West Side

Today: Sunny. Highs 74 to 79. East winds up to 15 mph.

Tonight: Partly cloudy. Lows 64 to 70. Light winds.

Tuesday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 75 to 80. Light winds. Chance of rain 40 percent.

South Side

Today: Sunny. Highs around 82. North winds around 10 mph.

Tonight: Mostly clear. Lows 65 to 72. Light winds.

Tuesday: Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs around 81. Light winds. Chance of rain 40 percent.

North Shore

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 77 near the shore to around 63 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows around 68 near the shore to around 50 near 5000 feet. Southeast winds 10 to 15 mph. Chance of rain 40 percent.

Tuesday: Mostly cloudy with numerous showers. Highs around 78 near the shore to around 64 near 5000 feet. Southeast winds around 10 mph. Chance of rain 70 percent.

Central Maui

Today: Sunny. Highs 78 to 83. Northeast winds 10 to 15 mph decreasing to up to 15 mph in the afternoon.

Tonight: Partly cloudy. Lows around 67. Northeast winds around 10 mph in the evening becoming light.

Tuesday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs around 80. Light winds. Chance of rain 40 percent.

Upcountry

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 59 at the visitor center to around 63 at the summit. South winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly clear in the evening then becoming mostly cloudy. Breezy. Isolated showers. Lows around 46 at the visitor center to around 40 at the summit. South winds 10 to 20 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs 55 to 72. Southwest winds 10 to 20 mph. Chance of rain 50 percent.

East Maui

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 77 near the shore to around 63 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows around 68 near the shore to around 50 near 5000 feet. Southeast winds 10 to 15 mph. Chance of rain 40 percent.

Tuesday: Mostly cloudy with numerous showers. Highs around 78 near the shore to around 64 near 5000 feet. Southeast winds around 10 mph. Chance of rain 70 percent.

Lanai City

Today: Sunny with isolated showers. Highs 69 to 76. Northeast winds up to 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Lows 61 to 66. Light winds.

Tuesday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 69 to 76. Light winds. Chance of rain 40 percent.

Kaunakakai

:

Detailed Forecast

Synopsis

Mostly dry and pleasant trade wind weather will continue today, with brief passing showers favoring windward and mauka areas. A significant pattern change is then expected by Tuesday as an upper disturbance and surface low pressure evolve northwest of the islands. This system is expected to draw deep tropical moisture northward over the state, leading to an extended period of southerly winds, increased chances for widespread rainfall, and renewed flooding concerns from the middle of the week through the weekend.

Discussion

The forecast has been nudged closer to the National Blend of Models, with some fine tuning of things like the QPF for the Wednesday through Friday time span.
A digging shortwave trough east of Midway will push rapidly to the east-southeast down the Northwest Hawaiian Islands today. The high resolution ensembles show the trough aloft should be close enough to begin locally enhancing showers over and near Kauai tonight in the southeast flow. A few of these might become briefly heavy as this leading shortwave gets close and mid-level temperatures cool for a while, but instability will still be limited at this point.
High pressure to the north will continue to bring some moderate trades to the islands today, but a cold front northwest of the islands that is moving to the east will help to push the ridge closer to the islands. The result will be weakening winds that will begin to veer to a southerly direction. Tonight or tomorrow morning, a broad surface trough is expected to develops northwest of the islands, helping to reinforce the background southeast to south winds from Tuesday through Wednesday.
This is about the time a series of shortwave troughs, like the one mentioned above, will begin to dig towards the islands. As background flow becomes more southerly, models remain in good agreement that deep tropical moisture will be drawn northward once again over the islands as early as Tuesday but especially by Wednesday. The increased moisture, combined with daytime heating, sea breezes, and a potent shortwave trough moving through, may even trigger some heavy showers over interior areas on Tuesday.
From Wednesday through the end of the week, there remains the potential for more widespread rainfall and flooding. Upper-level forcing is expected to strengthen as a strong shortwave rounds the base of the trough, potentially enhancing lift over the region while low pressure organizes west of the islands. The combination of deep moisture, increasing large-scale forcing for ascent, and southerly winds (which could be gusty at times) all point towards yet another widespread and organized rainfall event for the state. In addition to the rainfall concerns during this period, some strong to severe thunderstorms along with gusty downsloping winds for north and windward sides of the islands can't be ruled out.
Differences remain in the global models for next weekend, but the general consensus is that the active pattern could linger in the area. The ECMWF clears out much of the state of the bulk of the rain, but the GFS continues the potential for rain across at least portions of the state through the weekend and beyond, where the deep moisture axis anchors.
As previous discussions have mentioned, one important consideration with this week's rainfall is antecedent conditions. The islands experienced significant flash flood events in recent weeks, and despite several days of drier trade wind weather, soils remain vulnerable in many areas. As a result, any time period of higher rainfall rates could quickly lead to enhanced runoff, renewed rises in streams and reservoirs, and localized flash flooding concerns.
This system will continue to be closely monitored over the coming days, and additional adjustments to timing, duration, and impact messaging are possible as details become more clear.

Aviation

A ridge north of the islands continues to bring moderate trades to the islands. As the ridge slowly sinks southward, in response to a front far to the northwest pushing to the east, trades will weaken and veer to a more southerly direction. Passing showers being carried in on the trade wind flow could bring brief MVFR conditions, however VFR conditions are generally expected
AIRMET Sierra is in effect for clouds and showers impacting the east side of Oahu, but anticipate this to be dropped shortly after daybreak. AIRMET Tango is in effect for upper level turbulence over the islands.

Marine

Moderate to locally fresh trades will hold through this afternoon as high pressure far north of the islands moves slowly eastward. Winds will ease and shift southeasterly tonight through Wednesday as a front stalls just west of the islands. The winds will turn more southerly and increase to moderate and strong levels on Thursday as a low pressure system develops along the stalled frontal boundary.
Small northwest swells will keep some small surf along north facing shores through today. A moderate long-period northwest swell will fill in tonight and Tuesday, giving more of a boost to north shore surf late Tuesday through Wednesday. A small, short period north northeast swell will fill in during the day Tuesday before peaking Wednesday and subsiding Thursday. This overlap will make for some rough choppy conditions.
A small southerly swell will keep some small surf in place along south facing shores through today. A slightly larger, long-period south swell, will fill in tonight. This swell will give a more noticeable increase to south shore surf Tuesday and possibly reaching advisory levels by Wednesday before slowly easing Thursday into the weekend. Strengthening southerly winds could make for rough choppy surf by late next week.
East shore surf will remain small and below the seasonal average during the next 7 days due to a lack of strong trade winds over and upstream of the islands, except for some wrap from the northerly swells.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov