Hilo

Today: Partly sunny with scattered showers. Highs 77 to 84 near the shore to 63 to 70 at 4000 feet. Light winds becoming east up to 10 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 63 to 72 near the shore to 54 to 59 at 4000 feet. Light winds. Chance of rain 50 percent.

Monday: Partly sunny with scattered showers. Highs 77 to 84 near the shore to 64 to 70 at 4000 feet. Light winds becoming east around 10 mph in the afternoon. Chance of rain 50 percent.

Kona

Today: Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 84 near the shore to around 67 near 5000 feet. Light winds. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening. Lows around 72 near the shore to 51 to 56 near 5000 feet. Light winds. Chance of rain 20 percent.

Monday: Sunny in the morning, then mostly cloudy with isolated showers in the afternoon. Highs 82 to 87 near the shore to around 67 near 5000 feet. Light winds. Chance of rain 20 percent.

Waimea

Today: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 63 to 84. East winds around 10 mph. Chance of rain 50 percent.

Tonight: Mostly clear with isolated showers. Lows 63 to 70 near the shore to 56 to 62 near 3000 feet. Light winds. Chance of rain 20 percent.

Monday: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 64 to 85. Light winds. Chance of rain 20 percent.

Kohala

Today: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 63 to 84. East winds around 10 mph. Chance of rain 50 percent.

Tonight: Mostly clear with isolated showers. Lows 63 to 70 near the shore to 56 to 62 near 3000 feet. Light winds. Chance of rain 20 percent.

Monday: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 64 to 85. Light winds. Chance of rain 20 percent.

South Big Island

Today: Mostly sunny. Isolated showers in the afternoon. Highs around 83 near the shore to around 65 near 5000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Isolated showers in the evening. Lows around 73 near the shore to around 53 near 5000 feet. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Monday: Mostly sunny. Isolated showers in the afternoon. Highs around 83 near the shore to around 65 near 5000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Puna

Today: Partly sunny with scattered showers. Highs 77 to 84 near the shore to 63 to 70 at 4000 feet. Light winds becoming east up to 10 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 63 to 72 near the shore to 54 to 59 at 4000 feet. Light winds. Chance of rain 50 percent.

Monday: Partly sunny with scattered showers. Highs 77 to 84 near the shore to 64 to 70 at 4000 feet. Light winds becoming east around 10 mph in the afternoon. Chance of rain 50 percent.

Waikoloa

Today: Mostly sunny. Isolated showers in the afternoon. Highs 83 to 89 near the shore to 66 to 71 above 4000 feet. Light winds. Chance of rain 20 percent.

Tonight: Mostly clear. Isolated showers in the evening. Lows 70 to 75 near the shore to 50 to 56 above 4000 feet. Light winds. Chance of rain 20 percent.

Monday: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 83 to 89 near the shore to 66 to 72 above 4000 feet. Light winds becoming northwest up to 10 mph in the afternoon. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A surface trough east of the Big Island is causing the trades to weaken through today. Further weakening of the trades is on tap Monday through Tuesday while a surface trough passes north of the islands. The weakness of the trades will lead to a daytime sea breeze, bringing a few more clouds and showers the interior and lee areas in the afternoons. Breezy trade winds return to the islands during the second half of the week. Some tropical moisture may graze the Big Island and Maui Wednesday through Thursday.

Discussion

A gradual trending down of the trade winds from light to moderate will continue into Monday, where once it is done, a background light easterly wind flow will prevail through Tuesday. This is brought upon by a surface trough that is currently east of the Big Island. This trough, although it will pass north of the islands between Monday and late Tuesday night, will be sufficient in weakening the trades further. A light to moderate east-southeast wind flow follows immediately east of the trough that will linger over the area through Wednesday morning before easing to easterly trades Wednesday afternoon. Trades will strengthen to locally strong Wednesday night.
The light winds over land will favor an onshore sea breeze during the day, and a offshore land breeze at night. The onshore sea breeze will lead to some afternoon clouds and showers over the lee and interior areas of all islands. At night, the land breeze will clear most of the day time, heat driven clouds and showers, to off the island or to near the shoreline. In the mean time, a background light easterly flow will be bringing in a few loose showers into the windward areas.
The models are suggesting in a surface trough originating in the ITCZ southeast of the Big Island, scraping the Big Island and possibly Maui Wednesday afternoon and Wednesday night with an uptick in trade showers. Models, thus far, keep the brunt of the tropical moisture south of the remaining islands, although dense mid and high layered clouds will mask these islands. This tropical moisture is slated to clear Kauai Thursday morning.
A 1029 mb surface high north of the islands, will be generating moderate to strong breezy trades through the second half of the week.
Current weather radar is showing widely dispersed showers laced across the windward waters. These showers are favoring the windward and mountain areas of all islands exposed to this flow. There are some large patches of low clouds further upwind of Maui, but sufficient daytime mixing will burn off these patches before reaching these islands.

Aviation

Moderate trade winds will persist through the remainder of this morning, then weaken slightly by afternoon. Thus, expect scattered showers to mainly be confined to windward locations. Weak instability aloft will allow for some heavier showers with brief periods of MVFR ceilings and visibility. Otherwise, mainly VFR conditions will prevail elsewhere.
No AIRMETs are currently in effect.

Marine

A high pressure ridge far north of the state will interact with a surface trough northeast of the area. This trough will produce light background easterly trade winds across the region. Local scale land and sea breezes will develop into Tuesday near the islands. Moderate to breezy trades will likely return from late Wednesday into Thursday as the trough passes to the west and high pressure builds into the region.
A small south swell will likely peak later today then lower slowly into Tuesday. A series of small south and southeast swells will continue to keep south shore surf above flat levels through the end of the week.
Surf will continue to diminish along east facing shores with nearly flat conditions expected by Monday night. Surf along east facing shores will gradually increase later this week as trade winds strengthen. No other significant swells are expected.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov