Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Mostly cloudy with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 86 to 92 near the shore to around 77 above 3000 feet. East winds up to 15 mph. Chance of rain 40 percent.

Tonight: Mostly clear. Lows around 73 near the shore to around 62 above 3000 feet. Northeast winds up to 15 mph.

Thursday: Mostly sunny. Highs 87 to 92 near the shore to around 77 above 3000 feet. Northeast winds up to 10 mph shifting to the southwest in the afternoon.

South Kaua’i

Today: Breezy. Mostly cloudy with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 82 to 90. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 74. Northeast winds 10 to 15 mph. Chance of rain 30 percent.

Thursday: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 83 to 90. Northeast winds 10 to 20 mph. Chance of rain 30 percent.

Kaua’i Mountains

Today: Mostly cloudy with numerous showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 76 to 86 in the valleys to around 67 above 4000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 64 to 72 in the valleys to around 60 above 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Thursday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 76 to 87 in the valleys to around 68 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

North Kaua’i

Today: Mostly cloudy with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 78 to 90. Southeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with scattered showers. Lows 66 to 74. Southeast winds up to 10 mph. Chance of rain 40 percent.

Thursday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 78 to 89. East winds up to 15 mph. Chance of rain 40 percent.

East Kaua’i

Today: Mostly cloudy with numerous showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 74 to 87. East winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows 65 to 77. Northeast winds up to 10 mph. Chance of rain 50 percent.

Thursday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 76 to 88. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Moderate east to east-southeast winds will continue with passing windward and mauka showers through today. As winds weaken Thursday into the weekend, the development of afternoon sea breezes and overnight land breezes can be expected. An upper level disturbance may enhance showers this weekend. Then moderate trades may return early next week.

Discussion

A swath of increased low level moisture is making its way northwestward across the western end of the island chain early this morning, with low clouds and showers mainly favoring windward and mauka areas. However, with a southeasterly steering component, some showers will be able to better circumnavigate the island terrain and move across leeward areas at times. In addition, a weak mid level low northeast of Kauai may help to enhance some of these showers as the swath of moisture moves up the island chain through the early morning hours. By late morning, drier air will move in from east to west and help to reduce some of the shower coverage.
A surface ridge centered well northeast of the state will maintain moderate trades through this evening before a combination of lows and troughs weaken the ridge and allow the trades to become light to moderate through the weekend. This will allow for an expansion in sea breeze activity across the island chain, increasing cloud build up and showers across inland trade wind-protected areas each afternoon. Whether or not winds become light enough to allow for a more pure sea breeze pattern is yet to be seen. Forecast guidance continues to show a mid level cutoff low setting up over the state this weekend, which would increase the potential for shower enhancement Saturday and/or Sunday with the increased instability aloft and allow for heavier downpours in showers.
Heading into early next week, while forecast guidance begins to diverge more significantly, the mid level low will eventually begin to fill in and lift northeastward, allowing the pressure gradient to increase and trades to become moderate once again.

Aviation

A ridge north of the state will maintain the trade winds over the region today, with clouds and showers focused over windward areas. A batch of clouds moved through the islands overnight, initially causing some mountain obscuration to the Big Island, Maui and Molokai. That area shifted to the west around midnight, bringing mountain obscuration to Oahu and Kauai. AIRMET Sierra currently in effect for those islands will likely be dropped sometime in the next several hours as the batch of clouds lifts north and west as it thins. Otherwise, VFR conditions are expected to prevail over leeward areas.
Background winds are expected to gradually become lighter Wednesday night onward, which would allow for daytime sea breezes and overnight land breezes.

Marine

Surface high pressure centered approximately 1,100 nautical miles from Oahu is creating a tight enough pressure gradient across the islands to maintain generally moderate trade winds through the day. Local channeled winds, especially through the Pailolo and Alenuihaha Channels, will frequently attain fresh magnitudes. High pressure northeast of the state will weaken as a low and associated front north of the islands slowly approaches and works on the high from the west. This will slacken the high's gradient over the islands and will result in late week trades falling off to gentle to locally moderate breezes. High pressure northwest of the islands will build east through the remainder of the week. This will reestablish the regional gradient and ultimately restrengthen trades back to moderate to locally fresh speeds Sunday into Monday.
An ongoing small, short to medium period northwest north swell has reached its peak, will hold today and then begin the gradual decline tonight into Thursday. A pair of overlapping small, short to medium period north swells will keep small surf in place along north-facing shores this weekend. There is the potential for the arrival of a larger long period northwest swell Monday and Tuesday from late week gales in association with a Gulf of Alaska frontal passage. As of now, this swell will generate surf that will likely be below High Surf Advisory (HSA) criteria. The current near 2 foot, long period south southwest swell peaked early this morning and will hold through this afternoon before declining late this evening. A new and larger, long period more southerly swell originating from gales east southeast of New Zealand is timed to fill in Saturday night or early Sunday, peak Sunday and then hold into Monday. This swell will provide a sizable late season boost to south shore surf, potentially pushing surf to near HSA levels.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov