Photo Credit: Tyler Rooke

West Side

Today: Isolated showers before 1pm. Partly sunny, with a high near 83. East wind around 6 mph becoming calm in the afternoon. Chance of precipitation is 20%.

Tonight: Isolated showers after 1am. Mostly cloudy, with a low around 69. East wind 6 to 8 mph. Chance of precipitation is 20%.

Sunday: Isolated showers before 1pm. Mostly sunny, with a high near 83. East northeast wind 6 to 11 mph becoming light and variable in the afternoon. Chance of precipitation is 20%.

South Side

Today: Isolated showers after 1pm. Partly sunny, with a high near 83. Light and variable wind becoming west northwest around 6 mph in the afternoon. Chance of precipitation is 20%.

Tonight: Isolated showers before 7pm. Mostly cloudy, with a low around 67. Calm wind becoming northeast around 5 mph after midnight. Chance of precipitation is 20%.

Sunday: Isolated showers after 1pm. Mostly sunny, with a high near 83. Light and variable wind becoming west northwest around 6 mph in the afternoon. Chance of precipitation is 20%.

North Shore

Today: Scattered showers, mainly before noon. Partly sunny, with a high near 81. Breezy, with an east wind 13 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.

Tonight: Isolated showers. Mostly cloudy, with a low around 68. Breezy, with an east wind 13 to 20 mph, with gusts as high as 29 mph. Chance of precipitation is 20%.

Sunday: Isolated showers. Partly sunny, with a high near 81. Breezy, with an east wind 16 to 22 mph, with gusts as high as 30 mph. Chance of precipitation is 20%.

Central Maui

Today: Isolated showers. Partly sunny, with a high near 81. Breezy, with an east northeast wind 10 to 15 mph increasing to 16 to 21 mph in the afternoon. Winds could gust as high as 29 mph. Chance of precipitation is 20%.

Tonight: Isolated showers after midnight. Mostly cloudy, with a low around 66. Northeast wind 6 to 14 mph, with gusts as high as 18 mph. Chance of precipitation is 20%.

Sunday: Isolated showers. Partly sunny, with a high near 81. Breezy, with a northeast wind 9 to 17 mph, with gusts as high as 24 mph. Chance of precipitation is 20%.

Upcountry

Today: Partly sunny, with a high near 69. Calm wind becoming west 5 to 7 mph in the afternoon.

Tonight: Mostly cloudy, with a low around 55. West wind around 5 mph becoming calm in the evening.

Sunday: Mostly sunny, with a high near 69. Light and variable wind becoming east 9 to 14 mph in the afternoon. Winds could gust as high as 18 mph.

East Maui

Today: Scattered showers. Mostly cloudy, with a high near 79. Breezy, with an east southeast wind 11 to 16 mph, with gusts as high as 22 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers. Mostly cloudy, with a low around 64. Breezy, with an east southeast wind 13 to 16 mph, with gusts as high as 22 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Sunday: Scattered showers. Mostly cloudy, with a high near 79. Breezy, with an east southeast wind 11 to 16 mph, with gusts as high as 22 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Lanai City

Today: Isolated showers after noon. Partly sunny, with a high near 74. North wind 5 to 9 mph becoming calm in the morning. Chance of precipitation is 20%.

Tonight: Mostly cloudy, with a low around 64. Calm wind becoming north around 6 mph after midnight.

Sunday: Isolated showers after noon. Partly sunny, with a high near 74. Calm wind becoming east 5 to 9 mph in the afternoon. Chance of precipitation is 20%.

Kaunakakai

Today: Partly sunny, with a high near 80. Breezy, with an east wind 8 to 13 mph increasing to 15 to 20 mph in the afternoon. Winds could gust as high as 29 mph.

Tonight: Mostly cloudy, with a low around 70. Breezy, with an east wind 13 to 18 mph, with gusts as high as 26 mph.

Sunday: Mostly sunny, with a high near 80. Breezy, with an east wind 15 to 20 mph, with gusts as high as 29 mph.

Detailed Forecast

Synopsis

High pressure northeast of the state will keep moderate to breezy trade winds in place through the weekend, with showers favoring windward and mauka areas and a stray shower reaching leeward areas from time to time. Dry trade wind weather is expected to build back in Sunday night through Monday night. Trade showers should increase in coverage and intensity Tuesday through late next week as old frontal remnants move through the islands and moisture moves in from the southeast. Quite windy weather could develop statewide Wednesday through late next week as a very strong high builds northeast of the island chain.

Discussion

Currently at the surface, a broad 1038 mb high is centered around 1400 miles northeast of Honolulu, and is driving moderate trade winds trade winds across the island chain early this morning. Infrared satellite imagery shows high cloud streaming over the state, resulting in mostly cloudy conditions in most areas. Radar imagery shows a fairly typical trade wind shower regime, with scattered showers moving into windward areas, and a few of these showers making the trip over the mountains and into leeward communities. Main short term concerns revolve around trade wind trends and the potential for a few pop up thunderstorms on the Big Island this afternoon and again Sunday afternoon.
Strong high pressure will remain far northeast of the islands through the weekend and the first half of next week, while a front slowly approaches from the northwest, stalling out around 400-500 miles west of the state by Wednesday. This will keep a moderate to breezy trade wind pattern in place across the islands, with the trades strongest over the eastern islands. Additionally, the low level boundary layer flow may shift east-southeasterly enough to allow for some local land and sea breeze development over the western islands at times, most likely Monday through Tuesday. The trades appear to ramp up to breezy and windy levels Wednesday through late next week, as a very strong high (1045-1048 mb) is forecast to develop far to the northeast of the state as the front west of the islands weakens into a trough and begins to retrograde westward and away from the area.
The airmass over the islands will continue to stabilize through the weekend as the upper troughing breaks down and upper level ridging begins to become more dominant. With precipitable water values hovering in the 1.2 to 1.5 range through the weekend however, we should continue to see a bit more trade wind shower coverage than normal. The showers will continue to favor windward and mauka areas with a few showers making the trip into leeward communities at times. Additionally, the airmass appears unstable enough that daytime heating could allow a thunderstorm or two to develop over the Big Island this afternoon and again Sunday afternoon.
A drier and more typical trade wind pattern should settle over the islands Sunday night through Monday night as precipitable water values lower to around 1 inch. Model solutions then show an increase in trade wind shower coverage Tuesday through late next week, as some old frontal remnants move through and some moisture advects into the region on east-southeasterly boundary layer flow. Showers will continue to favor windward and mauka areas, with a few showers reaching leeward locales at times.

Aviation

Moderate to breezy easterly trade winds will focus clouds and showers over windward and mountain locations through the weekend. MVFR ceilings and visibilities are possible in and around these showers.
AIRMET Sierra is currently in effect for mountain obscuration over the windward slopes of Kauai and Oahu.

Marine

Large, strong high pressure off the mainland west coast will produce a tight enough pressure gradient across the eastern Pacific to produce and maintain fresh to strong trades over the local Hawaiian waters the next several days. A Small Craft Advisory (SCA) is still in effect for those notoriously windier channels and bays surrounding Maui County and waters south of the Big Island, with the inclusion of the Maui and Big Island windward waters, through Sunday afternoon. This SCA will likely need to be extended into next week and possibly expanded westward to account for these strengthened trades. Seas will eventually climb to and exceed SCA level heights under this persistent trade flow next week.
A couple of small, longer period west northwest swells will travel around the islands in the coming days. The first of these swells will be arriving today and be leveling out from Sunday night through Tuesday afternoon. The second set of similar low west to northwest swells will be moving through around mid week. In response to strengthened trades over and upstream of the islands, east-facing shore surf will increase going into early next week. Recent satellite observations verify a large region of strong trades upstream of the state that will likely generate a long enough fetch region to produce near advisory level surf along eastern exposures by Monday. Energy from far Southern Hemispheric gales clipping the islands this weekend will provide a subtle boost to south-facing shoreline surf.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Sunday for Maui County Windward Waters, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov