Weather Forecast

Hawaii County Weather Forecast for October 23, 2021

October 23, 2021, 7:16 AM HST
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Photo Credit: James Grenz

Hilo

Today: Cloudy with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 77 to 82 near the shore to 63 to 69 at 4000 feet. East winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 62 to 70 near the shore to around 55 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Sunday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 78 to 83 near the shore to 63 to 70 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Kona

Today: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 83 to 88 near the shore to around 69 near 5000 feet. Light winds. Chance of rain 20 percent.

Tonight: Mostly clear with isolated showers. Lows 68 to 74 near the shore to 49 to 56 near 5000 feet. Light winds. Chance of rain 20 percent.

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Sunday: Sunny in the morning then becoming mostly cloudy. Isolated showers. Highs 83 to 88 near the shore to around 68 near 5000 feet. Light winds. Chance of rain 20 percent.

Waimea

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Today: Breezy. Mostly cloudy with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 65 to 84. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Tonight: Breezy. Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 63 to 70 near the shore to 55 to 62 near 3000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Sunday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 65 to 84. East winds 10 to 25 mph. Chance of rain 50 percent.

Kohala

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Today: Breezy. Mostly cloudy with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 65 to 84. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Tonight: Breezy. Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 63 to 70 near the shore to 55 to 62 near 3000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Sunday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 65 to 84. East winds 10 to 25 mph. Chance of rain 50 percent.

South Big Island

Today: Breezy. Partly sunny with scattered showers. Highs around 83 near the shore to around 66 near 5000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Tonight: Mostly clear. Lows around 71 near the shore to around 52 near 5000 feet. Northeast winds 10 to 15 mph.

Sunday: Sunny in the morning then becoming partly sunny. Breezy. Highs around 84 near the shore to around 66 near 5000 feet. East winds 10 to 20 mph.

Puna

Today: Cloudy with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 77 to 82 near the shore to 63 to 69 at 4000 feet. East winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 62 to 70 near the shore to around 55 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Sunday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 78 to 83 near the shore to 63 to 70 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Waikoloa

Today: Mostly sunny. Breezy. Scattered showers in the morning. Highs 82 to 89 near the shore to 67 to 73 above 4000 feet. Northeast winds up to 20 mph. Chance of rain 50 percent.

Tonight: Mostly clear with isolated showers. Lows around 73 near the shore to 49 to 55 above 4000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Sunday: Sunny. Isolated showers in the morning. Highs 82 to 88 near the shore to 67 to 73 above 4000 feet. North winds up to 15 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Mostly sunny conditions will prevail over most of the area this afternoon followed by increasing showers late tonight, especially over windward and mauka areas. Locally breezy trades will weaken to moderate by Tuesday and will remain on the drier side of normal well into next week.

Discussion

Widespread rain over Windward Big Island, including the Kau district is beginning to diminish as evidenced by warming cloud tops during the last couple of hours. With the mid-level trough axis now working across the Big Island, drier air has eroded shower activity over the windward zone while backing mid-level flow is now shifting rainfall away from the Kau district. Total rainfall amounts so far have generally averaged under an inch. An additional quarter inch or less will be possible during the pre-dawn hours as rain steadily diminishes.
Per regional low-level water vapor vapor imagery and the latest guidance, much drier air is poised to move into the area today. Dry advection in the low levels will be further reinforced by strengthening mid-level subsidence. This lends credence to forecast soundings which indicate inversion heights falling below 5kft this afternoon. The dry and highly stable regime will favor mostly sunny skies areawide with the exception of Leeward Big Island. Locally breezy trades will be accompanied by nothing more than a passing isolated shower over windward sections.
A batch of showers embedded within the trades is seen on IR imagery crossing 150W this morning. The high res guidance captures this well and ushers through the state late tonight. Given its organized appearance and expected timing, elected to carry very low pops through the first half of tonight followed by likely to categorical over windward areas during the second half. Locally breezy trades will continue into early next week. For the most part, a dearth of deeper moisture is expected to favor drier- than-normal trades through at least the middle of next week. However, an upper low that is forecast to deepen over the eastern end of the state may support increased afternoon convection over Leeward Big Island by Tuesday and Wednesday. This will largely be conditional on degree of mid-level moisture availability over the eastern end of the state which has thus far been a source of poor continuity among the global models.

Aviation

Gusty trade winds are expected to persist this weekend. Therefore, AIRMET Tango remains in effect for TEMPO moderate low- level turbulence downstream of the higher terrain on all islands. This AIRMET will likely remain in place through this evening.
The relatively strong low-level trade wind flow will continue to transport low clouds and showers into the east facing sections of some of the islands into mid-morning, especially the Big Island. This may result in brief periods of MVFR conditions due to lower ceilings and reduced visibilities. The forecast guidance indicates the atmosphere will become more stable with a drying trend into this evening. Based on this, the windward sides of the smaller islands are forecast to have less precipitation later today with VFR conditions prevailing from Maui to Kauai. There may still be a few low clouds and brief showers over the Big Island, but VFR conditions will likely prevail there also by mid-morning.
AIRMET Sierra remains in effect early this morning for mountain obscuration along the windward slopes of the Big Island and Maui. This AIRMET may be needed for few hours after sunrise on the Big Island, but it will likely be lowered by mid-morning.

Marine

High pressure far north of the state will maintain fresh to locally strong trade winds through rest of the weekend, possibly Monday as well. Winds are expected to decrease next week. A Small Craft Advisory (SCA) is in effect for the typical windier waters near Maui county and the Big Island through Sunday afternoon.
The current north swell impacting the state peaked overnight and is on the decline early this morning. This swell will gradually decrease over the next couple of days. Due to the northerly direction, Kahului and Hilo harbors will likely see some light harbor surges through this morning. East facing shores with northerly exposure will also be impacted by this swell.
A slightly smaller reinforcing north swell is expected to fill in Monday, and peak on Monday night into Tuesday. Following this swell, there should be a series of north swells during the second half of next week into next weekend as the North Pacific heats up.
Small, mainly background south swells are expected through Monday with a slightly larger south swell expected to fill in Tuesday and Wednesday. Short-period choppy surf is expected along east facing shores though Monday with a slight downward trend expected into the middle of next week as trade wind speeds decrease.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Sunday 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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