Photo Credit: Braden Jarvis

West Kaua’i

Today: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Haze in the afternoon. Highs around 82 near the shore to around 72 above 3000 feet. Southeast winds around 10 mph shifting to the south in the afternoon. Chance of rain 50 percent.

Tonight: Mostly clear. Isolated showers in the evening. Haze through the night. Lows 66 to 71 near the shore to around 59 above 3000 feet. East winds around 10 mph in the evening becoming light. Chance of rain 20 percent.

Monday: Mostly sunny. Haze through the day. Scattered showers in the afternoon. Highs 80 to 85 near the shore to around 73 above 3000 feet. Light winds. Chance of rain 30 percent.

South Kaua’i

Today: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Haze in the afternoon. Highs around 82. Southeast winds around 10 mph. Chance of rain 60 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Haze through the night. Lows around 66. Northeast winds around 10 mph. Chance of rain 40 percent.

Monday: Sunny with isolated showers. Haze. Highs 81 to 86. Light winds becoming east around 10 mph in the afternoon. Chance of rain 20 percent.

Kaua’i Mountains

Today: Partly sunny with scattered showers. Haze in the afternoon. Highs 73 to 80 in the valleys to around 66 above 4000 feet. Southeast winds around 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Haze. Lows 59 to 65 in the valleys to around 57 above 4000 feet. East winds around 10 mph. Chance of rain 40 percent.

Monday: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Haze. Highs 73 to 79 in the valleys to around 67 above 4000 feet. Light winds. Chance of rain 40 percent.

North Kaua’i

Today: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Haze through the day. Highs 74 to 82. East winds around 10 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with scattered showers. Haze. Lows 61 to 70. East winds around 10 mph in the evening becoming light. Chance of rain 40 percent.

Monday: Mostly sunny with isolated showers. Haze. Highs 75 to 82. Light winds. Chance of rain 20 percent.

East Kaua’i

Today: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Haze in the afternoon. Highs 74 to 83. East winds around 10 mph. Chance of rain 60 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Haze. Lows 61 to 72. Light winds. Chance of rain 40 percent.

Monday: Mostly sunny with isolated showers. Haze. Highs 74 to 84. Light winds becoming northeast around 10 mph in the afternoon. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Moisture associated with a stalled front will maintain cloudy skies over Kauai this morning, with showers gradually diminishing as the front dissipates. Otherwise, developing light to moderate east- southeast winds will bring a few showers to windward areas through Tuesday. Winds will be light enough to allow land and sea breezes to develop in most leeward areas, with a chance of an afternoon shower. A trend toward wetter weather may occur after mid-week as another front moves into the area. A powerful northwest swell will bring very high surf today that will likely bring coastal impacts along most north and west facing shores into Monday.

Discussion

Low-level convergence associated with a stalled and dissipating frontal boundary near Kauai continues to fuel cloud and shower development over portions of Kauai and Oahu this morning, with the bulk of the showers over the Kauai Channel and well N of Oahu. Meanwhile, an area of moisture moving into portions of windward Big Island looked to bring some much-needed rainfall to the Puna and S Hilo districts, but amounts have been rather light thus far. Maui County has been mostly clear and dry overnight. A surface ridge over the islands is keeping winds light, with offshore-flowing land breezes in most areas. Radar data indicates easterly flow is in place above the surface statewide, at speeds of 10 kt or less.
The stalled frontal boundary will become increasingly diffuse and gradually drift NW today, as will the associated clouds and showers. This will allow the ridge to briefly move N and strengthen, only to have it weakened again Monday night and Tuesday as another front approaches from the NW. This means that light to moderate E- SE winds will trend upward today and generally remain in place through Tuesday, bringing clouds and a few showers to windward areas that will favor nights and mornings. Winds will remain sufficiently light that land and sea breezes will prevail over leeward areas, with the potential for an afternoon shower. A building mid-level ridge will limit rainfall intensity, and heavy showers are not anticipated.
Forecast guidance is fair agreement as to the general large-scale scenario over the central N Pacific by mid-week, as a pattern change leads to an amplifying trough aloft accompanying the approaching front. However, the details surrounding the eventual location and strength of the trough remain in question, which will have profound differences on local weather. Generally speaking, a frontal boundary is expected Tuesday night and Wednesday, bringing shifting winds and a potential for showers. The longer range outlook indicates increasing potential for a trend toward wetter weather as a longwave trough dominates the central N Pacific through the end of the month.

Aviation

Early this morning, a band of organized showers continues to stream across the Kauai Channel. Meanwhile, a frontal boundary just to the northwest of Kauai is also producing widespread showers and cloud cover northwest of the Garden Isle. Showers have impacted southeast Kauai and northern Oahu at times overnight, though the bulk of the activity has remained in the channel. MVFR conditions with isolated IFR ceilings and visibilities will remain in the forecast for Kauai through the morning as lingering moisture is pushed back towards the island.
Elsewhere today, winds will transition to become more easterly, marking a return of moderate trade winds and shower chances for typical windward locations. VFR conditions will prevail, though brief MVFR conditions will be possible, especially across eastern sections of the Big Island where clouds and showers will be more favorable.
AIRMET Sierra for mountain obscuration remains in effect for Kauai early this morning. This AIRMET will likely remain in effect through at least the rest of the morning, though it may be allowed to expire this afternoon as showers and cloud cover diminish.

Marine

The tail end of a diffuse front is stalling in the vicinity of the Kauai waters and will lift north this morning. This will transition early morning northeast winds over the far west waters to more areawide moderate easterlies by late this morning. There will be higher probabilities along and west of this boundary, or the Kauai Channel westward, for more widespread showers. A Small Craft Advisory is in effect through Monday to account for very large seas generated by the passage of an extra large west northwest swell. Surface high pressure centered off the U.S. west coast will create a tight enough pressure gradient back toward the islands to generally produce moderate east trades the next few days. The next cold front may make it further east along the island chain Wednesday but this will be dependent upon the push of backing high pressure off to the far northwest. If this occurs, easterlies will back northeasterly and strengthen to more moderate to locally fresh magnitudes going into Thursday. Confidence is low on the late week weather pattern as the potential for the formation of a closed low north to northwest of the state creates more uncertainty in the late January wind pattern.
An extra large, long period northwest (310-320 degree) swell is quickly filling in around the islands this morning. Swell observations at the northwest offshore buoys rapidly shot up to 25 feet or greater this morning. This XL swell will produce dangerous giant size surf along many north and west-facing shores through Monday afternoon. A High Surf Warning (HSW) is in effect through Monday afternoon for many north and west-facing shores. There will be adverse impacts to coastal properties, harbors and infrastructure, including coastal roadways impacted by overwash, today and Monday, especially during periods of high tide. A westerly component to the swell has increased the potential for elevated surf along the western shores of Maui and Lanai. A High Surf Advisory (HSA) is in effect for these shores. The swell will gradually subside through Monday but will then be followed by large northwest (310-330 degree) swell that is timed to arrive at mid week. This swell will likely lift surf back up to HSW levels Wednesday. Surf along south-facing shores will remain small but, due to the more westerly component the swell, select areas could experience increased surf in response to a westerly wrap. Short period, choppy wave conditions along eastern shores will be associated with persistent moderate east trades through at least Tuesday.

HFO Watches/Warnings/Advisories

High Surf Warning until 6 PM HST Monday for North and West facing shores of Niihau Kauai Oahu Molokai and for North Facing shores of Maui.
High Surf Warning until 6 PM HST Monday for West facing shores of the Big Island.
High Surf Advisory until 6 PM HST Monday for West facing shores of Maui and Lanai.
Small Craft Advisory until 6 PM HST Monday for all Hawaiian waters except Maalaea Bay.

Data Courtesy of NOAA.gov