Photo Credit: Tyler Rooke

West Side

Rest Of Today: Mostly sunny with isolated showers. Highs 81 to 88. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 65 to 72. East winds 10 to 15 mph decreasing to up to 10 mph after midnight. Chance of rain 50 percent.

Labor Day: Mostly sunny with isolated showers. Highs 81 to 88. East winds up to 15 mph. Chance of rain 20 percent.

South Side

Rest Of Today: Mostly sunny. Isolated showers in the afternoon. Highs 85 to 90. North winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Lows around 66. Northwest winds up to 15 mph.

Labor Day: Mostly sunny. Isolated showers in the afternoon. Highs 85 to 90. Northwest winds up to 15 mph. Chance of rain 20 percent.

North Shore

Rest Of Today: Partly sunny. Breezy. Showers likely in the morning, then scattered showers in the afternoon. Highs 80 to 86 near the shore to 60 to 66 near 5000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then showers likely after midnight. Lows 62 to 69 near the shore to around 50 near 5000 feet. Southeast winds 10 to 15 mph. Chance of rain 70 percent.

Labor Day: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs 80 to 86 near the shore to 60 to 65 near 5000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Central Maui

Rest Of Today: Mostly sunny with isolated showers. Highs around 88. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 64 to 70. East winds up to 15 mph. Chance of rain 20 percent.

Labor Day: Mostly sunny with isolated showers. Highs around 88. Northeast winds up to 15 mph. Chance of rain 20 percent.

Upcountry

Rest Of Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 58 at the visitor center to around 54 at the summit. East winds up to 10 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with scattered showers. Lows around 45 at the visitor center to around 41 at the summit. East winds up to 10 mph. Chance of rain 50 percent.

Labor Day: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 57 at the visitor center to around 53 at the summit. East winds up to 10 mph. Chance of rain 50 percent.

East Maui

Rest Of Today: Partly sunny. Breezy. Showers likely in the morning, then scattered showers in the afternoon. Highs 80 to 86 near the shore to 60 to 66 near 5000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then showers likely after midnight. Lows 62 to 69 near the shore to around 50 near 5000 feet. Southeast winds 10 to 15 mph. Chance of rain 70 percent.

Labor Day: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs 80 to 86 near the shore to 60 to 65 near 5000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Lanai City

Rest Of Today: Breezy. Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 73 to 82. Northeast winds 10 to 20 mph. Chance of rain 30 percent.

Tonight: Partly cloudy. Breezy. Lows around 66. Northeast winds 10 to 20 mph decreasing to up to 10 mph after midnight.

Labor Day: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 73 to 82. Light winds becoming northeast up to 15 mph in the afternoon. Chance of rain 30 percent.

Kaunakakai

Rest Of Today: Mostly sunny with isolated showers. Highs 78 to 88. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 61 to 72. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Labor Day: Mostly sunny with isolated showers. Highs 78 to 88. East winds 10 to 15 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Moderate trade winds will hold in place today, with showers favoring windward and mauka areas, although a disturbance aloft will allow a few more showers to reach leeward areas as well. The trades will weaken into the light to moderate range Labor Day through Tuesday. Showers will favor windward slopes and coasts during to overnight and early morning hours, with a few showers developing over leeward and interior areas each afternoon. Moderate trades and more typical windward and mauka showers will return Tuesday night and continue into next weekend.

Discussion

Currently at the surface, a west to east oriented ridge of high pressure centered around 750 miles north of Honolulu, is driving moderate trade winds across the island chain early this morning. Infrared satellite imagery shows mostly cloudy conditions in many windward areas, with partly cloudy skies prevailing in most leeward locales. Radar imagery shows scattered to numerous showers moving into windward slopes and coasts, with some of these showers spilling over into leeward communities. Main short term concerns revolve around trade wind trends and rain chances during the next few days.
A ridge of high pressure north of the islands will keep moderate trade winds in place today, with the trades then trending down into the light to moderate range Labor Day and Tuesday as the ridge weakens. A new high building north of the islands should increase trades slightly Wednesday and Thursday, before a weak trough approaching from the east eases the trades a notch once again Friday into next weekend.
As for the remaining weather details, fairly typical trade wind weather will prevail through tonight, with showers favoring windward and mauka areas. With an upper level low remaining in place just to the northeast of the state, elevated inversion heights will allow a few more of these showers to make it into leeward areas as well. A slightly lighter wind pattern Labor Day through Tuesday, will have showers favoring windward and mauka areas during the overnight and early morning hours, with a few showers then expected over interior and leeward areas during the afternoon into the early evening hours. A more typical trade wind pattern is then expected Tuesday night through next weekend, with showers again favoring windward and mauka areas, particularly at night and during the early morning hours, with a stray shower reaching leeward communities from time to time.

Aviation

Trade wind speeds are gradually coming down as a surface ridge north of the islands near 32N continues to slowly weaken. The 12z soundings and radar VAD wind profiles still showing 20-25 kt, so will leave AIRMET TANGO up at least until it’s regular update at 1545z. Should be able to drop it at that time but will make a final assessment then.
A weak upper level low just NE of the islands will continue to enhance incoming tradewind showers over the next couple of days. This will lead to episodes of MVFR and probable MTN OBSC at times over windward and mauka sections (AIRMET SIERRA is in effect now for portions of windward Big Island). Some showers will spread leeward at times, with brief MVFR possible there.

Marine

A high pressure ridge north of the Hawaiian Islands will weaken through Friday as two frontal systems pass from west to east across the North Pacific basin. Trade wind speeds will decrease over the area into Friday as the ridge north of the islands remains in a weakened state. The Small Craft Advisory (SCA) was cancelled this morning as wind speeds have dropped below 25 knots. Conditions will likely remain below SCA levels for all coastal waters through Friday.
A few medium to long period south swells will keep surf heights along southern exposures near seasonal normal levels into tonight, with slightly smaller surf heights forecast from Monday through Wednesday.
Surf heights along northeast and east facing shores will trend lower into early next week as the trade wind speeds decrease, lowering wave heights across the region. No significant swells are expected from the north or west direction through Saturday.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov