Photo Credit: Tyler Rooke

West Side

Today: Breezy. Mostly sunny with isolated showers. Highs 80 to 87. Northeast winds 10 to 25 mph. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows 68 to 75. East winds 15 to 25 mph. Chance of rain 20 percent.

Friday: Mostly sunny with isolated showers. Highs 80 to 87. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

South Side

Today: Sunny and breezy. Isolated showers in the morning. Highs 84 to 89. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows around 69. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Friday: Sunny and breezy. Highs 84 to 89. Northeast winds 15 to 20 mph.

North Shore

Today: Breezy. Mostly cloudy with scattered showers. Highs 79 to 85 near the shore to 63 to 68 near 5000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 70 near the shore to around 53 near 5000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Friday: Breezy. Mostly cloudy with scattered showers. Highs 79 to 85 near the shore to 63 to 68 near 5000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Central Maui

Today: Breezy. Mostly sunny with isolated showers. Highs around 87. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows around 70. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Friday: Breezy. Mostly sunny with isolated showers. Highs around 87. Northeast winds 15 to 20 mph. Chance of rain 20 percent.

Upcountry

Today: Breezy. Mostly sunny with scattered showers. Highs 54 to 71. East winds 15 to 25 mph shifting to the northeast 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Tonight: Breezy. Partly cloudy with scattered showers. Lows around 45 at the visitor center to around 42 at the summit. East winds 10 to 20 mph. Chance of rain 50 percent.

Friday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 54 to 71. East winds 10 to 15 mph. Chance of rain 50 percent.

East Maui

Today: Breezy. Mostly cloudy with scattered showers. Highs 79 to 85 near the shore to 63 to 68 near 5000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 70 near the shore to around 53 near 5000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Friday: Breezy. Mostly cloudy with scattered showers. Highs 79 to 85 near the shore to 63 to 68 near 5000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Lanai City

Today: Breezy. Partly sunny with isolated showers. Highs 72 to 81. East winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Breezy. Mostly cloudy with isolated showers. Lows around 68. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Friday: Partly sunny with isolated showers. Highs 73 to 82. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Kaunakakai

Today: Breezy. Mostly sunny with isolated showers. Highs 76 to 86. East winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows 63 to 73. Northeast winds 10 to 25 mph. Chance of rain 20 percent.

Friday: Breezy. Mostly sunny with isolated showers. Highs 77 to 87. East winds 15 to 20 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Moderate to locally breezy trade winds will continue to focus low clouds and showers over windward and mauka sections through this weekend. Brief trade showers may be transported over to the leeward sections of the smaller islands, especially during the late night and early morning hours. Clouds and isolated showers will also likely develop over some upslope sections of the leeward Big Island each afternoon.

Discussion

A broad 1032 mb surface high pressure system centered near 37N 152W, or about 1150 miles north-northeast of Honolulu, continues to dominate the local weather across the main Hawaiian Islands early this morning. The tight pressure gradient south of this feature is maintaining moderate to locally breezy trade winds in the vicinity of the island chain. Elsewhere, the diffuse leading edge of a band of scattered to broken low clouds with embedded scattered showers, which is some of the remnant moisture from a dissipated frontal boundary, is evident about 75 miles northeast of Hilo. This leading edge has been moving toward the west-southwest at about 15 mph. Loops of water vapor satellite imagery show an upper-level low centered near 24N 159W, or about 125 miles north-northeast of Lihue. This feature has been drifting slowly westward.
The upper-level low has weakened the trade wind inversion, especially across the eastern and central islands. At the same time, enhanced low-level moisture is being transported into the area by the relatively strong trade winds. As a result, scattered to broken low clouds with embedded scattered showers are evident in satellite imagery and radar reflectivity data just upstream of Maui and the Big Island. There are also scattered low clouds and isolated showers upstream of the islands from Molokai to Kauai.
The forecast guidance shows the surface high will shift slowly east-southeast to a position far northeast of the islands during the next few days. At the same time, the upper-level low will linger just north of the western islands. There may be a subtle weakening of the trade winds into tonight, but they will likely strengthen again from Friday through this weekend.
The close proximity of the upper-level low to the state will likely keep the trade wind inversion relatively weak. Therefore, the enhancement of the low clouds and trade showers will continue through early Friday morning. In addition, the leading edge of the area of clouds and showers will eventually reach the islands later this morning. Therefore, low clouds and showers will continue to favor windward and mauka sections. However, there may be brief showers over some leeward areas of the smaller islands, especially during the late night and early morning hours. In addition, clouds and spotty showers will also likely develop over upslope sections of the leeward Big Island each afternoon, and then continue into the early evening hours.
As the upper-level low departs the region this weekend, there may be a gradual increase in atmospheric stability over the state. The forecast models appear to show another area of increased moisture moving into the islands from late Friday into Saturday, so low clouds and showers may increase again over windward and mauka areas heading into the weekend. Expect a slight drying trend from Sunday into early next week, but some trade showers will likely continue along windward facing slopes, especially during the late night and early morning hours.

Aviation

Moderate to locally breezy trade winds will continue to push patches of stable and showery low clouds over the islands from the ENE, leading to periods of MVFR VIS/CIG, mainly over windward areas. AIRMET Sierra for mountain obscuration is currently posted for windward Kauai, but coverage immediately upstream of that island is diminishing, and it will likely be dropped soon. However, additional moisture is approaching the other islands from the E, likely leading to an change in the areas covered by AIRMET Sierra.
A nearby low aloft has led to some destabilization of the island atmosphere, thus some cloud tops are growing as high as 12 kft, leading to a few small heavy showers. Little change is expected into Friday. AIRMET Tango for low-level turbulence downwind of the terrain is posted for Maui County and the Big Island, and may need to be expanded to the entire island chain as trade winds remain on the locally strong side.

Marine

A ridge north of the islands is expected to remain in place over the next several days, maintaining moderate to locally strong trade wind pattern over the coastal waters. The Small Craft Advisory posted for the typical windier waters near Maui County and the Big Island has been extended through 6 AM HST Saturday, and may be further extended through the weekend.
Locally generated wind waves from the trades will continue to bring rough, choppy surf to east facing shores through early next week. A small northwest swell will slowly build today, peak tomorrow, then slowly subside into the weekend. Another slightly larger northwest swell will fill in late Saturday and Sunday, then slowly subside into early next week. Background southerly swells will continue into tomorrow. A series of slightly larger and longer period southerly swells will boost surf heights along south facing shores beginning as early as Saturday, and persisting through mid-week next week.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Saturday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov