Photo Credit: James Grenz

Hilo

Today: Mostly sunny with isolated showers. Highs around 84 near the shore to around 71 at 4000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 64 to 69 near the shore to around 53 at 4000 feet. East winds up to 10 mph shifting to the northwest after midnight. Chance of rain 40 percent.

Tuesday: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 84 near the shore to around 72 at 4000 feet. East winds up to 10 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 40 percent.

Kona

Today: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 79 to 85 near the shore to around 67 near 5000 feet. West winds up to 10 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy in the evening then becoming mostly clear. Isolated showers. Lows 67 to 74 near the shore to around 54 near 5000 feet. Light winds. Chance of rain 20 percent.

Tuesday: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 79 to 86 near the shore to 65 to 70 near 5000 feet. Light winds becoming northwest up to 15 mph in the afternoon. Chance of rain 20 percent.

Waimea

Today: Mostly sunny with scattered showers. Highs around 82 near the shore to 68 to 78 near 3000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 40 percent.

Tonight: Breezy. Partly cloudy with scattered showers. Lows around 66 near the shore to 51 to 61 near 3000 feet. East winds 10 to 20 mph. Chance of rain 40 percent.

Tuesday: Breezy. Mostly sunny with scattered showers. Highs around 82 near the shore to 69 to 79 near 3000 feet. East winds 10 to 20 mph. Chance of rain 40 percent.

Kohala

Today: Mostly sunny with scattered showers. Highs around 82 near the shore to 68 to 78 near 3000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 40 percent.

Tonight: Breezy. Partly cloudy with scattered showers. Lows around 66 near the shore to 51 to 61 near 3000 feet. East winds 10 to 20 mph. Chance of rain 40 percent.

Tuesday: Breezy. Mostly sunny with scattered showers. Highs around 82 near the shore to 69 to 79 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 84 near the shore to around 68 near 5000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Lows around 69 near the shore to around 52 near 5000 feet. Northeast winds 10 to 20 mph.

Tuesday: Breezy. Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 84 near the shore to around 68 near 5000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 20 percent.

Puna

Today: Mostly sunny with isolated showers. Highs around 84 near the shore to around 71 at 4000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 64 to 69 near the shore to around 53 at 4000 feet. East winds up to 10 mph shifting to the northwest after midnight. Chance of rain 40 percent.

Tuesday: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 84 near the shore to around 72 at 4000 feet. East winds up to 10 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 40 percent.

Waikoloa

Today: Mostly sunny. Isolated showers in the afternoon. Highs around 84 near the shore to 65 to 74 above 4000 feet. North winds up to 10 mph shifting to the northwest in the afternoon. Chance of rain 20 percent.

Tonight: Mostly clear. Lows 68 to 73 near the shore to 49 to 58 above 4000 feet. Southeast winds up to 15 mph.

Tuesday: Mostly sunny. Highs around 85 near the shore to 65 to 75 above 4000 feet. Northeast winds up to 10 mph shifting to the northwest around 10 mph in the afternoon. Gusts up to 30 mph.

Detailed Forecast

Synopsis

A surface ridge will lift north of the area later today and tonight, which will cause the trade winds to gradually strengthen. The trades are expected to become locally breezy from Tuesday through mid-week. The atmosphere will also become stable and dry this week, so expect some low clouds and brief showers over windward and mauka areas, mainly late at night and during the early morning hours. The trade winds may weaken slightly heading into next weekend.

Discussion

The western end of a weak east-northeast to west-southwest oriented surface ridge is about 260 miles north of Lihue. Elsewhere, a nearly stationary front is about 450 miles north- northwest of Lihue. The close proximity of these features to the islands continues to disrupt the pressure gradient across the region. This is keeping the background flow weak, which has resulted in local land breezes over most of the individual islands. The winds will likely remain weak enough to allow local afternoon sea breezes to develop over the leeward sections of some islands again this afternoon, especially on Kauai and Oahu.
Loops of water vapor satellite imagery show a weak mid-level trough just west of Kauai, while a broad mid-level ridge is located just east of the Big Island. The upper-level south to southwest flow along the eastern flank of the trough aloft continues to transport some thin cirrus clouds over parts of the state between Oahu and the Big Island, but these are decreasing in coverage and thickness this morning. The mid-level trough will move southwest as the mid-level ridge noses across the area from the east during the next couple of days. Radar reflectivity data indicate isolated showers are over portions of the coastal waters, especially southeast and west of the Big Island early this morning. Otherwise, dry conditions prevail over most areas.
The stalled front described above is beginning to weaken, so the surface ridge will eventually be able to lift north later today and tonight. At the same time, a new surface high will migrate down toward the region from the north-northwest on Tuesday. This will tighten the pressure gradient across the area, which will cause the trade winds to gradually strengthen from later today and tonight through Tuesday, with moderate to locally breezy trade winds expected through the mid-week. Once the mid-level ridge becomes established across the area this week, it will produce stable atmospheric conditions. There are no significant sources of low-level moisture, so expect low clouds and modest trade showers mainly over windward and mauka areas through mid- week. The greatest coverage of low clouds and showers will be late at night and during the early morning hours. Looking ahead, the trades may weaken slightly heading into next weekend.

Aviation

The overnight soundings from Lihue and Hilo show a trade wind inversion topping out around 7000 feet. Both soundings show an uptick in precipitable water. Winds remain light across the region with the high pressure ridge north of the state. The ridge is expected to lift northward later today, allowing trades to strengthen late today and tonight. Some localized sea breezes are still possible today, particularly over the western end of the state. Overall VFR conditions are expected to prevail, with pockets of MVFR in passing clouds and showers.
No AIRMETs are in effect early this morning. Depending on the extent of afternoon sea breezes today, we could see the need for an AIRMET for mountain obscuration. As the trades strengthen tonight, low level mechanical turbulence could prompt the issuance of an AIRMET.

Marine

A high pressure system building north of the state will increase trade winds a bit through the week. Sea breezes will linger over the terrain sheltered western slopes of each island in a hybrid trade wind pattern today. Trade winds will remain in the gentle to fresh range for most Hawaiian coastal waters into the weekend. Wind speeds will increase just above Small Craft Advisory thresholds on Tuesday over the windier waters and channels near Maui and the Big Island.
The next south swell will fill into the region later this afternoon and evening, likely exceeding High Surf Advisory levels from Tuesday morning through Wednesday afternoon with south swell heights peaking around 4 to 4.5 feet with an 18 to 20 second period. This south swell energy will slowly fade into near to below normal background summer season levels from Thursday through the upcoming weekend.
A medium period northwest swell will slowly decline through the week and flatten out by Thursday. A small, medium period north swell may fill in on Friday with a slight bump to surf heights along north facing shores. Surf heights along west and east facing shores will increase over the next three days as the incoming long period south swell energy wraps around each island. Surf heights for these shores will fade from Thursday onward as the south swell diminishes to background levels.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov