Photo Credit: Brendan Stephen

West Kaua’i

Today: Breezy. Mostly sunny with isolated showers. Highs around 85 near the shore to around 73 above 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Isolated showers early in the evening. Lows 69 to 74 near the shore to around 60 above 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny. Highs around 86 near the shore to around 74 above 3000 feet. East winds up to 15 mph.

South Kaua’i

Today: Breezy. Partly sunny with showers likely in the morning, then mostly sunny with scattered showers in the afternoon. Highs around 82. East winds 15 to 20 mph. Chance of rain 70 percent.

Tonight: Partly cloudy. Breezy. Scattered showers early in the evening, then isolated showers in the late evening and overnight. Lows 67 to 73. Northeast winds 15 to 20 mph. Chance of rain 40 percent.

Tuesday: Breezy. Mostly sunny with isolated showers. Highs around 83. Northeast winds 15 to 20 mph. Chance of rain 20 percent.

Kaua’i Mountains

Today: Mostly cloudy. Breezy. Frequent showers in the morning, then scattered showers in the afternoon. Highs 72 to 79 in the valleys to around 63 above 4000 feet. East winds 10 to 20 mph. Chance of rain 80 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 60 to 65 in the valleys to around 55 above 4000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Tuesday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 73 to 80 in the valleys to around 64 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

North Kaua’i

Today: Partly sunny with scattered showers. Highs 75 to 84. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers early in the evening, then mostly cloudy with isolated showers in the late evening and overnight. Lows 63 to 73. East winds up to 15 mph. Chance of rain 40 percent.

Tuesday: Mostly sunny with isolated showers. Highs 76 to 85. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

East Kaua’i

Today: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs 75 to 83. East winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Scattered showers early in the evening, then isolated showers in the late evening and overnight. Lows 61 to 74. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tuesday: Partly sunny in the morning then becoming mostly sunny. Isolated showers. Highs 76 to 84. East winds 10 to 15 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Breezy trades will continue through Tuesday, before easing Wednesday and giving way to sea and land breezes Thursday and Friday. A wet trade wind pattern will continue this morning, otherwise trade wind showers will be on the decrease through the middle of the week as a more stable airmass gradually settles overhead. Over the Big Island however, a disturbance aloft may allow for a thunderstorm or two to develop during the afternoon hours today and Tuesday. Very dry conditions will overspread the islands by Thursday and linger through the weekend, greatly limiting shower activity across the entire state.

Discussion

Currently at the surface, a 1028 mb high is centered around 850 miles north-northeast of Honolulu, driving breezy trade winds across the island chain. Infrared satellite imagery shows mostly cloudy conditions for windward and mauka areas, with partly cloudy skies in most leeward locales. Radar imagery shows scattered to numerous showers affecting windward slopes and coasts, with some of these showers spilling Leeward at times. Main short term focus revolves around trade wind trends and rain chances.
The high to the north-northeast of the islands will weaken as it shifts southeastward during the next few days, with the ridge axis then moving over or very near the western islands Thursday and Friday. Breezy trade winds will continue through Tuesday, before easing into the moderate range for Wednesday. The winds are then expected to become light and variable over the smaller islands Thursday and Friday, allowing for daytime sea breezes and overnight land breezes to be dominant. Meanwhile, light trades will likely hold in the unprotected areas of the Big Island. The surface ridge axis is forecast to shift northward over the weekend, which should bring a return and gradual strengthening of the trade winds.
As for the remaining weather details, a band of low clouds will keep rather wet conditions in place over windward slopes and coasts this morning. We should see a typical reduction in trade wind shower coverage by late morning into the afternoon hours, and instability aloft will likely allow for a thunderstorm or two to pop over the Big Island and possibly over the slopes of Haleakala on Maui as well. Fairly typical trade wind weather should then prevail tonight into Tuesday morning, with the trade wind inversion then crashing down to around 5 kft greatly limiting trade wind showers for Tuesday afternoon. Once again, instability aloft will likely allow a thunderstorm or two to pop over the Big Island interior during the afternoon hours. Rather dry trade wind weather will continue Tuesday night through Wednesday night as the trade wind inversion holds around 5 kft, with most leeward areas not seeing any rain. Little change in the trade wind inversion height is expected Thursday through the weekend, greatly limiting shower activity across the entire state. We will likely see a few showers pop over the leeward slopes of the Big Island each afternoon, with very little shower activity elsewhere. A slight increase in windward showers is possible over the weekend as the trades gradually return.

Aviation

Breezy to strong trades will continue for the next couple of days, as surface high pressure remains north of the area. Low cigs and SHRA will favor windward and mauka areas with periods of MVFR conds possible. VFR should prevail elsewhere.
AIRMET Sierra is in effect for windward Big Island as well as N thru SE areas of the smaller islands.
AIRMET Tango remains in effect for moderate low-level turb S through W of terrain due to the breezy trades.
AMD NOT SKED for PMDY as equipment remains unavailable with no time table for return to service.
AMD NOT SKED for PHLI as equipment is unavailable. Techs are scheduled for later today.

Marine

Strong surface ridge north of the islands will remain stationary through Tuesday leading to strong east northeast trade winds. A Small Craft Advisory (SCA) has been expanded for the all zones around Maui County and the Big Island and select areas of Kauai and Oahu through Tuesday. On Wednesday and Thursday, unseasonably strong low pressure rapidly developing north of the area will weaken the high and displace the ridge southward over the islands. Winds will respond by becoming light and variable Thursday and Friday.
A conveyor belt set up in the south Pacific has lead to an extended period of elevated surf along south facing shores through potentially the first half of June with numerous swell pulses expected, mainly from the south- southwest. The current south swell has peaked, leveled off and will gradually ease before additional long period energy arrives later in the week. A High Surf Advisory (HSA) is likely to be needed for the largest of the swells, which may not arrive until next weekend.
A small, long-period north swell has begun to fill in early this morning, it is expected to build through the day, and continue into Tuesday, with the potential for a small follow- up swell later in the week. A small north swell is also possible next weekend. Trade winds will continue to generate short-period wind waves the next couple of days, leading to choppy surf along exposed east facing shores. Wind waves will diminish significantly after Wednesday coinciding with the light winds.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Tuesday for Kauai Northwest Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov