Photo Credit: Jason Weingardt

West Kaua’i

Today: Mostly sunny. Isolated showers in the afternoon. Highs 87 to 92 near the shore to around 78 above 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows around 74 near the shore to around 63 above 3000 feet. Light winds becoming east up to 10 mph after midnight. Chance of rain 20 percent.

Wednesday: Mostly sunny. Isolated showers in the afternoon. Highs 87 to 92 near the shore to around 78 above 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

South Kaua’i

Today: Mostly sunny with isolated showers. Highs 83 to 90. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 74. East winds around 10 mph. Chance of rain 50 percent.

Wednesday: Partly sunny in the morning then becoming mostly sunny. Isolated showers. Highs 82 to 90. East winds around 10 mph. Chance of rain 20 percent.

Kaua’i Mountains

Today: Mostly sunny with scattered showers in the morning, then partly sunny with isolated showers in the afternoon. Highs 77 to 87 in the valleys to around 68 above 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 64 to 72 in the valleys to around 60 above 4000 feet. East winds around 10 mph. Chance of rain 50 percent.

Wednesday: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 76 to 87 in the valleys to around 68 above 4000 feet. East winds around 10 mph. Chance of rain 50 percent.

North Kaua’i

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

Tonight: Mostly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 67 to 74. East winds up to 10 mph. Chance of rain 50 percent.

Wednesday: Partly sunny in the morning then becoming mostly sunny. Isolated showers. Highs 78 to 89. East winds up to 10 mph. Chance of rain 20 percent.

East Kaua’i

Today: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 76 to 88. East winds around 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 66 to 77. East winds around 10 mph. Chance of rain 50 percent.

Wednesday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 75 to 88. East winds around 10 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Moderate east to east-southeast winds will continue with passing windward and mauka showers into Wednesday. Winds are expected to weaken Thursday into the weekend, that will support afternoon sea breezes and overnight land breezes. Moderate trades may return early next week.

Discussion

The PoPs have been nudged downwards, following the trend of the National Blend of Models. Winds have also been nudged downwards following a blend of the GFS and ECMWF for the longer range for the background flow.
High pressure remains far to the northeast, with a ridge north of the islands overnight. The overnight ASCAT-B pass captured east- southeast winds near the Big Island, while winds near Maui County were more easterly. Little change in wind speeds upstream of the islands.
Earlier runs of the GFS and ECMWF showed an upper level low west of the islands moving east and weakening on Wednesday. The latest run has an even weaker upper level low, so it will likely have minimal impact on the local weather.
North of the above mentioned ridge, and to the north-northwest of Kauai, a low pressure system is moving to the northeast. Its associated front will move slowly to the northeast and linger, helping to disrupt the ridge. This will lead to a weakening of the trades during the second half of the week, resulting in some afternoon sea breezes and overnight land breezes. This pattern will bring some afternoon clouds and showers over the interior of the islands, with some clearing overnight. The models suggest the showers may still favor windward areas.
The GFS continues to show an upper level trough digging south towards the islands Saturday, but the latest run of the ECMWF has backed off significantly. At the surface, a ridge begins to re- establish itself north of the islands that will allow trades to return.

Aviation

Surface high pressure ridge north of the state will keep moderate trade winds in the forecast. Expect continued periods of low clouds and showers, mainly over windward and mountain areas, with brief MVFR cigs/vis through the overnight to early morning hours.
No AIRMETs are in effect.

Marine

High pressure northeast of the islands will maintain moderate to locally fresh trades through Thursday. The trades are expected to ease into the light to locally moderate range Friday and Saturday as the ridge to the north weakens. A new high building northwest of the area may restrengthen trades into the moderate to fresh range Sunday into early next week.
A new medium-period northwest swell will build today, peak near 4 feet tonight, then decline as it becomes northerly Wednesday and Thursday. A pair of overlapping small short to medium-period north swells will keep some small surf in place along north facing shores over the weekend. There is the potential for a much larger long-period northwest swell Monday, which could bring advisory level surf to most north and west facing shores.
The current building long-period south-southwest swell will peak today through Wednesday, then gradually decline during the rest of the work week. A new and larger long-period south-southwest swell will gradually fill in late Saturday and Saturday night, then peak with swell heights of 3 to 4 feet Sunday and Monday. This swell will give a sizable late season boost to south shore surf, potentially reaching advisory levels.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov