Photo Credit: Braden Jarvis

West Kaua’i

Today: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 85 near the shore to around 74 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers. Lows around 71 near the shore to around 60 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Sunday: Breezy. Mostly sunny with isolated showers. Highs around 85 near the shore to around 73 above 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

South Kaua’i

Today: Breezy. Mostly cloudy with scattered showers. Highs 81 to 86. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 71. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Sunday: Breezy. Partly sunny with scattered showers. Highs 81 to 86. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Mostly cloudy. Breezy. 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 up to 20 mph shifting to the east 10 to 20 mph in the afternoon. Chance of rain 90 percent.

Tonight: Mostly cloudy. Breezy. Numerous showers in the evening, then scattered showers after midnight. Lows 62 to 67 in the valleys to around 57 above 4000 feet. East winds up to 20 mph increasing to 10 to 20 mph after midnight. Chance of rain 70 percent.

Sunday: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 72 to 79 in the valleys to around 65 above 4000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

North Kaua’i

Today: Partly sunny with scattered showers. Highs 75 to 84. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 64 to 72. East winds 10 to 15 mph decreasing to up to 10 mph after midnight. Chance of rain 50 percent.

Sunday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 75 to 84. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

East Kaua’i

Today: Mostly cloudy with scattered showers. Highs 73 to 83. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 63 to 74. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Sunday: Partly sunny with scattered showers. Highs 73 to 83. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

An upper trough will exit east of the region today, while a surface trough northeast of the central islands weakens. Abundant moisture and some lingering instability, will enhance rainfall across portions of the windward areas today. Trade winds will strengthen and become locally strong this weekend, as high pressure redevelops northeast of the islands. A front could bring showers and much stronger northeast winds to the state as we head into the Thanksgiving holiday.

Discussion

Current radar trends show the areal coverage of showers has diminished greatly since earlier this morning, as the best dynamics have moved eastward with the exiting upper trough. Radar precipitation rate estimates, show rainfall rates that were nearing two inches per hour earlier this morning, have also diminished in areal coverage. Additionally, satellite and lightning obs show a similar trend of weakening instability, as the upper trough exits the region.
The latest thunderstorm probabilities suggests that any lingering chance for a thunderstorm, will be exiting the windward coastal waters in the vicinity of the Big Island yet this morning. However, modeled moisture stability and modeled moisture depths (lingering around 10k ft or greater) would support some enhanced rainfall rates over the central smaller islands and Big Island into this afternoon. Additionally, satellite based layered precipitable water values, show PWs between 1.50 inches and 1.70 inches, continuing to stream across some windward areas this morning. However, expect that the areal coverage and intensity of showers will diminish by the afternoon over the western end of the state, as drier air and easterly trade winds strengthen.
Remainder of the weekend into Wednesday…High pressure will be well established north of the islands through early next week, reinforcing locally strong trades. 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. One area to watch will be for increasing surface winds over land early next week, as the area of high pressure becomes entrenched to the north. Will have to monitor winds that may potentially near advisory criteria.
Wednesday night through Thanksgiving Day. Models are still indicating a front approaching Hawaii from the northwest beginning Wednesday night. A band of showers and large area of strong northeast winds behind the front, could move into the island chain. The models are trying to come into better agreement with this idea for the holiday, but there remains considerable flip- flopping in the timing and strength of the trades behind the front. We will need to keep an eye on this time period, since some of the guidance suggests winds could reach impactful levels.

Aviation

Thunderstorms fired off on the east side of the Big Island earlier in the night, in part due to a shortwave that moved through the area. The thunderstorms, heavier rain and clouds prompted AIRMET Sierra for mountain obscuration on the windward side of the Big Island. Some clouds and showers persist in the area, however widespread mountain obscuration is no longer an issue, so that AIRMET has been cancelled.
A surface trough remains to the northeast of the central islands early this morning, but that trough is expected to weaken today, allowing the ridge to become the dominant feature. This will allow more widespread moderate to locally breezy trade winds to spread across the islands. Anticipate AIRMET Tango will be needed later today for low level mechanical turbulence to the lee of the mountains.
Otherwise, some clouds and showers will ride in on the trades, with some MVFR conditions possible, most likely over windward and mauka areas. Overall VFR conditions are expected to persist.

Marine

Trade winds will reestablish themselves and strengthen to fresh to locally strong magnitudes the next several days. This will occur as upper troughing departs to the northeast and the associated weak surface trough over the central waters dissipates on its northward trek early today. The threat for early day marine thunderstorms will primarily be east of this trough or more focused over the northeastern near and offshore waters around Big Island eastward. High pressure will build in to the north and northeast of the island chain through the weekend and this will tighten the pressure gradient down across the state. This will result in fresh to locally strong trades from this afternoon through Monday night. A Small Craft Advisory (SCA) is in effect early this morning for the typically windier zones around Maui County and Big Island through tomorrow afternoon. An all-water SCA will be in effect from Sunday evening through early Monday morning with a likely required extension in time through Monday night or into Tuesday morning.
The current 3 foot, medium period north swell (350 degrees) will continue to fall through the day. The next similar size, medium period west northwest swell (310 degrees) will build in Sunday and peak late Sunday night into Monday. At its peak, this swell will produce near double head high to approach low end (~15 foot) advisory level surf. This may prompt a short fuse High Surf Advisory on Monday. A long fetch created along the backside of a gale low over the West Aleutians Monday, in tandem with a strong northwest push behind an aggressive late Wednesday into Thanksgiving Day cold frontal passage, will be the source(s) for a large, medium period northwest north swell (330-360 degrees) that is scheduled to reach the islands around Thanksgiving Day. The peak of this swell that will likely produce High category surf will coincide with the month's higher high tides. This may exacerbate overwash issues within lower lying coastal regions along north-facing shorelines late next week. South-facing shore surf will be trailing off today as the latest very small south swell fades. Choppy, more rough conditions will trend up along east-facing shores the next few days as the islands will be under a robust trade flow.

HFO Watches/Warnings/Advisories

Small Craft Advisory from 6 PM Sunday to 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, Big Island Windward Waters.
Small Craft Advisory until 6 AM HST Monday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov