Photo Credit: James Grenz

Hilo

Today: Partly sunny with numerous showers in the morning, then mostly sunny with scattered showers in the afternoon. Highs 82 to 88 near the shore to around 73 at 4000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then frequent showers after midnight. Lows around 69 near the shore to around 54 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 80 percent.

Sunday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 82 to 88 near the shore to around 73 at 4000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Kona

Today: Sunny in the morning, then cloudy with scattered showers in the afternoon. Highs 82 to 87 near the shore to around 70 near 5000 feet. Southwest winds up to 10 mph shifting to the west in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 72 to 77 near the shore to around 55 near 5000 feet. Light winds. Chance of rain 20 percent.

Sunday: Sunny in the morning, then cloudy with scattered showers in the afternoon. Highs 82 to 87 near the shore to around 70 near 5000 feet. West winds up to 10 mph. Chance of rain 40 percent.

Waimea

Today: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 82 near the shore to 76 to 81 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 69 near the shore to 57 to 62 near 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Sunday: Breezy. Partly sunny with scattered showers. Highs around 82 near the shore to 76 to 81 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Kohala

Today: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 82 near the shore to 76 to 81 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 69 near the shore to 57 to 62 near 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Sunday: Breezy. Partly sunny with scattered showers. Highs around 82 near the shore to 76 to 81 near 3000 feet. East winds up to 20 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 71 near 5000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening. Lows 68 to 74 near the shore to around 53 near 5000 feet. East winds up to 20 mph shifting to the northeast 10 to 20 mph after midnight. Chance of rain 20 percent.

Sunday: Breezy. Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 86 near the shore to around 71 near 5000 feet. East winds up to 25 mph. Chance of rain 20 percent.

Puna

Today: Partly sunny with numerous showers in the morning, then mostly sunny with scattered showers in the afternoon. Highs 82 to 88 near the shore to around 73 at 4000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then frequent showers after midnight. Lows around 69 near the shore to around 54 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 80 percent.

Sunday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 82 to 88 near the shore to around 73 at 4000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Waikoloa

Today: Mostly sunny. Isolated showers in the afternoon. Highs 83 to 88 near the shore to 70 to 76 above 4000 feet. North winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening. Lows 72 to 77 near the shore to 51 to 58 above 4000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Sunday: Mostly sunny. Highs 83 to 88 near the shore to 70 to 76 above 4000 feet. North winds up to 15 mph.

Detailed Forecast

Synopsis

Moderate trade winds will prevail through Sunday. An upper trough moving near the islands may trigger a modest increase in shower activity, with the highest rainfall chances remaining over windward areas. Expect windy, very gusty, and dry conditions late Monday into Wednesday.

Discussion

Moderate trade winds and a typical pattern of mainly windward showers persist this morning. Overnight soundings confirm that an upper ridge over the islands maintains stable conditions, while moisture within trade wind flow remains slightly below normal. As a result, windward rainfall has been quite limited, and, with the exception of a few afternoon showers over the Kona slopes of the Big Island, leeward areas have been dry.
Moderate trades will prevail through Sunday as a weakness in the surface high persists north of the islands. An upper trough will drop down toward the state on Saturday and stall near Kauai on Sunday. This will likely support a modest increase in shower activity, especially across the western end of the state. On Sunday night, the upper trough will weaken and be pushed away by strong upper ridging moving in from the east. This will lead to rebuilding trade winds and increased stability. Models have been consistently advertising a narrow band of deeper showers just ahead of the surging trade winds pushing through Sunday night through Monday morning.
Expect windy and very gusty trade winds early next week, along with a period of stable and dry conditions. While it should continue to be monitored, models show Dora passing south of the islands with deep high pressure moving in tandem to the north of Hawaii. This will result in a strong and rather dry trade wind flow with scant showers. Models show a very low and strong subsidence inversion developing as early as late Monday, along with winds of 40 to 50 kt around the inversion level. Under this stable and strong flow, winds over and downwind of terrain should exceed the Wind Advisory threshold, and localized damaging wind gusts to High Wind Warning levels are a real possibility. Trade winds will gradually decline on Wednesday.

Aviation

A high pressure ridge far north of the state will keep moderate trade winds in the forecast through Sunday. Brief passing showers are possible, mainly across north through east sections of each island, favoring the overnight through early morning hours. Mostly VFR conditions will prevail outside of showers.
No AIRMETs in effect and none are expected.

Marine

Easterly trades have lowered into the moderate to fresh range over the past 24-Hrs due to a weakness that has formed in the ridge to the north, which should hold through tonight. A transition period is anticipated Sunday through early next week as the ridge strengthens to the north and Hurricane Dora enters the central Pacific on a westward track. This upward trend will continue Monday, then peak Tuesday as Dora passes well to the south. Wind speeds will reach the strong category for all waters through the day Monday, with gales expected over the windier channels and waters around Maui County and the Big Island late Monday through Tuesday. Seas will become rough and quickly exceed the Small Craft Advisory level over exposed waters beginning Monday into Monday night.
Surf along east facing shores will small into Sunday, then quickly ramp up and become rough Sunday night through early next week due to a combination of the aforementioned strong trades and large seas and a moderate long-period easterly swell generated from Dora. The largest surf is expected over the eastern end of the state, where heights may near the warning level late Monday through Tuesday night. A downward trend is expected through the second half of the week as a more typical trade wind pattern returns and seas lower.
Surf along south facing shores will remain small through the weekend with mainly a combo of background south and south- southwest swell energy rolling through. A short- to medium-period southeast swell is expected to fill in Tuesday through midweek as Dora passes far to the south. This will be a short-lived event with a peak occurring late Tuesday into early Wednesday.

Fire weather

There are no significant fire weather concerns through the weekend, but critical fire weather conditions are looking highly likely early next week. Dry, stable, and breezy to windy trades are expected as deep high pressure to the north moves in tandem with Hurricane Dora, which is forecast to pass south of the islands. Conditions could develop as early as late Monday, but Tuesday has the greatest potential as the Keetch Byram Drought Index (KBDI) is expected to reach the critical 600 mark and models show leeward relative humidity falling below 45 percent. A Fire Weather Watch will be issued sometime later this weekend to highlight this threat.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov