Photo Credit: Jeni Ji Cousins

West Side

Today: A 20 percent chance of showers after noon. Mostly sunny, with a high near 86. Calm wind becoming west around 5 mph.

Tonight: A 20 percent chance of showers before 8pm. Mostly clear, with a low around 70. Light south southeast wind.

Wednesday: Mostly sunny, with a high near 87. Calm wind becoming east northeast 5 to 7 mph in the afternoon.

South Side

Today: A 20 percent chance of showers after noon. Mostly sunny, with a high near 86. West wind 5 to 7 mph becoming calm in the afternoon.

Tonight: A 20 percent chance of showers before 8pm. Partly cloudy, with a low around 68. Calm wind becoming north around 5 mph after midnight.

Wednesday: Isolated showers after noon. Increasing clouds, with a high near 88. Light and variable wind becoming northeast 5 to 8 mph in the afternoon. Chance of precipitation is 20%.

North Shore

Today: A 20 percent chance of showers after noon. Mostly sunny, with a high near 83. Light and variable wind becoming east 6 to 11 mph in the afternoon.

Tonight: A 20 percent chance of showers. Partly cloudy, with a low around 69. East southeast wind 5 to 9 mph.

Wednesday: A 20 percent chance of showers before noon. Mostly sunny, with a high near 84. Breezy, with an east wind 7 to 12 mph increasing to 13 to 18 mph in the morning. Winds could gust as high as 26 mph.

Central Maui

Today: A 20 percent chance of showers after noon. Increasing clouds, with a high near 84. Calm wind becoming northeast 5 to 9 mph in the afternoon.

Tonight: A 20 percent chance of showers before 8pm. Mostly cloudy during the early evening, then becoming mostly clear, with a low around 68. North northwest wind around 6 mph.

Wednesday: Mostly sunny, with a high near 85. Breezy, with a north northwest wind 5 to 15 mph becoming northeast in the afternoon. Winds could gust as high as 21 mph.

Upcountry

Today: A 20 percent chance of showers after noon. Increasing clouds, with a high near 71. Calm wind becoming west northwest around 6 mph.

Tonight: A 20 percent chance of showers before 8pm. Cloudy during the early evening, then clearing, with a low around 56. Calm wind.

Wednesday: Mostly sunny, with a high near 72. Calm wind becoming east 5 to 7 mph in the afternoon.

East Maui

Today: A 20 percent chance of showers. Partly sunny, with a high near 80. Southeast wind 6 to 11 mph.

Tonight: A 40 percent chance of showers, mainly after 8pm. Mostly cloudy, with a low around 67. Southeast wind 5 to 8 mph becoming calm after midnight. New precipitation amounts of less than a tenth of an inch possible.

Wednesday: A 40 percent chance of showers. Partly sunny, with a high near 81. Light and variable wind becoming east southeast 5 to 10 mph in the morning. New precipitation amounts of less than a tenth of an inch possible.

Lanai City

Today: A 20 percent chance of showers after noon. Increasing clouds, with a high near 73. Calm wind becoming northwest around 5 mph.

Tonight: A 20 percent chance of showers before 8pm. Mostly cloudy during the early evening, then becoming mostly clear, with a low around 65. Light and variable wind.

Wednesday: Scattered showers after noon. Increasing clouds, with a high near 76. Calm wind becoming northeast 5 to 9 mph in the afternoon. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Kaunakakai

Today: A 20 percent chance of showers after noon. Mostly sunny, with a high near 81. Calm wind.

Tonight: A 20 percent chance of showers before 8pm. Mostly clear, with a low around 69. Calm wind.

Wednesday: Sunny, with a high near 84. Calm wind becoming east 5 to 8 mph in the afternoon.

Detailed Forecast

Synopsis

A low pressure system north of the state will keep light and variable winds in the forecast today. Light large scale winds will allow local scale land and sea breezes to develop. Sea breezes will build clouds over island interior sections with a few showers developing in the afternoon to early evening hours. Overnight land breezes will tend to clear out cloud cover with decreasing shower activity. Light to moderate trade winds will return from Wednesday through Friday with lingering modified sea breezes over some leeward slopes. Trade winds will diminish once again over the holiday weekend with drier trends by Memorial Day.

Discussion

The satellite imagery this morning continues to show a low pressure system and cold front breaking down the high pressure ridge north of the state. A weakened ridge at the surface will keep light and variable winds in the forecast today. Lighter large scale winds will keep the Hawaiian Islands in a land and sea breeze weather pattern for one more day. Radar imagery shows a fairly stable pattern with land breezes suppressing clouds and showers over most islands. A few convergent shower bands are still lingering over some of the coastal waters.
Afternoon sea breezes will produce convergent winds blowing from the ocean into island interior sections. These convergent winds along with island heating during the day will build clouds over each island. Clouds will begin to lose heating and surface wind convergence in the afternoon to early evening hours and a few shower may develop favoring these island mountain and interior sections. Isolated thunderstorms may develop over the higher elevations of the Big Island in the afternoon hours.
On Wednesday, the low pressure system north of the islands weakens and forms a cut off low northeast of the state. The ridge will build back in over the region and will be strong enough to produce light to moderate trade winds. The upper level low will keep subsidence inversion heights elevated, around the 7000 to 8000 foot level, producing a little instability for passing shower activity. Clouds and passing showers will shift a back towards windward and mountain areas. However, afternoon sea breezes will probably linger over western slopes of each island and the convergence between the weak trade winds and sea breezes may produce late afternoon shower activity over some leeward locations. This weak trade wind weather pattern will last through Friday.
Saturday through Memorial Day, another cold frontal system will move into the Central Pacific basin from Friday into Saturday. This low pressure system will weaken the high pressure ridge north of the islands. Weak trade winds will transition back a light and variable land and sea breeze weather pattern lasting through the holiday weekend. Clouds and a few showers will develop over island interior sections during this period. Drier and more stable conditions are forecast for Memorial Day as the surface ridge axis moves over the state.

Aviation

Land breezes are supporting mostly clear skies and prevailing VFR across the area early this morning. For this afternoon, sea breezes will again favor an expansion of afternoon cloud cover and a few inland showers. Isolated thunder will be possible over the Big Island slopes during peak heating.
No AIRMETs in effect.

Marine

A weak boundary passing through the northwestern offshore waters will stall north of the islands as a trough today. This has weakened maritime winds to gentle northeasterlies around Kauai and Oahu while veering gentle to moderate trades more east southeast over eastern island windward waters. As the weak trough washes out north of the islands through Wednesday, high pressure far northeast of the state will reestablish itself. This tighter pressure gradient back toward the islands will produce more widespread moderate trades across the chain during the second half of the week.
A small north northwest swell that bumped up north and west facing shore surf yesterday will be fading through the morning. The next small northwest swell is expected to increase north and west facing shore surf Wednesday night through Friday. While confidence is still somewhat low this far out, the arrival of a larger Memorial Day Weekend northwest swell Sunday could significantly pick up Memorial Day surf along many northern and western exposures. A series of small, long period southwest to south swells originating from the southern hemisphere are arriving and will persist through Friday. These swells will provide a minor boost to surf heights to near seasonal values throughout the week. Trade winds upstream of the islands are producing moderate surf along east facing shores despite the relatively weak trade winds around the islands. This elevated eastern coast surf will fade during the second half of the week.
Peaking monthly high astronomical tides, along with water levels running up to a third of a foot above normal, will combine to produce nuisance coastal flooding during this week’s late afternoon or early evening high tides. Any flooding impacts will be the inundation of normally dry beaches and coastal infrastructure.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov