Hilo

Today: Mostly sunny with isolated showers. Highs around 85 near the shore to 70 to 75 at 4000 feet. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 68 near the shore to around 54 at 4000 feet. North winds up to 10 mph shifting to the northwest after midnight. Chance of rain 50 percent.

Monday: Mostly sunny with scattered showers in the morning, then partly sunny with isolated showers in the afternoon. Highs around 85 near the shore to 70 to 75 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Kona

Today: Mostly sunny in the morning, then mostly cloudy with isolated 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 20 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 69 to 75 near the shore to around 55 near 5000 feet. Light winds. Chance of rain 20 percent.

Monday: Mostly sunny in the morning then becoming mostly cloudy. Isolated showers. Highs 83 to 88 near the shore to around 70 near 5000 feet. Light winds. Chance of rain 20 percent.

Waimea

Today: Mostly sunny with isolated showers. Highs around 83 near the shore to 70 to 80 near 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with scattered showers. Lows around 68 near the shore to 56 to 62 near 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Monday: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 83 near the shore to 70 to 80 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Kohala

Today: Mostly sunny with isolated showers. Highs around 83 near the shore to 70 to 80 near 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with scattered showers. Lows around 68 near the shore to 56 to 62 near 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Monday: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 83 near the shore to 70 to 80 near 3000 feet. East winds up to 20 mph. 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 20 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy in the evening then becoming mostly clear. Lows around 70 near the shore to around 53 near 5000 feet. Northeast winds up to 15 mph.

Monday: 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 15 mph. Chance of rain 20 percent.

Puna

Today: Mostly sunny with isolated showers. Highs around 85 near the shore to 70 to 75 at 4000 feet. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 68 near the shore to around 54 at 4000 feet. North winds up to 10 mph shifting to the northwest after midnight. Chance of rain 50 percent.

Monday: Mostly sunny with scattered showers in the morning, then partly sunny with isolated showers in the afternoon. Highs around 85 near the shore to 70 to 75 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Waikoloa

Today: Mostly sunny. Isolated showers in the afternoon. Highs around 87 near the shore to 71 to 77 above 4000 feet. North winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Lows 70 to 75 near the shore to 51 to 58 above 4000 feet. East winds up to 15 mph.

Monday: Mostly sunny. Isolated showers in the afternoon. Highs around 87 near the shore to 71 to 77 above 4000 feet. North winds up to 15 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Moderate trades will continue across the islands through Monday as high pressure remains anchored northwest of the state. Trades will become breezy Tuesday through Thursday as high pressure builds to the distant north and a potential tropical cyclone passes by well south of the island chain. The trades will ease back to moderate levels late next week. Rather dry trade wind weather will prevail through the forecast period, with minimal shower activity confined primarily to windward slopes and coasts.

Discussion

Currently at the surface, a 1023 mb high is centered around 1000 miles west-northwest of Kauai, while a weak trough is positioned around 450 miles north-northeast of Honolulu. The gradient locally is producing moderate trade winds across the island chain early this morning. Infrared satellite imagery shows mostly clear to partly cloudy conditions across the state. Radar imagery and rain gage observations indicate very dry conditions persist, with only a few sites reporting measurable rainfall in the past several hours. Main short term focus revolves around rain chances and trade wind trends.
Models show little change in the overall weather pattern through Monday, with a weak high remaining northwest of the state and a weak trough holding in place to the north. This should keep trades at moderate strength. Expect trades to strengthen to breezy levels Tuesday through Thursday as the pressure gradient increases between a strengthening high north of the state and a potential tropical cyclone (currently Invest 99E) passing westward well to the south of the island chain. This scenario continues to appear significantly different than what was experienced during Dora. The winds are expected to be not nearly as strong, as high pressure will be displaced much farther north, inversion heights not nearly as low, and the potential tropical system not nearly as strong. The trades are forecast to ease back to moderate levels Friday into next weekend as the pressure gradient relaxes once again.
Expect rather dry trade wind weather through much of the next seven days, with the minimal shower activity confined primarily to windward slopes and coasts during the late night and early morning hours. We could see a slight increase in shower coverage Monday night and Tuesday, particularly over windward portions of Maui and the Big Island as a band of moisture moves through.

Aviation

An upper level low far north to northeast of the islands will continue to weaken the high pressure ridge north of the region. Expect moderate trade winds to continue through Monday. Brief passing showers will develop mainly over windward and mountain areas. VFR conditions will prevail and no AIRMETs are expected.

Marine

Moderate to fresh easterly trades will persist into Monday, then trend up into the fresh to strong category late Monday through midweek as a potential tropical cyclone begins to pass south of the area and high pressure builds to the north.
Surf along south facing shores will remain up today due to a lingering south-southwest swell moving through. Morning observations at the offshore buoys support this with the peak energy holding around the 14 second band. A downward trend is expected through the first half of the week, with heights returning to background levels.
Surf along north facing shores could trend up above the summertime flat levels on Monday as a tiny north-northwest swell arrives from a distant packet of fresh to strong northwest breezes that developed near the Date Line/Aleutians over the past few days.
Surf along east facing shores will remains small through Monday, then trend up Tuesday through midweek as the trades pick up.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov