Weather Forecast

Hawaii County Weather Forecast for September 05, 2021

September 5, 2021, 7:15 AM HST
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Photo Credit: James Grenz

Hilo

Today: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs around 85 near the shore to 70 to 75 at 4000 feet. East winds up to 10 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with showers likely. Lows around 67 near the shore to around 53 at 4000 feet. Southeast winds up to 10 mph shifting to the southwest after midnight. Chance of rain 70 percent.

Labor Day: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs around 85 near the shore to 70 to 75 at 4000 feet. East winds up to 10 mph. Chance of rain 70 percent.

Kona

Today: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 83 to 88 near the shore to around 70 near 5000 feet. Southwest winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 68 to 74 near the shore to around 54 near 5000 feet. Light winds. Chance of rain 40 percent.

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Labor Day: Mostly sunny in the morning, then partly sunny 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 50 percent.

Waimea

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Today: Partly sunny with scattered showers. Highs around 83 near the shore to 70 to 80 near 3000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 67 near the shore to 55 to 61 near 3000 feet. Southeast winds up to 10 mph. Chance of rain 50 percent.

Labor Day: Partly sunny with scattered showers. Highs around 83 near the shore to 70 to 80 near 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Kohala

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Today: Partly sunny with scattered showers. Highs around 83 near the shore to 70 to 80 near 3000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 67 near the shore to 55 to 61 near 3000 feet. Southeast winds up to 10 mph. Chance of rain 50 percent.

Labor Day: Partly sunny with scattered showers. Highs around 83 near the shore to 70 to 80 near 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

South Big Island

Today: Mostly sunny in the morning, then partly sunny with scattered 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 40 percent.

Tonight: Partly cloudy. Isolated showers in the evening. Lows around 69 near the shore to around 52 near 5000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Labor Day: Breezy. Mostly sunny in the morning, then partly sunny with scattered 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 40 percent.

Puna

Today: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs around 85 near the shore to 70 to 75 at 4000 feet. East winds up to 10 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with showers likely. Lows around 67 near the shore to around 53 at 4000 feet. Southeast winds up to 10 mph shifting to the southwest after midnight. Chance of rain 70 percent.

Labor Day: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs around 85 near the shore to 70 to 75 at 4000 feet. East winds up to 10 mph. Chance of rain 70 percent.

Waikoloa

Today: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs around 87 near the shore to 71 to 77 above 4000 feet. Northeast winds up to 10 mph shifting to the northwest in the afternoon. Chance of rain 30 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy after midnight. Lows 69 to 74 near the shore to 50 to 57 above 4000 feet. Light winds. Chance of rain 40 percent.

Labor Day: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs around 87 near the shore to 71 to 77 above 4000 feet. Northwest winds up to 10 mph. Chance of rain 30 percent.

Detailed Forecast

Synopsis

Moderate trade winds will hold in place today, with showers favoring windward and mauka areas, although a disturbance aloft will allow a few more showers to reach leeward areas as well. The trades will weaken into the light to moderate range Labor Day through Tuesday. Showers will favor windward slopes and coasts during to overnight and early morning hours, with a few showers developing over leeward and interior areas each afternoon. Moderate trades and more typical windward and mauka showers will return Tuesday night and continue into next weekend.

Discussion

Currently at the surface, a west to east oriented ridge of high pressure centered around 750 miles north of Honolulu, is driving moderate trade winds across the island chain early this morning. Infrared satellite imagery shows mostly cloudy conditions in many windward areas, with partly cloudy skies prevailing in most leeward locales. Radar imagery shows scattered to numerous showers moving into windward slopes and coasts, with some of these showers spilling over into leeward communities. Main short term concerns revolve around trade wind trends and rain chances during the next few days.
A ridge of high pressure north of the islands will keep moderate trade winds in place today, with the trades then trending down into the light to moderate range Labor Day and Tuesday as the ridge weakens. A new high building north of the islands should increase trades slightly Wednesday and Thursday, before a weak trough approaching from the east eases the trades a notch once again Friday into next weekend.
As for the remaining weather details, fairly typical trade wind weather will prevail through tonight, with showers favoring windward and mauka areas. With an upper level low remaining in place just to the northeast of the state, elevated inversion heights will allow a few more of these showers to make it into leeward areas as well. A slightly lighter wind pattern Labor Day through Tuesday, will have showers favoring windward and mauka areas during the overnight and early morning hours, with a few showers then expected over interior and leeward areas during the afternoon into the early evening hours. A more typical trade wind pattern is then expected Tuesday night through next weekend, with showers again favoring windward and mauka areas, particularly at night and during the early morning hours, with a stray shower reaching leeward communities from time to time.

Aviation

Trade wind speeds are gradually coming down as a surface ridge north of the islands near 32N continues to slowly weaken. The 12z soundings and radar VAD wind profiles still showing 20-25 kt, so will leave AIRMET TANGO up at least until it’s regular update at 1545z. Should be able to drop it at that time but will make a final assessment then.
A weak upper level low just NE of the islands will continue to enhance incoming tradewind showers over the next couple of days. This will lead to episodes of MVFR and probable MTN OBSC at times over windward and mauka sections (AIRMET SIERRA is in effect now for portions of windward Big Island). Some showers will spread leeward at times, with brief MVFR possible there.

Marine

A high pressure ridge north of the Hawaiian Islands will weaken through Friday as two frontal systems pass from west to east across the North Pacific basin. Trade wind speeds will decrease over the area into Friday as the ridge north of the islands remains in a weakened state. The Small Craft Advisory (SCA) was cancelled this morning as wind speeds have dropped below 25 knots. Conditions will likely remain below SCA levels for all coastal waters through Friday.
A few medium to long period south swells will keep surf heights along southern exposures near seasonal normal levels into tonight, with slightly smaller surf heights forecast from Monday through Wednesday.
Surf heights along northeast and east facing shores will trend lower into early next week as the trade wind speeds decrease, lowering wave heights across the region. No significant swells are expected from the north or west direction through Saturday.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov

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