Weather Forecast

Hawaii County Weather Forecast for May 21, 2022

May 21, 2022, 7:15 AM HST
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Hilo

Today: Mostly sunny with isolated showers. Highs around 83 near the shore to 66 to 71 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with numerous showers. Lows 65 to 70 near the shore to around 54 at 4000 feet. Northwest winds up to 15 mph. Chance of rain 70 percent.

Sunday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 83 near the shore to 66 to 71 at 4000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

Kona

Today: Sunny. Isolated showers in the afternoon. Highs 81 to 86 near the shore to around 66 near 5000 feet. Light winds. Chance of rain 20 percent.

Tonight: Partly cloudy. Scattered showers in the evening. Lows 68 to 75 near the shore to around 55 near 5000 feet. Light winds. Chance of rain 40 percent.

ARTICLE CONTINUES BELOW AD

Sunday: Mostly sunny. Isolated showers in the afternoon. Highs 81 to 86 near the shore to around 66 near 5000 feet. Light winds becoming west up to 10 mph in the afternoon. Chance of rain 20 percent.

Waimea

ARTICLE CONTINUES BELOW AD

Today: Mostly sunny with isolated showers. Highs around 82 near the shore to 66 to 77 near 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 67 near the shore to 55 to 62 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Sunday: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs around 82 near the shore to 66 to 77 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Kohala

ARTICLE CONTINUES BELOW AD

Today: Mostly sunny with isolated showers. Highs around 82 near the shore to 66 to 77 near 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 67 near the shore to 55 to 62 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Sunday: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs around 82 near the shore to 66 to 77 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

South Big Island

Today: Sunny and breezy. Highs around 84 near the shore to around 70 near 5000 feet. East winds up to 20 mph.

Tonight: Mostly clear. Breezy. Isolated showers in the evening. Lows around 69 near the shore to around 54 near 5000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.

Sunday: Sunny and breezy. Highs around 84 near the shore to around 70 near 5000 feet. East winds 10 to 20 mph.

Puna

Today: Mostly sunny with isolated showers. Highs around 83 near the shore to 66 to 71 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with numerous showers. Lows 65 to 70 near the shore to around 54 at 4000 feet. Northwest winds up to 15 mph. Chance of rain 70 percent.

Sunday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 83 near the shore to 66 to 71 at 4000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

Waikoloa

Today: Sunny. Highs around 85 near the shore to 67 to 73 above 4000 feet. Northeast winds up to 15 mph.

Tonight: Mostly clear. Lows 69 to 75 near the shore to 51 to 58 above 4000 feet. Southeast winds up to 15 mph.

Sunday: Sunny. Highs around 85 near the shore to 67 to 73 above 4000 feet. North winds up to 10 mph increasing to 10 to 15 mph in the afternoon.

Detailed Forecast

Synopsis

A high pressure ridge builds in north of the islands this weekend resulting in strengthening trade winds through Sunday. The returning easterly trades will push clouds associated with the remnants of a frontal band slowly northwest and away from the islands. More stable conditions are expected with the weather pattern shifting back to brief passing windward and mountain showers through Friday.

Discussion

Satellite imagery this morning shows a band of clouds associated with the remnants of a frontal band is currently located in the Kauai Channel between Kauai and Oahu. Local radar imagery indicates scattered showers developing within this cloud band. Expect the cloud band to drift back over Kauai later this morning through evening with some enhanced shower activity over the Garden Isle.
The pattern once again shifts back to our typical trade wind weather as the high pressure ridge builds back in north of the Hawaiian Islands. Easterly trade winds, flowing out of this high pressure system, will spread from east to west across the state and strengthen through Sunday. These trade winds will push the remnant cloud band northwestward back through Kauai today and then clear out of the state by Sunday.
The easterly trade wind weather will produce more stable weather conditions with a high pressure ridge aloft strengthening the subsidence inversion over the region. Expect temperature inversion heights between 6000 and 8000 feet elevation through the week. This inversion serves as a thermal stable cap on vertical cloud development and at these heights will limit shower activity. For most islands expect brief windward and mountain showers developing mainly in the overnight to early morning hours from Sunday onward. Leeward areas will see mostly sunny skies each day. The one exception to this forecast will be afternoon cloud cover on the western slopes of the Big Island, as typical afternoon sea breezes will build mostly cloudy skies each day with down slope mountain breeze clearing at night.
Decreased shower activity in this mornings forecast from numerous showers into a more isolated to scattered range to account for the increasing atmospheric stability over the next few days. This matches well with model cross sections over the island chain. Windward and mountain sections will typically see the higher shower coverage in the range as the trade winds return. Let the dry season begin.

Aviation

A remnant boundary remains over the western part of the state this morning. Most of the showers have ended over land, but pockets of low ceilings remain in Kauai and Oahu. However, high pressure is strengthening far northeast of the area. Thus, trade winds have been gradually spreading across the island chain from east to west, and will become moderate to locally breezy later today through Sunday. Most of the moisture associated with the old boundary will be shunted to the west of the state as the trades fill in.
AIRMETs for mountain obscuration remain in effect for Kauai and Oahu, but will likely be dropped later this morning or early in the afternoon.

Marine

A dissipating cloud band in the Kauai channel will continue to weaken and drift northward. High pressure will build into the region rest of today, with easterly trade winds strengthening from east to west through tomorrow. A Small Craft Advisory goes into effect at noon today for the typical windier waters and channels around Maui County and the Big Island through Monday afternoon. Typical trade wind weather with more stable conditions will continue into the middle of next week.
Surf heights along south facing shores will fluctuate between near to slightly below average, as a couple of long- period south swells move through the region today through mid-week. The next long-period swell will fill in Thursday through the rest of next week, bringing above average surf. In the long range, models continue to show quite a bit of activity in the southern hemisphere, which could translate to additional south shore surf events lasting into early June.
Surf along north and west facing shores will slowly decline today and become nearly flat tomorrow through the first half of next week. The next small bump is expected to arrive middle of next week.
East facing shores surf will get a slight boost tomorrow and Monday as the trades strength near the coast and upstream.

HFO Watches/Warnings/Advisories

Small Craft Advisory from noon today to 6 PM HST Monday 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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