Photo Credit: Tyler Rooke

West Side

Today: Windy. Sunny with isolated showers. Highs 82 to 88. Northeast winds 20 to 30 mph with gusts to 50 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Windy. Isolated showers in the evening, then scattered showers after midnight. Lows 67 to 74. Northeast winds 15 to 30 mph with gusts to 50 mph decreasing to 15 to 20 mph after midnight. Chance of rain 40 percent.

Saturday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 82 to 88. East winds 10 to 15 mph. Chance of rain 40 percent.

South Side

Today: Sunny and breezy. Highs 86 to 91. Northeast winds 10 to 25 mph with gusts to 50 mph.

Tonight: Mostly clear. Breezy. Lows around 67. North winds 10 to 25 mph. Gusts up to 50 mph in the evening.

Saturday: Sunny. Highs 86 to 91. North winds 10 to 15 mph.

North Shore

Today: Breezy. Partly sunny with showers likely early in the morning, then partly sunny with scattered showers in the late morning and afternoon. Highs around 82 near the shore to around 68 near 5000 feet. East winds 10 to 25 mph. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with showers likely. Lows 65 to 71 near the shore to around 52 near 5000 feet. East winds 10 to 25 mph. Chance of rain 70 percent.

Saturday: Occasional showers in the morning, then scattered showers in the afternoon. Highs around 82 near the shore to around 68 near 5000 feet. East winds 10 to 15 mph. Chance of rain near 100 percent.

Central Maui

Today: Sunny and windy. Scattered showers early in the morning. Highs 85 to 91. Northeast winds 15 to 30 mph with gusts to 50 mph. Chance of rain 40 percent.

Tonight: Windy. Mostly clear with isolated showers. Lows 65 to 71. Northeast winds 15 to 30 mph. Gusts up to 50 mph in the evening. Chance of rain 20 percent.

Saturday: Mostly sunny. Isolated showers in the morning. Highs 85 to 91. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Upcountry

Today: Breezy. Mostly sunny with scattered showers. Highs around 64 at the visitor center to around 60 at the summit. East winds 10 to 25 mph. Chance of rain 50 percent.

Tonight: Breezy. Partly cloudy with scattered showers. Lows around 46 at the visitor center to around 43 at the summit. East winds 10 to 25 mph becoming around 20 mph after midnight. Chance of rain 50 percent.

Saturday: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 64 at the visitor center to around 60 at the summit. East winds 15 to 20 mph. Chance of rain 50 percent.

East Maui

Today: Breezy. Partly sunny with showers likely early in the morning, then partly sunny with scattered showers in the late morning and afternoon. Highs around 82 near the shore to around 68 near 5000 feet. East winds 10 to 25 mph. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with showers likely. Lows 65 to 71 near the shore to around 52 near 5000 feet. East winds 10 to 25 mph. Chance of rain 70 percent.

Saturday: Occasional showers in the morning, then scattered showers in the afternoon. Highs around 82 near the shore to around 68 near 5000 feet. East winds 10 to 15 mph. Chance of rain near 100 percent.

Lanai City

Today: Sunny and windy. Isolated showers in the late morning and afternoon. Highs 76 to 83. Northeast winds 15 to 30 mph with gusts to 50 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Windy. Lows around 66. Northeast winds 20 to 30 mph. Gusts up to 50 mph in the evening.

Saturday: Sunny. Isolated showers in the afternoon. Highs 76 to 83. East winds 10 to 15 mph. Chance of rain 20 percent.

Kaunakakai

Today: Sunny and breezy. Isolated showers in the late morning and afternoon. Highs 76 to 90. Northeast winds 15 to 25 mph. Chance of rain 20 percent.

Tonight: Breezy. Mostly clear with isolated showers. Lows 61 to 72. East winds 20 to 25 mph. Chance of rain 20 percent.

Saturday: Mostly sunny. Breezy. Isolated showers in the morning. Highs 76 to 90. East winds 15 to 20 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Strong trade winds on Friday will ease slightly on Saturday, diminish more substantially Sunday, and then remain on the lighter side for most of next week. The trades will deliver passing clouds and showers to windward areas, with a few showers drifting leeward while the trades remain strong. When the trades diminish, passing windward showers will likely diminish in frequency, while leeward areas may see some afternoon clouds and showers.

Discussion

Trade winds will strengthen tonight and Friday as high pressure to the distant NE moves W and builds slightly. Moisture embedded in the trades will provide for passing showers through Friday morning over windward and mauka areas, with showers spreading leeward on all islands but the Big Island, where afternoon pop-up showers will linger into the evening. Winds may become sufficiently strong in terrain-accelerated areas of Maui and Hawaii Counties to warrant a Wind Advisory on Friday.
The high will remain nearly stationary but weaken somewhat on Saturday, with winds expected to diminish ever-so-slightly. A more significant reduction in trade wind speeds is expected Sunday and Monday as a low and front pass far N of the area. This will weaken the high while also splitting it into two centers to the NW and NE of the islands, with a break in the associated ridge to the N of the islands.
Another reason the winds will remain light for most of next week will be due to the presence of yet another cutoff closed low to the N of the islands inducing the formation a weak and broad surface trough. Aloft, this feature is currently an E-W trough near 30N 152W. In this case, the developing low is expected to linger several hundred miles to the NNE of the islands at its closest approach. It may drift close enough to introduce modest instability to the islands atmosphere beginning early next week. The light trades may deliver a few windward showers during nights and mornings, with afternoon sea breezes driving clouds and a few showers over leeward areas. The intensity of these showers will be dependent on how close the low gets to the islands, but the potential for a few heavy showers appears to exist.

Aviation

Surface high pressure north of the islands will maintain strong breezy trade winds across the area through Friday. AIRMET Tango for low level turbulence below 8k feet, south through west of all mountain ranges, will continue until further notice. Random clouds and showers embedded in this trade wind flow will favor the windward and mountain areas, causing brief MVFR ceiling and vis. The frequency of these clouds and showers will be highest during the morning hours. A shower or two is still possible along the Kona coast of the Big Island this evening. Afternoon clouds will reappear over the lee side of the Big Island tomorrow with a few showers.

Marine

A high north of the state will drive stronger trade winds across local waters through Saturday. A Small Craft Advisory (SCA) remains in effect through Saturday afternoon for all waters through tomorrow. Trades will gradually weaken tomorrow night through Saturday, thus the SCA will be scaled back to the typical windy waters around Maui County and the Big Island. Winds will then become light to moderate the rest of the weekend into early next week.
A small, long period south swell filling in through Saturday will be reinforced by small, medium period south and low period southeast swells over the next several days. These swells will maintain near seasonal south facing shore surf through the holiday weekend. A series of small, medium to slightly longer period south swells will arrive Labor Day and hold through most of next week. Strengthened trades over and upstream of the islands will provide a bump to the east facing shore surf by another foot or two into the weekend.

Fire weather

With locally strong trade winds expected on Friday, and the Keetch- Byram Drought Index (KBDI) over 600, critical fire weather behavior is possible over leeward areas Friday late morning/afternoon as dew points over leeward areas lower into the mid-60s. A Fire Weather Watch is posted for leeward areas of nearly all islands. Although winds may ease slightly on Saturday, similar conditions are possible Saturday afternoon.

HFO Watches/Warnings/Advisories

Fire Weather Watch from Friday morning through Friday afternoon for Kauai Leeward, Oahu South Shore, Waianae Coast, Oahu North Shore, Olomana, Central Oahu, Waianae Mountains, Molokai Leeward, Maui Leeward West, Maui Central Valley, Leeward Haleakala, Kona, Kohala, Big Island Interior.
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 PM HST Friday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Big Island Windward Waters.

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Data Courtesy of NOAA.gov