Photo Credit: Laila Reiss

West Side

Today: Isolated showers. Mostly sunny, with a high near 82. Light and variable wind becoming south southeast around 5 mph in the afternoon. Chance of precipitation is 20%.

Tonight: Scattered showers. Mostly cloudy, with a low around 70. South wind 6 to 9 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Wednesday: Scattered showers, then occasional showers and possibly a thunderstorm after noon. Some of the storms could produce gusty winds and heavy rain. High near 77. Breezy, with a south southwest wind 15 to 17 mph, with gusts as high as 25 mph. Chance of precipitation is 90%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

South Side

Today: Isolated showers. Mostly sunny, with a high near 82. Southeast wind 6 to 9 mph. Chance of precipitation is 20%.

Tonight: Scattered showers. Mostly cloudy, with a low around 68. Calm wind becoming south southwest around 6 mph after midnight. Chance of precipitation is 30%. New precipitation amounts between a tenth and quarter of an inch possible.

Wednesday: Scattered showers, then occasional showers and possibly a thunderstorm after noon. Some of the storms could produce gusty winds and heavy rain. High near 77. Breezy, with a south wind around 15 mph, with gusts as high as 24 mph. Chance of precipitation is 90%. New rainfall amounts between a half and three quarters of an inch possible.

North Shore

Today: Isolated showers. Mostly sunny, with a high near 80. East southeast wind 8 to 10 mph. Chance of precipitation is 20%.

Tonight: Scattered showers. Mostly cloudy, with a low around 69. South wind 3 to 6 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Wednesday: Scattered showers, then occasional showers and possibly a thunderstorm after noon. Some of the storms could produce gusty winds and heavy rain. High near 75. South southwest wind 10 to 14 mph, with gusts as high as 24 mph. Chance of precipitation is 90%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Central Maui

Today: Isolated showers. Mostly sunny, with a high near 80. East southeast wind around 7 mph. Chance of precipitation is 20%.

Tonight: Scattered showers. Mostly cloudy, with a low around 67. South wind 3 to 6 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Wednesday: Scattered showers, then occasional showers and possibly a thunderstorm after noon. Some of the storms could produce gusty winds and heavy rain. High near 75. South southwest wind around 14 mph, with gusts as high as 24 mph. Chance of precipitation is 90%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Upcountry

Today: Isolated showers. Mostly sunny, with a high near 67. East southeast wind 5 to 8 mph. Chance of precipitation is 20%.

Tonight: Scattered showers, mainly after 7pm. Mostly cloudy, with a low around 56. Light and variable wind becoming south southwest 5 to 9 mph after midnight. Chance of precipitation is 30%. New precipitation amounts between a quarter and half of an inch possible.

Wednesday: Scattered showers, then occasional showers and possibly a thunderstorm after 1pm. Some of the storms could produce gusty winds and heavy rain. High near 61. Breezy, with a south southwest wind 9 to 18 mph, with gusts as high as 30 mph. Chance of precipitation is 90%. New rainfall amounts between 1 and 2 inches possible.

East Maui

Today: Showers likely, mainly before noon. Partly sunny, with a high near 78. Breezy, with a southeast wind 13 to 15 mph, with gusts as high as 21 mph. Chance of precipitation is 70%. New precipitation amounts between a tenth and quarter of an inch possible.

Tonight: Scattered showers. Mostly cloudy, with a low around 65. Southeast wind 5 to 11 mph. Chance of precipitation is 40%. New precipitation amounts between a tenth and quarter of an inch possible.

Wednesday: Scattered showers, then occasional showers and possibly a thunderstorm after noon. Some of the storms could produce gusty winds and heavy rain. High near 73. Southwest wind 11 to 13 mph, with gusts as high as 23 mph. Chance of precipitation is 90%. New rainfall amounts between a half and three quarters of an inch possible.

Lanai City

Today: Scattered showers. Partly sunny, with a high near 74. Light and variable wind becoming south southeast around 6 mph in the afternoon. Chance of precipitation is 30%. New precipitation amounts between a tenth and quarter of an inch possible.

Tonight: Scattered showers. Mostly cloudy, with a low around 65. Breezy, with a south wind 9 to 18 mph, with gusts as high as 25 mph. Chance of precipitation is 40%. New precipitation amounts between a quarter and half of an inch possible.

Wednesday: Scattered showers and thunderstorms, then occasional showers and possibly a thunderstorm after noon. Some of the storms could produce gusty winds and heavy rain. High near 70. Windy, with a south southwest wind 18 to 23 mph, with gusts as high as 33 mph. Chance of precipitation is 90%. New rainfall amounts between 1 and 2 inches possible.

Kaunakakai

Today: Scattered showers. Partly sunny, with a high near 79. Light and variable wind. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers. Mostly cloudy, with a low around 69. South wind 6 to 14 mph, with gusts as high as 18 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Wednesday: Occasional showers and possibly a thunderstorm. Some of the storms could produce gusty winds and heavy rain. High near 75. Breezy, with a south southwest wind around 17 mph, with gusts as high as 26 mph. Chance of precipitation is 90%. New rainfall amounts between a quarter and half of an inch possible.

Detailed Forecast

Synopsis

Winds will shift out of the south over the next 24 hours as a front approaches. These kona winds will carry some showers over the islands and the showers may be locally heavy. The front will reach Kauai Wednesday, move across Oahu and Maui County Wednesday night, then move across the Big Island Thursday. The front will produce widespread rain and a few thunderstorms and gusty winds. Snow will blanket Mauna Kea and Mauna Loa. Drier and cooler air will spread over the islands behind the front and continue into the weekend.

Discussion

As of 2 AM, a 1025 mb surface high was far northeast of the islands. The high is producing locally fresh easterly trade winds from the Big Island to Oahu with winds veering out of the east southeast near Kauai. The low level flow has been pushing showery low clouds across the smaller islands. The showers are mostly missing the Big Island and have been most active over Oahu and Kauai.
Satellite imagery at 2 AM showed a front about 550 miles northwest of Kauai moving southeast at 15 to 20 mph. Winds over the islands are veering ahead of the front, from out of the southeast around the Big Island and out of the southwest near Kauai. These kona winds will carry some showers over the islands. The kona winds will strengthen just ahead of the front and may be especially strong where they accelerate downslope over the northeast sides of the islands.
The front will move over Kauai on Wednesday, Oahu and Maui County Wednesday night, and the Big Island Thursday. There will be a broad band of rain clouds along and ahead of the front. A deep trough aloft will make the atmosphere unstable, so there will be heavy showers and thunderstorms along the front. Temperatures will be cold enough for snow over the summits of Mauna Kea and Mauna Loa on the Big Island. The coldest air will likely move over the islands after the frontal moisture has moved to the east. The atmosphere may dry out soon enough to keep much snow over Haleakala on Maui but any lingering moisture could produce icy roads as the temperature drops well below freezing at the summit.
High pressure will build east behind the front bringing locally strong northeast winds and cool dry air through the end of the week. Winds will subside early next week.

Aviation

A front approaching from the northwest will enhance shower activity over the islands today. Low level flow will steer clouds and showers towards east and southeast facing sections. Isolated MVFR conditions are expected in brief showers, otherwise VFR conditions will prevail through the day.
Starting this evening, the air mass over the state will become increasingly moist and unstable. Mountain obscuration will likely become an issue, especially along east and southeast facing slopes. Thunderstorms possible after midnight.

Marine

A front will approach the islands and surrounding waters from the northwest over the next couple of days. The front is expected to enter the northwest coastal waters by Tuesday night, and then proceed down the island chain through Wednesday night.
Ahead of the front, winds will veer to the southeast and south. Behind the front, stronger northwest winds will initially move over the area, followed by northerly winds spreading across the coastal waters on Thursday. Winds are expected to return to a northeast direction on Friday, with some areas seeing Small Craft Advisory (SCA) levels winds, that will persist into the weekend.
The front will be accompanied by some thunderstorms, and with those you can expect some heavier showers along with gusty and erratic winds. Initially these are expected to impact the waters near Kauai late Tuesday night, and then spread to the central waters Wednesday morning. By Wednesday afternoon, improving conditions are expected over the waters near Kauai, as the impacts of the front start to reach the Big Island waters. Wednesday night should focus most of the frontal activity to waters near Maui County and the Big Island.
A series of small, northerly swells are expected through tonight, maintaining surf pretty much as is along the north facing shores. A much larger northwest swell will likely produce extra large surf along north and west facing shores of Kauai and Oahu, and slightly smaller surf along exposed north facing shores of Maui County. The swell is expected to have enough of a west component that the possibility exists for the west facing shores of the Big Island to reach advisory levels. Early energy from this swell will likely arrive on Kauai late today, and then steadily build, peaking late Thursday into Friday. This swell will also bring SCA level seas to much of the coastal waters during the event. SCA level winds could reach the Kauai coastal waters as early as Wednesday morning, then spread to most remaining waters by Thursday morning. Many areas will continue to experience SCA level seas into the weekend.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov