Weather Forecast

Hawaii County Weather Forecast for October 01, 2021

October 1, 2021, 7:15 AM HST
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Photo Credit: James Grenz

Hilo

Today: Mostly cloudy. Scattered showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs 80 to 86 near the shore to 68 to 73 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Cloudy. Showers likely in the evening, then occasional showers after midnight. Lows around 69 near the shore to around 55 at 4000 feet. Northwest winds up to 15 mph. Chance of rain 90 percent.

Saturday: Mostly cloudy. Showers likely in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs 80 to 86 near the shore to 68 to 73 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

Kona

Today: Mostly sunny in the morning, then mostly cloudy with scattered showers and slight chance of thunderstorms in the afternoon. Highs around 86 near the shore to around 73 near 5000 feet. West 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 69 to 76 near the shore to around 55 near 5000 feet. Light winds. Chance of rain 50 percent.

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Saturday: Mostly sunny in the morning, then mostly cloudy with scattered showers and slight chance of thunderstorms in the afternoon. Highs around 86 near the shore to around 73 near 5000 feet. Southwest winds up to 10 mph. Chance of rain 50 percent.

Waimea

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Today: Partly sunny. Breezy. Scattered showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs around 82 near the shore to 73 to 80 near 3000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then showers likely after midnight. Lows around 68 near the shore to 55 to 62 near 3000 feet. East winds up to 20 mph. Chance of rain 70 percent.

Saturday: Mostly cloudy. Breezy. Showers likely in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs around 82 near the shore to 73 to 80 near 3000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Kohala

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Today: Partly sunny. Breezy. Scattered showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs around 82 near the shore to 73 to 80 near 3000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then showers likely after midnight. Lows around 68 near the shore to 55 to 62 near 3000 feet. East winds up to 20 mph. Chance of rain 70 percent.

Saturday: Mostly cloudy. Breezy. Showers likely in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs around 82 near the shore to 73 to 80 near 3000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

South Big Island

Today: Breezy. Mostly sunny in the morning, then mostly cloudy with scattered showers and slight chance of thunderstorms in the afternoon. Highs around 85 near the shore to around 74 near 5000 feet. East winds up to 25 mph. Chance of rain 40 percent.

Tonight: Breezy. Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows around 69 near the shore to around 54 near 5000 feet. Northeast winds up to 20 mph increasing to 10 to 20 mph after midnight. Chance of rain 40 percent.

Saturday: Breezy. Mostly sunny in the morning, then partly sunny with scattered showers and slight chance of thunderstorms in the afternoon. Highs around 85 near the shore to around 74 near 5000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Puna

Today: Mostly cloudy. Scattered showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs 80 to 86 near the shore to 68 to 73 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Cloudy. Showers likely in the evening, then occasional showers after midnight. Lows around 69 near the shore to around 55 at 4000 feet. Northwest winds up to 15 mph. Chance of rain 90 percent.

Saturday: Mostly cloudy. Showers likely in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs 80 to 86 near the shore to 68 to 73 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

Waikoloa

Today: Breezy. Mostly sunny in the morning, then partly sunny with scattered showers and slight chance of thunderstorms in the afternoon. Highs around 85 near the shore to 69 to 75 above 4000 feet. North winds up to 20 mph. Chance of rain 40 percent.

Tonight: Breezy. Mostly cloudy with scattered showers in the evening, then partly cloudy after midnight. Lows 70 to 76 near the shore to 51 to 58 above 4000 feet. Southeast winds up to 20 mph. Chance of rain 50 percent.

Saturday: Breezy. Mostly sunny in the morning, then mostly cloudy with scattered showers and slight chance of thunderstorms in the afternoon. Highs around 85 near the shore to 69 to 75 above 4000 feet. Northeast winds up to 20 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Moderate to locally breezy trade winds will continue into next week as high pressure persists to the north of the islands. The trade winds will deliver clouds and showers to windward areas, with a few showers spreading leeward on the smaller islands. A developing disturbance aloft will bring the potential for some heavier showers Friday night through Sunday, with a thunderstorm or two possible over the Big Island each afternoon. A wet trade wind pattern is then expected much of next week, with the trades becoming breezy and possibly windy during the second half of the week.

Discussion

Currently at the surface, a 1030 mb high centered around 1900 miles northeast of Honolulu is driving moderate trade winds across the island chain early this morning. Meanwhile, aloft a deep upper level trough is evident in water vapor imagery around 800 miles northeast of the state, with upper troughing extending southwestward and just to the north of Kauai. Infrared satellite imagery shows mostly cloudy conditions over windward sections of the smaller islands, with mostly clear to partly cloudy conditions present elsewhere. Radar imagery shows scattered showers affecting windward sections of the smaller islands, with a few of these showers spilling into leeward communities from time to time. Very little shower activity remains over the Big Island early this morning. Main short term concerns revolve around the potential for thunderstorms and some heavier showers during the next few days.
High pressure to the north and northeast of the state, and an active Inter-Tropical Convergence Zone (ITCZ) to the south, will keep a general moderate to locally breezy trade wind flow in place through Tuesday, with only minor fluctuations in strength. The trades appear to ramp up to breezy and possibly even windy levels during the middle to latter part of next week as a new strong high builds north of the island chain.
As for the remaining weather details, a weakness aloft will remain over the islands throughout the next 7 days, keeping the island atmosphere more unstable than normal. The remnants of a slug of moisture will shift westward this morning, with showers mainly affecting windward sections of Kauai and Oahu this morning, with much drier conditions building in over the eastern islands. We should see a fairly dry trade wind pattern set up statewide this afternoon, with showers mainly confined to windward areas. The exception will be over the Big Island where the airmass will likely remain unstable enough to allow for a thunderstorm or two to develop.
The airmass will become more unstable tonight through Sunday as an upper level low closes off a few hundred miles north of Kauai. This should bring an increase in trade wind shower coverage and intensity, particularly to windward areas. The elevated inversion heights will also allow for a few more showers than normal to reach leeward areas. Additionally, a thunderstorm or two may develop each afternoon over the Big Island. Some locally heavy downpours will be possible during this time, mainly over windward areas, but the trades should keep the showers moving along enough to prevent flooding concerns.
The airmass should begin to stabilize Sunday night, but will remain unstable enough to keep a wet trade wind pattern in place, which is expected to continue through much of next week. Windward areas will continue to be the primary recipient of these trade wind showers, although leeward ares will see more shower activity than usual due to inversion heights remaining elevated.

Aviation

A band of clouds moving slowly through the western islands will bring periods of showers with MVFR CIG and VIS to the windward and mountain sections through the early morning hours. Drier trends are forecast to fill in from east to west today with improving conditions. Trade winds in the moderate to locally breezy range will continue for the next several days.
AIRMET Sierra for Mountain Obscuration remains in effect over the windward and mountain sections from the Big Island to Kauai. These low cloud ceilings will likely decrease in coverage later this morning.
AIRMET Tango is in effect for Moderate Turbulence between FL250-500 near Kauai. This turbulence AIRMET is caused by strong upper level winds.

Marine

High pressure north to northeast of the state will keep the pressure gradient tight enough across the region to support moderate to locally strong trade winds through Friday. The Small Craft Advisory that is in effect for the typically windier waters surrounding Maui County and the Big Island has been extended into early Saturday morning. An upper level low developing north of the islands may destabilize the regional air mass enough to warrant a slight chance for weekend thunderstorms across our far north offshore waters.
A small, medium period north swell will hold through today and then be reinforced by a slightly higher north swell tonight into Saturday. These primarily north swells will maintain low end north, along with a west wrap, surf the next couple of days. A small, medium period west northwest swell generated by Typhoon Mindulle will likely reach the western islands Tuesday. The ongoing overlapping small, medium to long period south southwest swells that have kept south surf from going completely flat will begin to fade today. Choppy wind wave surf along most eastern exposures will remain small. A stronger trade fetch upstream of the islands through Saturday will provide a slight boost to east facing shore surf this weekend.

HFO Watches/Warnings/Advisories

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

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Data Courtesy of NOAA.gov

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