Photo Credit: Brendan Stephen

West Kaua’i

Today: Mostly cloudy. Numerous showers early in the morning, then scattered showers in the late morning and afternoon. Highs around 82 near the shore to around 70 above 3000 feet. Light winds. Chance of rain 70 percent.

Tonight: Partly cloudy with isolated showers. Lows around 67 near the shore to around 56 above 3000 feet. Light winds. Chance of rain 20 percent.

Wednesday: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 82 near the shore to around 70 above 3000 feet. Light winds becoming northeast around 10 mph in the afternoon. Chance of rain 30 percent.

South Kaua’i

Today: Mostly cloudy with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 81. Light winds. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers. Lows 63 to 68. Light winds. Chance of rain 20 percent.

Wednesday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs around 81. Northeast winds around 10 mph. Chance of rain 40 percent.

Kaua’i Mountains

Today: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 69 to 77 in the valleys to around 64 above 4000 feet. Light winds. Chance of rain 70 percent.

Tonight: Partly cloudy with isolated showers. Lows 56 to 61 in the valleys to around 50 above 4000 feet. Light winds. Chance of rain 20 percent.

Wednesday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 69 to 77 in the valleys to around 64 above 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

North Kaua’i

Today: Partly sunny with scattered showers. Highs 74 to 81. Light winds. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers. Lows 59 to 68. Light winds. Chance of rain 20 percent.

Wednesday: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 74 to 81. East winds up to 10 mph. Chance of rain 40 percent.

East Kaua’i

Today: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 74 to 81. Light winds. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers. Lows 57 to 69. Light winds. Chance of rain 20 percent.

Wednesday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 74 to 81. Northeast winds up to 10 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

A low pressure system far north of the Hawaii region will continue to weaken the large scale winds over the state through Wednesday afternoon. Periods of showers will remain in the forecast today with locally heavy showers possible in thunderstorms. On Wednesday, we transition back to more stable trade winds lasting through Saturday as a high pressure system builds into the region from the north. A cold front approaching the islands from the northwest will break down the ridge north of the state producing lighter winds on Sunday.

Discussion

A small band of nearly stationary thunderstorms continues to develop over the coastal waters of East Maui this morning. These nearly stationary thunderstorms initially formed over the East Maui slopes Monday evening and triggered a flash flood advisory and warning with 4 to 6 inches of rainfall totals based on rain local area rain gauges. This mornings satellite imagery continues to show a large plume of deep tropical moisture drawing up over the islands. Small scale convergence boundaries and island mountains will help to produce rain and isolated thunderstorms across the state today. Brief periods of rainfall will continue today for most islands with locally heavy rainfall possible under thunderstorms.
A low pressure system far north of Hawaii and an upper level disturbance will continue to weaken the winds near the islands through Wednesday afternoon. Temperatures will hover near freezing near the summits of Mauna Loa and Mauna Kea today and a Winter Weather Advisory for ice and snow was issued through this afternoon. Light southerly to southeasterly winds just above the surface, coupled with deep tropical moisture, will continue to produce brief periods of showers with cloudy skies through Tuesday. On Wednesday, we transition back to more stable trade winds lasting through Saturday as a high pressure system builds into the region from the north. Light to moderate trade winds will continue through Sunday with drying trends and only brief passing showers possible over windward and mountain areas.
The long range forecast remains very uncertain as there continue to be large differences in the forecast guidance between the American (GFS) and the European (ECMWF) model solutions from Monday onward. Weather and winds for early next week will change as this long range forecast will likely evolve over time. Stay tuned.

Aviation

Shower activity significantly decreased overnight, with the exception of persistent enhanced convection over eastern Maui and the adjacent waters. AIRMET Sierra continues for tempo mountain obscuration on Maui early this morning, though conditions are expected to improve there later this morning. Showers will continue to decrease today, though lingering tropical moisture and light southeast winds will keep periods of showers in the forecast through this afternoon. Lingering instability will continue the chance for thunderstorms over and east of Maui County through this afternoon as well. Light icing remains possible in layered clouds across the islands through this morning.

Marine

A surface trough northwest of Kauai and an upper level disturbance near Maui County will bring enhanced showers and thunderstorms through today. Otherwise, a surface low pressure system passing by far north of the islands will result in weak south to southeast winds across the waters through today. A high pressure ridge will slowly build in from the north on Wednesday bringing gentle trade winds over the islands through the end of the week.
A new long-period west-northwest swell (310 degrees) will build in through the island chain today before gradually declining Wednesday. A High Surf Advisory (HSA) has been issued for most north and west facing shores of the smaller islands through tonight. Another larger, west-northwest (310 degrees) swell is expected to build Thursday into Friday and will produce peak surf heights well above the advisory threshold along most north and west facing shores. Some of the swell energy may get into parts of west Big Island but a HSA for the area remains low at this time. Further out, a moderate period northeast swell is expected over the weekend as a low far to the northeast develops over the next couple of days.
Only minimal background surf is forecast along south facing shores this week. Surf along east facing shores will remain small through the next several days as winds remain light.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 AM HST Wednesday for north and west facing shores of Niihau, Kauai, Oahu, Molokai, and north facing shores of Maui.
Winter Weather Advisory until 6 PM HST this evening for Big Island Summits above 12,000 feet.

Data Courtesy of NOAA.gov