Photo Credit: Travis Guthrie

West Side

Today: Mostly cloudy. Windy. Scattered showers and isolated thunderstorms in the morning, then scattered showers in the afternoon. Highs 76 to 82. Northeast winds 25 to 30 mph. Chance of rain 50 percent.

Tonight: Windy. Mostly cloudy with scattered showers. Lows 62 to 68. Northeast winds 25 to 30 mph decreasing to 10 to 30 mph after midnight. Chance of rain 50 percent.

Wednesday: Breezy. Partly sunny with scattered showers. Highs 76 to 82. Northeast winds 10 to 25 mph with gusts to 45 mph. Chance of rain 50 percent.

South Side

Today: Partly sunny. Windy. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 82. Northeast winds 10 to 30 mph increasing to 25 to 30 mph in the afternoon. Chance of rain 30 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 63. Northeast winds 10 to 25 mph with gusts to 45 mph. Chance of rain 20 percent.

Wednesday: Breezy. Partly sunny with scattered showers. Highs around 82. Northeast winds 10 to 25 mph with gusts to 45 mph. Chance of rain 50 percent.

North Shore

Today: Breezy. Occasional showers and isolated thunderstorms in the morning, then occasional showers in the afternoon. Locally heavy rainfall possible in the morning. Highs 74 to 79 near the shore to around 57 near 5000 feet. East winds 10 to 25 mph. Chance of rain near 100 percent.

Tonight: Breezy. Occasional showers and isolated thunderstorms. Lows 60 to 66 near the shore to 44 to 49 near 5000 feet. East winds 10 to 25 mph. Chance of rain near 100 percent.

Wednesday: Breezy. Occasional showers and isolated thunderstorms. Highs 74 to 79 near the shore to around 57 near 5000 feet. East winds 10 to 20 mph. Chance of rain near 100 percent.

Central Maui

Today: Mostly cloudy. Breezy. Scattered showers and isolated thunderstorms in the morning, then scattered showers in the afternoon. Locally heavy rainfall possible in the morning. Highs 78 to 83. Northeast winds 15 to 25 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with numerous showers and isolated thunderstorms. Lows 61 to 66. Northeast winds 20 to 25 mph decreasing to 10 to 25 mph after midnight. Chance of rain 60 percent.

Wednesday: Breezy. Mostly cloudy with numerous showers and isolated thunderstorms. Highs 78 to 83. East winds 10 to 25 mph. Chance of rain 70 percent.

Upcountry

Today: Breezy. Occasional showers and isolated thunderstorms in the morning, then occasional showers in the afternoon. Locally heavy rainfall possible in the morning. Highs around 52 at the visitor center to around 47 at the summit. East winds up to 25 mph. Chance of rain near 100 percent.

Tonight: Breezy. Occasional showers and isolated thunderstorms. Lows around 42 at the visitor center to around 36 at the summit. East winds 10 to 25 mph. Chance of rain near 100 percent.

Wednesday: Breezy. Occasional showers and isolated thunderstorms. Highs around 52 at the visitor center to around 47 at the summit. East winds 10 to 25 mph. Chance of rain near 100 percent.

East Maui

Today: Breezy. Occasional showers and isolated thunderstorms in the morning, then occasional showers in the afternoon. Locally heavy rainfall possible in the morning. Highs 74 to 79 near the shore to around 57 near 5000 feet. East winds 10 to 25 mph. Chance of rain near 100 percent.

Tonight: Breezy. Occasional showers and isolated thunderstorms. Lows 60 to 66 near the shore to 44 to 49 near 5000 feet. East winds 10 to 25 mph. Chance of rain near 100 percent.

Wednesday: Breezy. Occasional showers and isolated thunderstorms. Highs 74 to 79 near the shore to around 57 near 5000 feet. East winds 10 to 20 mph. Chance of rain near 100 percent.

Lanai City

Today: Partly sunny. Windy. Isolated showers in the afternoon. Highs 67 to 74. Northeast winds 10 to 30 mph increasing to 25 to 30 mph in the afternoon. Chance of rain 20 percent.

Tonight: Mostly cloudy. Windy. Lows around 62. Northeast winds 15 to 30 mph.

Wednesday: Breezy. Partly sunny in the morning, then mostly sunny with isolated showers in the afternoon. Highs 67 to 74. Northeast winds 20 to 25 mph. Chance of rain 20 percent.

Kaunakakai

Today: Mostly cloudy. Windy. Scattered showers and isolated thunderstorms in the morning, then isolated showers in the afternoon. Highs 70 to 80. Northeast winds 15 to 30 mph. Chance of rain 50 percent.

Tonight: Windy. Mostly cloudy with scattered showers. Lows 57 to 69. Northeast winds 15 to 30 mph. Chance of rain 50 percent.

Wednesday: Partly sunny. Windy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 70 to 80. East winds 15 to 30 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

A wet trade wind pattern with isolated thunderstorms and locally heavy rain, especially over windward areas, will prevail through Wednesday night. Breezy trades will further strengthen during the middle part of the week.

Discussion

Overall the forecast seems to be on track, so no changes to the short term forecast with the morning package. Overnight saw showers carried in on the trades focused over the windward and mauka slopes. Kauai, Maui and the Big Island experienced the heavier showers, and on the Big Island, a few of the area stream gages did respond. Fortunately there has been enough of a break in the showers for the streams to periodically get a break an
High pressure to the north, and a weakening surface trough moving west away from the main Hawaiian islands is helping to bring breezy trade winds to the region. An upper level trough sinking southward over the islands is responsible for the unstable airmass, allowing trade wind showers to be more intense than normal. In addition, this instability could trigger a few thunderstorms.
This set up over the next couple of days will continue the wet trade wind weather with the potential for moderate to locally heavy rain focused windward and mauka, particularly over the western end of the state through early Tuesday morning and the Big Island and Maui Tuesday and Wednesday.
The Winter Storm Warning remains in effect through Tuesday night for the Big Island, with the primary concern being freezing rain leading to ice accumulation.
As the above mentioned upper level trough lingers over the islands, a couple more rounds of moderate to locally heavy rain potential exist both Tuesday night and Wednesday night. In both cases, the focus is expected to be mainly over Maui and the Big Island, but can't completely rule out Oahu and Kauai from seeing additional showers.
Trade winds will linger through the week with high pressure to the north. Winds are expected to increase mid-week so the above mentioned surface trough dissipates. Toward the end of the week, the high will move to the east, and be replaced by a new high, which will maintain the moderate to locally windy trade winds.
From Thursday on into the weekend the upper level trough lifts to the north and northeast, just enough to cut off some of the instability that is leading to the heavier showers. As such look for a return to a more typical trade wind pattern.

Aviation

Moderate to breezy trade winds will persist for the next several days as strong surface high pressure holds north of the state. Clouds and showers will favor windward slopes and coasts. Periods of MVFR conditions with low ceilings and visibility in showers are expected mainly over windward airfields, especially in the late night and morning hours.
A deepening upper level trough will enhance convective activity. There is a slight chance of thunderstorms statewide through forty- eight hours and possibly beyond.
AIRMET Sierra is now in effect for northeast facing slopes of Kauai, Oahu, and the Big Island. Conditions are expected to improve later this morning.
AIRMET Tango is in effect for moderate leeward mountain wave turbulence over all islands due to breezy trade winds, and is expected to remain necessary through twenty-four hours and possibly beyond. Additionally, areas of moderate upper level turbulence remain an issue for the eastern third of the state. Upper level turbulence conditions are expected to rapidly improve this morning as the subtropical jet shifts to the east.

Marine

A strong high pressure system will drift eastward, slowly passing north of Hawaii over the next few days. Expect strong to near- gale east-northeast trade winds through much of this week as another strong high pressure system builds into the region from the west as the first one retreats eastward on Thursday. A Small Craft Advisory remains in effect for all waters, and will likely remain in place through much of this week. A persistent trough aloft will keep the island atmosphere unstable, with briefly heavy showers producing periods of strong wind gusts and low visibility. Isolated thunderstorms are also in the forecast into Thursday.
The persistent trade winds will generate rough and choppy surf along east facing shores through the week. Gradually diminishing medium period swells out of the northwest and north will continue to trend down today. A small, medium period northwest swell will arrive on Wednesday. Followed by a larger and longer period northwest swell, building surf heights to near advisory thresholds along exposed north and west facing shores from Friday to Saturday.
South shores will remain seasonably small with mainly medium period background swell energy pulses.

HFO Watches/Warnings/Advisories

Winter Storm Warning until 6 AM HST Wednesday for Big Island Summits.
Small Craft Advisory until 6 AM HST Thursday for all Hawaiian waters,

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Data Courtesy of NOAA.gov