Photo Credit: Pamela Goguen Lynch

West Side

Today: Breezy. Mostly sunny with isolated showers. Highs 80 to 89. Northeast winds 15 to 25 mph. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows 68 to 75. Northeast winds 10 to 20 mph decreasing to up to 20 mph after midnight. Chance of rain 20 percent.

Wednesday: Mostly sunny with isolated showers. Highs 81 to 90. East winds up to 15 mph. Chance of rain 20 percent.

South Side

Today: Mostly sunny. Breezy. Highs around 89. Northeast winds 10 to 20 mph.

Tonight: Partly cloudy. Breezy. Lows around 70. North winds up to 20 mph.

Wednesday: Mostly sunny. Breezy. Highs around 90. North winds up to 20 mph increasing to 10 to 20 mph in the afternoon.

North Shore

Today: Breezy. Partly sunny with scattered showers. Highs 80 to 85 near the shore to around 67 near 5000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 67 to 72 near the shore to around 54 near 5000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

Wednesday: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 81 to 86 near the shore to around 67 near 5000 feet. East winds up to 15 mph. Chance of rain 40 percent.

Central Maui

Today: Breezy. Mostly sunny with isolated showers. Highs 85 to 90. Northeast winds 10 to 25 mph. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows 68 to 73. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny. Breezy. Isolated showers in the morning. Highs 86 to 91. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Upcountry

Today: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 60 at the visitor center to around 57 at the summit. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly clear with scattered showers. Lows around 48 at the visitor center to around 44 at the summit. East winds up to 20 mph. Chance of rain 50 percent.

Wednesday: Sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 60 at the visitor center to around 56 at the summit. East winds up to 15 mph. Chance of rain 50 percent.

East Maui

Today: Breezy. Partly sunny with scattered showers. Highs 80 to 85 near the shore to around 67 near 5000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 67 to 72 near the shore to around 54 near 5000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

Wednesday: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 81 to 86 near the shore to around 67 near 5000 feet. East winds up to 15 mph. Chance of rain 40 percent.

Lanai City

Today: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs 73 to 83. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Breezy. Lows around 67. Northeast winds 10 to 20 mph.

Wednesday: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs 73 to 83. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Kaunakakai

Today: Breezy. Mostly sunny with isolated showers. Highs 73 to 88. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows 62 to 75. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny. Breezy. Isolated showers in the morning. Highs 74 to 90. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A high pressure system far north of the Hawaiian Islands will keep moderate to locally breezy trade winds in the forecast through early Wednesday, with clouds and passing showers favoring windward and mountain areas of each island. A passing low level trough, associated with the remnants of Estelle, will pass through the island chain from late Wednesday through Friday. Humidity levels will increase as trade wind speeds diminish into the light to moderate range with land and sea breezes strengthening. Shower potential will decrease on Wednesday afternoon, then increase on Thursday and Friday. Expect moderate to breezy trade winds with dry and stable weather returning this weekend, as the trough passes west of the state and the surface ridge builds back into the Hawaii region.

Discussion

The satellite picture this morning shows bands of clouds riding into the islands on the trade winds, producing passing showers mainly over windward and mountain areas. The leading edge of a large easterly wave (trough), associated with remnants of former Tropical Cyclone Estelle, is roughly 700 miles east of Hilo drifting westward towards the islands on the trade winds. This trough will pass through the Hawaii region from late Wednesday through Friday, decreasing the trade wind speeds as it moves through the region.
A high pressure system far north of the islands will keep moderate to locally breezy trade winds in the forecast into early Wednesday. Upper level stability (subsidence) will keep the trade wind inversion heights at the 6,000 to 9,000 foot range through tonight allowing scattered to numerous showers to develop mainly over windward and mountain areas of each island. Wednesday will be the transition day, as a short wave ridge moves over the islands just ahead of the approaching easterly wave. This ridge will enhance upper level subsidence, briefly dropping the trade wind inversion heights into 4,000 to 6,000 foot range, diminishing clouds and showers from late Wednesday morning to afternoon.
Expect decreasing trade winds into the light to moderate range from Wednesday afternoon through Friday with strengthening land and sea breezes as this trough passes through the islands. Land and sea breezes will add small scale cloud and shower features to complicate our island weather for the second half of the week. Shower activity will trend higher on Thursday as the low level trough pushes inversion heights higher, much of the shower activity will occur along sea breeze convergence bands and the windward Big Island. Deeper tropical moisture will move up the eastern side of this trough as it begins to move away from the islands on Friday and an upper level low dropping into the region from the north will combine forces to enhance shower activity. These showers will favor the late morning to afternoon time periods with sea breeze convergence and island heating triggers.
On Saturday, the low level trough passes west of the state and moderate to breezy trade winds return as high pressure builds back over the region. Strong subsidence aloft will increase stability across the state, limiting cloud development and shower potential from Saturday afternoon through Sunday. Moderate to breezy trade winds continue on Monday with passing showers mainly over windward and mountain areas.
Global model guidance between the American (GFS) and the European (ECMWF) shows good agreement on this large scale weather pattern through the weekend.

Aviation

Moderate to locally breezy trades will persist today and tonight due to a surface ridge located far north of the islands. An area of scattered to broken low clouds with embedded trade showers continues to push from east to west across the area early this morning. As a result, the low clouds and showers will likely produce periods of MVFR ceilings / visibilities over most windward facing coasts and slopes through mid to late morning. AIRMET Sierra for mountain obscuration remains in effect for the windward sides of most islands. This AIRMET may need to be extended through this morning if the areal coverage of these clouds and showers does not decrease during the next couple of hours. By this afternoon, clouds and showers are forecast to develop in daytime heating over most upslope sections of the leeward Big Island. Otherwise, expect VFR conditions to prevail over most leeward sections of the smaller islands during the next 24 hours.
AIRMET Tango remains in effect for low-level mechanical turbulence downwind of the higher terrain on the Big Island early this morning. We will monitor observations to determine if this AIRMET may need to be extended. In addition, it may possibly be expanded to include other parts of the state based on recent trends in VAD wind profile observations from at least one WSR-88D radar site.

Marine

Fresh to strong easterly trade winds will continue into Wednesday, then ease into the light to moderate category Wednesday night through Friday as a weak trough associated with former Tropical Cyclone Estelle passes north of the area. As a result, the Small Craft Advisory has been extended through Wednesday for the typically windier waters. East-northeast trade winds will surge back Friday night through the weekend as the aforementioned trough moves out and the subtropical ridge builds to the north.
Surf along south facing shores will remain up today, then ease through midweek as a south swell moves out. A larger south swell is expected to fill in through the day Thursday, then peak late Friday through Saturday just below or near the advisory threshold (10 ft on the face). Latest observations at the PacIOOS American Samoa buoy supports this, with the swell moving through overnight at levels slightly above the predicted.
Surf along east facing shores will remain small and choppy through Wednesday, then drop off through the second half of the week as the trades ease.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Wednesday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov