Photo Credit: James Grenz

Hilo

Today: Partly sunny with scattered showers. Highs around 84 near the shore to 68 to 73 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 65 to 71 near the shore to around 56 at 4000 feet. North winds up to 15 mph. Chance of rain 70 percent.

Wednesday: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 83 near the shore to 67 to 73 at 4000 feet. North winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 40 percent.

Kona

Today: Mostly sunny in the morning, then cloudy with scattered showers in the afternoon. Highs around 86 near the shore to around 70 near 5000 feet. West winds up to 10 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 70 to 75 near the shore to around 55 near 5000 feet. Light winds. Chance of rain 20 percent.

Wednesday: Mostly sunny in the morning, then cloudy with isolated showers in the afternoon. Highs around 85 near the shore to around 69 near 5000 feet. Southwest winds up to 10 mph. Chance of rain 20 percent.

Waimea

Today: Breezy. Partly sunny with scattered showers. Highs around 81 near the shore to 71 to 80 near 3000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 67 near the shore to 57 to 63 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Wednesday: Mostly sunny with scattered showers in the morning, then partly sunny with isolated showers in the afternoon. Highs around 81 near the shore to 71 to 80 near 3000 feet. East winds up to 15 mph. Chance of rain 40 percent.

Kohala

Today: Breezy. Partly sunny with scattered showers. Highs around 81 near the shore to 71 to 80 near 3000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 67 near the shore to 57 to 63 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Wednesday: Mostly sunny with scattered showers in the morning, then partly sunny with isolated showers in the afternoon. Highs around 81 near the shore to 71 to 80 near 3000 feet. East winds up to 15 mph. Chance of rain 40 percent.

South Big Island

Today: Breezy. Sunny in the morning, then mostly cloudy with isolated showers in the afternoon. Highs around 87 near the shore to around 71 near 5000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Tonight: Breezy. Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Lows around 72 near the shore to around 53 near 5000 feet. Northeast winds up to 20 mph decreasing to up to 10 mph after midnight. Chance of rain 20 percent.

Wednesday: Sunny in the morning, then mostly cloudy with isolated showers in the afternoon. Highs around 86 near the shore to around 70 near 5000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Puna

Today: Partly sunny with scattered showers. Highs around 84 near the shore to 68 to 73 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 65 to 71 near the shore to around 56 at 4000 feet. North winds up to 15 mph. Chance of rain 70 percent.

Wednesday: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 83 near the shore to 67 to 73 at 4000 feet. North winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 40 percent.

Waikoloa

Today: Breezy. Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 87 near the shore to 69 to 76 above 4000 feet. Northeast winds up to 25 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening. Lows around 73 near the shore to 52 to 58 above 4000 feet. Southeast winds up to 20 mph. Chance of rain 20 percent.

Wednesday: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 87 near the shore to 69 to 75 above 4000 feet. North winds up to 15 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