Weather Forecast

Hawaii County Weather Forecast for August 13, 2021

August 13, 2021, 7:15 AM HST
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Hilo

Today: Partly sunny with scattered showers. Highs 78 to 84 near the shore to 65 to 72 at 4000 feet. North winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 63 to 72 near the shore to 54 to 59 at 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Saturday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 77 to 84 near the shore to 65 to 73 at 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Kona

Today: Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs around 85 near the shore to around 69 near 5000 feet. Southwest winds up to 10 mph. Chance of rain 30 percent.

Tonight: Partly cloudy. Lows 69 to 75 near the shore to 50 to 56 near 5000 feet. Light winds.

ARTICLE CONTINUES BELOW AD

Saturday: Mostly sunny. 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.

Waimea

ARTICLE CONTINUES BELOW AD

Today: Breezy. Partly sunny with scattered showers. Highs 66 to 85. East winds 10 to 25 mph. Chance of rain 40 percent.

Tonight: Breezy. Mostly cloudy with isolated showers in the evening, then partly cloudy with scattered showers after midnight. Lows 63 to 71 near the shore to 56 to 63 near 3000 feet. East winds 10 to 20 mph. Chance of rain 40 percent.

Saturday: Breezy. Mostly sunny with isolated showers. Highs 65 to 84. East winds 10 to 20 mph. Chance of rain 20 percent.

Kohala

ARTICLE CONTINUES BELOW AD

Today: Breezy. Partly sunny with scattered showers. Highs 66 to 85. East winds 10 to 25 mph. Chance of rain 40 percent.

Tonight: Breezy. Mostly cloudy with isolated showers in the evening, then partly cloudy with scattered showers after midnight. Lows 63 to 71 near the shore to 56 to 63 near 3000 feet. East winds 10 to 20 mph. Chance of rain 40 percent.

Saturday: Breezy. Mostly sunny with isolated showers. Highs 65 to 84. East winds 10 to 20 mph. Chance of rain 20 percent.

South Big Island

Today: Breezy. Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 84 near the shore to around 67 near 5000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy in the evening then becoming clear. Breezy. Lows around 72 near the shore to around 53 near 5000 feet. East winds 10 to 20 mph.

Saturday: Mostly sunny. Isolated showers in the afternoon. Highs around 84 near the shore to around 68 near 5000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Puna

Today: Partly sunny with scattered showers. Highs 78 to 84 near the shore to 65 to 72 at 4000 feet. North winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 63 to 72 near the shore to 54 to 59 at 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Saturday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 77 to 84 near the shore to 65 to 73 at 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Waikoloa

Today: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs 83 to 89 near the shore to 66 to 73 above 4000 feet. Northeast winds up to 25 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Breezy. Lows around 73 near the shore to 50 to 56 above 4000 feet. Northeast winds up to 20 mph.

Saturday: Sunny. Highs 83 to 90 near the shore to 67 to 74 above 4000 feet. Northeast winds up to 15 mph.

Detailed Forecast

Synopsis

A 1026 mb surface high far north-northeast of the islands will continue to generate trade winds through the weekend as it shifts slowly to the west. A surface trough will be approaching the islands from the northeast over the weekend and bring on a couple of days of light winds over land between Monday and Tuesday. But for today through Sunday night, expect trade wind showers to grace the windward and mountain areas. The frequency of these showers will be highest during the nights and mornings. Expect plenty of sunshine over the south and leeward coasts each afternoon.

Discussion

We are looking for a rather quiet stretch of locally strong typical trade winds through Sunday. The air mass is stable that will support some mainly light trade showers, especially during nights and mornings. Current satellite and radar shows scattered showers approaching the islands from the northeast, most abundant east of Kauai. So do expect some wet roads during the early morning commute over the windward and mountain areas. A good amount of these clouds and showers will dissipated by mid morning, resulting in plenty of sunshine, especially the south and leeward shorelines.
A slow down in the trades is expected to begin Saturday night as the surface trough nears the islands. On Monday, the trades will have given way to a light easterly wind flow, including winds from the southeast. The interior and south sections will encounter an onshore flow, combine that with daytime heating, result in some spotty afternoon clouds and showers. A night, an offshore land breeze takes over, moving most of these clouds and showers into the adjacent waters and shoreline. All the while the background easterly flow carries in few showers into the windward sections.
The surface trough will be accompanied by an upper level trough. Models continue to suggest that the dynamics with the upper trough will stay north of the islands, meaning the air mass over the islands will be stable enough to ward off any heavy or widespread showers.
Trade winds are slated to return Tuesday night, building to locally strong by Wednesday afternoon or evening.

Aviation

A moderate to occasionally breezy trade regime will be in place through the remainder of this morning and into the afternoon. Thus, most shower activity will occur along the windward coasts and slopes. There may be brief periods of MVFR ceilings and visibility associated with this activity. Otherwise, expect mainly dry weather with VFR conditions along leeward areas.
SIGMET SIERRA remains in effect for north thru east areas of the Big Island above 2500 feet due to low clouds and showers.

Marine

Fresh to strong northeast trades will continue through Saturday, then ease into the light category Sunday through the first half of next week with an east to southeast background flow. The strong trades expected through Saturday will be across the typical areas between Maui County and the Big Island. The lighter winds returning Sunday into next week will translate to a land and sea breeze pattern around the coasts each day.
Surf along exposed north and west facing shores will remain up as small, west-northwest pulses move through in response to recurving tropical sources across the far northwest Pacific. The small west- northwest swell that arrived on Wednesday will steadily lower into the weekend. An upward trend is expected tonight into Saturday as a slightly larger west-northwest swell arrives and builds down the island chain. This will linger into early next week before lowering back toward the summertime average mid/late week.
After a long stretch with limited surf along south facing shores due to a blocking high that had set up within Hawaii’s swell window down around New Zealand, the flood gates have opened featuring a series of gale- to storm-force systems moving through and east of New Zealand. This has translated to an active spell locally with a series of south-southwest to southwest swells expected. As the swell that peaked earlier in the week moves out by tonight, expect the surf to hold through the weekend as a small, long- period southwest swell arrives and moves through. The largest in the series is set to arrive on or by Monday with a peak centered around the Tuesday and Wednesday period. The swell may come in larger than anticipated at its peak, which could drive surf heights along south facing shores to/above our new advisory threshold of 10 ft on the face (satellite data back on Tuesday showed seas above predicted within the fetch east of New Zealand — around 45 ft). Let’s see what happens down at the Pago Pago buoy today through Saturday as it moves through.
Surf along east facing shores will remain small each day through early next week, then potentially trend up by the second half as a small easterly swell from Hurricane Linda arrives (low confidence at this point — best chance eastern end of state).

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM 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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