Hilo

Today: Partly sunny with scattered showers. Highs around 85 near the shore to 70 to 75 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows around 70 near the shore to around 56 at 4000 feet. North winds up to 15 mph shifting to the northwest after midnight. Chance of rain 50 percent.

Wednesday: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs around 86 near the shore to 70 to 75 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Kona

Today: Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 83 to 88 near the shore to around 70 near 5000 feet. South winds up to 10 mph shifting to the west in the afternoon. Chance of rain 40 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 71 to 76 near the shore to around 57 near 5000 feet. Light winds. Chance of rain 20 percent.

Wednesday: Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 83 to 88 near the shore to around 70 near 5000 feet. West winds up to 10 mph. Chance of rain 40 percent.

Waimea

Today: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs around 83 near the shore to 70 to 80 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Breezy. Scattered showers. Lows around 70 near the shore to 58 to 64 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Wednesday: Breezy. Mostly sunny with scattered showers. Highs around 84 near the shore to 70 to 81 near 3000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Kohala

Today: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs around 83 near the shore to 70 to 80 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Breezy. Scattered showers. Lows around 70 near the shore to 58 to 64 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Wednesday: Breezy. Mostly sunny with scattered showers. Highs around 84 near the shore to 70 to 81 near 3000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

South Big Island

Today: Breezy. Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 87 near the shore to around 74 near 5000 feet. East winds up to 25 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 55 near 5000 feet. East winds up to 25 mph shifting to the northeast 10 to 20 mph after midnight. Chance of rain 20 percent.

Wednesday: Breezy. Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 87 near the shore to around 74 near 5000 feet. East winds up to 25 mph. Chance of rain 20 percent.

Puna

Today: Partly sunny with scattered showers. Highs around 85 near the shore to 70 to 75 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows around 70 near the shore to around 56 at 4000 feet. North winds up to 15 mph shifting to the northwest after midnight. Chance of rain 50 percent.

Wednesday: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs around 86 near the shore to 70 to 75 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Waikoloa

Today: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 87 near the shore to 71 to 77 above 4000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Lows around 74 near the shore to 53 to 60 above 4000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs around 87 near the shore to 71 to 77 above 4000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Moderate trades will continue across the islands tonight, then strengthen to breezy levels Tuesday through Thursday as high pressure builds to the distant north and Tropical Storm Greg passes by to the south. The trades will ease into the light to moderate range Friday through the weekend. Relatively dry trade wind weather will prevail through the forecast period. Shower activity will remain confined primarily to windward slopes and coasts, with a few showers reaching leeward communities at times. A period of wet trade wind weather could move through late Sunday through early next week as the remnants of Hurricane Fernanda move through.

Discussion

Currently at the surface, a 1029 mb high is centered around 1650 miles north-northeast of Honolulu. Meanwhile, Tropical Storm Greg is located around 850 miles southeast of the Big Island. The gradient locally continues to drive moderate trade winds across the island chain early this morning. Infrared satellite imagery shows partly to mostly cloudy conditions in most windward and mauka areas, with clear to partly cloudy skies in most leeward locales. Radar imagery shows isolated to scattered showers moving into windward slopes and coasts, with a few showers spilling into leeward communities at times. Main forecast focus revolves around rain chances and trade wind trends during the next few days.
The trades are expected to strengthen and hold at breezy levels Tuesday through Thursday as the pressure gradient tightens in response to a strengthening high far north of the state and Tropical Storm Greg passing westward well to the south of the island chain. Despite the modest increase in trade wind speeds, we are not expecting anything nearly as strong as the winds that were experienced when Hurricane Dora passed well south of the islands last week. This time, the high pressure system will be displaced much farther north, inversion heights will not be as low, and Tropical Storm Greg will be a much weaker system. The trades are forecast to ease back into the moderate range Friday through the weekend as the pressure gradient relaxes once again.
Relatively dry trade wind weather will prevail through much of the next seven days. Shower activity will continue to favor windward slopes and coasts, especially during the overnight through early morning hours each day, with a few showers reaching leeward communities at times. The Kona slopes of the Big Island will also see an increase in clouds and a few showers each afternoon as well. Looking ahead, a round of increased moisture associated with the remnants of what is currently Hurricane Fernanda could increase trade wind showers late Sunday into early next week.

Aviation

Moderate to locally breezy trade winds will continue through the TAF period. Clouds and light showers will tend to favor windward and mauka areas, with a slight uptick in coverage and intensity through the early morning hours and again tonight. Expect mainly VFR conditions with brief MVFR cigs and vsby under passing SHRA.
No AIRMETs are expected through the next 24 hours.

Marine

A high pressure system far north of the state will produce moderate to locally strong trade winds across the region through Thursday. A Small Craft Advisory (SCA) remains in effect for the windier waters near Maui and the Big Island through Thursday.
Tropical Storm Greg will pass well south of Hawaiian Coastal Waters from late Wednesday through Thursday. Trade winds will slightly strengthen during this time and could bring increasing seas across the far southern waters.
Background swells from the south and southeast will keep small surf heights along south facing shores through the week. A series of small north-northwest to northwest swells are expected throughout the week. The latest buoy observations from Hanalei this morning is showing a north-northwest swell holding at 3 feet 10 seconds. Another small reinforcing northwest swell is possible around Wednesday afternoon to evening. Surf along east facing shores should remain below average through most of the week due to the lack of upstream trade winds. A small northeast swell is possible over the weekend.

HFO Watches/Warnings/Advisories

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

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Data Courtesy of NOAA.gov