Photo Credit: Braden Jarvis

West Kaua’i

Today: Mostly sunny with isolated showers in the morning, then mostly cloudy with showers likely in the afternoon. Highs around 85 near the shore to around 73 above 3000 feet. Northeast winds up to 15 mph shifting to the southwest in the afternoon. Chance of rain 70 percent.

Tonight: Partly cloudy with isolated showers. Lows 67 to 72 near the shore to around 58 above 3000 feet. Northeast winds 10 to 15 mph decreasing to up to 10 mph after midnight. Chance of rain 20 percent.

Tuesday: Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs around 86 near the shore to around 74 above 3000 feet. East winds up to 10 mph shifting to the south around 10 mph in the afternoon. Chance of rain 50 percent.

South Kaua’i

Today: Mostly cloudy with scattered showers. Highs around 82. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 64 to 70. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tuesday: Mostly sunny with isolated showers. Highs around 83. East winds around 10 mph. Chance of rain 20 percent.

Kaua’i Mountains

Today: Mostly cloudy. Occasional showers in the morning, then showers likely in the afternoon. Highs 72 to 79 in the valleys to around 63 above 4000 feet. East winds 10 to 15 mph. Chance of rain 80 percent.

Tonight: Mostly cloudy. Showers likely in the evening, then scattered showers after midnight. Lows 58 to 63 in the valleys to around 53 above 4000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

Tuesday: Partly sunny with scattered showers. Highs 73 to 80 in the valleys to around 64 above 4000 feet. East winds around 10 mph. Chance of rain 50 percent.

North Kaua’i

Today: Partly sunny. Scattered showers in the morning, then showers likely in the afternoon. Highs 75 to 84. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 70 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 61 to 71. East winds 10 to 15 mph. Chance of rain 50 percent.

Tuesday: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs 76 to 85. East winds 10 to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs 75 to 84. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows 59 to 71. East winds 10 to 15 mph. Chance of rain 50 percent.

Tuesday: Mostly sunny with isolated showers. Highs 76 to 84. East winds around 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Light to moderate trade winds will push a band of moisture over the islands today, bringing clouds and showers to both windward and leeward areas. Trades will remain on the lighter side through Tuesday, then strengthen Wednesday and Thursday, remaining breezy into the weekend. Limited windward showers are expected after tomorrow.

Discussion

Water vapor imagery shows a well-developed, slow-moving closed low aloft centered just N of Oahu. Early morning sounding from Lihue shows an unstable profile, while the Hilo sounding shows a subsidence inversion based around 8000 feet, with PWAT near normal at 1.3″ at both locations. Seasonably light to moderate trade winds are being driven by a persistent high centered far NE of the islands.
The instability associated with the low aloft has combined with an overnight increase in low-level moisture to bring increased showers to windward areas, with some small heavy rain cores noted on radar. Satellite images show some cooler cloud tops associated with towering cumulus, and there was an isolated lightning strike over the outer Oahu leeward waters earlier in the night.
The forecast anticipates that windward showers will persist today, with just a few showers spreading to leeward areas this morning. There will likely be a greater chance of leeward showers this afternoon as the trades will be light enough to allow leeward sea breezes to trigger the development of clouds and showers. A few downpours are possible both windward and leeward, and while not likely, an isolated lightning strike cannot be ruled out.
Increasingly stable conditions will develop Tuesday into Wednesday as the upper low moves N and a building mid-level ridge leads to significant mid-level warming. Trade winds will be on the lighter side through Tuesday as a distant front weakens the ridge N of the area. Trades will deliver a few windward showers, and the leeward afternoon sea breezes may drive some cloud and showers formation on Tuesday.
Trade winds will strengthen Wednesday and Thursday as high pressure builds N of the islands. Stable conditions will prevail, and a typical trade wind weather pattern is expected, with brief windward showers favoring nights and mornings. Leeward Big Island can expect typical afternoon and evening clouds delivering a few showers as well.

Aviation

Surface high pressure far northeast of the state will continue to bring moderate trades across the islands through this afternoon. An upper level low, located less than 100 miles north of Oahu will help to enhance shower activity this morning, especially along the windward coasts and slopes. Periods of MVFR ceilings and visibility may accompany any of the more robust shower activity.
By this afternoon, the highest concentration of showers will likely shift towards interior and leeward locations.
No AIRMETs are currently in effect, but AIRMET for SIERRA may be warranted later this morning, as low cloud and shower coverage increases along windward locations.

Marine

A high pressure system far north-northeast of the state will keep trade winds in the forecast through much of the week. An upper low over the Hawaiian Islands will continue to weaken the surface winds by producing a broad trough over the region, keeping trade winds in the moderate to locally fresh range through Tuesday. This upper low will weaken and drift northeastward, away from the islands from Tuesday into Wednesday, allowing wind speeds to strengthen into the moderate to locally breezy range from Wednesday through next weekend. Small Craft Advisory conditions will return to the windier waters in channels around Maui and the Big Island from Wednesday onward.
Surf along exposed north and west facing shores will see increasing surf heights today as a new medium period west-northwest (300-310 degree) swell fills in. Buoy 51001 and 51101 readings are showing deep water swell heights averaging around 6 feet 13 seconds. This swell should peak across the state today, then begin to gradually decline on Tuesday with only background energy expected by the end of the week.
Small and choppy surf along east facing shores will ease slightly over the next couple of days due to weaker trades. An upward trend will develop from Wednesday onward as the local and upstream trades increase in strength.
Surf along south facing shores will remain small each day through the week with mainly background south (170-220 degree) swell energy moving through the region. Although high pressure is currently parked in our typical swell window southeast of New Zealand, a powerful gale to storm force low currently evolving far south of Tahiti will be enough to generate a long period south (170-180 degree) swell for the weekend of June 24th and 25th. This swell should fill in next weekend and will likely produce surf heights above the summer average heights.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov