Photo Credit: Braden Jarvis

West Kaua’i

Today: Mostly sunny with isolated showers. Highs around 84 near the shore to around 74 above 3000 feet. East winds up to 15 mph shifting to the southeast in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 66 to 71 near the shore to around 57 above 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Monday: Partly sunny with scattered showers. Highs around 83 near the shore to around 73 above 3000 feet. Southeast winds 10 to 15 mph. Chance of rain 40 percent.

South Kaua’i

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 82. East winds around 10 mph. Chance of rain 40 percent.

Tonight: Partly cloudy with isolated showers. Lows 64 to 70. Light winds. Chance of rain 20 percent.

Monday: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 81. East winds 10 to 15 mph. Chance of rain 30 percent.

Kaua’i Mountains

Today: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs around 77 in the valleys to around 66 above 4000 feet. Southeast winds up to 10 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers. Lows around 60 in the valleys to around 52 above 4000 feet. Southeast winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Monday: Partly sunny with scattered showers. Highs around 76 in the valleys to around 65 above 4000 feet. Southeast winds up to 15 mph. Chance of rain 50 percent.

North Kaua’i

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 77 to 83. Southeast winds up to 15 mph. Chance of rain 40 percent.

Tonight: Partly cloudy with isolated showers. Lows 60 to 69. Southeast winds up to 10 mph. Chance of rain 20 percent.

Monday: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 76 to 82. Southeast winds up to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 75 to 81. East winds up to 10 mph shifting to the southeast in the afternoon. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers. Lows 58 to 71. Southeast winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Monday: Partly sunny with scattered showers. Highs 74 to 80. Southeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Moderate trade winds will gradually shift out of the southeast across much of the state today and Monday, causing the focus of showers to move from typical windward slopes to southeast terrain. An approaching front will produce increasing southerly winds on Tuesday. The front will likely move through Kauai Tuesday night, then move down much of the island chain Wednesday and Wednesday night, before stalling out and weakening near the Big Island Thursday. A period of heavy rainfall and thunderstorms will likely accompany the front as it moves through.

Discussion

Currently at the surface, a 1029 mb high is centered around 1150 miles north-northeast of Honolulu, while a cold front is located around 850 miles west-northwest of Kauai. The high remains the dominant weather feature early this morning, with moderate trade winds persisting in unsheltered areas. Infrared satellite imagery shows a mix of high and low clouds moving through the islands, resulting in partly to mostly cloudy conditions. Radar imagery shows scattered to numerous showers over windward Big Island, with isolated to scattered showers affecting windward portions of the other islands. Most leeward areas remain dry, although a few showers are moving into leeward sections of Oahu. Main forecast focus revolves around the potential for some heavy rain and thunderstorms associated with an incoming cold front this week.
The front northwest of the islands will edge closer to the state today and Monday. This will disrupt the trades and shift winds southeasterly over Kauai and Oahu, with the sheltering effects from the upstream terrain allowing for sea and land breezes to develop in many areas. Meanwhile, easterly trades will persist in the unsheltered sections of Maui County and the Big Island. As a result, showers will continue to favor windward and southeast facing slopes and coasts at night and during the morning, and interior and leeward areas each afternoon.
The front will approach Monday night and Tuesday, allowing southerly flow to gradually develop and increase from west to east across the islands. Fairly dry conditions are expected overall, although a few showers are expected to develop in the increasing southerly flow and move into the islands from the south and southeast. A few interior and mauka showers will be possible Tuesday afternoon as well. Kauai will likely have the highest chance for seeing some heavier showers and perhaps a thunderstorm late Tuesday afternoon as the front and associated deeper moisture edges closer.
Model solutions are in good agreement showing the front moving through Kauai Tuesday night, then steadily progressing down the island chain Wednesday and Wednesday night. Numerous to widespread showers and scattered thunderstorms can be expected as the front sweeps southeastward through the state. Some locally heavy rainfall will be possible as well, with the potential for some flooding not out of the question. In addition, breezy southerly winds are expected to develop along and ahead of the front. Gusty downslope winds of 30 to 40 mph will be possible to the north and east of the terrain from Kauai to Maui.
The best forcing will shift east of the islands by Thursday, leaving a weakening front in the vicinity of the Big Island which appears to linger here through Thursday night. Rain chances will remain highest near the front over the eastern end of the state, while drier conditions overspread the western islands. The front appears to weaken into a trough on Friday with the lingering moisture then shifting westward as the trades attempt to briefly return. This could bring some more showery weather back to windward areas statewide. Winds appear to shift back east- southeasterly by Saturday as the next front approaches from the northwest, but confidence in this portion of the forecast is quite low given large differences in the latest model guidance.

Aviation

Moderate trade winds will persist through the remainder of the weekend, with trades veering southeasterly through today. This will maintain a trade wind weather pattern through the TAF period, focusing a majority of showers and lower clouds across windward areas and along southeast terrain. Local sea breeze development is possible this afternoon across some sheltered leeward areas.
Mainly VFR conditions are expected through this evening, however periods of MVFR conditions can be expected within heavier showers.
No AIRMETs are currently in effect.

Marine

Winds will begin to veer to southeasterlies across the western waters today through Monday while trades hold over the eastern end of the state. Moderate to locally strong southerlies will develop Tuesday and Wednesday as a front moves eastward across the island chain. A Small Craft Advisory (SCA) for winds will likely be needed for the western waters as early as Monday night as southerlies strengthen ahead of the front. There is also a chance for thunderstorms over the nearshore waters waters adjacent Kauai and Oahu Tuesday night through Wednesday. Light southeast to east southeast winds will fill in Thursday and Friday.
Tiny, medium period northwest (320-330) swell will be quickly followed by a similar north (360-010) swell building through Tuesday and peaking Tuesday night. Moderate, shorter period northwest (300-310) swell emanating from a developing low northwest of the islands will also build Tuesday, eventually peaking Wednesday night into Thursday. Models show another medium sized and borderline long period northwest (310-320) swell affecting the islands, resulting in moderate surf next weekend. Small surf over south-facing shores will gradually decline today. A tiny, long period south (190) swell is slated to arrive Friday, bringing elevated surf to south-facing shores next weekend. Surf along east facing shores will change little through the weekend, then gradually decline through the upcoming work week.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov