West Side

Today: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs 81 to 87. East winds up to 20 mph shifting to the northeast 10 to 20 mph in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Isolated showers. Lows 69 to 76. East winds up to 20 mph. Chance of rain 20 percent.

Wednesday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 81 to 87. East winds up to 15 mph. Chance of rain 50 percent.

South Side

Today: Sunny and breezy. Highs around 90. North winds up to 15 mph shifting to the northeast in the afternoon.

Tonight: Mostly clear. Isolated showers after midnight. Lows 69 to 77. North winds up to 15 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny with isolated showers in the morning, then partly sunny in the afternoon. Highs around 89. North winds up to 15 mph. Chance of rain 20 percent.

North Shore

Today: Breezy. Mostly sunny with scattered showers. Highs 80 to 85 near the shore to around 68 near 5000 feet. East winds up to 20 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows around 73 near the shore to around 53 near 5000 feet. Southeast winds up to 15 mph. Chance of rain 70 percent.

Wednesday: Showers in the morning, then scattered showers in the afternoon. Highs 80 to 85 near the shore to around 68 near 5000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain near 100 percent.

Central Maui

Today: Mostly sunny. Breezy. Highs 83 to 90. Northeast winds up to 20 mph increasing to 10 to 20 mph in the afternoon.

Tonight: Breezy. Partly cloudy in the evening, then mostly cloudy with numerous showers after midnight. Lows 69 to 74. Northeast winds up to 20 mph decreasing to up to 10 mph after midnight. Chance of rain 60 percent.

Wednesday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 83 to 90. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Upcountry

Today: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs around 65 at the visitor center to around 71 at the summit. East winds up to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening, then scattered showers after midnight. Lows around 50 at the visitor center to around 47 at the summit. East winds up to 20 mph. Chance of rain 50 percent.

Wednesday: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs around 65 at the visitor center to around 68 at the summit. East winds up to 20 mph. Chance of rain 50 percent.

East Maui

Today: Breezy. Mostly sunny with scattered showers. Highs 80 to 85 near the shore to around 68 near 5000 feet. East winds up to 20 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows around 73 near the shore to around 53 near 5000 feet. Southeast winds up to 15 mph. Chance of rain 70 percent.

Wednesday: Showers in the morning, then scattered showers in the afternoon. Highs 80 to 85 near the shore to around 68 near 5000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain near 100 percent.

Lanai City

Today: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs 75 to 82. Northeast winds up to 15 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Isolated showers after midnight. Lows around 67. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny. Isolated showers in the afternoon. Highs 75 to 83. Northeast winds up to 10 mph. Chance of rain 20 percent.

Kaunakakai

Today: Mostly sunny. Breezy. Highs 74 to 91. Northeast winds 10 to 20 mph.

Tonight: Partly cloudy. Isolated showers after midnight. Lows 60 to 76. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Wednesday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 73 to 90. East winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

The subtropical ridge north of the Hawaiian Islands will slowly weaken this week with light to moderate trade winds in the forecast lasting through Wednesday. The ridge north of the islands will weaken and winds will veer out of an east to southeast direction from Thursday onward, allowing an expansion of onshore sea breezes over each island during the daylight hours.An unstable band of clouds, the remnants of an old East Pacific cold front, will drift through the islands on the trade winds from Wednesday morning into Thursday enhancing showers statewide. Unsettled bands of showers will continue to ride into the islands from Thursday on into the weekend.

Discussion

The satellite picture this morning shows a weakening upper low with embedded thunderstorms roughly 400 miles northwest of Kauai. Bands of stable stratocumulus clouds are drifting into the islands on the moderate easterly trade winds today. An unsettled cloud band roughly 230 miles northeast of the state continues to ride towards the island chain. Upper air balloon soundings at Lihue and Hilo from 2 AM HST (12Z) this morning show subsidence temperature inversion heights today in the 5,000 to 6,000 foot elevation range. At this range only brief passing showers are forecast, mainly limited to windward and mountain areas. These stable weather conditions will continue through tonight.
Trade wind speeds will trend lower this week as the high pressure ridge north of the islands weakens in response to a passing high latitude cold front. A band of unstable clouds associated with an old East Pacific cold front will ride into the islands from early Wednesday morning into Thursday. Expect wet weather conditions during this time period as these unstable clouds are forced orographically over island mountain ranges. The best shower coverage and rainfall amounts will favor windward island mountain ranges during this time period. Some of the stronger showers with this system will reach the drier leeward areas.
These weakening trade winds will veer from a more east to southeast direction from Thursday onward. Decreasing large scale winds will allow thermally driven local scale sea breezes to strengthen during the daylight hours over all islands. Shower trends in this sea breeze pattern will tend to favor island mountain and interior sections each afternoon. The latest weather model solutions also show good chances for converging winds along the leeward sides of island mountains producing shower bands extending from west to northwest of each island. These developing shower bands may briefly enhance rainfall amounts over Oahu and Kauai in this southeasterly wind regime from Thursday through Saturday.

Aviation

Moderate trade winds will persist through the forecast period with clouds and showers focused mainly over windward and mauka areas. An uptick of moisture is expected tonight through Wednesday from remnants of an old frontal band. Localized MVFR possible within passing showers, but most sites will remain VFR.
AIRMET Sierra remains in effect for mountain obscuration due to low clouds and showers over windward Big Island. Conditions expected to improve later this morning but may return tonight.

Marine

Moderate to locally fresh easterly trade winds will persist through Wednesday before slowly diminishing through the latter have of the week into early next week.
A small medium period north swell filled in yesterday and will gradually fade today. A series of small medium period swells from the north and northwest will trickle in through the rest of the week. A moderate medium period northwest (330 degrees) swell is expected to arrive on Saturday and Sunday, building surf heights along north and west facing shores late this weekend into early next week.
A series of small medium period south swells will keep surf along south facing shores from going flat through the week.
Surf along east facing shores will remain on the small side in moderate trade wind flow, despite some small medium period swell moving into the region over the next couple of days from former tropical cyclone Narda.

Fire weather

Wind speeds will remain below critical fire weather thresholds for the next seven days. Temperature inversion heights near the Big Island and Maui will range from 5,000 to 6,000 feet today.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov