Photo Credit: Tyler Rooke

West Side

Today: Isolated showers before 11am. Mostly sunny, with a high near 81. Breezy, with an east northeast wind 9 to 18 mph, with gusts as high as 26 mph. Chance of precipitation is 20%.

Tonight: Isolated showers after midnight. Mostly clear, with a low around 65. East northeast wind 8 to 14 mph, with gusts as high as 18 mph. Chance of precipitation is 20%.

Monday: Isolated showers. Mostly sunny, with a high near 82. East northeast wind 5 to 8 mph becoming calm. Chance of precipitation is 20%.

South Side

Today: Isolated showers after 11am. Increasing clouds, with a high near 81. Calm wind becoming south southwest around 6 mph in the afternoon. Chance of precipitation is 20%.

Tonight: Partly cloudy, with a low around 63. South southwest wind around 5 mph becoming calm.

Monday: Scattered showers after noon. Mostly sunny, with a high near 82. Light and variable wind becoming east 5 to 10 mph in the afternoon. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

North Shore

Today: Isolated showers before noon. Partly sunny, with a high near 79. Breezy, with a northeast wind 15 to 20 mph, with gusts as high as 28 mph. Chance of precipitation is 20%.

Tonight: Isolated showers after 7pm. Partly cloudy, with a low around 64. Breezy, with an east wind 13 to 16 mph, with gusts as high as 22 mph. Chance of precipitation is 20%.

Monday: Isolated showers before 1pm. Mostly sunny, with a high near 80. East wind 9 to 14 mph becoming north northeast in the afternoon. Winds could gust as high as 18 mph. Chance of precipitation is 20%.

Central Maui

Today: Isolated showers before noon. Mostly sunny, with a high near 79. Breezy, with a northeast wind 11 to 20 mph, with gusts as high as 28 mph. Chance of precipitation is 20%.

Tonight: Isolated showers after 1am. Mostly clear, with a low around 62. North northeast wind 8 to 13 mph. Chance of precipitation is 20%.

Monday: Isolated showers before 1pm. Sunny, with a high near 80. North northeast wind 6 to 10 mph. Chance of precipitation is 20%.

Upcountry

Today: Mostly sunny, with a high near 66. Calm wind becoming west around 6 mph in the afternoon.

Tonight: Mostly clear, with a low around 52. West wind around 6 mph becoming calm in the evening.

Monday: Scattered showers after noon. Mostly sunny, with a high near 67. Calm wind becoming east 5 to 9 mph in the afternoon. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

East Maui

Today: Showers likely, mainly before 11am. Mostly cloudy, with a high near 77. East wind 10 to 13 mph. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers. Mostly cloudy, with a low around 60. East wind 6 to 10 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Monday: Scattered showers. Mostly cloudy, with a high near 78. East southeast wind 7 to 13 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Lanai City

Today: Isolated showers after 11am. Partly sunny, with a high near 74. Breezy, with a northeast wind 9 to 16 mph, with gusts as high as 22 mph. Chance of precipitation is 20%.

Tonight: Partly cloudy, with a low around 61. Northeast wind 9 to 14 mph becoming light after midnight. Winds could gust as high as 18 mph.

Monday: Scattered showers after noon. Mostly sunny, with a high near 74. Calm wind becoming east northeast around 6 mph in the afternoon. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Kaunakakai

Today: Scattered showers before 11am. Mostly sunny, with a high near 79. Breezy, with an east wind 14 to 16 mph, with gusts as high as 22 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Mostly clear, with a low around 66. Breezy, with an east wind 9 to 16 mph, with gusts as high as 22 mph.

Monday: Isolated showers after noon. Mostly sunny, with a high near 79. East wind 9 to 14 mph, with gusts as high as 18 mph. Chance of precipitation is 20%.

Detailed Forecast

Synopsis

Breezy easterly trade winds will prevail into Monday, with clouds and showers favoring windward and mountain locations. Rainfall chances will quickly rise Tuesday as the winds shift out of the south to southwest ahead of a strong cold front approaching. This front will quickly advance down the island chain late Tuesday through Thursday. Heavy showers and a few thunderstorms will accompany the front. Cooler and drier conditions will follow the front Wednesday into Thursday with breezy north to northwest winds.

Discussion

A mostly dry and stable trade wind pattern is anticipated into Monday due to surface high pressure far north of the state and an upper ridge in place. Clouds and showers will favor windward and mountain locations, mainly through the overnight and early morning hours as bands of moisture move through from east to west. A transition period is expected Monday into Monday night as a strong shortwave trough and its attendant cold front approach the region. Although mostly dry conditions should prevail Monday, the low-level flow will begin to shift out of the east-southeast and trend down – potentially enough for sea breezes and a few interior/leeward showers to develop Monday afternoon.
The long-term guidance remains in decent agreement initially and shows this cold front approaching through the day Tuesday, then quickly advancing down the island chain Tuesday night through midweek. Winds will shift out of the south to southwest and increase to moderate levels ahead of the front. Plenty of moisture pooling northward over the state combined with lowering upper heights will drive the rainfall chances up along and ahead of this feature. Although guidance does show this boundary quickly moving through, localized flooding will be a concern. In addition to the rainfall potential, a few thunderstorms will be possible.
Cooler/drier and breezy conditions will fill in over Kauai and Oahu Wednesday through Thursday in the wake of the front. Guidance depicts dewpoints dipping into the low-to-mid 50s over these areas by Wednesday evening. Forecast confidence lowers quickly beyond this point and will depend mostly on how far the front progresses eastward. The latest model cycles are now indicating the front will push east of the state with northeast trades returning Friday into the weekend.

Aviation

A high pressure system far north of the Hawaiian Islands will keep moderate to breezy easterly trade winds in the forecast through Monday. A band of low clouds moving in from the east will continue to produce showers over windward and mountain areas, mainly in the overnight to early morning hours. Brief periods of MVFR conditions will occur along north and east sections of each island favoring the overnight hours.
AIRMET Sierra for Mountain Obscuration in effect for north through east sections of Oahu, Molokai, Maui, and the Big Island. This AIRMET will diminish in coverage later this morning.
AIRMET Tango for moderate low level turbulence remains in effect over mountains and areas immediately south through west of mountain ranges. Wind speeds will decrease this morning likely canceling this AIRMET.

Marine

Fresh to locally strong trades should hold across the local Hawaiian waters through the day. A downward trend in both swell and sea heights have scaled back the Small Craft Advisory for just strong winds over those notoriously windier channels and bays surrounding Maui County and waters south of the Big Island. Monday’s trades will weaken to more moderate speeds as the pressure gradient relaxes ahead of an approaching cold front from the northwest. This front will quickly advance down the island chain late Tuesday through midweek, then east of the state by Friday. Winds will shift out of the south and increase to moderate levels ahead of the front, then to the northwest and become gusty in its wake Wednesday through Thursday. In addition to the winds, heavy showers and thunderstorms will accompany the front as it pushes through.
Recent upstream offshore buoy observations indicate that the current northwest swell has lowered and this trend is expected to continue through Monday. A series of small, northerly swells will arrive early in the week. A much larger northwest swell that will likely produce XL surf along smaller island north and west-facing shorelines is timed to pass through the islands Wednesday and peak surf on Thursday.

HFO Watches/Warnings/Advisories

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

Data Courtesy of NOAA.gov