Photo Credit: Brendan Stephen

West Kaua’i

Today: Sunny. Highs around 86 near the shore to around 75 above 3000 feet. East winds up to 15 mph.

Tonight: Partly cloudy with isolated showers. Lows around 70 near the shore to around 60 above 3000 feet. Light winds becoming northeast up to 10 mph after midnight. Chance of rain 20 percent.

Monday: Mostly sunny. Isolated showers in the morning. Highs 83 to 88 near the shore to around 74 above 3000 feet. East winds around 10 mph. Chance of rain 20 percent.

South Kaua’i

Today: Mostly sunny with scattered showers. Highs 81 to 87. East winds 10 to 15 mph. Chance of rain 30 percent.

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

Monday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 82 to 87. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Mostly sunny with scattered showers. Highs 74 to 81 in the valleys to around 66 above 4000 feet. East winds up to 15 mph. Chance of rain 30 percent.

Tonight: Mostly cloudy with scattered showers. Lows 63 to 68 in the valleys to around 59 above 4000 feet. Light winds becoming east up to 15 mph after midnight. Chance of rain 50 percent.

Monday: Partly sunny with scattered showers. Highs 74 to 81 in the valleys to around 66 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

North Kaua’i

Today: Mostly sunny with scattered showers. Highs 77 to 86. Southeast winds up to 15 mph. Chance of rain 30 percent.

Tonight: Mostly cloudy with scattered showers. Lows 64 to 72. Southeast winds up to 10 mph. Chance of rain 50 percent.

Monday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 76 to 85. East winds 10 to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Mostly sunny with scattered showers. Highs 74 to 84. East winds up to 15 mph. Chance of rain 30 percent.

Tonight: Mostly cloudy with scattered showers. Lows 64 to 74. Northeast winds up to 10 mph. Chance of rain 50 percent.

Monday: Partly sunny with scattered showers. Highs 75 to 85. East winds around 10 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Mostly dry weather will persist into Monday, with the exception of a few light showers around Kauai today from a dissipating front. Expect moderate to locally breezy trade winds to build back over the islands over the next couple of days. Strong northeast trade winds may develop on Tuesday, with a potential increase in windward showers through the rest of the week.

Discussion

Some minor changes to the grids with the morning package, mainly with regards to the winds over the coastal waters. Winds have been nudged upwards over the first 48 hours mainly over the typical windier waters near Maui County and the Big Island. Have held off on making any changes to the winds beyond that, as we wait to see how the high resolution models handle the uptick in winds expected by Tuesday.
The overall forecast philosophy remains the same. A dissipating front north of the islands, with a ridge to the north of the front. This is allowing trade winds to return to the region. Another front passing north of the islands on Tuesday will help to add more moisture to the airmass over and upstream of the islands. Right behind this front is a strong high pressure system that will help to increase winds around the islands to locally strong levels. These winds are likely going to stick around into Thursday. Another front approaching from the north-northwest will help to boost shower activity during the second half of the week.

Aviation

Trade winds will gradually strengthen to become moderate today as a surface high builds to the northeast of the state and the remnants of a front just north of Kauai lift northward. VFR conditions are expected to generally prevail today as limited atmospheric moisture and atmospheric stability hinder substantial low level cloud or shower development. However, windward areas will see brief periods of MVFR conditions in any showers that manage to develop. Shower coverage and intensity will increase slightly overnight tonight, increasing the chances of seeing MVFR conditions along the windward portions of mainly the eastern end of the state.
AIRMET Sierra is in effect for mountain obscuration across the windward slopes of the Big Island and Maui due to low level clouds and showers. This activity will likely continue through mid morning before improving. If shower activity expands across the state, additional windward slopes may need to be added to AIRMET Sierra.
In addition, if the ridgetop flow can strengthen enough under the inversion today as the trades increase, will need to watch for moderate low level turbulence over and lee of the terrain, but current model guidance is showing that winds will remain under criteria.

Marine

A ridge of high pressure will become the dominate feature for the next day or two as the parent high settles far northeast of the state. This will translate to the gradual return of moderate to locally strong easterly trades by this afternoon. A Small Craft Advisory (SCA) has been issued for typically windy zones around Maui and the Big Island through Monday night. A front will pass north of the state Monday into Tuesday. A strong high pressure will build behind the front. Winds will back to more of a northeasterly direction and strengthen first over the western half of the state to moderate to strong with the possibility of more exposed channels and points reaching near gale Tuesday and Wednesday. These strong northeasterly winds will then spread to the rest of the state through the second half of next week. Thus more zones may be added to the SCA and extended through the forecast period.
A moderate size, medium period northwest (330-340 degree) will veer to a more northerly direction (340-360 degree) and will continue to subside into Monday. A large, moderate to long period northwest swell (310-360 degrees) may produce high end advisory level or low end warning level surf late Tuesday into Wednesday, before subsiding Thursday. Latest guidance suggests a small decline in predicted swell height. However, ASCAT and altimeter data shows the captured fetch region has expanded in size and strengthen to near severe gales which will mean a possible secondary peak late Wednesday in swell height after the first. Also observations are more agreeable with model guidance at this time. As this swell source tracks north and northeast of the state Wednesday into Thursday, the swell direction will become more northerly (360-010 degrees) as it subsides. Building seas with this swell, in tandem with stronger trades, will likely prompt an all-water SCA as early as Tuesday and persist through the forecast period.
Moderate choppy east shore surf will persist for the next couple of days. Above average east shore choppy conditions can be expected Tuesday through the rest of the week as northeasterly trades strengthen and persist through the forecast period and the large northwest swell mentioned above, wraps into exposed locations, especially as it transitions into a more northerly direction.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Tuesday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov