Hilo

Today: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 81 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 40 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 62 to 67 near the shore to around 51 at 4000 feet. Northwest winds up to 15 mph. Chance of rain 40 percent.

Thursday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 80 near the shore to around 67 at 4000 feet. East winds up to 10 mph. Chance of rain 30 percent.

Kona

Today: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 80 to 85 near the shore to around 66 near 5000 feet. West winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Lows 68 to 73 near the shore to around 53 near 5000 feet. Northeast winds up to 10 mph. Chance of rain 20 percent.

Thursday: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 81 to 86 near the shore to around 66 near 5000 feet. Light winds. Chance of rain 20 percent.

Waimea

Today: Breezy. Mostly sunny with isolated showers. Highs around 80 near the shore to 65 to 75 near 3000 feet. East winds 10 to 25 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Windy. Isolated showers in the evening, then scattered showers after midnight. Lows around 64 near the shore to 52 to 59 near 3000 feet. East winds 10 to 30 mph decreasing to 10 to 15 mph after midnight. Chance of rain 40 percent.

Thursday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 79 near the shore to 64 to 74 near 3000 feet. East winds 10 to 20 mph. Chance of rain 40 percent.

Kohala

Today: Breezy. Mostly sunny with isolated showers. Highs around 80 near the shore to 65 to 75 near 3000 feet. East winds 10 to 25 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Windy. Isolated showers in the evening, then scattered showers after midnight. Lows around 64 near the shore to 52 to 59 near 3000 feet. East winds 10 to 30 mph decreasing to 10 to 15 mph after midnight. Chance of rain 40 percent.

Thursday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 79 near the shore to 64 to 74 near 3000 feet. East winds 10 to 20 mph. Chance of rain 40 percent.

South Big Island

Today: Breezy. Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 83 near the shore to around 69 near 5000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Lows around 69 near the shore to around 54 near 5000 feet. Northeast winds 10 to 20 mph decreasing to up to 20 mph after midnight.

Thursday: Mostly sunny. Breezy. Highs around 84 near the shore to around 70 near 5000 feet. East winds up to 20 mph becoming 10 to 15 mph in the afternoon.

Puna

Today: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 81 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 40 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 62 to 67 near the shore to around 51 at 4000 feet. Northwest winds up to 15 mph. Chance of rain 40 percent.

Thursday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 80 near the shore to around 67 at 4000 feet. East winds up to 10 mph. Chance of rain 30 percent.

Waikoloa

Today: Sunny. Isolated showers in the afternoon. Highs around 84 near the shore to 66 to 72 above 4000 feet. North winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Lows 67 to 72 near the shore to 49 to 58 above 4000 feet. Southeast winds up to 15 mph.

Thursday: Sunny and breezy. Highs around 85 near the shore to 66 to 73 above 4000 feet. North winds up to 20 mph in the morning becoming light.

Detailed Forecast

Synopsis

Moderate to locally breezy trade winds are expected through Thursday. Conditions will be rather dry, with brief trade showers mainly along some windward facing sections late at night and during the early morning hours. The background trade flow will begin to weaken and shift around from the east-southeast this weekend. This will allow local afternoon sea breezes to develop with clouds and isolated showers mainly over leeward and interior sections.

Discussion

A 1021 mb surface high pressure system is near 32N 163W, or about 780 miles north-northwest of Honolulu. This feature is moving toward the east at 10 to 15 mph, so it will be due north of the islands in about 24 hours. This is causing the pressure gradient to tighten over the state, so moderate to locally breezy easterly trade winds are expected during the next 36 hours or so.
The atmosphere over the islands remains dry and stable. Loops of infrared satellite imagery show patches of stable low clouds upwind of Maui and the Big Island. There are also scattered to locally broken low clouds along some windward sections of the Big Island, and scattered low clouds over portions of windward Oahu and Kauai. Radar reflectivity data indicate there are a few light showers embedded within some of the low clouds. Overall, tranquil weather conditions appear to be the rule across the Aloha State early this morning.
The forecast guidance shows the surface high will eventually move far northeast of the state from late Thursday night through Friday. This will cause the trade winds to begin to weaken slightly. The stable and dry atmospheric conditions will also remain in place, so there will be some low clouds and brief trade showers along windward sections. The trade showers will tend to be most prevalent during the late night and early morning hours. The upslope sections of the leeward Big Island will continue to have clouds and a few showers during the afternoon and early evening hours.
As we head into the weekend, a surface front will move toward the region from the northwest. This will likely cause additional weakening of the background flow, with light and variable winds over the western half of the state, and light to locally moderate east to east-southeast winds over the eastern half of the state by Sunday. In addition, a weak mid-level trough may develop in the vicinity of the islands, while a mid- and upper-level trough will dig down toward the region from the northwest. The main influence we currently anticipate with the troughing aloft will be to increase the high clouds over portions of the state as a sub- tropical jet sets up. The lighter background winds will also allow the establishment of a pattern of afternoon sea breezes and nighttime land breezes. This may produce some clouds and isolated showers over leeward and interior sections during the afternoon and early evening hours. The overall rainfall amounts should remain modest, since there does not appear to be any significant increase in moisture.

Aviation

Dry and stable trade wind pattern will result in VFR conditions prevailing through much of the 24-hour period. Brief periods with MVFR conditions can't be ruled out in and around passing showers this morning.
There are currently no AIRMETs.

Marine

he subtropical ridge will remain in place north of the islands into the weekend, producing gentle to moderate easterly trade winds for most areas through Saturday. Wind speeds today will exceed Small Craft Advisory (SCA) criteria for the windier eastern waters and channels through Thursday morning and an SCA was issued for these areas. A cold front approaching the region from the northwest on Sunday will weaken the ridge north of the islands, causing the trade winds to weaken over the western islands. Moderate to locally breezy easterly trade winds return on early next week with wind speeds over the eastern windier areas approaching SCA thresholds.
Surf heights along south facing shores will remain on the small side today. However, two rather large south swells generated over the waters just east of New Zealand are on the way to the Hawaiian Islands. The forerunners of the first large south swell will arrive on Thursday, increasing surf heights as the swell builds along south facing shores of all islands to low end High Surf Advisory (HSA) levels from Friday through Saturday. This swell energy begins to slowly decline from Saturday night to Sunday, before the forerunners of the next swell begins to hit south facing shores by Sunday night. This next large south swell will quickly build south shore surf heights to HSA levels by Monday and then peak near High Surf Warning levels on Tuesday.
Surf along north and west facing shores will get a small, short- period bump through Thursday, with declining surf heights on Friday. Another medium period west-northwest swell (300 degrees) arrives on Saturday producing a small increase in north and west shore surf heights into the weekend, before declining into the first half of next week. Surf heights along east facing shores will remain small and choppy through the week.

HFO Watches/Warnings/Advisories

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

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Data Courtesy of NOAA.gov