Photo Credit: Allen Tate

West Side

Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 73 to 88. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers. Lows 63 to 73. Light winds. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 73 to 89. Light winds. Chance of rain 50 percent.

South Side

Today: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 76 to 87. Light winds becoming north around 10 mph in the afternoon. Chance of rain 40 percent.

Tonight: Partly cloudy with isolated showers. Lows 65 to 70. East winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers. Highs 75 to 87. Light winds. Chance of rain 20 percent.

North Shore

Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 76 to 81 near the shore to around 66 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Isolated showers. Lows 68 to 73 near the shore to around 53 near 5000 feet. Southeast winds up to 10 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 77 to 82 near the shore to around 66 near 5000 feet. Southeast winds up to 10 mph. Chance of rain 50 percent.

Central Maui

Today: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 80 to 86. Northeast winds up to 15 mph. Chance of rain 40 percent.

Tonight: Partly cloudy with isolated showers. Lows around 68. East winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers. Highs 80 to 86. Light winds. Chance of rain 20 percent.

Upcountry

Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 50 to 70. Light winds. Chance of rain 40 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then clear after midnight. Lows around 47 at the visitor center to around 44 at the summit. Light winds. Chance of rain 50 percent.

Tuesday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 51 to 70. Southwest winds up to 10 mph. Chance of rain 50 percent.

East Maui

Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 76 to 81 near the shore to around 66 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Isolated showers. Lows 68 to 73 near the shore to around 53 near 5000 feet. Southeast winds up to 10 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 77 to 82 near the shore to around 66 near 5000 feet. Southeast winds up to 10 mph. Chance of rain 50 percent.

Lanai City

Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 68 to 78. Light winds. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 59 to 66. Light winds. Chance of rain 40 percent.

Tuesday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 67 to 78. Light winds. Chance of rain 50 percent.

Kaunakakai

Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 66 to 86. East winds up to 10 mph. Chance of rain 40 percent.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 56 to 73. Light winds. Chance of rain 40 percent.

Tuesday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 66 to 86. Light winds becoming southwest up to 10 mph in the afternoon. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Light southeasterly winds, afternoon sea breezes and weak troughing aloft will produce brief periods of slow moving showers over some islands through Tuesday. Some of these showers may become heavy at times especially along the eastern slopes of Oahu and Maui, and the southeastern slopes of the Big Island. On Wednesday the weather pattern trends more unstable as southerly winds develop over the state in response to a kona low approaching the islands from the north. Deep unstable tropical moisture will move over all islands from the south, resulting in periods of heavy rainfall, thunderstorms and strong gusty winds. The threats from flooding and thunderstorms will be elevated for all islands from Wednesday into the weekend.

Discussion

Local radar imagery this morning shows moderate showers anchored over the Koolau Mountains on Oahu from a Molokai convergence plume caught up in the light southeasterly winds. Showers over the eastern mountain slopes of Oahu will continue at least through the morning hours. Satellite imagery using the water vapor channel continues to show the weak upper low drifting northeastward away from the Hawaiian Islands today. Upper air balloon soundings from Hilo and Lihue show very weak to non-existent subsidence inversion. This means periods of wet weather should be expected today statewide. The forecast grids were updated significantly this morning in the medium to long range forecast to include higher chances for showers and thunderstorms from Wednesday on into the weekend.
The weather pattern for the next few days keeps the Hawaiian Islands in a light southeasterly wind pattern with land and sea breezes forming over each island through Tuesday. Forecast guidance and satellite water vapor imagery continues to show weak upper level troughing that will enhance some shower activity across the state. Southeasterly winds tend to produce small scale convergence plumes in the lee of island mountains and when combined with upper level instability tend to create enhanced showers over eastern Oahu. Southeasterly flow will also combine with sea breezes to drive clouds and low moving moderate to heavy showers up the mountain slopes of east Maui and the southeast slopes of the Big Island over the Kau and Puna districts. Localized slow moving heavy rain may also develop and Flood Advisories may be needed mainly in the afternoon to early evening hours through Tuesday.
Wednesday through Friday…Another unstable weather pattern develops across the Hawaiian Islands as a unseasonably deep kona low approaches the islands from the north. A cold front riding in ahead of this system will help to produce southerly kona winds over the islands starting early Wednesday morning. These southerly winds will draw up a deep and unstable tropical moisture plume ahead of the approaching cold front. The cold front will weaken into a trough on Thursday as it merges with the tropical moisture plume right over the islands. Forecast models have been remarkably consistent in showing both features will impact all islands with heavy rain and thunderstorm threats during this time period.
Several threats are likely in this weather pattern from Wednesday onward including heavy rain with flooding, thunderstorms in the strong to severe range, and strong gusty winds. The severe thunderstorm threat will favor the western islands closer to the approaching surface front/trough, the upper level cold pool and the strongest wind shear. The forecast guidance over the past few days suggests these threats will last for several days from Wednesday through Friday and possibly linger into next weekend. A very wet and unstable pattern for this time of year. Stay tuned.

Aviation

Lingering instability aloft combined with a moist southeasterly flow will allow for a few heavy showers across the state through the forecast period, with the slight possibility remaining for isolated thunderstorms over the Big Island today. The heaviest showers will mostly be focusing over southeast facing slopes of each island. Winds will remain light enough to allow for a land/sea breeze pattern where clouds and showers will build up over island interiors during the afternoon/early evening hours and clear out overnight. MVFR conditions are expected in any heavier showers, with brief IFR conditions possible.
AIRMET Sierra for tempo mountain obscuration is in effect over the the southeast facing areas of the Big Island and east facing areas of Oahu. AIRMET Sierra for IFR conditions may also be needed for the southeastern slopes of the Big Island later today as showers periodically become heavy.

Marine

Moderate trade winds will gradually ease today and tonight, then become more southerly on Tuesday as troughing amplifies to the west of the state. Moderate southerly winds will develop in advance of a front Wednesday. The front will move into the western islands Wednesday night and Thursday, then weaken into a trough and shift westward Friday. Light to moderate northwest winds may briefly develop behind the front over the far western end of the state, otherwise moderate southerly winds should prevail into the weekend.
Surf along south facing shores will slowly decline today and tonight. A series of overlapping, long-period south swells will then move through the islands Tuesday into the weekend. This will be a long lived south shore event, with surf holding well above the summertime average Wednesday through the weekend.
A small, long-period northwest swell will peak today, then slowly decline Tuesday, giving north shore surf a slight boost. A series of reinforcing northwest swells will keep some small to moderate sized surf moving into north facing shores Wednesday through the weekend.
Surf along east facing shores will remain well below normal levels through the weekend.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov