Photo Credit: Tyler Rooke

West Side

Today: Scattered showers and thunderstorms. Some of the storms could produce heavy rainfall. Mostly cloudy, with a high near 76. Breezy, with a northeast wind 11 to 16 mph becoming light east northeast in the afternoon. Winds could gust as high as 22 mph. Chance of precipitation is 50%. New precipitation amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Tonight: Scattered showers. Mostly cloudy, with a low around 68. Calm wind becoming east 5 to 9 mph after midnight. Chance of precipitation is 40%. New precipitation amounts between a tenth and quarter of an inch possible.

Wednesday: Isolated showers after noon. Mostly cloudy, with a high near 79. East wind around 10 mph. Chance of precipitation is 20%.

South Side

Today: Scattered showers and thunderstorms. Some of the storms could produce heavy rainfall. Mostly cloudy, with a high near 76. Northeast wind around 6 mph becoming light and variable. Chance of precipitation is 30%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Tonight: Scattered showers, mainly before 7pm. The rain could be heavy at times. Mostly cloudy, with a low around 66. North northeast wind around 5 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Wednesday: Partly sunny, with a high near 79. North wind 6 to 13 mph.

North Shore

Today: Showers and possibly a thunderstorm before noon, then showers likely. Some of the storms could produce heavy rainfall. High near 74. Breezy, with an east wind 13 to 17 mph, with gusts as high as 24 mph. Chance of precipitation is 90%. New precipitation amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Tonight: Scattered showers. Mostly cloudy, with a low around 67. East wind 8 to 13 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Wednesday: Scattered showers, mainly after noon. Mostly cloudy, with a high near 77. Breezy, with an east northeast wind 8 to 16 mph, with gusts as high as 22 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Central Maui

Today: Showers and possibly a thunderstorm before noon, then scattered showers. Some of the storms could produce heavy rainfall. High near 74. North northeast wind 8 to 14 mph, with gusts as high as 18 mph. Chance of precipitation is 80%. New precipitation amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Tonight: Scattered showers. Mostly cloudy, with a low around 65. East northeast wind 5 to 8 mph becoming north after midnight. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Wednesday: Scattered showers after noon. Mostly cloudy, with a high near 77. North wind 5 to 14 mph becoming east northeast in the morning. Winds could gust as high as 18 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Upcountry

Today: Scattered showers and thunderstorms. Some of the storms could produce heavy rainfall. Mostly cloudy, with a high near 61. East northeast wind 6 to 11 mph becoming light and variable in the morning. Chance of precipitation is 50%. New precipitation amounts between 1 and 2 inches possible.

Tonight: Scattered showers before midnight. Mostly cloudy, with a low around 55. Calm wind. Chance of precipitation is 30%. New precipitation amounts between a tenth and quarter of an inch possible.

Wednesday: Partly sunny, with a high near 64. Light and variable wind becoming east 8 to 13 mph in the afternoon.

East Maui

Today: Showers likely and possibly a thunderstorm. Some of the storms could produce heavy rainfall. Cloudy, with a high near 72. Breezy, with a north wind 6 to 15 mph becoming east southeast in the afternoon. Winds could gust as high as 21 mph. Chance of precipitation is 70%. New rainfall amounts between a half and three quarters of an inch possible.

Tonight: Showers likely. The rain could be heavy at times. Cloudy, with a low around 63. East southeast wind 6 to 10 mph. Chance of precipitation is 70%. New precipitation amounts between a quarter and half of an inch possible.

Wednesday: Showers likely. Mostly cloudy, with a high near 75. Breezy, with an east wind 7 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.

Lanai City

Today: Showers likely and possibly a thunderstorm. Some of the storms could produce heavy rainfall. Cloudy, with a high near 70. Windy, with a northeast wind 19 to 24 mph decreasing to 6 to 11 mph in the afternoon. Winds could gust as high as 34 mph. Chance of precipitation is 70%. New rainfall amounts between 1 and 2 inches possible.

Tonight: Scattered showers. Mostly cloudy, with a low around 61. Northeast wind 6 to 13 mph. Chance of precipitation is 40%. New precipitation amounts between a quarter and half of an inch possible.

Wednesday: Mostly cloudy, with a high near 72. East wind 9 to 13 mph.

Kaunakakai

Today: Showers likely and possibly a thunderstorm. Some of the storms could produce heavy rainfall. Cloudy, with a high near 74. Breezy, with a northeast wind 8 to 16 mph, with gusts as high as 22 mph. Chance of precipitation is 70%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Tonight: Scattered showers and thunderstorms. Mostly cloudy, with a low around 69. East northeast wind 5 to 8 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Wednesday: Isolated showers after noon. Partly sunny, with a high near 77. Breezy, with an east wind 7 to 12 mph increasing to 13 to 18 mph in the morning. Winds could gust as high as 25 mph. Chance of precipitation is 20%.

Detailed Forecast

Synopsis

An unstable cloud band associated with a low level trough begins to drift westward over Oahu and Kauai today with shower trends increasing over the western islands through tonight. Strong northeasterly winds will begin to ease over the eastern islands later this morning, becoming moderate to breezy trade winds for Maui and Hawaii Counties. Windy and wet weather conditions will continue over Oahu and Kauai through this afternoon. Improving weather trends are forecast from Wednesday through the end of the week with moderate to breezy easterly trade winds forecast with periods of showers favoring windward and mountain areas. Trade winds are expected to strengthen through the weekend with more scattered shower activity.

Discussion

Abundant unstable moisture associated with a low level trough currently over Maui County this morning will move westward today spreading widespread rain and locally heavy showers back into Oahu and Kauai. This large band of showers will combine forces with strong and gusty northeasterly trade winds to produce several inches of rainfall along the windward and mountain slopes from Kauai to Maui today. The Flash Flood Watch to cover the elevated flooding threat was expanded westward to include Kauai County today. Enough dynamic forcing and instability over the region may produce a few thunderstorms along this unstable cloud band. Stronger winds are expected to shift back into Kauai today, and the Wind Advisory was expanded to include Kauai County.
Meanwhile out east, the Big Island will see improving weather trends through the day, with gradually decreasing rainfall amounts over Maui by this afternoon. A Winter Weather Advisory remains in effect for the highest peaks on the Big Island above 12,000 feet elevation, where an additional 1 to 2 inches of snow accumulations are forecast with patchy freezing fog until this evening. Wind speeds will be weaker today over these eastern islands. The Flash Flood Watch was cancelled for the Big Island. The Wind Advisory for Maui County was also cancelled due to these more moderate trade wind speeds.
Wednesday through Friday, trade winds will become moderate to breezy with periods of showers favoring windward and mountain areas, less showers are forecast over leeward areas.
Saturday and Sunday, trade winds will increase through the weekend, becoming breezy to windy easterlies on Sunday. Isolated to scattered showers remain in the forecast for both days favoring typical windward and mountain areas.

Aviation

The front in the area has weakened to a trough and is moving slowly west, nearing Molokai as of this writing. Areas of MVFR cigs/vsbys can be expected along and near the trough, particularly in windward areas. Moderate to strong north to northeast winds will persist, mainly to the the west of the trough axis, as robust high pressure remains far north of the islands.
AIRMET Sierra remains in effect for mountain obscuration for windward sections of Kauai and Oahu, and for all of Molokai, Lanai and Maui.
AIRMET Tango remains in effect for low level turbulence over and downwind of the terrain from Kauai eastward to Maui. AIRMET Tango is also posted for high level turbulence over the western portion of the island chain.
AIRMET Zulu is in effect for TEMPO moderate rime icing from Kauai eastward to Maui.

Marine

A surface trough, which appears to be near Maui early this morning, is moving slowly westward. There is also a broad surface high pressure system far north of the region. The tight pressure gradient between the trough and the surface high is producing gusty northeasterly winds and elevated, rough seas over most of the waters along and west of the trough. There are also elevated seas near the Big Island. A Small Craft Advisory (SCA) is now in effect for all waters, except Maalaea Bay. In addition to the strong winds and rough seas, widespread cloud cover, locally heavy downpours and isolated thunderstorms will likely continue across most of the state into tonight. Once the surface trough moves west of the state, expect a wet trade wind weather pattern to begin to set up later this week as a surface high builds far north- northeast of the region.
A large north-northwest swell combined with the locally generated wind waves is producing very large and disorganized surf along north and west facing shores of most of the islands early this morning. As a result, a High Surf Warning remains in effect through this morning for most north and west facing shores of the smaller islands. There is also a High Surf Advisory (HSA) in effect for north and west facing shores of the Big Island. The forecast guidance shows the swell direction will become more northerly later today and tonight. Therefore, we expect a HSA will be needed for the north and west facing shores of the smaller islands from this afternoon into tonight. Expect the HSA to eventually be cancelled by early Wednesday as the local winds decrease and the north swell gradually subsides.
Expect modest surf along most east facing shores due to the locally strong winds during the next couple of days. The surf will decrease somewhat by Thursday, but will increase again along east facing shores this weekend as the trade winds strengthen. Small background surf will persist along south facing shores through next weekend.

HFO Watches/Warnings/Advisories

Flash Flood Watch through this afternoon for Niihau, Kauai, Oahu, Molokai, Lanai, Kahoolawe, Maui.
Wind Advisory until 6 PM HST this evening for Niihau, Kauai, Oahu.
High Surf Warning until noon HST today for Niihau, Kauai Windward, Kauai Leeward, Waianae Coast, Oahu North Shore, Oahu Koolau, Olomana, Molokai, Maui Windward West, Maui Central Valley, Windward Haleakala.
High Surf Advisory until noon HST today for Kona, Big Island North and East, Kohala.
Winter Weather Advisory until 6 PM HST this evening for Big Island Summits.
Flash Flood Watch through this afternoon for Maalaea Bay.
Small Craft Advisory until 6 PM HST this evening for all Hawaiian waters except Maalaea Bay.

Data Courtesy of NOAA.gov