Photo Credit: James Grenz

Hilo

Today: Mostly cloudy with scattered showers. Highs 79 to 84 near the shore to around 71 at 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 64 to 69 near the shore to around 53 at 4000 feet. East winds 10 to 15 mph shifting to the west after midnight. Chance of rain 50 percent.

Friday: Mostly cloudy with scattered showers. Highs 78 to 84 near the shore to around 71 at 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Kona

Today: Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs around 84 near the shore to around 68 near 5000 feet. West winds 10 to 15 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 70 to 75 near the shore to around 54 near 5000 feet. Northeast winds up to 10 mph. Chance of rain 20 percent.

Friday: Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs around 83 near the shore to around 67 near 5000 feet. North winds around 10 mph shifting to the southeast in the afternoon. Chance of rain 40 percent.

Waimea

Today: Breezy. Mostly cloudy with scattered showers. Highs 77 to 82 near the shore to 68 to 78 near 3000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 66 near the shore to 51 to 62 near 3000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Friday: Breezy. Mostly cloudy with scattered showers. Highs 77 to 82 near the shore to 68 to 78 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Kohala

Today: Breezy. Mostly cloudy with scattered showers. Highs 77 to 82 near the shore to 68 to 78 near 3000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 66 near the shore to 51 to 62 near 3000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Friday: Breezy. Mostly cloudy with scattered showers. Highs 77 to 82 near the shore to 68 to 78 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

South Big Island

Today: Breezy. Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs around 83 near the shore to around 66 near 5000 feet. East winds 10 to 25 mph. Chance of rain 30 percent.

Tonight: Breezy. Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Lows around 70 near the shore to around 53 near 5000 feet. Northeast winds 10 to 25 mph. Chance of rain 20 percent.

Friday: Breezy. Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs around 84 near the shore to around 66 near 5000 feet. East winds 15 to 20 mph. Chance of rain 40 percent.

Puna

Today: Mostly cloudy with scattered showers. Highs 79 to 84 near the shore to around 71 at 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 64 to 69 near the shore to around 53 at 4000 feet. East winds 10 to 15 mph shifting to the west after midnight. Chance of rain 50 percent.

Friday: Mostly cloudy with scattered showers. Highs 78 to 84 near the shore to around 71 at 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Waikoloa

Today: Breezy. Mostly sunny with isolated showers. Highs around 85 near the shore to 67 to 75 above 4000 feet. Northwest winds 10 to 20 mph. Gusts up to 40 mph in the afternoon. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows around 72 near the shore to 49 to 58 above 4000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Friday: Sunny in the morning then becoming partly sunny. Isolated showers. Highs around 85 near the shore to 66 to 74 above 4000 feet. North winds around 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Moderate to locally breezy trade winds will continue to focus low clouds and showers over windward and mauka sections through this weekend. Brief trade showers may be transported over to the leeward sections of the smaller islands, especially during the late night and early morning hours. Clouds and isolated showers will also likely develop over some upslope sections of the leeward Big Island each afternoon.

Discussion

A broad 1032 mb surface high pressure system centered near 37N 152W, or about 1150 miles north-northeast of Honolulu, continues to dominate the local weather across the main Hawaiian Islands early this morning. The tight pressure gradient south of this feature is maintaining moderate to locally breezy trade winds in the vicinity of the island chain. Elsewhere, the diffuse leading edge of a band of scattered to broken low clouds with embedded scattered showers, which is some of the remnant moisture from a dissipated frontal boundary, is evident about 75 miles northeast of Hilo. This leading edge has been moving toward the west-southwest at about 15 mph. Loops of water vapor satellite imagery show an upper-level low centered near 24N 159W, or about 125 miles north-northeast of Lihue. This feature has been drifting slowly westward.
The upper-level low has weakened the trade wind inversion, especially across the eastern and central islands. At the same time, enhanced low-level moisture is being transported into the area by the relatively strong trade winds. As a result, scattered to broken low clouds with embedded scattered showers are evident in satellite imagery and radar reflectivity data just upstream of Maui and the Big Island. There are also scattered low clouds and isolated showers upstream of the islands from Molokai to Kauai.
The forecast guidance shows the surface high will shift slowly east-southeast to a position far northeast of the islands during the next few days. At the same time, the upper-level low will linger just north of the western islands. There may be a subtle weakening of the trade winds into tonight, but they will likely strengthen again from Friday through this weekend.
The close proximity of the upper-level low to the state will likely keep the trade wind inversion relatively weak. Therefore, the enhancement of the low clouds and trade showers will continue through early Friday morning. In addition, the leading edge of the area of clouds and showers will eventually reach the islands later this morning. Therefore, low clouds and showers will continue to favor windward and mauka sections. However, there may be brief showers over some leeward areas of the smaller islands, especially during the late night and early morning hours. In addition, clouds and spotty showers will also likely develop over upslope sections of the leeward Big Island each afternoon, and then continue into the early evening hours.
As the upper-level low departs the region this weekend, there may be a gradual increase in atmospheric stability over the state. The forecast models appear to show another area of increased moisture moving into the islands from late Friday into Saturday, so low clouds and showers may increase again over windward and mauka areas heading into the weekend. Expect a slight drying trend from Sunday into early next week, but some trade showers will likely continue along windward facing slopes, especially during the late night and early morning hours.

Aviation

Moderate to locally breezy trade winds will continue to push patches of stable and showery low clouds over the islands from the ENE, leading to periods of MVFR VIS/CIG, mainly over windward areas. AIRMET Sierra for mountain obscuration is currently posted for windward Kauai, but coverage immediately upstream of that island is diminishing, and it will likely be dropped soon. However, additional moisture is approaching the other islands from the E, likely leading to an change in the areas covered by AIRMET Sierra.
A nearby low aloft has led to some destabilization of the island atmosphere, thus some cloud tops are growing as high as 12 kft, leading to a few small heavy showers. Little change is expected into Friday. AIRMET Tango for low-level turbulence downwind of the terrain is posted for Maui County and the Big Island, and may need to be expanded to the entire island chain as trade winds remain on the locally strong side.

Marine

A ridge north of the islands is expected to remain in place over the next several days, maintaining moderate to locally strong trade wind pattern over the coastal waters. The Small Craft Advisory posted for the typical windier waters near Maui County and the Big Island has been extended through 6 AM HST Saturday, and may be further extended through the weekend.
Locally generated wind waves from the trades will continue to bring rough, choppy surf to east facing shores through early next week. A small northwest swell will slowly build today, peak tomorrow, then slowly subside into the weekend. Another slightly larger northwest swell will fill in late Saturday and Sunday, then slowly subside into early next week. Background southerly swells will continue into tomorrow. A series of slightly larger and longer period southerly swells will boost surf heights along south facing shores beginning as early as Saturday, and persisting through mid-week next week.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Saturday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast 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