Weather Forecast

Hawaii County Weather Forecast for September 19, 2021

September 19, 2021, 7:15 AM HST
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Hilo

Today: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 84 near the shore to 69 to 74 at 4000 feet. North winds up to 15 mph shifting to the east in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with showers. Lows around 67 near the shore to around 53 at 4000 feet. East winds up to 10 mph. Chance of rain 90 percent.

Monday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 84 near the shore to 69 to 74 at 4000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Kona

Today: Sunny with isolated showers in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 82 to 87 near the shore to around 69 near 5000 feet. West winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then mostly clear after midnight. Lows 68 to 74 near the shore to around 54 near 5000 feet. Southeast winds up to 10 mph shifting to the north after midnight. Chance of rain 50 percent.

ARTICLE CONTINUES BELOW AD

Monday: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 82 to 87 near the shore to around 69 near 5000 feet. Light winds. Chance of rain 40 percent.

Waimea

ARTICLE CONTINUES BELOW AD

Today: Mostly sunny in the morning then becoming partly sunny. Breezy. Isolated showers. Highs around 82 near the shore to 69 to 79 near 3000 feet. East winds up to 25 mph increasing to 10 to 25 mph in the afternoon. Chance of rain 20 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows around 67 near the shore to 55 to 61 near 3000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Monday: Partly sunny with scattered showers. Highs around 82 near the shore to 69 to 79 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Kohala

ARTICLE CONTINUES BELOW AD

Today: Mostly sunny in the morning then becoming partly sunny. Breezy. Isolated showers. Highs around 82 near the shore to 69 to 79 near 3000 feet. East winds up to 25 mph increasing to 10 to 25 mph in the afternoon. Chance of rain 20 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows around 67 near the shore to 55 to 61 near 3000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Monday: Partly sunny with scattered showers. Highs around 82 near the shore to 69 to 79 near 3000 feet. East winds 10 to 15 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 86 near the shore to around 73 near 5000 feet. East winds 10 to 25 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Lows around 69 near the shore to around 52 near 5000 feet. East winds 10 to 20 mph.

Monday: Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 86 near the shore to around 73 near 5000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Puna

Today: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 84 near the shore to 69 to 74 at 4000 feet. North winds up to 15 mph shifting to the east in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with showers. Lows around 67 near the shore to around 53 at 4000 feet. East winds up to 10 mph. Chance of rain 90 percent.

Monday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 84 near the shore to 69 to 74 at 4000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Waikoloa

Today: Mostly sunny. Isolated showers in the afternoon. Highs around 86 near the shore to 70 to 76 above 4000 feet. North winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Lows 69 to 74 near the shore to 50 to 57 above 4000 feet. East winds up to 10 mph.

Monday: Mostly sunny. Isolated showers in the afternoon. Highs around 86 near the shore to 70 to 76 above 4000 feet. Light winds becoming north up to 10 mph in the afternoon. Chance of rain 20 percent.

Detailed Forecast

Synopsis

The high pressure center northeast of the islands will continue to drift eastward as a cold front moves into the Central Pacific basin weakening the ridge north of the islands. Trade winds will ease a bit today into the moderate to locally breezy range through Saturday. A band of unstable showers moving through the islands will continue to increase shower activity this morning favoring windward and mountain areas. Passing windward and mountain showers will continue through the week, with higher coverage in the overnight to early morning hours.

Discussion

Radar imagery this morning shows numerous showers along windward and mountain sections of each island. An unstable cloud band shown on Infra-Red satellite imagery continues to drift slowly westward through the island chain this morning. Shower activity will trend downward later this afternoon as most of the cloud band passes to the west of the state.
A 1026 mb high center far northeast of the state will drift eastward over the next 12 to 24 hours as a cold front moves into the Central Pacific basin weakening the ridge north of the state. This change in pressure pattern will cause trade winds to decrease a bit into the moderate to locally breezy range through Saturday.
More typical passing trade wind showers remain in the forecast for most areas after the low level cloud band passes through the islands from later this afternoon through Friday. A weak disturbance brushes by the Big Island starting Monday night, deeper moisture and instability with this weak trough may bring higher shower activity into the eastern half of the Big Island into Tuesday. Otherwise brief passing windward and mountain showers will favor the typical overnight to early morning hours.

Aviation

Breezy trades will bring moderate showers to windward and mauka areas through the early morning hours. Periods of MVFR are occurring with this activity and AIRMET Sierra for mountain obscuration has been issued. Improvement to prevailing VFR is expected by mid to late morning as showers diminish and shift west of the area.
AIRMET Tango for lee turbulence will remain in effect through the forecast period.

Marine

A ridge of high pressure far north of the state will maintain fresh to locally strong trades this week. A slight increase of winds are expected late Tuesday into Wednesday. Small Craft Advisory is expected for the typical windier waters around Maui County and the Big Island for much of this week.
A tiny west-northwest swell filled yesterday evening and the Waimea buoy is holding steady near 2 feet and 13 seconds. This swell should hold today then decline tonight. A slightly larger northwest is expected to fill in late Monday and peak late Tuesday into Wednesday. Another similar or slightly larger northwest swell is possible over next weekend.
Surf along south facing shores will remain below average through early next week. Small, long-period south swell energy from recent storms southeast of New Zealand is timed to arrive around midweek, allowing surf to build back to near summer average during the second half of the week. Breezy trades will maintain rough and choppy short-period energy along east facing shores throughout this week week.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Tuesday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.
Small Craft Advisory until 6 PM HST this evening for Kaiwi Channel, Maui County Windward Waters.

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Data Courtesy of NOAA.gov

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