Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Mostly sunny with isolated showers in the morning, then partly sunny in the afternoon. Highs around 84 near the shore to around 72 above 3000 feet. Northeast winds up to 15 mph shifting to the southeast in the afternoon. Chance of rain 20 percent.

Tonight: Mostly clear. Lows 64 to 69 near the shore to around 56 above 3000 feet. Light winds.

Saturday: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 84 near the shore to around 72 above 3000 feet. Light winds. Chance of rain 20 percent.

South Kaua’i

Today: Mostly sunny. Isolated showers in the morning. Highs 81 to 87. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows around 65. Northeast winds around 10 mph in the evening becoming light. Chance of rain 20 percent.

Saturday: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 81 to 87. Light winds. Chance of rain 20 percent.

Kaua’i Mountains

Today: Mostly sunny in the morning then becoming mostly cloudy. Isolated showers. Highs 73 to 79 in the valleys to around 64 above 4000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 57 to 63 in the valleys to around 53 above 4000 feet. East winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Saturday: Mostly sunny in the morning then becoming mostly cloudy. Isolated showers. Highs 73 to 79 in the valleys to around 64 above 4000 feet. Light winds. Chance of rain 20 percent.

North Kaua’i

Today: Mostly sunny with isolated showers in the morning, then partly sunny in the afternoon. Highs 75 to 83. Southeast winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 58 to 68. Southeast winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Saturday: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 74 to 83. Light winds. Chance of rain 20 percent.

East Kaua’i

Today: Mostly sunny with isolated showers in the morning, then partly sunny in the afternoon. Highs 73 to 83. Northeast winds up to 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 58 to 69. East winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Saturday: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 73 to 84. Light winds. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A surface high pressure ridge positioned just north of the Hawaiian Islands will be weakened by two passing cold fronts over the next several days. Expect mostly light to moderate winds with shifting background wind directions from east to southeast into early next week as the pressure pattern changes north of the state. A ridge aloft will limit shower potential as dry and stable trends continue into early next week. A dry cold front will drift through the islands on Tuesday with a northeast wind shift and only isolated shower potential as it passes through the western half of the state.

Discussion

A large blanket of stable stratocumulus clouds remains in place over the region as the approaching cold front, currently stalled northwest of Kauai, slowly lifts and passes to the north of the state. Background large scale easterly winds will interact with daytime sea breezes over each island today. Isolated showers are possible over each island today, especially along sea breeze and easterly trade wind convergence boundaries just after noon HST.
The surface high pressure ridge will remain just north of the state over the next several days with progressive eastward moving high pressure centers split by two approaching cold frontal troughs. The close proximity of the ridge relative to the Hawaiian Islands and the passing of two frontal troughs will keep winds speeds in the light to moderate range into early next week with a background east to southeast wind direction with periods of land and sea breezes over each island, especially along terrain sheltered western slopes. One exception to this wind forecast may develop on Tuesday as both the American (GFS) and the European (ECMWF) show a fairly 'dry cold front' moving down the island chain. This cold frontal passage will be felt more as a moderate to locally breezy northeast wind shift with slightly cooler temperatures based on the latest model consensus.
Forecast guidance continues to show a dry and stable weather pattern with this east to southeasterly wind pattern as the upper level ridge will remain directly over the islands into next week. Downward vertical motions (subsidence) under this ridge will produce warm and dry conditions aloft, keeping the trade wind temperature inversion heights in the 5,000 to 7,000 foot range through the next seven days. One exception to this precipitation forecast may develop on Tuesday as a fairly stable 'dry cold front' moves down the island chain. Only a slight increase in precipitation coverage is possible with this system mainly over the western islands of Niihau, Kauai and Oahu as the upper level ridge continues to limit instability. Any rainfall amounts are forecast to remain on the light side through Wednesday.

Aviation

Gradual clearing of deep moisture trapped beneath the trade inversion will continue through the early morning as land breezes erode low-level moisture over the islands. VFR conditions will persist as ceilings remain elevated, around 5-6 kft. As moderate trades build during late morning into the early afternoon, residual moisture and light showers will become increasingly focused over windward and mauka areas.
No AIRMETs in effect.

Marine

A ridge near the islands has kept winds in the light category. This feature will become reestablished north of the offshore waters later today as a front dissipates north and northwest of the area. Thus, trade winds will return in the light to moderate range by the afternoon. The ridge is expected to sink southward again this weekend as yet another front approaches from the northwest and eventually dissipates north of the islands by early next week. This will result in winds weakening yet again. A brief period of moderate trades may return to the region during part of the Monday-to-Wednesday time frame.
A new medium-period west-northwest swell has arrived in the coastal waters, with swell heights reaching 10 feet in Kauai waters. A High Surf Advisory was issued earlier for north and west facing shores, and a Small Craft Advisory has been issued this morning for combined seas of at least 10 feet in coastal waters from the Kauai Channel westward. Surf has reached advisory levels around Kauai and Oahu, and possibly Molokai and Maui, this early morning. And west facing shores of the Big Island could see advisory level surf by day break. Surf is expected to continue to build today. Also, a strong low developing east of Japan looks to merge with a large complex system that could generate a long- period and larger northwest swell that would reach the islands late Sunday into Monday. This looks to be a warning level surf event.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 AM HST Saturday for north and west facing shores of Niihau, Kauai, Oahu, Molokai, north facing shores of Maui and west facing shores of the Big Island.
Small Craft Advisory until 6 PM HST this evening for all coastal waters around the island of Kauai.

Data Courtesy of NOAA.gov