West Kaua’i

Today: Mostly sunny with isolated showers. Highs 84 to 90 near the shore to around 76 above 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 69 to 74 near the shore to around 61 above 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny with isolated showers. Highs 83 to 89 near the shore to around 75 above 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

South Kaua’i

Today: Mostly sunny with isolated showers. Highs 80 to 89. East winds around 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows around 72. East winds around 15 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny with isolated showers. Highs 80 to 88. East winds 10 to 15 mph. Chance of rain 20 percent.

Kaua’i Mountains

Today: Partly sunny with isolated showers. Highs 74 to 82 in the valleys to around 66 above 4000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with isolated showers. Lows 63 to 69 in the valleys to around 59 above 4000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Wednesday: Partly sunny with isolated showers. Highs 74 to 81 in the valleys to around 65 above 4000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

North Kaua’i

Today: Mostly sunny with isolated showers. Highs 77 to 86. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 65 to 72. East winds 10 to 15 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny with isolated showers. Highs 76 to 85. East winds 10 to 15 mph. Chance of rain 20 percent.

East Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Isolated showers. Highs 73 to 85. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 64 to 75. East winds 10 to 15 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny with isolated showers. Highs 73 to 85. East winds 10 to 15 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Breezy and generally dry statewide conditions the next several days. Occasional scattered showers caught up within enhanced trade flow will focus along windward facing exposures and across higher terrain. Light to locally breezy trades will be the theme through the weekend.

Discussion

A near 1040 mb surface high located approximately 1,800 miles northeast of Hilo, Hawaii will be the main driver to returning traditional trade winds the next several days. The downstream pressure gradient between the high and lower equatorial pressure will remain taunt enough to produce consistent light to occasionally breezy trades well into early next week. The resident air mass has been slowly drying out, yesterday's lower 70 dew points are now in the average middle 60s as lower level easterly dry air filters in. Monday's statewide rainfall fell off from Sunday's numbers with the wettest sites coming in between a half an inch to a inch and a half. Surface troughing that is the reflection of a weakening upper trough about 500 miles west of Kauai will slowly back away to the west and take higher moisture with it. Upstream precipitable waters around 1.20 inches over the eastern Pacific will be near or slightly below normal. Mid level drier air moving west under the belly of mid-level ridging will ensure that the islands experience primarily dry days. Shower activity on all islands will be limited and focused over windward areas and, aside from scattered afternoon showers developing along Big Island's kona slopes, leeward areas will remain mostly dry.
Trades will hold through the middle of the week with light showers continuing to favor windward exposures and mauka areas. Subtle changes will occur later this week as trades slightly ease in response to weak upper level troughing moving overhead while a broad surface trough forms west of the state. However, instability associated with the trough aloft and the available moisture both appear rather meager. The overall column does moisten up a touch as the drier mid layer shrinks and the boundary layer becomes deeper (higher trade inversions) by Friday. Thus, there may be slight enhancement of trade wind showers across windward mauka slopes and at higher elevation. Trades will remain locally breezy Thursday but may slightly drop off a bit on Friday as a result of a slackened gradient (per a weaker northeast surface high). Weak ridging, or the lack of any significant trough, this weekend has the extended forecast leaning toward pleasant conditions. Cloudier windward skies with more frequent showers…mainly clear and dry leeward with the occasional windward shower spilling over the ridgelines.

Aviation

As the trough west of the islands continues to drift west, drier, moderate easterly trade winds are expected later today across the island chain. VFR flight conditions are expected to prevail for most locations, though brief MVFR ceilings and visibilities will remain possible within any showers that pass through. Showers and low clouds will generally favor north through east sections of the islands. In addition, afternoon cloud buildups will be possible again along the Kona slopes of the Big Island this afternoon.
AIRMET Tango remains in effect for moderate low-level turbulence downwind of island terrain. This AIRMET will likely be needed through at least tonight.

Marine

High pressure to the far northeast will remain nearly stationary and weaken over the second half of the week resulting in moderate to locally strong trade winds slowly decreasing to gentle to locally fresh trades by Saturday. A Small Craft Advisory (SCA) has been scaled back this morning to the windier waters and channels around Maui County and the Big Island through Wednesday.
Surf along south facing shores will remain small today before a tiny to small long period southwest swell is expected to start filling in late tonight into Wednesday. A larger event from a fetch near New Zealand is trending to bring a moderate long period south-southwest swell to start filling in on Friday, and peak Saturday potentially near High Surf Advisory (HSA) criteria.
Surf along north facing shores will remain small today as the north-northwest swell lingers today before declining tonight into Wednesday. East-facing shore surf will remain choppy due to the moderate trade winds today. A combination of a strong high pressure to the far northeast and a low near California earlier this week has produced the potential for a moderate medium period east swell to fill in Thursday, peak Friday, and decline through the weekend.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 8 PM HST Wednesday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.