to around 58 above 3000 feet. Northeast winds around 10 mph. Chance of rain 50 percent.

Thanksgiving Day: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 84 near the shore to around 72 above 3000 feet. Northeast winds around 10 mph shifting to the southwest up to 10 mph in the afternoon. Chance of rain 50 percent.

South Kaua’i

Today: Mostly cloudy with showers likely. Highs around 82. East winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with showers likely. Lows 65 to 70. Northeast winds around 10 mph. Chance of rain 70 percent.

Thanksgiving Day: Mostly sunny with showers likely in the morning, then partly sunny with scattered showers in the afternoon. Highs around 83. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Kaua’i Mountains

Today: Cloudy with showers. Highs 70 to 78 in the valleys to around 64 above 4000 feet. East winds up to 10 mph. Chance of rain 80 percent.

Tonight: Cloudy with showers. Lows 58 to 63 in the valleys to around 52 above 4000 feet. East winds around 10 mph in the evening becoming light. Chance of rain 90 percent.

Thanksgiving Day: Partly sunny. Occasional showers in the morning, then scattered showers in the afternoon. Highs 71 to 79 in the valleys to around 66 above 4000 feet. East winds up to 10 mph. Chance of rain 90 percent.

North Kaua’i

Today: Mostly cloudy with showers likely. Highs 75 to 82. East winds up to 10 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with showers. Lows 61 to 70. East winds around 10 mph. Chance of rain 90 percent.

Thanksgiving Day: Mostly sunny with scattered showers. Highs 76 to 83. East winds up to 10 mph. Chance of rain 50 percent.

East Kaua’i

Today: Cloudy with showers. Highs 75 to 82. East winds 10 to 15 mph. Chance of rain 80 percent.

Tonight: Cloudy with showers. Lows 59 to 72. East winds around 10 mph. Chance of rain 90 percent.

Thanksgiving Day: Partly sunny with showers likely in the morning, then mostly sunny with scattered showers in the afternoon. Highs 76 to 83. Northeast winds around 10 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Windward areas will be cloudy and showery into Thursday, with showers diminishing thereafter. Light to moderate trade winds will continue to gradually weaken, with light and variable winds Friday and Saturday leading to mostly dry weather. Another front may bring increased showers and winds Sunday or Monday.

Discussion

Mostly cloudy and showery conditions continue to prevail across most of the islands this morning, particularly over windward and mauka areas, and most especially over windward Oahu. Orographically- induced moderate rainfall has been non-stop over the Koolau range through the night, with heavier bursts of rain producing observed rainfall rates near 2 inches per hour. 12-hour rainfall totals are approaching 9″ at the wettest rain gages. In contrast, most leeward areas remain dry, and are in varying levels of drought status, with only .13″ of rain observed at PHNL in the first 3 weeks of November.
The main contributor to the wet windward conditions is remnant frontal moisture that is being advected westward in a light to moderate trade wind flow, with weak low-level convergence supporting the showers. This moisture is E-W oriented near and upstream of the islands; in the form of broken to overcast showery and stable low clouds. Moisture that is fueling much-needed light to moderate rainfall over windward/SE Big Island is associated with a surface trough that is passing S of the area.
An upper-level trough just E of the Big Island will move E, allowing a ridge to build over the area from the W. Meanwhile, surface high pressure to the distant NNE will support light to moderate trade winds through Thursday night. Latest model guidance indicates the increased low-level moisture over the islands will gradually diminish through this time, keeping windward areas cloudy and wet in the short term, but less so Thursday into Friday.
Observations and model guidance both indicate that the recent propensity for sharp troughing aloft to lead to cutoff low formation W of the islands will continue, with another cutoff low developing along 175W this weekend. While this low may not initially impact island weather, the progressive portion of the parent trough will brush just N of the islands this weekend, potentially sending a front over the area. Run-to-run and model-to-model consistency is notably absent, and the details of the forecast become quite murky by the weekend, with lower than normal forecast confidence. Generally speaking, cyclogenesis to the NW will lead to veering and weakening winds Friday and Saturday, leading to a land/sea breeze pattern coincident with a drier airmass, resulting in little rainfall. The low may send a stalling front and increased showers over the islands on Sunday or Monday.
Thereafter, another sharp buckle in the jet has the potential to re- invigorate the closed low aloft to the W while also shifting it eastward closer to the islands. While there is some general agreement in this scenario, the forecast location of the low varies so greatly as to preclude much confidence in the forecast for early next week. Having said that, initial indications are that the stalled frontal moisture could help fuel a wet pattern.

Aviation

Light to moderate easterly flow will continue to push remnant low level moisture towards windward portions of the smaller islands today. This pattern will bring scattered to numerous showers to the windward slopes and coasts, especially for Maui, Molokai, and Oahu. MVFR conditions are likely to accompany this activity with isolated embedded areas of IFR ceilings and visibility. In addition, isolated showers may push over the terrain and onto the leeward slopes.
AIRMET SIERRA remains in effect above 2000 feet for north through east sections of the Big Island and Maui due to tempo mountain obscuration from low clouds and showers. AIRMET SIERRA also remains in effect for IFR ceilings, below 1000 feet, and/or visibility below 3SM in SHRA along north through east facing sections of Oahu.

Marine

Near shore buoys indicate that the current north swell (360-010 degrees) is still producing surf and seas near to just below advisory level. Offshore buoys are now showing a downward trend, thus one can expect surf and seas to trend down through today. Latest ASCAT and altimeter data show that the hurricane force low, roughly 1800 NM NW of the state has a broader and stronger fetch than predicted. Thus the forecast for the extra large, long period (17-20 seconds) northwest (320 degrees) swell has been bumped up a couple of feet and is on schedule to arrive Thursday. This swell will peak Thursday night into Friday, producing dangerously large surf for north and west facing shores that will warrant a High Surf Warning. This swell will also boost seas well into the Small Craft Advisory levels for most waters before slowly easing over the weekend.
Surf along east facing shores will remain rough and choppy for the next day or so, due to the combination of breezy trade winds and the decreasing north swell wrapping into exposed locations. Less choppy conditions are expected later in the week due to decreasing wind speeds, however locations exposed to north swell wrap may still see elevated surf due to the warning level swell mentioned above.
Surf along south facing shores will remain small through the rest of week. The next small, long-period south-southwest swell is expected to fill in over the weekend, keeping surf from going flat.
Moderate to fresh easterly trade winds will persist through Thursday, as a high pressure system remains far northeast of the state. Winds are expected to weaken and veer out of the southeast Friday into Saturday as a front approaches from the northwest. Winds may then shift out the northeast and strengthen into the moderate to locally strong range as the front stalls over the state Sunday.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov