Photo Credit: Braden Jarvis

West Kaua’i

Today: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 83 near the shore to around 71 above 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy. Scattered showers early in the evening, then isolated showers in the late evening and overnight. Lows around 70 near the shore to around 59 above 3000 feet. East winds up to 15 mph becoming around 10 mph after midnight. Chance of rain 50 percent.

Wednesday: Mostly sunny with isolated showers. Highs around 83 near the shore to around 71 above 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

South Kaua’i

Today: Partly sunny with scattered showers. Highs around 80. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 66 to 71. East winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday: Partly sunny with scattered showers. Highs around 80. East winds 10 to 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Mostly cloudy with showers likely. Highs 70 to 77 in the valleys to around 61 above 4000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with numerous showers. Lows 59 to 64 in the valleys to around 52 above 4000 feet. East winds up to 15 mph becoming around 10 mph after midnight. Chance of rain 70 percent.

Wednesday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 70 to 77 in the valleys to around 61 above 4000 feet. East winds around 10 mph. Chance of rain 70 percent.

North Kaua’i

Today: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs 73 to 83. East winds up to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Scattered showers early in the evening, then numerous showers in the late evening and overnight. Lows 62 to 70. East winds up to 15 mph becoming around 10 mph after midnight. Chance of rain 70 percent.

Wednesday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 73 to 83. East winds 10 to 15 mph. Chance of rain 70 percent.

East Kaua’i

Today: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs 73 to 82. East winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Scattered showers early in the evening, then numerous showers in the late evening and overnight. Lows 59 to 72. East winds 10 to 15 mph. Chance of rain 70 percent.

Wednesday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 73 to 82. East winds 10 to 15 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Moderate trades will focus showers over windward areas through the week. Afternoon showers, some of which may be heavy, will be common over leeward portions of Maui and the Big Island each afternoon. There is also a slight chance of afternoon thunderstorms over the Big Island today.

Discussion

Did make some tweaks to the PoPs and associated grids through tomorrow night, mainly to nudge PoPs up towards the National Blend of Models. This mostly impacted the Big Island, but some other areas were nudged upwards as well. The overall forecast philosophy remains the same.
An upper level trough to the north of the main Hawaiian islands is bringing southwesterly upper level winds over the region. High clouds just south of the Big Island will likely pass over the island from time to time. Thunderstorms have been noted on the edge of the coastal waters to the southwest of the islands, and into the offshore waters further southwest.
The upper level trough is expected to slowly lift north and move to the east over the next 24 hours or so. While thunderstorms didn't materialize over the Big Island yesterday afternoon, enough instability remains over the southern end of the state for the possibility of a thunderstorm or two over the slopes Tuesday afternoon.
The surface trough mentioned above is expected to move to the west away from the islands over the next couple of days, with a high pressure system remaining to the north to maintain a trade wind pattern over the islands. A broad upper level trough is expected to remain north of the islands through much of the week. The ECMWF develops another upper level low to the northwest of the islands at the end of the week, while the GFS isn't quite as keen on the development. The upper level trough will likely keep inversion levels a bit higher than normal in a trade wind pattern. With precipitable water on the high end of normal, there will be showers focused over the windward sides of the islands. The higher than normal inversion will help showers to develop over the leeward sides of the islands during the afternoon hours, particularly Maui and the Big Island, through the week.

Aviation

The air mass over the state is becoming increasingly unstable, the result of a nearby upper level trough of low pressure. With little or no capping inversion aloft, locally heavy showers are possible statewide. Daytime heating will further enhance convective activity, especially over island interiors. Isolated thunderstorms are expected over the higher elevations of the Big Island in the afternoon and early evening.
Early morning satellite and radar imagery revealed scattered light showers carried in by the trade winds approaching windward slopes and coasts. Meanwhile, a large area of layered clouds, punctuated with isolated moderate showers, hung over leeward waters. In the higher levels, ragged bands of cirrus streamed across the state from the southwest. Expect shower activity to be mainly light and intermittent this morning then intensify and become focused over island interiors in the afternoon.
There are currently no AIRMETs in effect.

Marine

High pressure far north of the state will drift south for the next couple of days. This will result in moderate to fresh trade winds with periods of locally strong trade winds. Winds will hover near the Small Craft Advisory (SCA) thresholds for the windier waters around Maui and the Big Island and could increase to SCA thresholds briefly Wednesday. Trades winds will weaken slightly as the high moves far northeast towards the end of the week into the weekend.
The current south southwest swell appears to have peaked and is expected to hold surf heights around the summer average (5 feet) today before gradually subsiding Wednesday. Background surf is expected along south facing shores from Thursday into Friday which will keep surf from going flat. A small, long- period south- southwest swell will arrive this weekend providing a slight increase in surf heights along south facing shores Saturday night into Sunday. A small south- southeast (160-170 degree) swell is possible early next week from a gale low located currently near 30S147W.
Persistent trade winds, should keep near to just below average choppy surf along east facing shores through most of the week. Surf is expected to drop well below average over the weekend as trade winds ease locally and upstream.
The current small west-northwest swell will provide a slight boost in surf heights along most exposed north and west facing shores today. This swell will fade overnight into tomorrow. Expect small, background summertime surf along north facing shores from tomorrow through next weekend. For the long-range, the latest guidance from the WAVEWATCH III Model continues to indicate a small, long- period west swell, produced by northwest Pacific Typhoon Mawar, may arrive around Tuesday, June 6.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov