Photo Credit: Tyler Rooke

West Side

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 79 to 89. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 67 to 74. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tuesday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 78 to 90. Northeast winds up to 15 mph. Chance of rain 40 percent.

South Side

Today: Sunny. Highs 86 to 91. North winds up to 15 mph increasing to 10 to 15 mph in the afternoon.

Tonight: Partly cloudy with isolated showers. Lows 66 to 74. North winds up to 15 mph. Chance of rain 20 percent.

Tuesday: Sunny. Isolated showers in the morning. Highs around 89. North winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

North Shore

Today: Showers in the morning, then scattered showers in the afternoon. Highs 76 to 86 near the shore to around 66 near 5000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain near 100 percent.

Tonight: Mostly cloudy with numerous showers. Lows around 70 near the shore to 48 to 53 near 5000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Tuesday: Showers in the morning, then scattered showers in the afternoon. Highs 77 to 85 near the shore to around 66 near 5000 feet. East winds up to 15 mph. Chance of rain near 100 percent.

Central Maui

Today: Mostly sunny. Isolated showers in the morning. Highs 82 to 89. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with scattered showers. Lows 66 to 71. Northeast winds 10 to 15 mph decreasing to up to 10 mph after midnight. Chance of rain 50 percent.

Tuesday: Mostly sunny. Scattered showers in the morning. Highs 81 to 88. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Upcountry

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 59 at the visitor center to around 55 at the summit. East winds 10 to 15 mph decreasing to up to 10 mph in the afternoon. Chance of rain 50 percent.

Tonight: Partly cloudy with scattered showers. Lows around 42 at the visitor center to around 40 at the summit. East winds around 10 mph. Chance of rain 50 percent.

Tuesday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 59 at the visitor center to around 54 at the summit. East winds up to 10 mph. Chance of rain 50 percent.

East Maui

Today: Showers in the morning, then scattered showers in the afternoon. Highs 76 to 86 near the shore to around 66 near 5000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain near 100 percent.

Tonight: Mostly cloudy with numerous showers. Lows around 70 near the shore to 48 to 53 near 5000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Tuesday: Showers in the morning, then scattered showers in the afternoon. Highs 77 to 85 near the shore to around 66 near 5000 feet. East winds up to 15 mph. Chance of rain near 100 percent.

Lanai City

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 72 to 81. Northeast winds 10 to 15 mph. Chance of rain 30 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 65. Northeast winds 10 to 15 mph. Chance of rain 30 percent.

Tuesday: Mostly sunny with isolated showers. Highs 73 to 82. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Kaunakakai

Today: Mostly sunny. Breezy. Scattered showers in the morning. Highs 68 to 89. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with scattered showers. Lows 59 to 76. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tuesday: Mostly sunny. Scattered showers in the morning. Highs 68 to 89. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

A high pressure ridge north of the islands will keep moderate trade winds in the forecast today. An upper level low northeast of the islands will drift slowly west through the week weakening the trade winds from Tuesday through early Thursday morning. Localized sea breezes will develop on Tuesday and Wednesday along the western slopes of each island. Instability associated with the upper low will keep periods of showers in the weather forecast for all islands through Thursday. Drying trends return from Friday onward as trade winds strengthen across the region.

Discussion

Looking at the satellite loops this morning we see bands of cumulus clouds drifting into each island on the trade winds. An unstable upper low, roughly 600 miles northeast of the state, is drifting slowly westward. Numerous thunderstorms are developing within the cold core of the low as it moves closer to the state. Local radar shows scattered showers drifting through the area with periods of numerous shower activity over the windward and mountain slopes of each island.
A weak high pressure ridge north of the islands will continue to produce moderate trade winds today. This ridge will weaken a bit with light to moderate trade winds forecast from Tuesday into Thursday as the upper level low passes just north of the island chain. Lighter large scale winds will allow a sea breeze pattern to set up along the terrain sheltered western slopes of each island from Tuesday to Wednesday. Stronger trade winds will return after the low passes by the islands from Thursday afternoon through next weekend.
Expect continued periods of enhanced showers through Thursday as a weakened ridge north of the state and the approaching upper level low will increase the trade wind inversion heights into the 7,000 to 10,000 foot range. The higher rainfall amount totals will favor windward and mountain areas with some of the stronger showers pushing into typically drier leeward areas, especially in the overnight to early morning time periods.
On Wednesday, forecast guidance continues to show the upper low passing just north of the state with increasing potential for heavy showers and isolated thunderstorms over the eastern islands from Wednesday into Thursday. Much of these weather impacts will depend on the strength and track of the approaching upper low.
By Thursday, the low will pass to the west of the islands and we will begin the transition to stronger trade winds. Drying trends are forecast from Friday into the weekend as a high pressure system builds far to the north of the Hawaiian Islands. Shower coverage was lowered a bit from Friday onward as the latest forecast guidance shows more stable conditions, with lower trade wind inversion heights, and stronger atmospheric subsidence.

Aviation

High pressure northeast of the the state will allow for moderate trades to persist across the island chain this morning and into early afternoon. Scattered shower activity will be mainly confined to the windward coasts and slopes though a few showers may pass over on leeward areas. Expect brief periods of MVFR ceilings and visibility associated with this activity.
There are currently no AIRMETs in effect.

Marine

High pressure north of the state will keep moderate to fresh trade winds in place through Tuesday, with winds flirting with Small Craft Advisory (SCA) levels across the typically windy waters around Maui and the Big Island. The trades will briefly ease on Wednesday as a surface trough slides by to the north of the islands. As this trough exits to the northwest of the state Wednesday night and Thursday, the trades will gradually ramp back up to locally strong levels, with winds reaching SCA thresholds over the typically windy Maui and Big Island waters by Thursday. The strong SCA level trades are expected to expand to most if not all waters Friday and continue into the weekend.
A series of long period south and southwest swells will keep surf near the September average through Thursday, before dropping to slightly below normal levels Friday through the weekend. Small surf will prevail on north facing shores through most of the week, with a small bump possible this weekend. East shore surf will remain well below normal through Wednesday. As trade winds ramp up Thursday through the weekend, surf along east facing shores will rise back to seasonal levels and will be quite rough Friday through the weekend.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov