Photo Credit: James Grenz

Hilo

Today: Partly sunny with scattered showers. Highs 82 to 88 near the shore to around 72 at 4000 feet. Northeast winds 10 to 15 mph decreasing to up to 15 mph in the afternoon. Chance of rain 40 percent.

Tonight: Mostly cloudy with scattered showers. Lows 65 to 72 near the shore to around 54 at 4000 feet. Northwest winds up to 15 mph. Chance of rain 50 percent.

Monday: Partly sunny with scattered showers. Highs 81 to 87 near the shore to around 71 at 4000 feet. North winds up to 10 mph shifting to the east around 10 mph in the afternoon. 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 68 to 74 near 5000 feet. West winds up to 10 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 70 to 75 near the shore to around 56 near 5000 feet. Light winds. Chance of rain 40 percent.

Monday: Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 82 to 87 near the shore to 68 to 73 near 5000 feet. Southwest winds up to 10 mph shifting to the northwest in the afternoon. Chance of rain 50 percent.

Waimea

Today: Mostly sunny. Breezy. Isolated showers in the morning, then scattered showers in the afternoon. Highs 69 to 84. East winds 10 to 25 mph. Chance of rain 40 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 67 near the shore to 55 to 64 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Monday: Breezy. Partly sunny with scattered showers. Highs 68 to 83. East winds 10 to 20 mph shifting to the northeast in the afternoon. Chance of rain 50 percent.

Kohala

Today: Mostly sunny. Breezy. Isolated showers in the morning, then scattered showers in the afternoon. Highs 69 to 84. East winds 10 to 25 mph. Chance of rain 40 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 67 near the shore to 55 to 64 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Monday: Breezy. Partly sunny with scattered showers. Highs 68 to 83. East winds 10 to 20 mph shifting to the northeast in the afternoon. Chance of rain 50 percent.

South Big Island

Today: Mostly sunny. Breezy. Highs around 86 near the shore to around 76 near 5000 feet. East winds 10 to 20 mph decreasing to up to 20 mph in the afternoon.

Tonight: Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Lows around 71 near the shore to around 55 near 5000 feet. Northeast winds up to 15 mph increasing to 10 to 15 mph after midnight. Chance of rain 20 percent.

Monday: Sunny in the morning then becoming partly sunny. Breezy. Highs around 86 near the shore to around 75 near 5000 feet. East winds up to 20 mph becoming 10 to 15 mph in the afternoon.

Puna

Today: Partly sunny with scattered showers. Highs 82 to 88 near the shore to around 72 at 4000 feet. Northeast winds 10 to 15 mph decreasing to up to 15 mph in the afternoon. Chance of rain 40 percent.

Tonight: Mostly cloudy with scattered showers. Lows 65 to 72 near the shore to around 54 at 4000 feet. Northwest winds up to 15 mph. Chance of rain 50 percent.

Monday: Partly sunny with scattered showers. Highs 81 to 87 near the shore to around 71 at 4000 feet. North winds up to 10 mph shifting to the east around 10 mph in the afternoon. Chance of rain 50 percent.

Waikoloa

Today: Sunny and breezy. Highs 84 to 89 near the shore to 70 to 77 above 4000 feet. Northeast winds up to 20 mph.

Tonight: Partly cloudy. Breezy. Lows around 74 near the shore to 51 to 60 above 4000 feet. East winds up to 20 mph.

Monday: Mostly sunny with isolated showers. Highs 83 to 88 near the shore to 69 to 76 above 4000 feet. North winds up to 15 mph shifting to the northwest in the afternoon. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Locally breezy trade winds combined with stable atmospheric conditions will result in a dry trade weather pattern through early Monday. The trade winds are expected to gradually weaken starting late Monday, which will allow local nighttime land breezes and afternoon sea breezes to develop from Monday night into mid-week. In addition, a disturbance aloft moving into the area plus increased low-level moisture may cause an increase in clouds and showers, including over leeward and interior areas Tuesday and Wednesday afternoons. The trade winds are expected to strengthen again later this week.

Discussion

A 1020 mb surface high pressure system is centered near 32N 138W, or about 1360 miles east-northeast of Hilo. A surface ridge extends west-southwest from this high through a point about 360 miles north of Lihue. The tight pressure gradient south and southwest of these features is producing locally breezy trade winds across the state early this morning. The atmosphere remains stable across the state due to upper-level ridging above the region. In addition, the air mass remains dry over most of the state. Loops of infrared satellite imagery and radar reflectivity data show scattered low clouds and isolated showers along some windward sections of the islands. Otherwise, skies are mostly clear across most of the state early this morning.
The forecast guidance shows that this dry trade wind weather pattern will likely persist through early Monday. Therefore, expect low clouds and minimal shower activity along windward facing sections. In addition, expect clouds and some showers over the upslope sections of the Big Island each afternoon through Monday.
By late Monday, the surface high will move east, and the associated surface ridge will start to weaken, and drift south closer to the state. A mid-level trough to the east of the islands will move west toward the region at the same time. A weak surface trough, which is a reflection of the mid-level feature, may also move into the islands from the east. This will cause the trade winds to weaken, so that local nighttime land breezes and afternoon sea breezes may become established starting Monday night. The forecast guidance also shows an increase in low-level moisture. This will likely lead to higher rain chances over windward and mauka areas, since the light background trade wind flow will transport low clouds and showers into these areas. There will also be an increase in cloud cover and showers over most leeward and interior sections once the sea breezes become established starting Tuesday afternoon.
The forecast guidance shows the surface ridge will begin to lift north, and build during the second half of the week. This will likely allow the trade winds to strengthen again later this week.

Aviation

Surface high pressure north of the state will maintain moderate to locally breezy trade winds through early Monday, and a ridge aloft will maintain stable conditions. Expect VFR conditions to dominate with isolated MVFR conditions periodically occurring over windward areas.
AIRMET Tango for turbulence over and downwind of terrain below 8000 ft will likely remain in effect through early Monday.

Marine

A high pressure ridge north of the islands will continue to produce moderate to locally strong trade winds today. This ridge will weaken late tonight with slightly lower trade wind speeds in the forecast from Monday onward. Small Craft Advisory (SCA) conditions are expected over the windier waters and channels near Maui and the Big Island lasting through early Monday morning. Winds will remain below SCA from Monday morning through Thursday.
Surf will peak along south facing shores today and tomorrow, with surf heights near advisory levels. Long period south swell energy will also bump up surf heights along most west facing shores due to wrap around effects. The current south swell will begin to decline by Monday afternoon and then gradually lower through the middle of next week. Only background south swells are expected through Friday.
Short period choppy surf will hold steady today along east facing shores, then lower slightly through much of next week as the trades weaken. Surf along north facing shores will remain just above summertime flat levels today. A new northwest swell is forecast to move into the Hawaii region on Monday, producing a slight boost to north shore surf heights.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM 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