West Side

Today: Mostly sunny. Haze. Highs 72 to 82. Southwest winds up to 10 mph increasing to 10 to 15 mph in the afternoon.

Tonight: Breezy. Partly cloudy with isolated showers. Haze. Lows 64 to 72. Southwest winds 10 to 20 mph. Chance of rain 20 percent.

Monday: Breezy. Mostly sunny with isolated showers. Highs 72 to 82. South winds 15 to 25 mph. Chance of rain 20 percent.

South Side

Today: Mostly sunny. Haze. Highs 75 to 84. South winds up to 15 mph shifting to the southwest in the afternoon.

Tonight: Partly cloudy with isolated showers. Haze. Lows 65 to 70. Southwest winds 10 to 15 mph. Chance of rain 20 percent.

Monday: Breezy. Mostly sunny with isolated showers. Highs 74 to 83. Southwest winds 15 to 25 mph. Chance of rain 20 percent.

North Shore

Today: Mostly sunny. Haze. Highs around 80 near the shore to around 65 near 5000 feet. Light winds becoming south up to 10 mph in the afternoon.

Tonight: Mostly clear. Breezy and haze. Lows around 68 near the shore to around 52 near 5000 feet. South winds up to 10 mph shifting to the southwest up to 20 mph after midnight.

Monday: Mostly sunny. Breezy. Highs around 82 near the shore to around 66 near 5000 feet. Southwest winds up to 25 mph with gusts to 45 mph.

Central Maui

Today: Mostly sunny. Haze. Highs 80 to 85. Southwest winds up to 15 mph.

Tonight: Breezy. Partly cloudy with isolated showers. Haze. Lows 64 to 69. South winds 10 to 20 mph. Chance of rain 20 percent.

Monday: Windy. Mostly sunny with isolated showers. Highs around 82. South winds 15 to 30 mph shifting to the southwest 25 to 30 mph in the afternoon. Chance of rain 20 percent.

Upcountry

Today: Sunny and breezy. Highs 51 to 68. Southwest winds up to 20 mph.

Tonight: Mostly clear. Breezy. Lows around 44 at the visitor center to around 41 at the summit. Southwest winds up to 25 mph.

Monday: Very windy. Sunny with isolated showers. Highs 50 to 68. Southwest winds up to 30 mph increasing to up to 40 mph in the afternoon. Chance of rain 20 percent.

East Maui

Today: Mostly sunny. Haze. Highs around 80 near the shore to around 65 near 5000 feet. Light winds becoming south up to 10 mph in the afternoon.

Tonight: Mostly clear. Breezy and haze. Lows around 68 near the shore to around 52 near 5000 feet. South winds up to 10 mph shifting to the southwest up to 20 mph after midnight.

Monday: Mostly sunny. Breezy. Highs around 82 near the shore to around 66 near 5000 feet. Southwest winds up to 25 mph with gusts to 45 mph.

Lanai City

Today: Mostly sunny. Haze. Highs 66 to 77. Light winds becoming southwest up to 15 mph in the afternoon.

Tonight: Breezy. Partly cloudy with isolated showers. Haze. Lows 59 to 65. Southwest winds 10 to 20 mph. Chance of rain 20 percent.

Monday: Breezy. Mostly sunny with isolated showers. Highs 67 to 77. Southwest winds 15 to 25 mph. Chance of rain 20 percent.

Kaunakakai

Today: Mostly sunny. Haze. Highs 66 to 83. South winds up to 15 mph.

Tonight: Breezy. Partly cloudy with scattered showers. Haze. Lows 54 to 70. Southwest winds 10 to 20 mph. Chance of rain 50 percent.

Monday: Breezy. Mostly sunny with isolated showers. Highs 67 to 83. Southwest winds 15 to 25 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Light large scale winds will keep daytime onshore sea breezes in the forecast today for all islands with stable weather conditions. A cold front will march eastward down the island chain from Monday evening through Tuesday, before stalling out and diminishing near the Big Island on Wednesday. Moderate to breezy southwesterly winds will blow in ahead of the front, from Sunday night through Monday afternoon, and northwest winds will move in after the front passes each island. A stronger cold front will spread showers across the Hawaii region from Friday into next weekend. This next cold front may bring periods of heavy rain and isolated thunderstorms as it passes.

Discussion

Looking into the big picture on infrared satellite imagery this morning we see a fairly stable atmosphere over the islands under the influence of a weak subtropical ridge. Lingering low clouds near the eastern slopes of the Big Island are diminishing at this hour. Light large scale winds under this high pressure ridge will allow local scale onshore sea breezes to develop over all islands during the late morning to afternoon hours. This stable atmosphere with relatively low temperature inversion heights will limit cloud and shower development today.
Far northwest of the islands the next cold front currently 750 miles northwest of Kauai continues to track towards the Hawaiian Islands. Southwesterly winds are evident in the cumulus cloud bands in the warm sector air between Kauai and the approaching cold front. These warm and humid southwesterly winds will move into the islands ahead of the cold front, generating some prefrontal clouds and increasing shower trends from Sunday night into Monday afternoon. Moderate to breezy southwesterly winds will produce enhanced wind gusts from 35 to 45 mph along favored north and east slopes of island mountain ranges, especially for Oahu along the Waianae and Koolau mountain ranges on Monday. These stronger wind gusts will remain just below our Wind Advisory thresholds.
The main rain event arrives with the cold front by Monday night as the cold front swiftly moves eastward through the western islands of Niihau, Kauai and Oahu. A brief period of increasing clouds and showers remains in the forecast along the cold frontal band. This front will move into the islands in Maui County by early Tuesday morning, reaching the Big Island around noon on Tuesday. The front will weaken as it passes through and breaks up over each set of island mountains. Rainfall amounts will be moderate for the western islands in the roughly 0.25 to 0.60 inch range with decreasing amounts over the eastern islands in Maui and Hawaii Counties in the roughly 0.10 to 0.40 inch range as the frontal cloud band weakens. Cool and drier, more stable northwesterly winds will move in as the cold front passes through each island. The best way to observe cold frontal passage: the onset of northwesterly winds.
This hana hou (encore) weather pattern continues into the middle of the week as a weak high pressure passes eastward just north of the Hawaiian Islands. Light large scale winds return to the region, allowing local scale land and sea breezes to develop from Wednesday into Thursday. Expect increasing southwesterly winds to strengthen across the islands with increasing clouds and shower trends ahead of the next cold front from late Thursday through Friday.
This next cold front appears stronger than the previous system, which means higher rainfall amounts, and the potential for periods of heavy rain and isolated thunderstorms along the frontal cloud band. The timing and island by island track of this next cold front, due to arrive late Friday into Saturday, remains less certain, especially for the eastern Hawaiian Islands. Operational guidance has recently decided to stall the forward progression of this cold front as a strong cut off low forms in the upper levels by Saturday night. This new wrinkle in the forecast may significantly alter the weather impacts for the Saturday to Sunday time period. Pay close attention to the weather forecast updates with this storm, as the track and intensity of this stronger cold front will evolve as the time period grows shorter.

Aviation

VFR conditions are expected today in a stable atmosphere. Light and variable large scale winds will keep daytime onshore seabreezes over all islands. Large scale southwesterly winds will develop and strengthen through the overnight hours, becoming moderate to breezy southwesterly winds on Monday. Cloud coverage and shower trends will increase starting on Monday as the next cold front approaches the islands from the northwest direction.
No AIRMETs in effect and none are expected.

Marine

A surface ridge will continue to drift southward over the islands today, leading to gentle to moderate south to southwest winds. Southwest winds will become fresh to strong tonight and Monday as a front approaches, and a Small Craft Advisory (SCA) will be needed for most waters. The front will move down the island chain Monday night and Tuesday, bringing gusty winds and heavy showers. Northwest winds behind the front will diminish and shift out of the east on Wednesday, followed by a return to southerly winds Thursday. Another front will likely reach the state late Friday or Saturday.
The current west-northwest swell will decline through Monday, with another round of extra-large surf due Tuesday. The High Surf Advisory for exposed north and west facing shores of most islands has been cancelled, as surf will be just below advisory levels this morning, and the SCA for elevated combined seas has also been dropped. Surf along north and west facing shores will diminish to small heights by Monday morning, followed by an increase during the afternoon as forerunners of the next northwest swell arrive. The next northwest swell (310 to 325 degrees) will build rapidly Monday night and will peak Tuesday and Wednesday as overlapping pulses pass through Hawaiian waters. Surf along most north and west facing shores will easily exceed High Surf Warning levels, and seas will exceed the 10 foot SCA threshold in many areas. The swell will decline Thursday and Friday, with surf falling below High Surf Advisory levels Thursday night. Another large swell is possible late Friday and Saturday.
Surf along east- and south-facing shores will remain small through much of the week, though an increase is possible along east shores next weekend.
A Coastal Flood Statement remains in effect through midday Monday, as peak monthly tides coincide with higher than predicted ocean levels. Expect minor flooding of low-lying coastal infrastructure as well as some some beach erosion during peak high tides between midnight and sunrise.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov