Photo Credit: Braden Jarvis

West Kaua’i

Rest Of Today: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs around 83 near the shore to around 71 above 3000 feet. Southwest winds around 10 mph. Chance of rain 20 percent.

Tonight: Mostly clear with isolated showers. Lows around 65 near the shore to around 54 above 3000 feet. Light winds. Chance of rain 20 percent.

Monday: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 82 near the shore to around 70 above 3000 feet. Light winds. Chance of rain 20 percent.

South Kaua’i

Rest Of Today: Mostly sunny with isolated showers. Highs around 82. West winds around 10 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Lows 61 to 66. Light winds.

Monday: Mostly sunny. Highs around 81. Light winds.

Kaua’i Mountains

Rest Of Today: Partly sunny with isolated showers. Highs 70 to 78 in the valleys to around 65 above 4000 feet. Southwest winds up to 10 mph shifting to the south in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 54 to 59 in the valleys to around 48 above 4000 feet. Southwest winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Monday: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 69 to 77 in the valleys to around 64 above 4000 feet. Light winds. Chance of rain 20 percent.

North Kaua’i

Rest Of Today: Mostly sunny with isolated showers. Highs 75 to 82. West winds around 10 mph shifting to the north in the afternoon. Chance of rain 20 percent.

Tonight: Mostly clear. Isolated showers in the evening. Lows 57 to 67. Light winds. Chance of rain 20 percent.

Monday: Mostly sunny. Isolated showers in the afternoon. Highs 74 to 81. Light winds. Chance of rain 20 percent.

East Kaua’i

Rest Of Today: Mostly sunny with isolated showers. Highs 75 to 82. West winds up to 10 mph shifting to the north in the afternoon. Chance of rain 20 percent.

Tonight: Mostly clear. Lows 55 to 69. Light winds.

Monday: Sunny. Isolated showers in the afternoon. Highs 74 to 81. Light winds. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A surface ridge in the vicinity of the islands will maintain tranquil and mostly dry weather conditions through Monday. The current light and variable winds will allow afternoon sea breezes and nighttime land breezes to develop. Some clouds and a few brief showers may form over interior and leeward sections each afternoon, but expect clearing skies at night. Light to moderate trade winds may return briefly starting Monday night or Tuesday. The trade winds will transport some low clouds and light showers into windward facing slopes. The winds will likely start to trend weaker again on Thursday.

Discussion

A weak, nearly east to west oriented surface ridge remains in the vicinity of the Big Island early this morning. Elsewhere, a strong cold front appears to be slightly more than 400 miles due north of Honolulu. This feature will move rapidly toward the east-northeast away from the region during the next 18 to 24 hours. Aloft, an upper-level trough far north of the area is transporting patches of cirrus clouds down over portions of the island chain.
Loops of satellite imagery and radar reflectivity data are showing a couple of narrow northeast to southwest oriented bands of scattered low clouds with embedded showers, one near southeastern Oahu, and the other southwest of Lanai and Molokai. There are also patches of low clouds and showers near the southeastern Big Island, west of the Kohala Districts of the Big Island, and near southwest Maui.
The forecast guidance shows the surface ridge will remain in the vicinity of the islands, with no significant sources of low- level moisture moving into the region. In addition, a mid- tropospheric ridge will likely nose in from the west across the state, which will cause the atmosphere to become more stable through mid-week. Therefore, expect light and variable background winds with a pattern of alternating local afternoon sea breeze and nighttime land breeze circulations forming on each of the individual islands. Some clouds and a few brief showers may develop over leeward and interior sections during the afternoon heating, but skies will likely become mostly clear after sunset each evening. In addition, we expect the area of high clouds to gradually diminish from tonight into Monday.
Looking ahead to Monday night and Tuesday, the surface ridge is forecast to shift north of the island chain. This will likely allow light to moderate trade winds to return to the state. This may result in a brief period of more typical trade wind weather, with low clouds and brief trade showers being transported into the windward sides of the islands, especially during the late night and early morning hours. Note that the mid-tropospheric ridge will likely remain in place, so stable and generally dry atmospheric conditions are expected to prevail.
By Thursday, a new front pushing down from the northwest toward Kauai is expected to cause the surface ridge to weaken, and be pushed closer to the islands once again. This will likely result in light and variable background winds, which will lead to alternating sea breezes and land breezes toward the end of the work week. Dry and stable conditions will also likely dominate, so showers will be minimal over most of the state late in the work week.

Aviation

Storm systems passing far north of the state will keep trade winds at bay during the next 24-hours with light southerly flow prevailing. Sea breeze development by late morning may allow for isolated showers to develop over the interior and higher elevation locations. Elsewhere, expect VFR conditions and partly cloudy skies.
AIRMET TANGO will remain in effect for the mid and upper levels over the islands as an upper level trough, north of Hawaii, moves east of the area.

Marine

As anticipated, the Small Craft Advisory (SCA) and High Surf Advisory (HSA) have each been extended with the morning package. Both have been extended through tonight. Not expecting a need to extend them further. Some minor tweaks have been made to the winds, but the overall flavor of the forecast remains the same.
A low and its associated front are passing north of the offshore waters, keeping a southwest flow over the waters near Kauai and Oahu today. A ridge over the Big Island is keeping winds light and variable over the remainder of the coastal waters. As the front moves away from the region, the ridge will lift northwards, initially over the islands. This will spread the light winds across the coastal waters. A brief return of moderate to fresh trades is possible Tuesday through midweek as the ridge shifts north of the area.
The new northwest swell has been noted on Buoy 51001 overnight, and we are starting to see some hints at the Hanalei buoy. Expect surf along north and west facing shores to increase today, but then be on the decline tonight. Models seems to be handling the arrival of this swell fairly well. If the swell builds further at 51001 or persists longer, the HSA will need to be extended. The swell is also bring seas in excess of 10 feet to the coastal waters exposed to the swell. Expect seas to be on the decline tonight, dropping below SCA levels by Monday morning. A couple smaller northwest swells are expected Wednesday through Saturday to maintain elevated surf along north and west facing shores, and could prompt further advisories. Surf along east and south facing shores will remain small due to the lack trade winds and any significant south swells.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 AM HST Monday for north and west facing shores of Kauai, Niihau, Oahu, and Molokai, and for north facing shores of Maui.
Small Craft Advisory until 6 AM HST Monday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Alenuihaha Channel, Big Island Windward Waters.

Data Courtesy of NOAA.gov