Photo Credit: Jeni Ji Cousins
West Side
Today: Mostly sunny. Isolated showers in the afternoon. Highs 80 to 85. East winds 10 to 15 mph. Chance of rain 20 percent.
Tonight: Partly cloudy with isolated showers. Lows 66 to 74. Northeast winds around 10 mph in the evening becoming light. Chance of rain 20 percent.
Sunday: Mostly sunny with scattered showers in the morning, then partly sunny with isolated showers in the afternoon. Highs around 81. East winds up to 10 mph. Chance of rain 40 percent.
South Side
Today: Mostly sunny. Highs around 88. Northeast winds 10 to 15 mph.
Tonight: Partly cloudy. Lows 67 to 75. Light winds.
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Sunday: Mostly sunny in the morning then becoming partly sunny. Highs around 86. Northeast winds around 10 mph.
North Shore
Today: Partly sunny with scattered showers. Highs 79 to 84 near the shore to around 65 near 5000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.
Tonight: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows around 70 near the shore to around 51 near 5000 feet. East winds around 10 mph in the evening becoming light. Chance of rain 70 percent.
Sunday: Partly sunny with scattered showers. Highs around 82 near the shore to around 65 near 5000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.
Central Maui
Today: Mostly sunny. Breezy. Highs 82 to 89. Northeast winds 10 to 20 mph.
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Tonight: Partly cloudy. Isolated showers in the evening. Lows 67 to 72. Northeast winds around 10 mph in the evening becoming light. Chance of rain 20 percent.
Sunday: Mostly sunny with isolated showers in the morning, then partly sunny in the afternoon. Highs 81 to 87. Northeast winds 10 to 15 mph. Chance of rain 20 percent.
Upcountry
Today: Mostly sunny with scattered showers in the morning, then partly sunny with isolated showers in the afternoon. Highs around 61 at the visitor center to around 67 at the summit. East winds up to 15 mph becoming around 10 mph in the afternoon. Chance of rain 50 percent.
Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows around 46 at the visitor center to around 43 at the summit. East winds up to 10 mph. Chance of rain 50 percent.
Sunday: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 61 at the visitor center to around 64 at the summit. East winds 10 to 15 mph. Chance of rain 40 percent.
East Maui
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Today: Partly sunny with scattered showers. Highs 79 to 84 near the shore to around 65 near 5000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.
Tonight: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows around 70 near the shore to around 51 near 5000 feet. East winds around 10 mph in the evening becoming light. Chance of rain 70 percent.
Sunday: Partly sunny with scattered showers. Highs around 82 near the shore to around 65 near 5000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.
Lanai City
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Today: Mostly sunny. Isolated showers in the afternoon. Highs 73 to 81. Northeast winds 10 to 15 mph. Chance of rain 20 percent.
Tonight: Partly cloudy with isolated showers. Lows around 65. East winds around 10 mph in the evening becoming light. Chance of rain 20 percent.
Sunday: Mostly sunny with scattered showers in the morning, then partly sunny with isolated showers in the afternoon. Highs 71 to 80. Light winds becoming east around 10 mph in the afternoon. Chance of rain 30 percent.
Kaunakakai
Today: Mostly sunny. Highs 72 to 88. Northeast winds 10 to 15 mph.
Tonight: Partly cloudy. Isolated showers after midnight. Lows 58 to 73. East winds around 10 mph in the evening becoming light. Chance of rain 20 percent.
Sunday: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs 71 to 87. East winds around 10 mph. Chance of rain 40 percent.
Synopsis
Moderate trade winds with stable conditions will continue today, with showers focused over windward and mauka areas. Trades will weaken tonight as a front and its associated upper level feature approach from the north. This will bring unsettled weather, particularly for Kauai, Sunday into Monday. Drier conditions are expected through much of the remainder of the new week as high pressure reestablishes itself north of the islands.
Discussion
While the grids have been updated to reflect the latest National Blend of Models (NBM) solution, the updates didn’t change much in the forecast.
High pressure to the northeast will continue to bring trade winds to the region today, along with showers limited to the typical windward and mauka locations. A front to the north of the islands will be sinking southward. This will lighten winds over the islands by tomorrow, with winds shifting to the southeast near the Big Island and Maui, and more to the northeast near Kauai and Oahu tonight and tomorrow. The surface front is expected to reach Kauai late Sunday evening before moving away from the islands. This will bring an increase in moisture, resulting in an uptick in shower activity, particularly over the western islands.
The upper level trough associated with the surface front will help to provide some instability as the upper level system sinks closer to the islands behind the front. The global models remain in good agreement with a mid to upper level low developing along the upper level trough later today. The last couple runs of the GFS showed little change in the placement of the upper low. The ECMWF solution is a little weaker than the GFS, but not enough to impact confidence levels. The southerly flow associated with the upper feature will pull additional moisture northward over the islands. The heaviest showers are expected to be over or near Kauai late Sunday into Monday.
That all being said, there remains a great deal of uncertainty with the placement of the upper low and the associated moisture. Little change in the NBM Probabilistic Quantitative Precipitation Forecast (PQPF) 90th percentile since yesterday afternoon. With 500 mb temperatures expected to be near -10C to -11C, the chance for thunderstorms remains in the forecast for Sunday, for Kauai and Niihau and surrounding coastal waters.
High pressure is expected to rebuild into the region from Tuesday through Thursday, allowing trades to become reestablished across the region. With drier air working into the region and stable conditions returning, showers will once again be confined to mainly windward and mauka areas.
Aviation
Moderate trade winds will continue today, but weaken tonight as a frontal system approaches the state from the north. Trade wind showers today will be focused over the windward and mauka areas of the islands. These showers will bring periods of MVFR conditions to those areas, otherwise VFR conditions will prevail into tomorrow.
No AIRMETs are in effect, and none are expected today.
As the above mentioned front approaches Kauai Sunday afternoon/evening, an AIRMET for mountain obscuration and/or IFR may be needed.
Marine
High pressure to the northeast will maintain moderate to locally fresh trade winds through this morning before decreasing through the day as a front northwest of the islands moves southeast towards the region and displaces the ridge. Isolated thunderstorms will be possible for the northwestern coastal waters by Sunday as the front approaches the western end of the state. The front is expected to stall and then get pushed to the west as high pressure builds back in by Monday, increasing trade winds to moderate to locally fresh speeds. Winds are expected to remain below SCA levels until Tuesday or Wednesday.
The approaching front is expected to enter the offshore waters later today, with strong breezes expected over the extreme northwest portion of the offshore waters tonight and Sunday. The front will also bring the possibility of thunderstorms to the offshore waters.
Surf along north facing shores will continue to increase through the morning in response to a medium to long period NNW swell (330) filling into the region with surf expected to reach High Surf Advisory (HSA) levels by the afternoon. Surf will hold at HSA levels through tonight, and a HSA is in place for that time frame for N and W facing shores. Another NNW swell (320-330) is expected to fill in on Sunday, followed by a medium period NNE swell Sunday evening, associated with an approaching front with near- gale winds, that will primarily impact the western end of the state. This mix of swells may maintain HSA level surf through Sunday before gradually fading early next week. A moderate to large swell is then possible around the middle of next week.
Surf along east facing shores will remain small to moderate through Sunday morning, and then may be impacted by the medium period NNE swell mentioned above. South shore surf will remain small through early next week before building slightly mid to late week as a long period SSW swell (190) fills in across the region.
Fire weather
Increased relative humidity values and decreasing trade wind speeds will keep fire weather conditions below critical thresholds into next week.
HFO Watches/Warnings/Advisories
High Surf Advisory from noon today to 6 AM HST Sunday for Niihau, Waianae Coast, Oahu North Shore, Maui Windward West, Kauai North, Molokai Windward, Molokai North, Molokai West, Maui Central Valley North, Windward Haleakala.
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Data Courtesy of NOAA.gov
