Photo Credit: Jeni Ji Cousins

West Side

Today: Mostly sunny with isolated showers. Highs 80 to 87. East winds up to 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with scattered showers. Lows 70 to 77. East winds up to 15 mph. Chance of rain 40 percent.

Tuesday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 80 to 87. East winds 10 to 25 mph. Chance of rain 30 percent.

South Side

Today: Mostly sunny. Highs around 89. Northwest winds up to 10 mph.

Tonight: Partly cloudy. Isolated showers after midnight. Lows 69 to 77. North winds up to 10 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny. Highs around 89. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon.

North Shore

Today: Mostly cloudy. Breezy. Showers in the morning, then scattered showers in the afternoon. Highs 80 to 85 near the shore to around 69 near 5000 feet. East winds up to 20 mph. Chance of rain 80 percent.

Tonight: Mostly cloudy. Breezy. Numerous showers in the evening, then showers after midnight. Lows around 73 near the shore to around 54 near 5000 feet. Southeast winds 10 to 20 mph. Chance of rain 90 percent.

Tuesday: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 79 to 84 near the shore to around 67 near 5000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Central Maui

Today: Breezy. Mostly sunny with isolated showers. Highs 83 to 90. East winds up to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 72. East winds up to 15 mph. Chance of rain 50 percent.

Tuesday: Breezy. Partly sunny with isolated showers in the morning, then mostly sunny in the afternoon. Highs 82 to 90. East winds up to 25 mph increasing to 10 to 25 mph in the afternoon. Chance of rain 20 percent.

Upcountry

Today: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 65 at the visitor center to around 68 at the summit. East winds up to 25 mph. Chance of rain 50 percent.

Tonight: Breezy. Partly cloudy with scattered showers. Lows around 50 at the visitor center to around 47 at the summit. East winds 10 to 25 mph. Chance of rain 50 percent.

Tuesday: Mostly sunny in the morning then becoming partly sunny. Windy. Scattered showers. Highs around 64 at the visitor center to around 70 at the summit. East winds up to 20 mph increasing to up to 30 mph in the afternoon. Chance of rain 50 percent.

East Maui

Today: Mostly cloudy. Breezy. Showers in the morning, then scattered showers in the afternoon. Highs 80 to 85 near the shore to around 69 near 5000 feet. East winds up to 20 mph. Chance of rain 80 percent.

Tonight: Mostly cloudy. Breezy. Numerous showers in the evening, then showers after midnight. Lows around 73 near the shore to around 54 near 5000 feet. Southeast winds 10 to 20 mph. Chance of rain 90 percent.

Tuesday: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 79 to 84 near the shore to around 67 near 5000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Lanai City

Today: Mostly sunny. Isolated showers in the afternoon. Highs 74 to 82. East winds up to 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers after midnight. Lows around 68. Northeast winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Tuesday: Sunny in the morning, then mostly cloudy with isolated showers in the afternoon. Highs 74 to 82. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

Kaunakakai

Today: Mostly sunny with isolated showers. Highs 71 to 91. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 61 to 77. East winds 10 to 15 mph. Chance of rain 20 percent.

Tuesday: Partly sunny. Breezy. Isolated showers in the morning. Highs 71 to 90. East winds 10 to 25 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Moderate trade winds will continue today with increasing shower activity as a weak low level trough passes westward through the Hawaiian Islands. Trade winds will strengthen later tonight as the subtropical ridge builds north of the state. Shower activity will trend lower from Tuesday to Wednesday, then increase yet again from Thursday into Saturday as another weak disturbance moves through the island chain.

Discussion

The satellite picture this morning shows a low level trough moving westward down the island chain. Low level cloud bands are currently thickest over the islands in Maui County and Oahu. These clouds will drift into Kauai over the next few hours. Local radar imagery shows numerous showers developing within this unstable cloud band. Additional unstable clouds are just east of the Big Island and should bring increasing shower trends to the east and southeast slopes later this morning.
The American (GFS) model 700 mb streamlines show a low level easterly wave moving westward through the islands today. Low level forcing with this trough will enhance local area shower activity, mainly over windward and mountain areas. The stronger showers will even produce brief periods of rainfall over the drier leeward slopes of each island into the evening hours. Drier conditions will then quickly spread from east to west as stability returns. Another low level trough will move into the eastern islands on Thursday, yet again briefly increasing shower trends across the state into Saturday. A weak upper level low drifting just east of the state may also assist in producing unstable clouds in the trade wind flow just upstream of the island chain.
Moderate trade winds will increase today becoming locally breezy through Thursday as the subtropical ridge strengthens slightly. Expect a slight decrease in trade winds with a hybrid expansion in daytime sea breeze winds along western terrain sheltered slopes from Friday into next weekend.

Aviation

Moderate trades are expected through midweek. SHRA and low cigs are possible along windward and mauka locations, with some isol spillover to leeward sides. Brief MVFR conds can be expected in SHRA, otherwise VFR should prevail.
AIRMET Sierra for mtn obsc is in effect for windward locations of all islands. Conds should improve later on this morning.

Marine

Easterly trade winds will begin to strengthen today into the moderate to locally strong range as the ridge to the north builds back in. A Small Craft Advisory (SCA) has been issued for most of the windier waters and channels around Maui County and the Big Island through Tuesday. Zones after Tuesday, may vary as some zones may need to be expanded and others taken out of the SCA. By the end of the week, trades look to decrease once again.
The current moderate to large, medium to long period north swell will continue to rise through the morning hours, peak this evening and slowly decline through the end of the week. A High Surf Advisory (HSA) has been issued starting at 6am today through Tuesday for all north facing shores across the state.
Surf along west facing shores will remain slightly elevated with the influence of the north swell today through Tuesday. East facing shore wind waves will remain relatively small but gradually pick up Tuesday in response to strengthening trades. Areas exposed to the north swell on the east shores will also see a wrap with this swell. Surf along south facing shores will remain small today with a south swell slowly fading through the day. For the rest of the week surf looks to remain tiny with background southerly swells.

HFO Watches/Warnings/Advisories

High Surf Advisory from 6 AM this morning to 6 PM HST Tuesday for north facing shores of Niihau, Kauai, Oahu, Molokai, Maui and the Big Island.
Small Craft Advisory from 6 AM this morning to 6 PM HST Tuesday for for most eastern Hawaiian Coastal Waters.

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Data Courtesy of NOAA.gov