Photo Credit: Jason Weingardt

West Kaua’i

Today: Mostly sunny. Isolated showers in the morning. Highs around 84 near the shore to around 72 above 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Lows around 68 near the shore to around 62 above 3000 feet. Northeast winds up to 15 mph.

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

South Kaua’i

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

Tonight: Mostly cloudy with scattered showers. Lows around 68. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Sunday: Cloudy and breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 81. Northeast winds 10 to 20 mph. Chance of rain 40 percent.

Kaua’i Mountains

Today: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 71 to 78 in the valleys to around 62 above 4000 feet. East winds up to 10 mph. Chance of rain 30 percent.

Tonight: Mostly cloudy with scattered showers. Lows 61 to 66 in the valleys to around 57 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Sunday: Cloudy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 71 to 78 in the valleys to around 62 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

North Kaua’i

Today: Mostly sunny with isolated showers. Highs 74 to 83. Southeast winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with scattered showers. Lows 63 to 69. Southeast winds up to 10 mph. Chance of rain 50 percent.

Sunday: Partly sunny with scattered showers in the morning, then cloudy with isolated showers in the afternoon. Highs 74 to 83. East winds up to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Mostly sunny with isolated showers. Highs 74 to 82. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

Tonight: Mostly cloudy with scattered showers. Lows 59 to 70. Northeast winds around 10 mph. Chance of rain 50 percent.

Sunday: Cloudy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 74 to 82. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Most islands will see fairly dry weather conditions through Sunday afternoon. A few exceptions include a shallow island convergence plume over the eastern half of Oahu this morning producing light to locally moderate showers. Long range models continue to show a kona low setting up just west of Kauai through much of next week. Expect hot humid conditions with wet weather trends from Tuesday through Friday. The potential for periods of heavy rainfall and thunderstorms are growing across the state next week with significant snowfall possible over the Big Island summits.

Discussion

Radar imagery this morning shows the Molokai island convergence plume producing nearly stationary showers along the windward mountains of Oahu. These moderate showers will continue through the early morning hours before diminishing. East Maui also shows some shower enhancement this morning in east to southeast low level wind flow. Satellite imagery remains fairly similar over the past 12 hours, with a large band of clouds lingering over the southern waters of the Big Island. Colder air behind the stalled cold front west of Kauai is slowly forming into an upper level low as shown on satellite water vapor imagery. This low will slowly drift eastward over the next few days and become a kona low positioned just west of the island chain.
Lighter large scale winds across the state will keep a sea breeze hybrid east to southeast wind pattern in effect today over to most islands. A migratory high pressure system, far north of the state, will drift eastward through Monday morning briefly increasing trade winds statewide. Passing shower activity will favor windward and mountain areas, mainly in the overnight to early morning hours.
Long range guidance continues to initialize well with satellite imagery as a kona low forms west of Kauai from Sunday to Monday. This low will then drift eastward towards the Hawaiian Islands on Monday night, with southerly kona surface winds and increasing showers developing near Kauai and Oahu by early Tuesday morning. Rainfall impacts, heavy at times, and thunderstorms will initially favor the western islands of Niihau, Kauai and Oahu on Tuesday. Additional unstable tropical moisture moving up from the south will spread these unstable wet weather conditions to the eastern islands from Wednesday into Friday. Flash flooding threats are growing as operational models start to show higher potential for heavy rain and thunderstorms mainly from Tuesday through Thursday. Stay tuned as the potentially heavy rainfall threats from this system evolve over time. Freezing levels will be low enough for much of this precipitation to fall as heavy snow over the highest summits of Mauna Kea and Mauna Loa on the Big Island.
The operational global models remain in fair agreement that wet kona weather is likely for most islands through much of next week. Island by island impacts are going to be highly dependent upon the actual location of where this low and upper level divergence plume sets up relative to each island. The heaviest rainfall and highest chances for thunderstorms associated with these kona lows will occur east of the low center, as cold air aloft and upper level wind divergence combine forces to produce a very unstable convective environment. The strength of this low also matters as stronger southerly winds can drive deeper tropical moisture into the southern slopes of each island, triggering deeper convective shower activity.

Aviation

Light to moderate east southeast winds will continue through the early morning hours, with moderate easterly trades building in later today and prevailing through tonight. Showers will be limited primarily to windward and mauka areas through the early morning hours, with a few leeward showers developing this afternoon with the assistance of localized sea breezes. A more typical trade wind pattern will return tonight.
No AIRMETs are currently in effect and none are anticipated.

Marine

Trade winds have eased and veered out of the east-southeast due to the ridge weakening and shifting southward as a front passes far north of the area. Moderate to fresh easterly trades will briefly return later today through Monday as high pressure builds north of the state trailing this front. Thereafter, deep low pressure evolving nearby to the west will lead to moderate southerly winds and increasing rainfall/thunderstorm chances through the week.
Early morning buoy observations show the large northwest swell slowly trending down, but still holding well above the predicted levels. As a result, the High Surf Warning and Small Craft Advisory for seas remain in place. Heights should dip below warning levels tonight into Sunday, then below advisory levels for exposed north and west facing shores by the end of the weekend. Surf will return to small levels early next week as the swell moves out. This small trend is expected to persist through next week, with a small northwest swell arriving around midweek.
Surf along south facing shores will remain small with mainly a background long-period south-southwest swell expected through the weekend.
Surf along east facing shores will remain small through the upcoming week due to the lack of persistent trades locally and upstream across the eastern Pacific.

HFO Watches/Warnings/Advisories

High Surf Warning until 6 AM HST Sunday for north and west facing shores of Niihau, Kauai, Oahu, Molokai, and north facing shores of Maui.
High Surf Advisory until 6 PM HST this evening for west facing shores of Big Island.
Small Craft Advisory until 6 AM HST Sunday for most Hawaiian Coastal Waters.

Data Courtesy of NOAA.gov