Photo Credit: James Grenz

Hilo

Today: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs around 86 near the shore to 71 to 76 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 69 near the shore to around 55 at 4000 feet. Northeast winds up to 10 mph in the evening becoming light. Chance of rain 50 percent.

Sunday: Partly sunny with scattered showers. Highs around 86 near the shore to 71 to 76 at 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Kona

Today: Sunny in the morning, then mostly cloudy with showers likely in the afternoon. Highs 84 to 89 near the shore to around 71 near 5000 feet. Light winds. Chance of rain 70 percent.

Tonight: Mostly cloudy with showers likely early in the evening, then partly cloudy with isolated showers in the late evening and overnight. Lows 70 to 75 near the shore to around 56 near 5000 feet. Light winds. Chance of rain 70 percent.

Sunday: Mostly sunny with isolated showers in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 84 to 89 near the shore to around 71 near 5000 feet. Light winds. Chance of rain 50 percent.

Waimea

Today: Partly sunny with scattered showers. Highs around 84 near the shore to 71 to 81 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers early in the evening, then partly cloudy with isolated showers in the late evening and overnight. Lows around 69 near the shore to 57 to 63 near 3000 feet. East winds 10 to 15 mph decreasing to up to 10 mph after midnight. Chance of rain 50 percent.

Sunday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs around 84 near the shore to 71 to 81 near 3000 feet. East winds up to 15 mph. Chance of rain 40 percent.

Kohala

Today: Partly sunny with scattered showers. Highs around 84 near the shore to 71 to 81 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers early in the evening, then partly cloudy with isolated showers in the late evening and overnight. Lows around 69 near the shore to 57 to 63 near 3000 feet. East winds 10 to 15 mph decreasing to up to 10 mph after midnight. Chance of rain 50 percent.

Sunday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs around 84 near the shore to 71 to 81 near 3000 feet. East winds up to 15 mph. Chance of rain 40 percent.

South Big Island

Today: Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs around 88 near the shore to around 75 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows around 71 near the shore to around 54 near 5000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Sunday: Breezy. Mostly sunny with isolated showers in the morning, then mostly cloudy with scattered showers in the afternoon. Highs around 88 near the shore to around 75 near 5000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Puna

Today: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs around 86 near the shore to 71 to 76 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 69 near the shore to around 55 at 4000 feet. Northeast winds up to 10 mph in the evening becoming light. Chance of rain 50 percent.

Sunday: Partly sunny with scattered showers. Highs around 86 near the shore to 71 to 76 at 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Waikoloa

Today: Sunny in the morning, then partly sunny with showers likely in the afternoon. Highs around 88 near the shore to 72 to 78 above 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

Tonight: Partly cloudy. Showers likely early in the evening. Lows around 73 near the shore to 52 to 59 above 4000 feet. East winds up to 10 mph. Chance of rain 70 percent.

Sunday: Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs around 88 near the shore to 72 to 78 above 4000 feet. North winds up to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Trade winds will be on the lighter side through the weekend, then increase slightly early next week. Showers will favor windward and mauka areas during the night and early morning hours this weekend. The light winds will also allow clouds and showers to develop over leeward areas each afternoon, with some brief downpours possible, and even a thunderstorm not out of the question over Kauai this afternoon. A return to a more typical trade wind pattern is expected Monday through much of next week, with showers favoring windward and mauka areas and a few showers reaching leeward areas from time to time.

Discussion

Currently at the surface, a front is positioned around 1100 miles north of Kauai, with a weak ridge axis located around 200 miles south of the front. Meanwhile, a 1008 mb low is embedded within the monsoon trough around 700 miles south of the Garden Isle. The resulting gradient is producing light to moderate trade winds across the island chain early this morning. Infrared satellite imagery shows mostly cloudy skies over most of Kauai and Oahu, with clear to partly cloudy conditions over most of Maui County and the Big Island. Radar imagery shows scattered showers moving into windward areas, with a few brief showers reaching leeward locales. Main short term focus during the next few days revolves around rain chances and trade wind trends.
The front north of the islands will shift slowly southward during the next few days, while the monsoon trough and embedded low to the south of the state shift slowly northward. The gradient across the islands will remain weak through the weekend, with light to moderate trades prevailing along with localized land and sea breezes in the more sheltered leeward areas. The ridge north of the islands will strengthen early next week, while the monsoon trough and perhaps an embedded low lift northward toward the state. This should strengthen the trades back to moderate levels Monday through late next week, with only minor fluctuations in strength from day to day.
As for the remaining weather details, very little change in the overall forecast is expected through the weekend. Showers will favor windward slopes and coasts overnight and during the early morning hours, with a few showers reaching leeward communities at times. During the afternoon and evening hours, showers are expected to favor the island interiors and leeward areas, although a few showers will continue to push onshore into windward areas. A few of these leeward and interior showers could produce brief downpours each afternoon through the weekend. Additionally, there appears to be enough instability around Kauai, that a thunderstorm or two is not out of the question this afternoon.
Troughing aloft will remain near the western islands through much of next week, keeping inversion heights elevated across the state. Meanwhile, precipitable water values will remain near to slightly above normal levels. Model guidance is offering differing solutions on the northward surge of some deep tropical moisture into the state in the Tuesday through Thursday time frame, with the 00Z ECMWF keeping it south of the islands and the 00Z GFS allowing it to sneak northward into the area. Given the differences in the model guidance and latest trends from the 06Z GFS, will lean the forecast in favor of a more typical trade wind pattern, with showers favoring windward and mauka areas and a few showers reaching leeward areas from time to time.

Aviation

Light to moderate trade winds along with an area of enhanced moisture and an upper trough in the area will support showery conditions continuing over some windward and mauka locations. Expect some showers to impact our dry leeward and interior locations periodically, especially through the afternoon hours where localized sea breezes form.
AIRMET Sierra for mountain tempo obscuration remains in effect for Kauai, and may need to be expanded to other locations through the morning hours where clouds and showers become focused.

Marine

With weak high pressure persisting far north of the islands, trade winds will be light to moderate through the weekend. Winds will strengthen modestly by next week, becoming moderate to fresh.
The incoming south-southwest swell will increase surf along south-facing shores, peaking near the High Surf Advisory height of 10 feet by late Sunday into Monday, then slowly fading through midweek. A medium-period southeast swell arriving Monday will be added to the mix and will hang on through Wednesday. Surf along east-facing shores will ease into the weekend as trades back off, but may come up to some extent Sunday if a medium period easterly swell from former East Pacific Hurricane Kay reaches our shores. Choppy wind-wave surf along east shores will pick up next week in response to strengthening trades.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov