Weather Forecast

Hawaii County Weather Forecast for October 19, 2021

October 19, 2021, 7:15 AM HST
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Photo Credit: James Grenz

Hilo

Today: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 76 to 82 near the shore to 62 to 69 at 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 60 to 70 near the shore to 51 to 57 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny with isolated showers. Highs 75 to 82 near the shore to 62 to 69 at 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Kona

Today: Mostly sunny in the morning then becoming partly sunny. Highs 81 to 87 near the shore to 66 to 71 near 5000 feet. Light winds.

Tonight: Partly cloudy. Lows 68 to 73 near the shore to 49 to 56 near 5000 feet. Light winds.

ARTICLE CONTINUES BELOW AD

Wednesday: Mostly sunny. Isolated showers in the afternoon. Highs 80 to 86 near the shore to around 67 near 5000 feet. Light winds. Chance of rain 20 percent.

Waimea

ARTICLE CONTINUES BELOW AD

Today: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 64 to 84. East winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 61 to 68 near the shore to 53 to 61 near 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny with isolated showers. Highs 63 to 83. East winds around 10 mph. Chance of rain 20 percent.

Kohala

ARTICLE CONTINUES BELOW AD

Today: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 64 to 84. East winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 61 to 68 near the shore to 53 to 61 near 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny with isolated showers. Highs 63 to 83. East winds around 10 mph. Chance of rain 20 percent.

South Big Island

Today: Mostly sunny in the morning then becoming partly sunny. Highs around 83 near the shore to around 65 near 5000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon.

Tonight: Partly cloudy. Lows around 72 near the shore to around 52 near 5000 feet. Northeast winds around 10 mph.

Wednesday: Mostly sunny. Isolated showers in the afternoon. Highs around 82 near the shore to around 64 near 5000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Puna

Today: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 76 to 82 near the shore to 62 to 69 at 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 60 to 70 near the shore to 51 to 57 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny with isolated showers. Highs 75 to 82 near the shore to 62 to 69 at 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Waikoloa

Today: Mostly sunny. Highs 81 to 88 near the shore to 67 to 73 above 4000 feet. North winds up to 10 mph in the morning becoming light.

Tonight: Partly cloudy. Lows around 71 near the shore to 49 to 55 above 4000 feet. Light winds.

Wednesday: Sunny. Highs 80 to 87 near the shore to 65 to 72 above 4000 feet. North winds around 10 mph in the morning becoming light.

Detailed Forecast

Synopsis

A ridge of high pressure approaching the islands will make for gentle trades the next couple of days. A dry and stable airmass will give lots of sunshine and relatively few showers to the Aloha State. The remnants of an old front will reach Kauai Thursday, and might also spread to Oahu Thursday night or Friday, bringing an increase in clouds and some showers. Trades will start to increase Thursday and become breezy over the weekend. A dry and stable airmass will also return this weekend with fine weather expected.

Discussion

No big surprises in the 12z soundings, with slightly lower inversions and similar precipitable water and moisture depth as in the 00z soundings. Satellite and radar showing relatively few clouds and showers. With mid-level ridging capping the vertical cloud growth, trade wind showers should be fairly sparse today and where rain does fall, amounts should be pretty light. Lots of sunshine expected again today as well.
Quiet weather will persist through tonight and Wed as a surface ridge about 275 miles NNE of the islands continues pushing slowly toward the state. Generally gentle background trades are expected today (although locally breezy in the typically windiest spots) and diurnal land and sea breeze circulations a little more prevalent in the usual areas more sheltered from the trades. Winds on Wed will be even slightly lower than today, but the models insist that we won’t completely lose the background trades even with the dissipating ridge coming to within about 75 miles of Kauai.
The remnants of a dissipating cold front about 500 miles N of Kauai are expected to bring an increase in clouds and showers to Kauai and probably Oahu starting about Thu (for the Garden Isle) and persisting into Friday before falling apart. The low level moisture will have marginal upper level support to work with in the form of a weak upper trough, but overall rainfall amounts are expected to be fairly modest with the frontal remnants.
It looks like after that, breezy trades return and bring drier and more stable air back to the Aloha State for the foreseeable future. Over the weekend, 700 mb temperatures reach double digits, model ensemble moisture depth drops back to 5000 to 6000 feet, and precipitable water drops to nearly 1 inch. Even though this is the time of year when we typically expect to start seeing the weather get a little more active near Hawaii, the models don’t show much of promise for significant rainfall into the longer range. This is not particularly good news with severe to extreme drought continuing in parts of the state.

Aviation

As a high pressure ridge moves towards the islands from the north, northeast trade winds have been easing into the moderate range as the pressure gradient loosens. Brief periods of low cloudiness and showers may affect mainly windward and mauka sections statewide from time to time, but overall conditions will be VFR as the atmosphere becomes more stable.
No AIRMETs are in effect, and none are anticipated through today.

Marine

Moderate trades will be gradually trending down to generally light to gentle breezes the next couple of days as a series of North Pacific cold fronts weaken the ridge north of the islands. These fronts will cross the north offshore waters Wednesday and Thursday and are expected to wash out before reaching the state. High pressure will re-establish itself north of the islands by Friday and this will strengthen weekend trades back into the moderate to locally strong category.
A series of north swells will move through the coastal waters this week. A recent small north pulse will be reinforced by a larger, medium period north-northwest swell tonight through Wednesday. An even larger north swell follows Thursday night and Friday that will likely drive late week north facing shore surf heights to High Surf Advisory levels. Kahului Harbor and other north facing harbors will become susceptible to harbor surges from this north swell. Weakened trades equates to lower east facing shore surf through the middle of the week. Strengthening trades on Friday will lead to increasing surf along the eastern shores with this heightened east wind wave chop persisting through the weekend. Small surf along the south facing shores will get a minor boost today as a small, but relatively long 14 to 16 second period south swell travels around the chain. This swell will linger through Wednesday before tapering off at the end of the week.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov

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