Photo Credit: Tyler Rooke

West Side

Today: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 76 to 85. East winds up to 20 mph. Chance of rain 40 percent.

Tonight: Partly cloudy with scattered showers. Lows 67 to 73. East winds up to 15 mph. Chance of rain 50 percent.

Wednesday: Mostly cloudy with scattered showers. Highs 76 to 84. Light winds becoming northeast up to 10 mph in the afternoon. Chance of rain 40 percent.

South Side

Today: Mostly sunny with isolated showers. Highs around 87. Northwest winds up to 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 65 to 73. Northwest winds up to 10 mph. Chance of rain 20 percent.

Wednesday: Mostly cloudy with scattered showers. Highs around 86. Light winds becoming north up to 10 mph in the afternoon. Chance of rain 30 percent.

North Shore

Today: Mostly cloudy. Breezy. Scattered showers and slight chance of thunderstorms in the morning, then showers likely and slight chance of thunderstorms in the afternoon. Locally heavy rainfall possible. Highs 74 to 82 near the shore to around 65 near 5000 feet. East winds 10 to 25 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with showers likely. Lows around 70 near the shore to 49 to 55 near 5000 feet. Southeast winds up to 15 mph. Chance of rain 70 percent.

Wednesday: Cloudy with showers likely. Highs 75 to 82 near the shore to around 65 near 5000 feet. East winds up to 10 mph. Chance of rain 70 percent.

Central Maui

Today: Breezy. Mostly sunny with isolated showers. Highs 81 to 87. East winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows around 68. East winds up to 15 mph. Chance of rain 20 percent.

Wednesday: Mostly cloudy with scattered showers. Highs 80 to 86. Light winds becoming northeast up to 10 mph in the afternoon. Chance of rain 50 percent.

Upcountry

Today: Windy. Partly sunny with scattered showers and slight chance of thunderstorms in the morning, then mostly sunny with slight chance of thunderstorms and isolated showers in the afternoon. Locally heavy rainfall possible. Highs around 61 at the visitor center to around 55 at the summit. East winds 10 to 35 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 48 at the visitor center to around 44 at the summit. East winds up to 25 mph. Chance of rain 50 percent.

Wednesday: Breezy. Mostly cloudy with scattered showers. Highs around 60 at the visitor center to around 55 at the summit. East winds up to 20 mph shifting to the southeast up to 10 mph in the afternoon. Chance of rain 50 percent.

East Maui

Today: Mostly cloudy. Breezy. Scattered showers and slight chance of thunderstorms in the morning, then showers likely and slight chance of thunderstorms in the afternoon. Locally heavy rainfall possible. Highs 74 to 82 near the shore to around 65 near 5000 feet. East winds 10 to 25 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with showers likely. Lows around 70 near the shore to 49 to 55 near 5000 feet. Southeast winds up to 15 mph. Chance of rain 70 percent.

Wednesday: Cloudy with showers likely. Highs 75 to 82 near the shore to around 65 near 5000 feet. East winds up to 10 mph. Chance of rain 70 percent.

Lanai City

Today: Mostly sunny with isolated showers. Highs 73 to 81. North winds up to 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows around 64. Light winds. Chance of rain 20 percent.

Wednesday: Mostly cloudy with showers likely. Highs 73 to 81. Light winds. Chance of rain 60 percent.

Kaunakakai

Today: Breezy. Mostly sunny with isolated showers. Highs 67 to 86. East winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 57 to 73. East winds 10 to 15 mph decreasing to up to 15 mph after midnight. Chance of rain 20 percent.

Wednesday: Mostly cloudy with scattered showers. Highs 67 to 86. East winds up to 10 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Wet and unsettled weather will remain this week. Locally breezy easterly winds will turn southeasterly and diminish during mid- week. Locally heavy rain will be possible throughout this time with a chance for thunderstorms over Maui and the Big Island. Gusty northerly winds will accompany a cold front that will push through the islands Thursday night through Friday. Heavy rain and flash flood potential will exist from Friday into next week.

Discussion

Model analysis pegged the temperature within the center of the closed low over the Big Island at an impressive -14C this morning, a slight moderation of the -16C observed yesterday afternoon. The mid-level cold pool has supported a broad region of lapse rates averaging around 7C/km which has been sufficient to support pockets of thunderstorms as conditionally unstable southerly flow is drawn around the eastern periphery of the low. Although the low will not move much during the next 24 hours, the favorable thermodynamic environment will nonetheless dwindle by Tuesday night as the cold pool warms by several degrees. Thunderstorms the associated heavy rain threat remain in the forecast over the Big Island, Maui, and adjacent waters into Tuesday night with conditions becoming more hostile for thunder by late Tuesday night into Wednesday. With that said, diurnal heating over the slopes of Leeward Big Island will still have the potential to touch off the occasional thunderstorm through the mid-week period.
Over the remaining islands, trade wind type showers have been locally heavy but progressive enough to preclude any flooding concerns. This will be a common theme through mid-week. Although periods of drier weather can be expected, occasional waves of moisture wrapping around the low and advecting westward across the smaller islands will support periods of heavier showers within the resident low stability environment.
The focus then turns to the potential for impactful weather late this week and potentially into next week. Model consensus remains outstanding that a deep trough will develop over the central Pacific and drive a cold front through most or all of island chain Thursday night through Friday. As the deepening trough approaches from the north, the closed low currently over the state will transition to an open wave and quickly shear eastward. However, lingering low and mid-level moisture will be readily available for the incoming front. With plenty of moisture already in place, a heavy rain rain and potential flood threat could materialize as early as Friday morning over north-facing slopes of Kauai within stout northerly flow. The threat would then quickly shift to the Big Island where the front appears most likely to stall Friday night through the first half of the weekend.
During the latter half of the weekend into early next week, the characteristic corridor of persistent moist southerly flow will develop east of the low as it closes off near or west of Kauai. This band will contain the greatest potential for heavy rain and flash flooding. Model depictions vary in their placement of their feature and exactly how progressive it is as it shifts westward toward the islands. This is to be expected given that this phase of the low’s life cycle is firmly in the extended range.
The general message is that the heavy rain threat and the potential for flooding will increase on Friday (possibly Kauai and more likely the Big Island) and has the potential to further escalate early next week.

Aviation

An upper low that is currently situated near the Big Island will linger near the eastern end of the state and gradually weaken today through tonight. This low will provide instability across the eastern half of the state. Early morning satellite and radar imagery show that enhanced low-level moisture is finally making its way into north and east sections of the Big Island and adjacent waters. Periodic heavy showers and even some isolated thunderstorms cannot be ruled out through the rest of today and tonight, especially for Maui County and the Big Island. Prevailing MVFR-level cloud ceilings and visibility are to be expected within the heavier shower activity. Elsewhere, MVFR conditions will be more isolated.
This morning, AIRMET Sierra remains in effect for for mountain obscuration above 2,000 feet across windward portions of the Big Island. This will likely remain in effect through much of the day. This AIRMET may need to be expanded to include portions of Maui County later this morning.
Additionally, AIRMET Tango remains in effect for tempo moderate upper-level turbulence between FL250 AND FL350 over Maui and the Big Island. This is expected to persist through early afternoon but then improve later today.

Marine

An upper level disturbance near the Big Island and Maui will continue to produce periods of showers across the region with isolated thunderstorms over the eastern half of the state. Trade winds remain elevated over eastern waters and channels with winds up to 25 kts near the Big Island. A Small Craft Advisory was expanded this morning to include the windier coastal waters and channels through this afternoon. Wind speeds will decrease with light and variable winds starting late Wednesday through Thursday.
Another stronger storm will develop over the Hawaii region by Friday as a cold front combines forces with an upper level disturbance forming a kona low near the islands. Unsettled weather conditions with widespread rain remains in the forecast from Friday onward as a cold front sweeps into the islands. Strong north to northwest winds will follow behind the front and southerly kona winds may develop from Saturday night onward. In addition, a very large north swell will begin to fill in Friday and peak over the weekend. Very rough ocean conditions are expected from Friday through the weekend.
A series of small northwest swells are expected today through Thursday. A much larger north-northwest swell is expected over the weekend and will likely bring warning level surf along north and west facing shores. Surf along east facing shores will lower as the trade winds fade. South facing shores will remain flat.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST this evening for Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

Maui Now Weather is brought to you by Blue Hawaiian Helicopters.

Check out their Maui Helicopter Tours today!

Data Courtesy of NOAA.gov