Photo Credit: Jason Weingardt

West Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Isolated showers. Highs around 82 near the shore to around 70 above 3000 feet. Northeast winds around 10 mph shifting to the southwest in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 69 near the shore to around 58 above 3000 feet. Northeast winds around 10 mph in the evening becoming light. Chance of rain 50 percent.

Wednesday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 83 near the shore to around 71 above 3000 feet. Light winds becoming south around 10 mph in the afternoon. Chance of rain 50 percent.

South Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs around 81. Northeast winds around 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with scattered showers in the evening, then mostly cloudy with showers likely after midnight. Lows 65 to 70. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Wednesday: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs around 82. Northeast winds around 10 mph shifting to the southeast in the afternoon. Chance of rain 70 percent.

Kaua’i Mountains

Today: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs 69 to 77 in the valleys to around 64 above 4000 feet. East winds around 10 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then occasional showers after midnight. Lows 58 to 63 in the valleys to around 52 above 4000 feet. East winds around 10 mph. Chance of rain 90 percent.

Wednesday: Mostly cloudy. Occasional showers in the morning, then scattered showers in the afternoon. Highs 70 to 78 in the valleys to around 65 above 4000 feet. East winds around 10 mph in the morning becoming light. Chance of rain 90 percent.

North Kaua’i

Today: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs 74 to 81. East winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows 61 to 70. East winds around 10 mph. Chance of rain 50 percent.

Wednesday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 75 to 82. East winds up to 10 mph. Chance of rain 50 percent.

East Kaua’i

Today: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs 74 to 81. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then showers likely after midnight. Lows 59 to 71. Northeast winds around 10 mph. Chance of rain 70 percent.

Wednesday: Mostly cloudy with showers likely in the morning, then mostly sunny with scattered showers in the afternoon. Highs 75 to 82. East winds around 10 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Clouds and showers associated with a dissipated front will continue to dampen windward areas from Maui to Kauai in the short term, producing low visibility and persistent rainfall. Breezy northeast trade winds over most of the state will gradually diminish over the next couple of days, with winds becoming light and variable by Friday. Windward showers will gradually diminish as winds weaken, but another front may bring increased showers next weekend.

Discussion

Low-level moisture associated with a dissipated front continues to advect (to varying degrees) into windward areas of the islands from Maui to Kauai while mostly dry conditions persist over the Big Island. Radar indicates that rainfall rates are relatively low with most of the showers, although there have been some localized moderate returns, while observers report briefly heavy downpours. Wettest windward rain gages have received over 7 inches of rainfall over the past 24 hours (i.e., Maunawili Oahu with 7.33″) , with widespread 2 to 4 inch rainfall totals. On the Big Island, mostly dry conditions are prevailing. Breezy NE winds exist on the N side of the boundary, with light NE to E winds over the Big Island. 12Z soundings show a subsidence inversion based near 9 thousand feet.
Model guidance is not consistent with the specifics regarding the movement and evolution of the low-level moisture pool over the next day or two, leading to decreased confidence in the details of the short-term cloud and shower forecast. Broadly speaking, it is expected to gradually dissipate as high pressure to the N moves away to the NE, with trade winds weakening and veering to the E by Wednesday. Windward showers should trend down as this occurs, with fewer showers for the second half of the week, with light to moderate trade winds prevailing. In the meantime, expect damp conditions to continue over windward areas from Kauai to Maui, with some sprinkles spreading leeward.
Meanwhile, satellite shows layered clouds and increased moisture over waters SE of the Big Island. Model guidance has trended toward a drier solution for windward and SE Big Island today, with the bulk of the moisture remaining offshore, thus PoPs have been lowered. Nonetheless, still expecting a few showers over the Big Island this afternoon and tonight.
A low developing NW of the islands will weaken and veer winds to the SE on Friday and Saturday, with light and variable winds likely allowing land/sea breezes to modulate island weather. An associated front may move over the island chain on Sunday, and the evolution of this feature is very unclear as models vary widely in the handling of a potential cutoff low to the W of the area.

Aviation

Remnant low level moisture from a dissipated front draped along the central islands will bring enhanced moisture to the windward portions of a Maui County and Oahu through mid morning. Periods of MVFR and IFR conditions, including low ceilings, 1000 to 2000 feet, and decreased visibility below a mile will likely accompany this activity. Isolated showers may occasionally push over the terrain and onto the leeward slopes. Mainly dry conditions will prevail on the Big Island. By this afternoon, however, typical moderate trades will bring a return of scattered showers to windward portions of all islands.
AIRMET SIERRA remains in effect through 15Z for periods of IFR conditions along north through east sections of Oahu, Molokai, and Maui due to tempo ceilings below 1000 feet and vis below 3SM in showers. Beyond 15Z, conditions may improve to MVFR for the aforementioned locations.
AIRMET TANGO remains in effect after for Kauai and Oahu due to tempo moderate turbulence between FL250 and FL380.

Marine

The large north northwest swell (340 degrees) that brought warning level surf has been steadily easing through the night based on latest near shore and offshore buoys. Thus the High Surf Warning has been downgraded to High Surf Advisory (HSA). The HSA for select west facing shores has been cancelled as the swell transitions to a more northerly direction. A HSA is now in effect for most north facing shores through today. There is a possibility the HSA may be extended due to another long period pulse out of the north reinforcing surf heights, but will continue to monitor latest guidance for now. In addition, a Small Craft Advisory is in effect for select coastal waters due to elevated seas from the large north swell through today. The proximity of this surf generation fetch introduces a wide spectrum of wave energy extending into the shorter periods, resulting in rough and choppy surf along north facing shores. A larger northwest (320 degrees) swell will build Thursday and continue through the weekend.
Surf along east facing shores will remain rough and choppy due to the combination of breezy trade winds and the north swell wrapping into exposed locations.
Overlapping, small, fading south swell and an incoming small, south- southwest swell will keep small surf along south facing shores for the next couple of days. The next small, long period south southwest swell is expected to fill in over the weekend.
A surface high north of the state is providing moderate to locally strong northeasterly trades early this morning. Trades are expected to become more easterly tonight out of the moderate to fresh range as the high tracks far northeast through Thursday. Winds may veer out of the southeast as early as Friday as a front approaches the state from the northwest.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST this evening for north facing shores of Niihau Kauai Oahu Molokai Maui and the Big Island.
Small Craft Advisory until 6 PM HST this evening for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Pailolo Channel, Big Island Windward Waters.

Data Courtesy of NOAA.gov