West Kaua’i

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows around 70 near the shore to around 60 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tuesday: Mostly sunny. Scattered showers in the morning. Highs 81 to 86 near the shore to around 73 above 3000 feet. Northwest winds up to 10 mph. Chance of rain 40 percent.

Tuesday Night: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 68 near the shore to around 59 above 3000 feet. East winds around 10 mph. Chance of rain 50 percent.

South Kaua’i

Tonight: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows around 70. Northeast winds 10 to 15 mph. Chance of rain 60 percent.

Tuesday: Mostly sunny. Scattered showers in the morning. Highs 76 to 85. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Tuesday Night: Mostly cloudy with scattered showers. Lows around 70. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Tonight: Mostly cloudy with numerous showers. Lows 62 to 68 in the valleys to around 58 above 4000 feet. East winds up to 10 mph. Chance of rain 70 percent.

Tuesday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 73 to 79 in the valleys to around 65 above 4000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Tuesday Night: Mostly cloudy. Numerous showers in the evening, then occasional showers after midnight. Lows 61 to 67 in the valleys to around 57 above 4000 feet. East winds around 10 mph. Chance of rain 90 percent.

North Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 63 to 72. East winds up to 15 mph. Chance of rain 50 percent.

Tuesday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 75 to 83. East winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 40 percent.

Tuesday Night: Mostly cloudy with scattered showers. Lows 63 to 71. East winds around 10 mph. Chance of rain 50 percent.

East Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 64 to 73. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tuesday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 73 to 83. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tuesday Night: Mostly cloudy with scattered showers. Lows 63 to 73. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Moderate easterly trade winds are expected to continue throughout the week. An upper level trough approaching the islands will deepen into an upper low near Kauai by Tuesday. This upper disturbance will pass by the islands, then linger northeast of the state throughout the week. This will result in increased clouds and showers across the region through the week. Shower activity will favor windward mountain areas in the overnight to early morning hours, with brief periods of showers drifting into leeward areas. Locations sheltered from the moderate easterly trade winds could also see increased clouds and a few showers during the afternoons.

Discussion

This afternoon, GOES water vapor imagery shows a deepening trough aloft northwest of the main Hawaiian Islands. Meanwhile, high pressure at the surface centered far northeast of the main state is supporting moderate easterly trade winds across the region. Latest radar and satellite imagery shows scattered showers along primarily windward and mauka areas, though some sheltered leeward and interior locations have experienced increases in clouds and showers this afternoon as well due to localized sea breezes.
The upper level trough northwest of the islands will approach the state over the next 24 hours. As it approaches, this trough is forecast to develop into a weak closed low aloft near Kauai by Tuesday. Further destabilization will occur as temperature inversion heights rise and clouds heights deepen. Therefore, expect enhanced trade wind shower activity throughout this period.
The developing low aloft will drift eastward on Tuesday, but then is expected to linger northeast of the state for several days thereafter. With this upper disturbance lingering nearby, a continued wet trade wind weather pattern will continue for much of the rest of the week. These showers will typically favor windward and mountain slopes, especially during the overnight through early morning hours. Trades will maintain at moderate speeds throughout the week, so sheltered leeward areas could also see increases in afternoon clouds and a few showers as localized sea breezes develop each day.

Aviation

Moderate to locally breezy trade winds will continue during the next couple of days. A few briefly heavy showers can be expected through over the next 24 hours or so as an upper level trough moves across the region. No AIRMETs are currently in effect this afternoon, though guidance suggests mountain obscuration could develop this evening, mainly on windward Kauai. Expect more extensive interior clouds and showers on the Big Island Tuesday afternoon as the upper trough passes overhead.

Marine

Moderate to fresh east-northeasterly trades will continue through Tuesday, then strengthen Tuesday night or Wednesday as a weak trough currently traversing the main Hawaiian islands shifts to the west and a ridge builds north of the state. This will likely correspond to Small Craft Advisory winds across the typically windier waters surrounding Maui County and the Big Island beginning by Wednesday.
Surf along exposed north- and west-facing shores eases tonight as a northwest swell fades. However, a small bump in surf is expected through the day on Tuesday with the arrival of a small northwest swell. An upward trend is expected during the second half of the week as another northwest swell arrives. Looking further ahead, a storm-force low east of Japan will send a moderate, longer-period northwest swell toward the islands for Friday and Saturday, with surf heights potentially approaching advisory levels along exposed north and west facing shores.
Surf along south-facing shores will remain small through much of the week, with mainly background south to southwest swell expected. Another south-southwest pulse may arrive by this weekend from recent activity within our swell window east of New Zealand, providing a small increase in surf.
Surf along east-facing shores will remain relatively small and choppy through midweek, with a slight rise possible later in the week as trades strengthen.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov