Weather Forecast

Hawaii County Weather Forecast for September 29, 2021

September 29, 2021, 7:15 AM HST
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Photo Credit: James Grenz

Hilo

Today: Partly sunny with scattered showers. Highs 79 to 85 near the shore to 65 to 71 at 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 64 to 72 near the shore to 54 to 59 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 70 percent.

Thursday: Showers in the morning, then numerous showers in the afternoon. Highs 78 to 84 near the shore to 64 to 71 at 4000 feet. Northeast winds up to 10 mph. Chance of rain near 100 percent.

Kona

Today: Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 83 to 88 near the shore to around 68 near 5000 feet. West winds up to 10 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with isolated showers in the evening, then partly cloudy after midnight. Lows 70 to 75 near the shore to 51 to 57 near 5000 feet. Light winds. Chance of rain 20 percent.

ARTICLE CONTINUES BELOW AD

Thursday: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 84 to 89 near the shore to around 69 near 5000 feet. Light winds. Chance of rain 50 percent.

Waimea

ARTICLE CONTINUES BELOW AD

Today: Partly sunny with scattered showers. Highs 65 to 84. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 64 to 70 near the shore to 56 to 63 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Thursday: Mostly cloudy with scattered showers. Highs 65 to 85. East winds 10 to 15 mph. Chance of rain 50 percent.

Kohala

ARTICLE CONTINUES BELOW AD

Today: Partly sunny with scattered showers. Highs 65 to 84. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 64 to 70 near the shore to 56 to 63 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Thursday: Mostly cloudy with scattered showers. Highs 65 to 85. East winds 10 to 15 mph. Chance of rain 50 percent.

South Big Island

Today: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs around 85 near the shore to around 67 near 5000 feet. East winds up to 15 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening. Lows around 73 near the shore to around 53 near 5000 feet. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Thursday: Mostly sunny with scattered showers in the morning, then mostly cloudy with numerous showers in the afternoon. Highs around 85 near the shore to around 67 near 5000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

Puna

Today: Partly sunny with scattered showers. Highs 79 to 85 near the shore to 65 to 71 at 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 64 to 72 near the shore to 54 to 59 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 70 percent.

Thursday: Showers in the morning, then numerous showers in the afternoon. Highs 78 to 84 near the shore to 64 to 71 at 4000 feet. Northeast winds up to 10 mph. Chance of rain near 100 percent.

Waikoloa

Today: Mostly sunny in the morning then becoming partly sunny. Highs 83 to 89 near the shore to 67 to 73 above 4000 feet. North winds up to 10 mph.

Tonight: Partly cloudy. Isolated showers in the evening. Lows around 73 near the shore to 51 to 56 above 4000 feet. Light winds. Chance of rain 20 percent.

Thursday: Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 83 to 90 near the shore to 68 to 74 above 4000 feet. Light winds becoming north up to 10 mph in the afternoon. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A high pressure ridge far north of the region will keep moderate to locally breezy trade winds in the forecast for the next seven days. A slight increase to more breezy wind speeds are expected late Thursday through Friday as a disturbance passes westward, just south of the island chain, possibly enhancing showers over the Big Island. A few upper level lows will drift through the region this week, keeping passing showers in the forecast each day mainly affecting windward and mountain areas during the overnight to early morning hours.

Discussion

The large scale satellite imagery this morning continues to show a narrow upper level trough (TUTT) over the islands chain with several weak upper lows embedded within this upper trough feature. This TUTT pattern near the islands is normal for this time of year. The Infra-red satellite loop shows a band of low clouds moving into the windward sections of the Big Island and Maui. These clouds look fairly stable in appearance with cloud heights up to 7000 feet based on cloud top temperatures of +10.0 to +12.0 degrees C. Expect continued passing showers this morning favoring windward and mountain areas of each island. Local island radar shows isolated to scattered showers this morning drifting from east to west on the trade winds.
A high pressure ridge far north of the region will keep trade winds in place through the next seven days. The strength of the trade winds will mostly range from moderate to locally breezy, however forecast guidance continues to show a weak disturbance located just south of the state from late Thursday through Friday. This passing low level trough will drift westward over the next two days and may be strong enough to tilt the trade wind speeds more towards the breezy range by Friday.
A few weak upper level lows will drift through the region along the narrow upper trough feature (TUTT) over the next seven days. Weather model cross sections suggest these disturbances will keep trade wind temperature inversion heights a bit elevated, ranging from the 6,000 to 8,000 feet. Producing enough room in the boundary layer for continued passing showers mainly over windward and mountain areas, favoring the overnight to early morning hours.

Aviation

Moderate, mostly dry, trade wind flow will continue through twenty-four hours and beyond. Scattered light showers will favor north and east facing slopes and coasts. Isolated spillover showers are to be expected across leeward areas, especially in the late night and morning hours.
Weak land breezes will promote clearing along the Big Island Leeward Coast through mid-morning. Light sea breezes will drive cumulus development over south and west facing slopes in the afternoon that will persist through the evening hours.
Localized MVFR CIG/VIS is to be expected in passing showers, otherwise VFR conditions will prevail all areas. No AIRMETs in effect or anticipated at this time.

Marine

A surface ridge far north of the state will maintain moderate trade winds into Thursday. A weak surface trough passing far south of the state from late Thursday into Friday will tighten the pressure gradient, and will likely cause the trade winds to become locally strong speeds by Friday. Therefore, a Small Craft Advisory (SCA) will likely be required staring Friday for the typically windier waters adjacent to the islands of Maui County and the Big Island. This SCA may be needed for these same waters into this weekend.
A tiny, short-period north swell will keep small background surf along north facing shores through Thursday. A small north- northwest swell is possible from Friday into Saturday. A small southwest swell originating from the Tasman Sea is possible from Thursday into Friday. Otherwise, only background swell energy is expected along south facing shores into early next week. Surf along east facing shores will remain small due to the lack of strong trade winds. A small, long-period west-northwest swell, which is being generated by northwest Pacific Typhoon Mindulle, may arrive early next next.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov

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