Photo Credit: Tyler Rooke

West Side

Today: Mostly sunny. Breezy. Isolated showers in the morning. Haze in the morning. Highs 78 to 86. East winds 10 to 25 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening, then scattered showers after midnight. Lows 67 to 75. East winds 10 to 25 mph. Chance of rain 40 percent.

Thursday: Breezy. Sunny with isolated showers. Highs 76 to 85. East winds 15 to 25 mph. Chance of rain 20 percent.

South Side

Today: Mostly sunny. Breezy. Haze in the morning. Highs around 86. Northeast winds 15 to 20 mph.

Tonight: Mostly clear. Breezy. Lows 67 to 75. Northeast winds 15 to 20 mph.

Thursday: Sunny and breezy. Highs around 86. Northeast winds 15 to 20 mph with gusts to 45 mph.

North Shore

Today: Mostly cloudy. Breezy. Haze in the morning. Showers likely in the morning, then scattered showers in the afternoon. Highs 75 to 84 near the shore to around 65 near 5000 feet. East winds 15 to 25 mph. Chance of rain 60 percent.

Tonight: Breezy. Mostly cloudy with showers likely. Lows around 70 near the shore to 49 to 54 near 5000 feet. East winds 15 to 25 mph. Chance of rain 70 percent.

Thursday: Breezy. Partly sunny with showers likely in the morning, then mostly sunny with scattered showers in the afternoon. Highs 75 to 83 near the shore to around 64 near 5000 feet. East winds 20 to 25 mph. Chance of rain 70 percent.

Central Maui

Today: Mostly sunny. Breezy. Isolated showers in the morning. Haze in the morning. Highs 82 to 87. Northeast winds 15 to 25 mph. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows 67 to 72. Northeast winds 15 to 20 mph. Chance of rain 20 percent.

Thursday: Sunny and breezy. Isolated showers in the morning. Highs 81 to 86. Northeast winds 15 to 25 mph. Chance of rain 20 percent.

Upcountry

Today: Partly sunny in the morning then becoming mostly sunny. Breezy. Haze in the morning. Scattered showers. Highs around 58 at the visitor center to around 52 at the summit. East winds 15 to 25 mph. Chance of rain 50 percent.

Tonight: Windy. Partly cloudy with scattered showers. Lows around 46 at the visitor center to around 41 at the summit. East winds 20 to 30 mph. Chance of rain 50 percent.

Thursday: Windy. Mostly sunny with scattered showers. Highs around 58 at the visitor center to around 52 at the summit. East winds 20 to 30 mph. Chance of rain 50 percent.

East Maui

Today: Mostly cloudy. Breezy. Haze in the morning. Showers likely in the morning, then scattered showers in the afternoon. Highs 75 to 84 near the shore to around 65 near 5000 feet. East winds 15 to 25 mph. Chance of rain 60 percent.

Tonight: Breezy. Mostly cloudy with showers likely. Lows around 70 near the shore to 49 to 54 near 5000 feet. East winds 15 to 25 mph. Chance of rain 70 percent.

Thursday: Breezy. Partly sunny with showers likely in the morning, then mostly sunny with scattered showers in the afternoon. Highs 75 to 83 near the shore to around 64 near 5000 feet. East winds 20 to 25 mph. Chance of rain 70 percent.

Lanai City

Today: Mostly sunny. Haze in the morning. Isolated showers in the afternoon. Highs 72 to 81. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Scattered showers in the evening. Lows around 65. Northeast winds 15 to 20 mph. Chance of rain 40 percent.

Thursday: Sunny and breezy. Isolated showers in the afternoon. Highs 71 to 79. East winds 15 to 20 mph. Chance of rain 20 percent.

Kaunakakai

Today: Mostly sunny. Breezy. Haze in the morning. Isolated showers in the afternoon. Highs 67 to 86. East winds 15 to 25 mph. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows 58 to 73. East winds 20 to 25 mph. Chance of rain 20 percent.

Thursday: Sunny and windy. Isolated showers in the afternoon. Highs 67 to 85. East winds 20 to 30 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

High pressure building north of the islands will bring increasingly strong trade winds the next couple of days, with a trend toward fewer showers. Little change is expected over the weekend.

Discussion

A somewhat unstable and humid ESE flow remains in place over the Kauai end of the island chain this morning, due to an expansive kona low centered about 1000 miles to the NW. Associated convergent low- level flow is triggering a few heavy showers and isolated thunderstorms over waters S of Kauai and Oahu. Elsewhere, relatively small fast-moving showers are noted over windward portions of all islands, although coverage has been diminishing overnight. High clouds associated with the kona low are streaming over the islands from the SW, and are obstructing a view of lower cloud coverage using traditional IR imagery. However, a well-illuminated nighttime visible image indicated very little in the way of showers immediately upstream of the islands. Air quality sensors indicate that an area of vog that moved over the islands from Maui to Kauai on Tuesday continues to linger.
A trend toward strong E trade winds and increasingly stable conditions will begin today as the kona low moves W, and deep-layer high pressure builds N of the islands. Over the past 24-hours, surface pressures have increased by 4-6 mb statewide, indicating that this process is well underway. A few heavy showers may linger near Kauai in the short-term, but otherwise expect typical trade wind conditions, with showers focused mainly across windward slopes. The UH VMAP model also suggests that the vog will be diminishing today, and a building inversion between 7000 to 8000 ft should keep future emissions from Mauna Loa largely trapped aloft and carried to the W of the Big Island. Additionally, high clouds will be diminishing today, and should be completely gone by Thursday.
Trade winds will continue to strengthen tonight and remain gusty for the next several days, potentially continuing through part of the weekend. A robust surface high developing far N of the state will drive the stronger trade winds, and a ridge aloft will bring an increasingly strong subsidence inversion. This will lead to acceleration of winds over and downwind of terrain that may require a Wind Advisory, likely including the saddle and summit areas of the Big Island. Expect rainfall to favor windward slopes, though some showers will be blown over to leeward areas from Maui to Kauai at times. An upper low passing S of the state this weekend could increase shower chances on the Big Island, but models have been trending drier, especially for Saturday.

Aviation

A high pressure ridge will build to the north of the islands as a deep low pressure system northwest of the state continues to drift slowly westward. Strong and gusty winds are forecast and winds will shift from a southeast to east direction today. Expect periods of showers with brief MVFR/IFR conditions over the next 24 hours mainly over windward and mountain areas.
AIRMET SIERRA in effect for mountain obscuration over east portions of the Big Island and Maui, and north through east sections of Oahu and Kauai due to low clouds and showers.
AIRMET Tango in effect for tempo moderate turbulence below 080 over and immediately SW through NW of island mountains due to strong winds.

Marine

High pressure centered far northeast of the islands, along with a strong low approximately 1,000 miles northwest of Kauai, will maintain a tight enough pressure gradient across and upstream of the local waters to support several days of fresh to locally strong east trade winds. Mid to late week winds channeling through the Pailolo and Alenuihaha Channels, as well as south of Big Island, will occasionally reach gale force. Thus, a Gale Watch is in effect for these marine zones from early Thursday morning through Friday night. As the low drifts further west away from the state, thunderstorms forming along the low's leading stationary boundary may graze and impact the waters west of Kauai and Niihau, or west of 160W, through the day. High pressure will build in the wake of the low and keep the northeast-to-southwest pressure gradient tight across the area. A Small Craft Advisory is now in effect for all waters to account for both strong winds and/or high seas.
A moderate, medium period northwest (310-320 degrees) swell is peaking early this morning and will begin to fall through the day. Due to this slow fall, the High Surf Advisory (HSA) has been extended through this afternoon for the north and west-facing shores of Niihau, Kauai, Oahu and Molokai. A very small, medium period reinforcing northwest bump arriving Thursday will keep swell from completely falling off, thus holding waist to head high surf through early Saturday along many north-facing shores. Strengthening trades will significantly increase east-facing shore chop. Rough east surf will stick around into the weekend and may near 10 foot HSA levels Thursday night and Friday.

Fire weather

Models are showing drying in the low levels on Thursday into Friday, which could significantly lower afternoon relative humidity across leeward areas, and trade winds will be strong and gusty during this time. Many leeward areas have yet to experience significant rainfall early this wet season, and critical fire weather conditions may occur.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST this evening for North and West facing shores of Niihau Kauai Oahu and Molokai.
Small Craft Advisory until 6 AM HST Saturday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Kaiwi Channel, Maui County Windward Waters, Big Island Windward Waters, Oahu Leeward Waters, Maui County Leeward Waters.
Small Craft Advisory until 6 AM HST Thursday for Maalaea Bay, Big Island Southeast Waters, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters.
Gale Watch from Thursday morning through late Friday night for Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov