Photo Credit: Jason Weingardt

West Kaua’i

Today: Breezy. Mostly sunny with isolated showers. Highs around 89 near the shore to around 77 above 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening, then scattered showers after midnight. Lows 69 to 74 near the shore to around 60 above 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Tuesday: Breezy. Mostly sunny with isolated showers. Highs around 89 near the shore to around 77 above 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

South Kaua’i

Today: Partly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 86. Northeast winds 15 to 25 mph. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 67 to 73. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Tuesday: Partly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 86. Northeast winds 15 to 20 mph. Chance of rain 70 percent.

Kaua’i Mountains

Today: Mostly cloudy. Breezy. Frequent showers in the morning, then scattered showers in the afternoon. Highs 76 to 83 in the valleys to around 67 above 4000 feet. East winds up to 25 mph increasing to 10 to 25 mph in the afternoon. Chance of rain 80 percent.

Tonight: Mostly cloudy. Breezy. Numerous showers in the evening, then frequent showers after midnight. Lows 60 to 65 in the valleys to around 55 above 4000 feet. East winds up to 25 mph. Chance of rain 80 percent.

Tuesday: Mostly cloudy. Breezy. Frequent showers in the morning, then scattered showers in the afternoon. Highs 76 to 83 in the valleys to around 67 above 4000 feet. East winds 10 to 20 mph. Chance of rain 80 percent.

North Kaua’i

Today: Breezy. Partly sunny with scattered showers. Highs 79 to 88. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 63 to 73. East winds up to 15 mph. Chance of rain 70 percent.

Tuesday: Breezy. Partly sunny with scattered showers. Highs 79 to 88. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

East Kaua’i

Today: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 79 to 87. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows 61 to 74. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

Tuesday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 79 to 87. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

The gusty easterly trade winds will continue into Tuesday, then ease slightly Tuesday night through the second half of the week. As areas of moisture move through, showers will be common over windward and mauka locations, while only a few make it over our drier leeward areas.

Discussion

The surface ridge located to our north will remain strong through the start of the week, which supports the gusty easterly trades holding. An area of moisture moving through this morning has led to frequent showers over windward and mauka locations. Some of these have made it into our leeward areas overnight, likely due to the slight increase in the trade inversion (Hilo upper air sounding up to around 9000 ft). Expect this trend to continue through the morning hours. Near-term guidance shows another area of enhanced moisture approaching and clipping the western end of the state Tuesday through Wednesday, which will keep the rainfall chances in the forecast, especially overnight through morning hours for windward/mauka locations. Thereafter, a slight weakness forming in the ridge to the north will translate to our strong trades easing into the moderate to breezy range beginning around or by Wednesday. Stable conditions aloft combined with plenty of mid-level dry air and the lighter trades will lead to the shower distribution and frequency for windward areas decreasing slightly.

Aviation

Moderate to locally breezy trade winds will continue through twenty-four hours and beyond. AIRMET Tango for moderate low level turbulence over and downwind of the terrain will remain in effect for all islands.
Low clouds and showers will favor north through east sections of the islands as bands of moisture move through from time to time. Brief periods of MVFR ceilings and visibilities are possible within any showers that occur, but VFR conditions are expected to prevail most areas today.
As of 2 am Monday, radar indicated active showers moving through Oahu and just upstream of Molokai and Oahu. AIRMET Sierra for mountain obscuration has been reissued for windward Oahu. Conditions are expected to end on Oahu later this morning but will likely redevelop late this evening. Mountain obscuration could also become an issue for windward Big Island this evening.

Marine

Surface high pressure far northeast of the islands will remain nearly stationary the next couple of days, weakening slightly around midweek. Strong to near-gale force trade winds continue, as does a Small Craft Advisory (SCA) for all waters. A slight decrease in wind speeds tonight may allow some zones to be removed from the SCA. A return to SCA over typical windy zones around Maui County and the Big Island is expected around midweek.
The current south-southeast swell is gradually diminishing, as another pulse of south-southeast swell is expected to bring south facing shores back into High Surf Advisory Criteria later today through Tuesday. Observations at the offshore buoys have shown an increase in the long period bands as reinforcements are expected to build later today. Surf along south shores will return to the summertime average (or lower) later in the week.
Nearshore PacIOOS Mokapu buoy shows that combined seas leveled off near 8 feet. Surf along east facing shores will remain rough and choppy with short-period wind waves due to the strong trades before easing slightly. A small NNW swell will bring some small surf to N facing shores the next couple of days, with some trade wind swell also wrapping into exposed locations.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST Tuesday for all south facing shores.
Small Craft Advisory until 6 PM HST this evening for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Maui County Leeward Waters, Big Island Windward Waters.
Small Craft Advisory until 6 PM HST Tuesday for Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov