Photo Credit: Brittney Cruz

West Side

Today: Mostly sunny. Isolated showers in the morning. Highs 72 to 79. West winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Lows 60 to 66. West winds around 10 mph.

Friday: Sunny. Highs 73 to 79. Southwest winds up to 10 mph.

South Side

Today: Sunny. Highs around 79. Southwest winds around 10 mph.

Tonight: Mostly clear. Lows around 63. Southwest winds around 10 mph.

Friday: Sunny. Highs around 79. Southwest winds 10 to 15 mph.

North Shore

Today: Mostly sunny. Isolated showers in the afternoon. Highs 72 to 77 near the shore to around 61 near 5000 feet. Southwest winds up to 15 mph shifting to the northwest in the afternoon. Chance of rain 20 percent.

Tonight: Mostly clear. Isolated showers after midnight. Lows around 63 near the shore to around 47 near 5000 feet. West winds around 10 mph in the evening becoming light. Chance of rain 20 percent.

Friday: Mostly sunny. Isolated showers in the morning. Highs 72 to 77 near the shore to around 60 near 5000 feet. Light winds. Chance of rain 20 percent.

Central Maui

Today: Mostly sunny. Highs around 77. Southwest winds up to 15 mph.

Tonight: Mostly clear. Lows around 62. Southwest winds around 10 mph in the evening becoming light.

Friday: Mostly sunny. Highs around 78. Southwest winds up to 10 mph.

Upcountry

Today: Mostly sunny. Windy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 55 at the visitor center to around 50 at the summit. Southwest winds 10 to 35 mph with gusts to 60 mph. Chance of rain 40 percent.

Tonight: Mostly clear. Windy. Lows around 43 at the visitor center to around 38 at the summit. Southwest winds 10 to 30 mph. Gusts up to 55 mph in the evening.

Friday: Sunny in the morning then becoming partly sunny. Breezy. Highs around 54 at the visitor center to around 49 at the summit. West winds 10 to 25 mph decreasing to up to 25 mph in the afternoon. Gusts up to 45 mph.

East Maui

Today: Mostly sunny. Isolated showers in the afternoon. Highs 72 to 77 near the shore to around 61 near 5000 feet. Southwest winds up to 15 mph shifting to the northwest in the afternoon. Chance of rain 20 percent.

Tonight: Mostly clear. Isolated showers after midnight. Lows around 63 near the shore to around 47 near 5000 feet. West winds around 10 mph in the evening becoming light. Chance of rain 20 percent.

Friday: Mostly sunny. Isolated showers in the morning. Highs 72 to 77 near the shore to around 60 near 5000 feet. Light winds. Chance of rain 20 percent.

Lanai City

Today: Mostly sunny with isolated showers. Highs 68 to 74. West winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Lows around 57. West winds 10 to 15 mph.

Friday: Mostly sunny. Highs 67 to 74. West winds up to 10 mph.

Kaunakakai

Today: Mostly sunny with isolated showers. Highs 64 to 78. West winds around 10 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Lows 50 to 65. West winds around 10 mph.

Friday: Mostly sunny. Highs 64 to 78. West winds around 10 mph.

Detailed Forecast

Synopsis

A potent surface low about 700 miles north of the state will drift to the northeast and weaken today, causing westerly winds to gradually ease and pushing a cooler and drier air mass over the islands. Active showers will linger on the Big Island today, though rainfall will be modest elsewhere and mainly confined to west facing slopes. A surface ridge will move over the islands during the weekend, leading to light winds and a few interior showers each afternoon. South to southwest winds will return late Sunday and early next week.

Discussion

Winds are easing over the islands, and a drier air mass is moving in from the west. The potent 990 mb surface low that passed 550 miles north of Kauai yesterday is weakening and lifting off to the northeast this morning, while its associated surface front has passed east of the Big Island. As a result, west to northwest winds have decreased significantly overnight and are gusting below 30 mph in most locations. Thus, the Wind Advisory for the lower elevations of the Big Island has been cancelled. Residual moisture from the front remains hung up across western Big Island and the southwest slopes of Haleakala, where scattered showers continue produce modest rain rates. Drier air is settling over Kauai, Oahu, and Molokai, where dew points have fallen into the mid to upper 50s, and the 2 AM Lihue sounding showed that precipitable water has fallen below three quarters of an inch. However, the circulation around the low continues to produce isolated showers over mainly west facing terrain.
Locally breezy west to northwest winds will continue to decline today as the surface low drifts to the northeast. A drier air mass settling in will produce limited showers over mainly western facing slopes and will cause dew points to drop into the lower 50s and even upper 40s in some areas. As a result, expect rather cool conditions with daytime highs struggling to reach 80 degrees and overnight lows dropping below 60 degrees at sea level in sheltered areas tonight. The exception will be on the Big Island, where showers will remain somewhat active on leeward slopes this morning, and scattered showers will develop over windward terrain this afternoon. The only places that will continue to experience high winds will be the highest elevations on the Big Island and Maui. Expect only a gradual decline in winds on the Big Island summits, where a High Wind Warning will remain in effect well into the weekend. On the Haleakala summit, the High Wind Warning has been downgraded to a Wind Advisory for today, followed by a decline in winds tonight and Friday.
Winds will decline further on Friday as the subtropical ridge, moves back over the islands from the south. The drier air mass will remain in place, maintaining limited rainfall and another cool night.
Light winds with a somewhat stable land and sea breeze pattern will dominate through much of the weekend as the subtropical ridge remains near or over the islands. The air mass will modify and not be as cool, though dew points probably will not get much higher than the lower 60s. Showers will remain limited and will favor interior sections each afternoon.
Another round of south to southwest winds is due late Sunday and early next week. The jet stream will remain displaced unusually far southward through the week. This will produce additional low latitude surface low pressure systems to the northwest and north of Hawaii. Details are unclear, but expect southerly winds to increase late Sunday and persist through the middle of next week, when a front may reach the state. At this time, these kona winds look to be significantly weaker than those being experienced now.

Aviation

The cold front has moved east of the Big Island. Gusty west to northwest winds will taper off by mid morning. Late night satellite imagery reveals multiple bands of scattered light showers speeding quickly eastward across the state. Showers are expected to taper off by mid afternoon as cooler and drier air moves in from the west.
AIRMET Tango remains in effect for occasional low level moderate turbulence along east sides of all islands due to the westerly winds. Conditions are expected to improve by late morning.
Isolated MVFR conditions are to be expected in passing showers, otherwise VFR conditions will prevail all areas.

Marine

A cold front is slowing down and weakening in the vicinity of the Big Island, but will shift east of the coastal waters this evening. Strong post-frontal westerlies will gradually weaken overnight, becoming moderate and northwesterly by Thursday afternoon. A Small Craft Advisory (SCA) remains in effect for both winds and seas tonight and has been extended through Thursday due to elevated seas for all zones and into Friday for the northern zones. Gentle to locally moderate WNW winds are forecast for this weekend.
A very large northwest swell (310-320) peaked at the upstream buoys (51001 and 51101) yesterday evening and is on the down trend. Based on the typical travel times from those buoys, the swell should be peaking early this morning locally. Due to the proximity of the source low around 600 nm north of Molokai, there are quite a mix of periods, ranging from around 10 to 18 seconds, making for very rough and messy conditions. This swell will continue to generate warning-level surf along north and west facing shores of most of the smaller islands, as well as leeward Big Island shores. Due to the lingering swell, the High Surf Warning has been extended through tonight. The combination of the northwest swell and westerly wind waves will lead to overwash of some coastal infrastructure and beach erosion today, as well. This swell will gradually subside late tonight into Friday as the parent low moves away to the northeast. A moderate, medium-period NNW (330-340) swell will move through beginning late Friday, keeping surf elevated, but below advisory level into the weekend.
Minimal trade wind swell is expected this week, though there is some potential for localized wave wrap along east facing shores exposed to the large northwest swell into Friday. Wind waves will dominate the surf signal along south-facing shores through this morning, then lower as winds diminish.

HFO Watches/Warnings/Advisories

High Surf Warning until 6 AM HST Friday for north and west facing shores of Niihau, Kauai, Oahu, and Molokai and for north facing shores of Maui.
Wind Advisory until 6 PM HST this evening for Haleakala Summit.
High Wind Warning until 6 PM HST Sunday for Big Island Summits.
Small Craft Advisory until 6 AM HST Friday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Kaiwi Channel, Maui County Windward Waters, Alenuihaha Channel, Big Island Windward Waters.
Small Craft Advisory until 6 PM HST this evening for Oahu Leeward Waters, Maui County Leeward Waters, Maalaea Bay, Pailolo Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov