Photo Credit: Jeni Ji Cousins

West Side

Today: Sunny, with a high near 94. Heat index values as high as 99. Breezy, with an east northeast wind around 15 mph, with gusts as high as 21 mph.

Tonight: Mostly clear, with a low around 76. East northeast wind around 14 mph, with gusts as high as 18 mph.

Saturday: Sunny, with a high near 94. Heat index values as high as 100. East northeast wind around 14 mph, with gusts as high as 18 mph.

South Side

Today: Isolated showers after noon. Mostly sunny, with a high near 87. East wind 8 to 10 mph. Chance of precipitation is 20%.

Tonight: Mostly clear, with a low around 70. East northeast wind around 9 mph.

Saturday: Isolated showers after noon. Mostly sunny, with a high near 87. East wind around 9 mph. Chance of precipitation is 20%.

North Shore

Today: Isolated showers before noon. Mostly sunny, with a high near 85. Breezy, with an east wind 17 to 21 mph, with gusts as high as 29 mph. Chance of precipitation is 20%.

Tonight: Scattered showers, mainly after midnight. Partly cloudy, with a low around 73. Breezy, with an east wind around 18 mph, with gusts as high as 25 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Saturday: Scattered showers before noon. Mostly sunny, with a high near 86. Breezy, with an east wind 17 to 20 mph, with gusts as high as 28 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Central Maui

Today: Sunny, with a high near 87. Breezy, with an east northeast wind 14 to 17 mph, with gusts as high as 24 mph.

Tonight: Scattered showers after midnight. Partly cloudy, with a low around 74. Breezy, with an east northeast wind around 15 mph, with gusts as high as 21 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Saturday: Isolated showers before noon. Mostly sunny, with a high near 87. Breezy, with an east northeast wind 14 to 16 mph, with gusts as high as 22 mph. Chance of precipitation is 20%.

Upcountry

Today: Sunny, with a high near 76. East northeast wind 8 to 10 mph.

Tonight: Mostly clear, with a low around 57. East wind around 11 mph.

Saturday: Isolated showers after noon. Sunny, with a high near 76. East northeast wind 7 to 10 mph. Chance of precipitation is 20%.

East Maui

Today: Showers likely, mainly before noon. Partly sunny, with a high near 79. Breezy, with an east 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: Showers likely, mainly after midnight. Mostly cloudy, with a low around 74. East wind around 14 mph, with gusts as high as 18 mph. Chance of precipitation is 60%. New precipitation amounts between a quarter and half of an inch possible.

Saturday: Showers likely, mainly before noon. Partly sunny, with a high near 79. East wind around 14 mph, with gusts as high as 18 mph. Chance of precipitation is 60%. New precipitation amounts between a tenth and quarter of an inch possible.

Lanai City

Today: Scattered showers after noon. Mostly sunny, with a high near 79. Breezy, with an east northeast wind 14 to 17 mph, with gusts as high as 24 mph. Chance of precipitation is 30%. New precipitation amounts between a tenth and quarter of an inch possible.

Tonight: Mostly clear, with a low around 67. Breezy, with an east northeast wind 14 to 17 mph, with gusts as high as 24 mph.

Saturday: Isolated showers after noon. Mostly sunny, with a high near 79. Breezy, with an east northeast wind 14 to 16 mph, with gusts as high as 22 mph. Chance of precipitation is 20%.

Kaunakakai

Today: Sunny, with a high near 91. Heat index values as high as 96. Breezy, with an east wind 9 to 17 mph, with gusts as high as 24 mph.

Tonight: Mostly clear, with a low around 75. East wind 9 to 14 mph, with gusts as high as 18 mph.

Saturday: Sunny, with a high near 91. Heat index values as high as 98. Breezy, with an east wind 9 to 16 mph, with gusts as high as 22 mph.

Detailed Forecast

Synopsis

Breezy trade winds will continue into the weekend, then ease slightly late Sunday into early next week. Showers will continue to ride in on the trades, with the possibility of more showers to end the weekend and start the new week due the remains of former Tropical Cyclone Guillermo.

Discussion

An overnight ASCAT pass shows winds remain elevated over more than the typical marine areas. A check of the latest high resolution models show several of them expect this uptick to continue through the next 24 hours. Winds have been boosted over the waters, with minimal changes to land. Some tweaks have been made to the PoPs and associated fields for the first 24 hours or so to bring the forecast into better alignment with some of the high resolution models.
A recent day/night band pass of the VIIRS satellite show the remnants of Tropical Cyclone Felicia south of the Big Island. The northern edge of the main cloud area with this surface trough was about 90 miles south of Hilo, and it extends to the south about 300 miles. Additional low clouds just east of the Big Island are loosing associated with this trough, and are expected to help maintain showers over the east side of the Big Island today. The VIIRS pass clearly shows the remnant low that was once Guillermo about 1000 miles east-southeast of the Big Island. The cloud associated with this system extend about 800 miles north. As these clouds and showers move to the east and mover over the islands this weekend and into early next week, we can expect another uptick in shower activity mainly over the windward and mountain areas.
Surface high pressure to the northwest of the islands, with an east to west near zonal flow over the islands will maintain the breezy to locally strong trade winds over the region as we head into the weekend. Some weakening of the pressure gradient over the islands is possible over the weekend. Heading into the middle of next week, the winds are likely to weaken and become more southeasterly as the high moves to the northeast of the islands.

Aviation

Breezy easterly trade winds will continue into the weekend, with clouds and showers favoring windward and mauka locations. MVFR CIGS/VSBYS are possible in and around passing showers, especially over the eastern end of the state where more moisture exists.
AIRMET Sierra remains in effect for mountain obscuration above 1500 feet for north through east sections of Maui and the Big Island. Conditions should gradually improve through the late morning and afternoon hours.
AIRMET Tango remains in effect for low-level mechanical turbulence immediately south through west of island mountains. This AIRMET will continue into the weekend.

Marine

A gradual weakening of the trade winds is expected mainly tonight through Saturday as high pressure north of the islands weaken. The Small Craft Advisory (SCA) covering most of the nearshore waters will continue through today before being scaled down to the normal typical areas of Maui County and waters south of the Big Island. Should this softening trend continues as forecast, we would likely lower the SCA late Saturday afternoon. The trades are expected to hold at light to moderate speeds through the first half of next week.
A blob of warm and humid unstable air belonging to once Tropical Cyclone Guillermo is forecast to settle over the islands between Sunday night and Tuesday. This air mass will be influenced by an upper level disturbance leading to a thunderstorm or two over the offshore waters.
The rough trade wind swell of 6 to 8 ft and 8 seconds will maintain surf along the east facing shores of 5 to 7 feet today. But with the weakening trades through Saturday, look for the surf to be a little smaller each day over the weekend. A long period pulse from the south is being picked up by the buoys far south of the islands. We are looking at 3 to 5 foot surf along the south facing shores today through Saturday before trending lower thereafter. No other significant swells are expected.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Saturday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.
Small Craft Advisory until 6 AM HST Saturday for Kauai Northwest Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters.

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Data Courtesy of NOAA.gov