Photo Credit: Jason Weingardt

West Kaua’i

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 91 near the shore to around 78 above 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with scattered showers. Lows around 75 near the shore to around 64 above 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Monday: Mostly sunny with scattered showers. Highs around 92 near the shore to around 80 above 3000 feet. East winds around 10 mph. Chance of rain 50 percent.

South Kaua’i

Today: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs 82 to 90. East winds around 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 75. East winds around 15 mph. Chance of rain 50 percent.

Monday: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs 83 to 91. East winds 10 to 15 mph. Chance of rain 70 percent.

Kaua’i Mountains

Today: Breezy. Mostly cloudy with occasional showers. Highs 76 to 88 in the valleys to around 67 above 4000 feet. East winds 15 to 20 mph. Chance of rain 90 percent.

Tonight: Occasional showers. Lows 66 to 73 in the valleys to around 61 above 4000 feet. East winds 10 to 15 mph. Chance of rain near 100 percent.

Monday: Occasional showers. Highs 78 to 89 in the valleys to around 69 above 4000 feet. East winds 10 to 15 mph. Chance of rain near 100 percent.

North Kaua’i

Today: Partly sunny with showers likely in the morning, then mostly sunny with scattered showers in the afternoon. Highs 78 to 91. East winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then showers likely after midnight. Lows 68 to 75. East winds 10 to 15 mph. Chance of rain 70 percent.

Monday: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs 79 to 92. East winds 10 to 15 mph. Chance of rain 70 percent.

East Kaua’i

Today: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs 75 to 87. East winds around 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then showers likely after midnight. Lows 67 to 78. East winds 10 to 15 mph. Chance of rain 70 percent.

Monday: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs 76 to 88. East winds 10 to 15 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Locally breezy trade winds will persist this week, delivering passing showers that will favor windward areas. Deeper moisture will move over the islands tonight and Monday, likely bringing increased shower coverage, especially over the Big Island, where some heavy showers may develop.

Discussion

Surface high pressure far NNE of the islands will remain nearly stationary this week, supporting breezy and locally gusty trade winds. A slight decrease in wind speeds is possible by next weekend as the high weakens. Generally speaking, fairly typical trade wind weather is expected, with brief windward showers occasionally spreading a few sprinkles leeward, most likely during nights and mornings.
A caveat to the typical trade wind forecast is an area of increased moisture approaching from the E. More specifically, the leading edge of a 300-mile-wide area of broken to overcast low- and mid-level clouds lies about 150 miles E of the Big Island. UW-CIMSS MIMIC analyses indicate PWAT near 2″ in this area, supported by what model guidance indicates is a sharp 700 mb trough.
As this trough moves W over the islands tonight and Monday, moisture will extend as high as 12-15 kft, mainly over the Big Island, bringing the potential for some heavy showers. While the moisture increase over the smaller islands is not expected to be as deep, an increase in windward showers is likely. Additionally, dew points in the low- to mid-70s will make it feel muggy statewide on Monday. After the trough moves W of the islands Tuesday and Wednesday, a return to a fairly typical trade wind weather pattern is expected as dew points drop slightly.

Aviation

High pressure centered far north of the state will maintain moderate to breezy trades over the next couple of days. Clouds and showers will favor windward and mauka areas, though the temperature inversion heights will remain elevated enough to allow occasional showers to pass over island terrain into leeward areas. Shower coverage and intensity will be greatest through the early morning hours today and then again tonight as a plume of deeper moisture moves in from the southeast. Periodic MVFR conditions are expected in heavier showers. Otherwise, VFR conditions will prevail.
With the increased trade winds, AIRMET Tango for low-level turbulence over and downwind of terrain is in effect and will likely continue into tonight.
AIRMET Sierra is in effect through this morning for tempo mountain obscuration across windward areas due to low clouds and showers. This AIRMET will likely be needed again by this evening for at least the southern end of the state.

Marine

Surface high pressure far north northeast of the waters near 45N will continue to provide moderate to locally strong trade winds through the first half of the week. A Small Craft Advisory has been extended for the windier waters and channels of Maui County and the Big Island through Monday night. A slight uptick in trade winds is expected Monday and Tuesday as the pressure gradient strengthens.
Surf along east facing shores will remain choppy through the first half of the week due to persistent trades locally and upstream of the islands. A small long period south swell will slowly decline today. A combination of background south and southeast swells will keep the surf from going flat over south facing shores through the first half of the week. North facing shores will remain nearly flat through much of the week. Models show a gale low developing and tracking along the Aleutian Islands that may send a small northwest swell into the local waters Friday into Saturday.
Water levels at local tide gauges are running over half a foot above predicted and are expected to reach above the 1 foot Mean Higher High Water threshold for coastal inundation over the next several afternoons due to above normal water levels coinciding with the spring tides. The Coastal Flood Statement is now in effect for this threat through Tuesday and may need to be extended through Wednesday.

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