Photo Credit: Tyler Rooke

West Side

Today: Sunny, with a high near 81. Breezy, with an east wind 15 to 20 mph becoming west southwest 5 to 10 mph in the morning. Winds could gust as high as 28 mph.

Tonight: Isolated showers. Partly cloudy, with a low around 66. Breezy, with an east northeast wind 13 to 16 mph, with gusts as high as 22 mph. Chance of precipitation is 20%.

Monday: Scattered showers. Cloudy, with a high near 81. Windy, with an east northeast wind 15 to 23 mph, with gusts as high as 32 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

South Side

Today: Isolated showers after noon. Mostly sunny, with a high near 81. West wind 9 to 14 mph, with gusts as high as 18 mph. Chance of precipitation is 20%.

Tonight: Scattered showers. Partly cloudy, with a low around 67. Northeast wind 11 to 14 mph, with gusts as high as 18 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Monday: Scattered showers. Cloudy, with a high near 78. Breezy, with a north wind 13 to 21 mph, with gusts as high as 29 mph. Chance of precipitation is 30%. New precipitation amounts between a tenth and quarter of an inch possible.

North Shore

Today: Showers likely, mainly before 9am. Partly sunny, with a high near 79. Windy, with an east wind 20 to 23 mph, with gusts as high as 32 mph. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Isolated showers. Partly cloudy, with a low around 66. Breezy, with an east wind 17 to 21 mph, with gusts as high as 29 mph. Chance of precipitation is 20%.

Monday: Scattered showers. Cloudy, with a high near 79. Windy, with an east wind 22 to 24 mph, with gusts as high as 34 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Central Maui

Today: Scattered showers, mainly before 9am. Mostly sunny, with a high near 79. Breezy, with an east northeast wind 11 to 16 mph, with gusts as high as 22 mph. Chance of precipitation is 30%.

Tonight: Isolated showers. Partly cloudy, with a low around 64. Northeast wind 8 to 11 mph. Chance of precipitation is 20%.

Monday: Scattered showers. Cloudy, with a high near 79. Breezy, with an east northeast wind 14 to 22 mph, with gusts as high as 31 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Upcountry

Today: Isolated showers after noon. Mostly sunny, with a high near 67. Southeast wind 5 to 9 mph becoming calm in the morning. Chance of precipitation is 20%.

Tonight: Isolated showers. Partly cloudy, with a low around 54. East southeast wind 6 to 8 mph. Chance of precipitation is 20%.

Monday: Scattered showers. Cloudy, with a high near 66. Breezy, with a light and variable wind becoming east 17 to 22 mph in the afternoon. Winds could gust as high as 31 mph. Chance of precipitation is 30%. New precipitation amounts between a half and three quarters of an inch possible.

East Maui

Today: Frequent showers, mainly before noon. High near 77. Breezy, with an east southeast wind 11 to 16 mph, with gusts as high as 22 mph. Chance of precipitation is 80%. New precipitation amounts between a tenth and quarter of an inch possible.

Tonight: Frequent showers. Low around 61. Breezy, with an east southeast wind 14 to 18 mph, with gusts as high as 25 mph. Chance of precipitation is 80%. New precipitation amounts between a tenth and quarter of an inch possible.

Monday: Frequent showers. High near 77. Windy, with an east southeast wind 15 to 23 mph, with gusts as high as 32 mph. Chance of precipitation is 80%. New precipitation amounts between a quarter and half of an inch possible.

Lanai City

Today: Scattered showers, mainly between noon and 3pm. Mostly sunny, with a high near 76. North northeast wind 5 to 7 mph becoming west southwest in the afternoon. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Isolated showers. Partly cloudy, with a low around 63. Calm wind becoming north northwest 5 to 7 mph. Chance of precipitation is 20%.

Monday: Scattered showers. Mostly cloudy, with a high near 74. East wind 7 to 11 mph. Chance of precipitation is 30%. New precipitation amounts between a quarter and half of an inch possible.

Kaunakakai

Today: Sunny, with a high near 80. Windy, with an east southeast wind 13 to 23 mph, with gusts as high as 32 mph.

Tonight: Isolated showers after 7pm. Partly cloudy, with a low around 68. Windy, with an east wind 18 to 24 mph, with gusts as high as 34 mph. Chance of precipitation is 20%.

Monday: Scattered showers, mainly after 7am. Mostly cloudy, with a high near 80. Windy, with an east wind 22 to 24 mph, with gusts as high as 34 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Detailed Forecast

Synopsis

Strong high pressure northeast of the area will maintain locally strong trade winds over the islands through much of the coming week. Windward areas will remain rather rainy. Rainfall will likely become more widespread tonight through Wednesday as a low aloft deepens northwest of the area.

Discussion

A strong 1041 mb high far north of the area is producing locally strong northeast to east trade winds over the main Hawaiian Islands. Windward areas have broken low clouds, while leeward areas have partly cloudy skies. Radars show numerous showers moving over windward areas with some of these showers spreading leeward on the smaller islands. These conditions will continue through the day today
The global models show a northwest to southeast trough aloft deepening west of the islands over the next few days. This trough will destabilize the atmosphere over the islands. The trough will also cause the low level flow to veer out of the southeast and bring very moist air towards the islands. Increased rainfall is likely starting tonight, especially over the Big Island of Hawaii. The global models disagree on how much of the moisture will move over the islands, so there is quite a bit of uncertainty in how widespread and heavy the rainfall will be.
The global models show the trough aloft lifting northwest starting Wednesday night as a ridge aloft builds over the area from the north. The atmosphere over the islands will become more stable and the moist air will move away to the west. That should bring a decrease in rainfall for the second half of the week, with showers focused over mainly windward areas.

Aviation

A strong high pressure system far north of the islands will maintain locally windy east to southeast winds through Monday. Scattered to numerous rain showers remain in the forecast today with the highest shower coverage developing over mountains and along east facing slopes. Expect brief periods of MVFR conditions in showers along the eastern slopes of most islands, extending into the southeastern slopes of the Big Island.
AIRMET SIERRA remains in effect for Tempo Mountain Obscuration above 2500 feet along north through east sections of Oahu and Kauai due to MVFR ceilings in showers.
AIRMET TANGO remains in effect for Moderate Turbulence below 8000 feet over and immediately southwest through northwest of all island mountains.

Marine

Strong east-southeast winds associated with high pressure will continue over the Hawaiian waters through the upcoming week. Rough conditions with seas at and above the Small Craft Advisory level of 10 ft will be the result across exposed waters.
Surf along east facing shores will remain rough due to the aforementioned strong onshore winds locally and upstream across the eastern Pacific driving large seas through the area. The advisory in place will continue through much of the week.
Surf along north and west facing shores will steadily lower through Monday as the northwest swell eases. Heights should dip below advisory levels for all exposed north and west facing shores by tonight. Large scale pattern change across the Pacific featuring a blocking pattern setting up east of the Date Line will translate to an end to the active period that began in the second half of December. Surf will respond and drop well below the January average Monday through midweek (near flat levels except for areas exposed to trade wind energy).
For the long range, guidance shows the current storm developing off the coast of Japan tracking northward tonight through Wednesday across the far western Pacific to the western Aleutians/Bering Sea. Wave models reflect this and show small, long-period energy arriving through the day Thursday out of the west-northwest, then trending up out of the northwest Friday and Friday night. Large errors typically associated with these sources lead to low forecast confidence.
Surf along south facing shores will trend up Tuesday through midweek, as an out-of-season Tasman source arrives. Nearshore PacIOOS buoy at Samoa reflected this source moving through 24 to 48 hrs ago, which increases confidence locally. Surf should drop and return to normal levels through the second half of the week.

HFO Watches/Warnings/Advisories

Winter Weather Watch until late Tuesday night for the summits of Mauna Loa and Mauna Kea on the Big Island of Hawaii.
High Surf Advisory until 6 PM today for north and west facing shores of Niihau, Kauai, Oahu and Molokai and north facing shores of Maui.
High Surf Advisory until 6 PM Sunday for west facing shores of the Big Island.
High Surf Advisory until 6 PM Monday for east facing shores of Kauai, Oahu, Molokai, Maui and the Big Island of Hawaii.
Small Craft Advisory until 6 PM Wednesday for all Hawaiian waters.

Data Courtesy of NOAA.gov