Hilo

Today: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs 78 to 84 near the shore to around 69 at 4000 feet. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 70 percent.

Tonight: Mostly cloudy with showers likely. Lows around 69 near the shore to around 55 at 4000 feet. North winds up to 15 mph. Chance of rain 70 percent.

Friday: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs 77 to 83 near the shore to around 68 at 4000 feet. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 70 percent.

Kona

Today: Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs around 85 near the shore to around 72 near 5000 feet. West winds up to 10 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then mostly clear after midnight. Lows 70 to 75 near the shore to around 55 near 5000 feet. Light winds. Chance of rain 40 percent.

Friday: Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 82 to 87 near the shore to 68 to 74 near 5000 feet. Light winds. Chance of rain 40 percent.

Waimea

Today: Breezy. Partly sunny with scattered showers. Highs around 80 near the shore to 71 to 78 near 3000 feet. East winds 10 to 25 mph with gusts to 45 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then showers likely after midnight. Lows around 68 near the shore to 55 to 64 near 3000 feet. East winds 10 to 25 mph with gusts to 45 mph. Chance of rain 70 percent.

Friday: Breezy. Partly sunny with scattered showers. Highs around 79 near the shore to 70 to 78 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Kohala

Today: Breezy. Partly sunny with scattered showers. Highs around 80 near the shore to 71 to 78 near 3000 feet. East winds 10 to 25 mph with gusts to 45 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then showers likely after midnight. Lows around 68 near the shore to 55 to 64 near 3000 feet. East winds 10 to 25 mph with gusts to 45 mph. Chance of rain 70 percent.

Friday: Breezy. Partly sunny with scattered showers. Highs around 79 near the shore to 70 to 78 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

South Big Island

Today: Windy. Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 83 near the shore to around 72 near 5000 feet. East winds up to 25 mph increasing to 15 to 30 mph in the afternoon. Chance of rain 20 percent.

Tonight: Windy. Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Lows around 70 near the shore to around 54 near 5000 feet. Northeast winds 10 to 30 mph. Chance of rain 20 percent.

Friday: Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs around 82 near the shore to around 71 near 5000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 30 percent.

Puna

Today: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs 78 to 84 near the shore to around 69 at 4000 feet. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 70 percent.

Tonight: Mostly cloudy with showers likely. Lows around 69 near the shore to around 55 at 4000 feet. North winds up to 15 mph. Chance of rain 70 percent.

Friday: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs 77 to 83 near the shore to around 68 at 4000 feet. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 70 percent.

Waikoloa

Today: Mostly sunny. Windy. Isolated showers in the afternoon. Highs 81 to 87 near the shore to 69 to 75 above 4000 feet. Northeast winds up to 30 mph. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows around 73 near the shore to 51 to 59 above 4000 feet. Southeast winds up to 25 mph with gusts to 45 mph. Chance of rain 20 percent.

Friday: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs 80 to 87 near the shore to 67 to 75 above 4000 feet. Northeast winds up to 20 mph shifting to the north up to 10 mph in the afternoon. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Breezy trade winds are expected to continue through this evening, followed by moderate trade wind speeds starting Friday. Low clouds and trade showers will remain focused over windward facing sections. The upslope sections of the leeward Big Island will have low clouds and a few showers each afternoon. Additional weakening of the trade winds may occur early next week.

Discussion

The tight pressure gradient south of a 1030 mb surface high pressure system centered near 34N 152W, or nearly 950 miles north-northeast of Honolulu, is maintaining breezy trade winds across the island chain early this morning. Aloft, an upper-level ridge is providing relatively stable atmospheric conditions across the region. Satellite imagery and radar reflectivity data indicate scattered to locally broken low clouds and isolated showers are being transported by the low-level trade wind flow into the windward sides of most islands. A few brief showers may also be carried by the gusty trade winds over to some leeward sections of the smaller islands through mid-morning.
The forecast guidance indicates the surface high will begin to weaken by this evening as it shifts toward the south-southwest. This will likely result in a slight decrease in trade wind speeds by late tonight. The relatively stable atmospheric conditions are also forecast to persist, so expect a rather typical trade wind weather pattern to continue. Low clouds and modest showers will occur mainly over windward and mauka areas, while most leeward areas from Maui to Kauai will remain rather dry during the daytime hours. The upslope sections of the leeward Big Island will have low clouds and a few showers during the afternoon.
Aloft, an upper-level trough is forecast to begin moving down toward the region from the north. At the same time, a weak surface front pushing down from the north will continue to cause the surface high to weaken Friday. This will result in additional relaxation of the pressure gradient across the island chain, which will likely produce moderate trade wind speeds starting Friday. The western end of the east-northeast to west-southwest oriented upper-level trough may move down to the vicinity of the western end of the island chain by this weekend. This will likely erode the low-level trade wind inversion, and possibly allow windward showers to be slightly heavier in some locations. However, no widespread heavy rainfall is expected at this time.
Early next week, the GFS and ECMWF forecast models remain in relatively good agreement that there will be additional weakening of the surface high pressure system to the north. This will likely mean a slight decrease in trade winds speeds. We expect little change in the trade wind weather pattern early next week.

Aviation

High pressure to the north continues to bring breezy to locally windy trade winds to the region. This is producing some mechanical turbulence to the lee of the mountains, and AIRMET Tango remains in place for this. Expect this to remain in place into tonight even as winds start to trend downward later today.
Clouds and showers being carried in on the trade wind flow are focused over the windward sides of the islands, and will bring some brief MVFR conditions. No mountain obscuration AIRMETs are currently in effect, but remain a possibility for an area of clouds and showers that are upstream of the islands early this morning. Anticipating this area to break up some with daylight, but if it holds together, an AIRMET may be warranted.

Marine

High pressure northeast of the islands will continue to support regional fresh to locally strong trade winds. The Small Craft Advisory is now in effect from the Oahu coastal waters eastward with an expected further eastern paring to just cover the typically windier areas around Maui County and south of Big Island tonight and Friday. High pressure to the northeast will transition east as another high from the west settles in north of the state this weekend. A front passing across the far North Pacific early next week will disrupt this high enough to weaken the regional pressure gradient. This will ultimately lower trades back to more gentle to moderate speeds by Monday.
Fresh trades will maintain elevated eastern shore surf. Trades will gradually weaken beginning Friday into the weekend that will allow this recent higher east wind wave surf to finally subside this weekend into early next week. A small, medium period northwest swell is expected to fill in tonight and peak late Friday into Saturday. This short-lived swell will provide a minor foot or two bump to north and west facing shore surf Friday and Saturday. A much larger north swell emanating from a North Pacific cold front is forecast to reach northern shores in about a week. This late week swell may produce advisory level surf along northern facing shores. Small, medium period south swell continues to fall, as will southern shore surf, through Friday. A series of gales passing around New Zealand the next day or two may push a small, long period south swell toward the islands that would reach us by Tuesday of next week. This will bring near flat early week south surf back up to waist to chest high by next Wednesday.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Friday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.
Small Craft Advisory until 6 PM HST this evening for Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Big Island Windward Waters.

Big Island Now Weather is brought to you by Blue Hawaiian Helicopters.

Check out their Big Island Helicopter Tours today!

Data Courtesy of NOAA.gov