Photo Credit: Tyler Rooke

West Side

Today: Partly sunny. Slight chance of thunderstorms and isolated showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs 76 to 82. Light winds. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 61 to 68. Light winds. Chance of rain 20 percent.

Tuesday: Partly sunny with scattered showers. Highs 77 to 83. Southwest winds up to 10 mph. Chance of rain 40 percent.

South Side

Today: Mostly cloudy. Slight chance of thunderstorms and isolated showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs around 82. Light winds. Chance of rain 40 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows around 62. Light winds. Chance of rain 20 percent.

Tuesday: Partly sunny with scattered showers. Highs around 83. Southwest winds up to 10 mph. Chance of rain 30 percent.

North Shore

Today: Mostly cloudy. Slight chance of thunderstorms and isolated showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs 74 to 79 near the shore to around 59 near 5000 feet. Light winds. Chance of rain 50 percent.

Tonight: Mostly cloudy with isolated showers. Lows 59 to 65 near the shore to around 47 near 5000 feet. Light winds. Chance of rain 20 percent.

Tuesday: Partly sunny with scattered showers. Highs 75 to 80 near the shore to around 61 near 5000 feet. Light winds. Chance of rain 40 percent.

Central Maui

Today: Mostly cloudy. Slight chance of thunderstorms and isolated showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs 78 to 83. Light winds. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 60 to 65. Light winds. Chance of rain 20 percent.

Tuesday: Partly sunny with scattered showers. Highs 79 to 84. Light winds. Chance of rain 30 percent.

Upcountry

Today: Mostly cloudy. Slight chance of thunderstorms and isolated showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs around 54 at the visitor center to around 49 at the summit. Southwest winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows around 43 at the visitor center to around 38 at the summit. South winds up to 10 mph. Chance of rain 20 percent.

Tuesday: Partly sunny with scattered showers. Highs around 55 at the visitor center to around 51 at the summit. Southwest winds up to 15 mph. Chance of rain 40 percent.

East Maui

Today: Mostly cloudy. Slight chance of thunderstorms and isolated showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs 74 to 79 near the shore to around 59 near 5000 feet. Light winds. Chance of rain 50 percent.

Tonight: Mostly cloudy with isolated showers. Lows 59 to 65 near the shore to around 47 near 5000 feet. Light winds. Chance of rain 20 percent.

Tuesday: Partly sunny with scattered showers. Highs 75 to 80 near the shore to around 61 near 5000 feet. Light winds. Chance of rain 40 percent.

Lanai City

Today: Mostly cloudy with scattered showers and slight chance of thunderstorms. Highs 72 to 79. Light winds. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows around 64. Light winds. Chance of rain 20 percent.

Tuesday: Partly sunny with scattered showers. Highs 73 to 80. Light winds. Chance of rain 40 percent.

Kaunakakai

Today: Mostly cloudy with scattered showers and slight chance of thunderstorms. Highs 71 to 81. Southeast winds up to 10 mph in the morning becoming light. Chance of rain 50 percent.

Tonight: Mostly cloudy with isolated showers. Lows 55 to 67. Light winds. Chance of rain 20 percent.

Tuesday: Partly sunny with scattered showers. Highs 71 to 81. Southwest winds up to 10 mph. Chance of rain 40 percent.

Detailed Forecast

Synopsis

Light winds will prevail through the first work week of the New Year, allowing for daytime sea breezes and overnight land breezes in most areas. Shower coverage and intensity will trend downward through mid week, with showers developing over interior and mauka areas during the day and near the south and southeast facing coasts at night. Conditions will remain unstable enough today to allow for a few downpours and even a thunderstorm or two. Much drier conditions are expected late in the week, with very little shower activity expected Thursday and Friday. A weakening front could bring a slight increase in rain chances as it moves into the islands next weekend.

Discussion

Currently at the surface, a cold front is located around 1000 miles west-northwest of Kauai, while a 1025 mb high is centered around 1750 miles east-northeast of the Big Island. In between these two features lies a broad north to south oriented convergence band of deep tropical moisture which extends over the island chain. Winds remain rather light across the islands early this morning, with land breezes present in most areas, while a light background southeast to south flow holds in place over the coastal waters. Infrared satellite imagery shows a mix of high and low clouds resulting in mostly cloudy conditions across the state. Radar imagery shows some rain affecting the southeast Big Island coast as well as the southern shoreline of Kauai. Mainly dry conditions are present over Oahu and Maui County at the moment. Meanwhile, scattered to numerous showers and thunderstorms are developing over the coastal waters south and southwest of the smaller islands. Main short term concern revolves rainfall trends during the next few days.
High pressure will remain centered to the distant east-northeast during the next few days, while a cold front approaches from the northwest and eventually stalls out and dissipates a few hundred miles northwest of Kauai on Wednesday. This will keep a light wind regime in place, with overnight land breezes and daytime sea breezes common in most areas. A weak and fast moving high will slide by to the north of the state Wednesday night and Thursday, which may allow for a brief return of light trade winds. The trades will likely be overpowered in many areas by overnight land breezes and daytime sea breezes however, particularly in leeward areas. Winds appear to remain light Thursday night and Friday, but will likely pick up slightly out of the west and southwest Friday night as a weakening front approaches from the northwest, with moderate northwest and north winds following the frontal passage Saturday and Saturday night. Light and variable winds appear to return for Sunday.
As for the remaining weather details, the airmass will slowly dry out and stabilize during the first half of the week, as the deepest moisture and troughing aloft lift slowly northeastward. With linger instability over the island chain today, we could see a some locally heavy downpours and even a thunderstorm or two. Precipitable water values fall below 1.5 inches Tuesday morning and drop to around 1.2 inches or less by late Wednesday, so we should see shower coverage and intensity gradually diminish during the next few days. The airmass appears to dry out further Thursday and Friday with precipitable water values dropping below 1 inch. This should result in mostly dry conditions expected across the majority of the state during this time. A predominantly land and sea breeze pattern is expected through much of the work week, which favors interior showers each afternoon and a few showers near the coast each night. A weakening cold front could bring a slight increase in showers next weekend as it moves into the islands and dissipates.

Aviation

An upper level low pressure system near Kauai will keep moist and unstable conditions over the Hawaii region today. Additional rain bands are redeveloping south of the Hawaiian Islands possibly producing periods of rain showers, heavy at times, with brief MVFR conditions and isolated thunderstorms.
No AIRMETs in effect. AIRMET Sierra for mountain obscurations are possible later this morning.

Marine

The islands lie between high pressure centered off the U.S. west coast and a cold front to the west that is associated with a gale low south of the Aleutian Islands. This has placed the region in an area of weaker pressure through Tuesday. Light to moderate south to southeast winds today will slowly veer more westerly Tuesday as the trough to the west lifts northeast and passes north of the state at mid week. A weak cold front may pass into the waters Wednesday and this will turn gentle winds more north northeast going into Thursday. The greater influence of a mid to upper ridge east of the region will support a more stable air mass. Thus, a drier pattern will prevail as early week scattered showers transition to more isolated mid to late week shower activity. While winds will remain below Small Craft Advisory (SCA) criteria through the period, larger northwest swells will likely produce combined seas greater than 10 feet SCA thresholds later on Wednesday through Thursday and again over the weekend.
Sunday's small west northwest swell will diminish through the day. A larger moderate size, long to medium period west northwest swell will build in from Tuesday through Thursday. During this time period a strong, slow-moving Bering Sea low will send a moderate size, long to medium period north swell into the local waters. This mixed west northwest and north swell will have resultant mid week surf heights along many exposed north and west facing shores likely achieving High Surf Advisory (HSA) heights by Thursday. An extended west fetch will develop far northwest of the islands later this week and push a third, even larger northwest swell into the island waters this weekend. If this swell does materialize, there is a good probability of it generating XL-size, warning level surf along north and west shores over the weekend.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov