West Kaua’i

Today: Mostly sunny. Breezy. Highs 87 to 93 near the shore to around 80 above 3000 feet. East winds up to 20 mph.

Tonight: Partly cloudy. Breezy. Lows 71 to 77 near the shore to around 63 above 3000 feet. Northeast winds up to 20 mph decreasing to up to 10 mph after midnight.

Sunday: Mostly sunny. Highs 88 to 93 near the shore to around 80 above 3000 feet. East winds up to 15 mph.

South Kaua’i

Today: Breezy. Mostly sunny with isolated showers. Highs 83 to 91. East winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows around 75. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Sunday: Mostly sunny with isolated showers. Highs 83 to 91. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Kaua’i Mountains

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 76 to 86 in the valleys to around 69 above 4000 feet. East winds up to 15 mph. Chance of rain 40 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 66 to 71 in the valleys to around 61 above 4000 feet. East winds up to 15 mph. Chance of rain 30 percent.

Sunday: Mostly sunny with isolated showers. Highs 76 to 86 in the valleys to around 69 above 4000 feet. East winds up to 15 mph. Chance of rain 20 percent.

North Kaua’i

Today: Breezy. Mostly sunny with isolated showers. Highs 79 to 90. East winds up to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 67 to 75. Southeast winds up to 15 mph. Chance of rain 30 percent.

Sunday: Mostly sunny with isolated showers. Highs 79 to 89. East winds up to 15 mph. Chance of rain 20 percent.

East Kaua’i

Today: Mostly sunny with isolated showers. Highs 75 to 89. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 67 to 79. Northeast winds up to 15 mph. Chance of rain 30 percent.

Sunday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 75 to 88. Northeast winds up to 10 mph shifting to the east in the afternoon. Chance of rain 30 percent.

Detailed Forecast

Synopsis

Broad high pressure will build over the region allowing trades to strengthen to moderate to locally breezy through much of the weekend. By Sunday, a low-level trough associated with the remnants of former Tropical Cyclone Ivo will propagate into the vicinity of the Hawaiian Islands, bringing and increase of clouds and shower activity to predominately windward and mauka areas through Monday. Thereafter, dry and stable conditions return and remain through the remainder of the week.

Discussion

Latest satellite imagery showcases a low-level trough well northwest of Kauai continuing to slowly propagate away from the islands. Broad high pressure ridging northeast of the Hawaiian Islands quickly fills the void, allowing trades to strengthen to moderate to locally breezy over the islands. Mid-level water vapor imagery continues to depict drier air east of the islands, reintroducing drier and more stable conditions through the weekend.
Deterministic model guidance continues to show another low-level trough associated with the remnants of former Tropical Cyclone Ivo moving near the state on Sunday and Monday. As the trough moves into the vicinity of the islands on Sunday, expect humidity levels to steadily increase. Inversion heights will also lift to around 8,000 to 9.000 feet on Sunday and Monday, which will help to enhance clouds and showers in a moderate to breezy trade pattern.
The latest model guidance have not been in the best of agreement with regards to the aforementioned trough. The GFS has depicted the trough moving toward the center of the islands, which would result in a day or two of wet trades across most of the islands. Conversely, the ECMWF depicts the trough shimmying further north, resulting less shower activity to the islands, limiting activity to predominately Oahu and Kauai. Given that remnant tropical system tend to be smaller in size, the track of this trough may oscillate further north or south as time passes. It will be critical to see what Hi-res model data shows as it becomes more readily available, and then confidence should increase track of the trough as it approaches the island chain.
By Tuesday, the second low-level trough is progged to exit the region to the west, with high pressure quickly rebuilding across the area once again. This will result in dry and stable conditions returning to the state under moderate to breezy trades. Expect a return to typical summer-like conditions at this time, with limited clouds and showers over windward and mauka areas.

Aviation

Moderate trades gradually strengthen as a low-level trough exits the region. Expect brief periods of MVFR conditions in clouds or shower activity, retained to windward and mauka during this time. Otherwise, VFR conditions prevail.
No AIRMETs in effect at this time.

Marine

A surface ridge building north of the state will allow fresh to locally strong easterly trades to persist across the local waters through this weekend. A Small Craft Advisory (SCA), has been expanded in area to include all coastal water and channel zones surrounding Maui and the Big Island. The advisory remains in effect through Sunday morning, but will likely need to be extended in time. Trades look to weaken slightly on Monday morning as remnants former Tropical Cyclone Ivo pass from east to west over the islands. Fresh to locally strong trades will rebuild late Monday through mid-week.
A south southwest (190-200) swell was noted at the nearshore buoys this morning at roughly 2 feet 15-16 seconds. This swell will stick around through Sunday and help bump surf heights to around the seasonal average. Several similar small, long- period, southerly swells will affect the waters early to mid next- week and keep small surf near the August average, well below advisory thresholds.
Surf along east facing shores may be slightly elevated and choppy today due to the fresh trades. North facing shores will remain flat to tiny through the forecast period.

Fire weather

Conditions should remain below critical fire weather thresholds into early next week. A low-level trough associated with the remnants of former Tropical Cyclone Ivo will move across the region on Sunday into Monday, bringing an increase in humidity and shower activity. Lower humidity and more stable conditions redevelop on Tuesday as high pressure rebuilds across the islands.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Sunday for Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.