Hilo

Today: Partly sunny with scattered showers. Highs around 85 near the shore to 70 to 75 at 4000 feet. North winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with numerous showers. Lows around 70 near the shore to around 56 at 4000 feet. North winds up to 15 mph. Chance of rain 70 percent.

Tuesday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 85 near the shore to 70 to 75 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

Kona

Today: Mostly sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 83 to 88 near the shore to around 70 near 5000 feet. Light winds. Chance of rain 40 percent.

Tonight: Mostly cloudy in the evening then becoming mostly clear. Isolated showers. Lows around 73 near the shore to around 57 near 5000 feet. Light winds. Chance of rain 20 percent.

Tuesday: Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 83 to 88 near the shore to around 70 near 5000 feet. Light winds. Chance of rain 40 percent.

Waimea

Today: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs around 83 near the shore to 70 to 80 near 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows around 70 near the shore to 58 to 64 near 3000 feet. East winds 10 to 15 mph decreasing to up to 15 mph after midnight. Chance of rain 50 percent.

Tuesday: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs around 83 near the shore to 70 to 80 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Kohala

Today: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs around 83 near the shore to 70 to 80 near 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows around 70 near the shore to 58 to 64 near 3000 feet. East winds 10 to 15 mph decreasing to up to 15 mph after midnight. Chance of rain 50 percent.

Tuesday: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs around 83 near the shore to 70 to 80 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

South Big Island

Today: Sunny in the morning, then mostly cloudy with isolated showers in the afternoon. Highs around 87 near the shore to around 74 near 5000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Breezy. Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Lows around 72 near the shore to around 55 near 5000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.

Tuesday: Breezy. Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 87 near the shore to around 74 near 5000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Puna

Today: Partly sunny with scattered showers. Highs around 85 near the shore to 70 to 75 at 4000 feet. North winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with numerous showers. Lows around 70 near the shore to around 56 at 4000 feet. North winds up to 15 mph. Chance of rain 70 percent.

Tuesday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 85 near the shore to 70 to 75 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

Waikoloa

Today: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 87 near the shore to 71 to 77 above 4000 feet. North winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening. Lows around 74 near the shore to 53 to 60 above 4000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Tuesday: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 87 near the shore to 71 to 77 above 4000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Moderate trades will continue across the islands today as a ridge of high pressure remains anchored to the northwest of the state. Trades will become breezy Tuesday through Thursday as high pressure builds to the distant north and Tropical Storm Greg passes by to the south. The trades will ease into the light to moderate range Friday through the weekend. Rather dry trade wind weather will prevail through the forecast period. Shower activity will remain confined primarily to windward slopes and coasts, with a few showers reaching leeward communities at times.

Discussion

Currently at the surface, a 1024 mb high is centered around 850 miles northwest of Kauai, while a weak trough is positioned around 300 miles north of Honolulu. Meanwhile, Tropical Storm Greg is located around 1100 miles east-southeast of the Big Island. The gradient locally continues to drive moderate trade winds across the island chain early this morning. Infrared satellite imagery shows partly to mostly cloudy conditions in windward and mauka areas, with mostly clear to partly cloudy skies in leeward locales. Radar imagery shows scattered showers moving into windward slopes and coasts, with a few showers spilling into leeward communities at times. Main forecast focus revolves around rain chances and trade wind trends during the next few days.
The overall weather pattern will change little today, with a weak high remaining northwest of the state and a weak trough holding in place to the north. This should keep trades at moderate strength. The trades are expected to strengthen to breezy levels Tuesday through Thursday as the pressure gradient tightens in response to a strengthening high north of the state and a Tropical Storm Greg passing westward well to the south of the island chain. This scenario continues to appear significantly different than what was experienced during Dora. The winds are expected to be much weaker as high pressure will be displaced much farther north, inversion heights not nearly as low, and the tropical cyclone not nearly as strong as Dora. The trades are forecast to ease back into the light to moderate range Friday through the weekend as the pressure gradient relaxes once again.
Rather dry trade wind weather will prevail through much of the next seven days. Shower activity will remain confined primarily to windward slopes and coasts during the late night and early morning hours, with a shower or two reaching leeward communities at times. A slight increase in shower coverage is expected tonight and Tuesday, particularly over windward portions of Maui and the Big Island as a band of moisture moves through. Another round of moisture associated with the remnants of Fernanda could increase trade wind showers late Sunday into early next week.

Aviation

Moderate to locally breezy easterly trade winds will continue through the 24-hr period, with clouds and a showers favoring windward and mauka locations, particularly at night and during the early morning hours. VFR conditions will prevail, with only brief periods of MVFR CIGS/VSBYS possible as showers pass through.
No AIRMETs are expected through the day.

Marine

A high pressure ridge north of the Hawaii region will keep moderate to fresh trade winds in the forecast for most areas today, with locally strong trades in the windier coastal waters and channels near Maui and the Big Island. The ridge will build far north of the region and produce moderate to strong trade winds from Tuesday through Thursday as tropical cyclone Greg passes well south of the island chain. Trades will trend lower from Friday into the weekend. A Small Craft Advisory was issued this morning for the windier waters and channels around Maui and the Big Island.
A lingering south-southwest swell will trend lower during the first half of the week. Small background south swell energy will keep surf heights small along south facing shores through the weekend. A small medium period north-northwest swell has reached buoy 51001 last night, the PACIOOS buoy at Hanalei, Kauai this morning, and is beginning to build at the Waimea buoy as of 3 AM HST. Surf heights along north facing shores will build today with some of this swell energy wrapping around into exposed west facing beaches of Kauai and Oahu. Surf heights along east facing shores will small and choppy due to increasing trade wind driven waves.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov