Photo Credit: Jeni Ji Cousins

West Side

Today: 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.

Tonight: Mostly clear, with a low around 76. East northeast wind around 10 mph.

Sunday: Mostly sunny, with a high near 94. Heat index values as high as 101. East northeast wind around 9 mph.

South Side

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

Tonight: Mostly clear, with a low around 71. Northeast wind around 11 mph.

Sunday: Isolated showers after noon. Mostly sunny, with a high near 87. Northeast wind around 10 mph. Chance of precipitation is 20%.

North Shore

Today: Isolated showers before noon. Sunny, with a high near 86. Breezy, with an east wind around 21 mph, with gusts as high as 29 mph. Chance of precipitation is 20%.

Tonight: Isolated showers. 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 20%.

Sunday: Isolated showers before noon. Mostly sunny, with a high near 86. Northeast wind around 14 mph, with gusts as high as 18 mph. Chance of precipitation is 20%.

Central Maui

Today: Sunny, with a high near 88. Breezy, with an east northeast wind around 18 mph, with gusts as high as 25 mph.

Tonight: Mostly clear, with a low around 75. Northeast wind around 13 mph.

Sunday: Mostly sunny, with a high near 87. Northeast wind around 11 mph.

Upcountry

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

Tonight: Mostly clear, with a low around 59. Breezy, with an east wind around 15 mph, with gusts as high as 21 mph.

Sunday: Sunny, with a high near 76. Breezy, with an east northeast wind 13 to 15 mph, with gusts as high as 21 mph.

East Maui

Today: 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 70%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Showers likely, mainly after midnight. Mostly cloudy, with a low around 74. East northeast wind around 10 mph. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

Sunday: Showers likely, mainly before noon. Mostly cloudy, with a high near 79. East northeast wind 10 to 13 mph. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

Lanai City

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

Tonight: Mostly clear, with a low around 67. East northeast wind 11 to 13 mph.

Sunday: Isolated showers after noon. Mostly sunny, with a high near 79. East northeast wind 10 to 14 mph, with gusts as high as 18 mph. Chance of precipitation is 20%.

Kaunakakai

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

Tonight: Mostly clear, with a low around 76. Breezy, with an east northeast wind around 16 mph, with gusts as high as 22 mph.

Sunday: Mostly sunny, with a high near 91. Heat index values as high as 99. Breezy, with an east northeast wind around 17 mph, with gusts as high as 24 mph.

Detailed Forecast

Synopsis

Breezy trade winds will ease slightly during the weekend and early next week. Showers will continue to ride in on the trades, with an increase in rainfall and humidity likely Sunday night into Tuesday.

Discussion

Satellite shows an area of low clouds over and immediately upstream of the Big Island this morning, with additional low clouds upstream of the smaller islands. High pressure to the north of the islands will maintain the trade winds flow, focusing clouds and showers over the windward and mauka locations.
An overnight ASCAT pass continues to show breezy trade winds over the waters near the islands. As a result, have upped the coastal winds, and some of the land winds have been nudged upwards as well. Several of the high resolution models were continuing to depict these pockets of stronger winds. The surace trough about 650 miles southeast of the Big Island (the remnants of former Tropical Cyclone Guillermo) is helping to maintain a tighter pressure gradient over the islands. Current forecast has the winds starting to ease a bit tonight with the high the north expected to weaken. However, its possible that as the surface trough gets closer to the islands, little change will be felt with the winds.
The surface trough will bring another batch of moisture to the islands, likely reaching the Big Island Sunday night, and then spreading to the smaller islands Monday and Tuesday. While the bulk of the shower activity is expected to remain over windward sides, some of those showers could reach leeward areas. An upper level trough to the northwest of the islands is expected to sink southward towards the islands early next week. This could provide some additional instability that could mean some higher rainfall totals, and still can’t rule out a bit of thunder. However the models are not in good agreement with the instability, so confidence remains low.
As we head into the middle of the week, the forecast continues the more typical trade winds showers. However a disturbance may pass south of the islands, which could once again tighter the pressure gradient over the islands.

Aviation

Moderate to breezy east northeast trades will persist today and generate tempo moderate turbulence above the lee of mountain ranges. See AIRMET section below. Expect scattered showers to mainly affect windward locations with brief periods of MVFR ceilings and visibility. Otherwise, partly cloudy with VFR conditions for leeward areas.
AIRMET TANGO remains in effect below 8000 feet over and immediately south thru west of mountains due to tempo moderate turbulence.
AIRMET SIERRA remains in effect for north thru east sections of Maui and the Big Island above 2000 feet for mountain obscuration from clouds and showers.

Marine

Rough marine conditions will continue through the weekend due to strong easterly trade winds. The highest seas will hover just below the 10 ft advisory threshold in the exposed windier areas and channels through early Sunday. A downward trend appears possible by early next week in response to a weakening ridge to the north. Winds may ease enough to relax the Small Craft Advisory for all marine areas by Monday. A return of fresh to strong easterly trades is possible later next week as low pressure passes to the south and high pressure builds to the north.
Surf along east facing shores will remain the highest around the islands through the weekend due to the strong trades. A downward trend is expected early next week as the trades ease locally and upstream across the eastern Pacific.
Surf along south facing shores will hold around the summertime average today, then ease by Sunday as a small, south swell moves out. Not much expected next week, other than short- to medium- period southeast trade wind swell along exposed shores. High pressure has parked itself over our swell window down around and east of New Zealand, which is projected to hold through early next week. As a result, small surf will linger into August.
Surf along exposed west and north facing shores could rise slightly late next week due to a potential small, west-northwest swell from the tropical activity across the far western Pacific (low confidence). Otherwise, summertime conditions are expected each day.

HFO Watches/Warnings/Advisories

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