Photo Credit: Jason Weingardt

West Kaua’i

Today: Sunny. Highs 81 to 87 near the shore to around 73 above 3000 feet. East winds up to 15 mph.

Tonight: Mostly clear. Lows 66 to 71 near the shore to around 60 above 3000 feet. Northeast winds 10 to 15 mph decreasing to up to 15 mph after midnight.

Friday: Mostly sunny. Isolated showers in the morning. Highs 82 to 87 near the shore to around 74 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

South Kaua’i

Today: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 78 to 85. Northeast winds 15 to 20 mph. Chance of rain 30 percent.

Tonight: Partly cloudy. Isolated showers in the evening. Lows around 71. Northeast winds around 15 mph. Chance of rain 20 percent.

Friday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 78 to 85. Northeast winds around 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs 71 to 80 in the valleys to around 63 above 4000 feet. East winds 10 to 20 mph. Chance of rain 40 percent.

Tonight: Partly cloudy. Breezy. Scattered showers in the evening, then isolated showers after midnight. Lows 61 to 69 in the valleys to around 58 above 4000 feet. East winds 10 to 20 mph. Chance of rain 30 percent.

Friday: Partly sunny with scattered showers. Highs 72 to 80 in the valleys to around 64 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

North Kaua’i

Today: Mostly sunny with scattered showers. Highs 73 to 84. East winds 10 to 15 mph. Chance of rain 40 percent.

Tonight: Partly cloudy with isolated showers. Lows 63 to 71. East winds 10 to 15 mph. Chance of rain 20 percent.

Friday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 74 to 85. East winds 10 to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 71 to 83. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 63 to 74. Northeast winds 10 to 15 mph. Chance of rain 30 percent.

Friday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 71 to 83. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Strong trade winds will continue today as the high pressure ridge north of the state will interact with a surface trough just south of the island chain. An upper level disturbance passing south of the islands will enhance showers a bit over the eastern slopes of the Big Island through Friday morning. Trade winds will start decreasing from Thursday night on into the weekend as the high pressure ridge north of the state weakens. Overall fairly dry conditions will persist into the first half of next week.

Discussion

The satellite picture remains fairly unchanged this morning as an upper level low just south of the island chain continues to drift westward and a high pressure ridge north of the state drives strong trade winds across the Hawaii region for one more day. Expect enhanced showers along the eastern slopes of the Big Island to last through Friday morning due instability associated with the upper level low. Otherwise, more stable conditions will prevail over the smaller islands from Maui to Kauai, with isolated to scattered shower activity, due to the downward vertical motions creating stable conditions under the upper level subtropical ridge.
The upper air weather balloon soundings observed this morning around 2 AM HST (12Z) at Hilo and Lihue show subsidence temperature inversion heights in the 5,000 to 7,000 foot range. These stable temperature inversion heights typically allow for isolated to scattered shower coverage mainly over windward and mountain areas in the overnight to early morning hours.
Strong and gusty trade winds will continue for one more day as the upper low passing to the south of the Hawaiian Islands is strong enough to reflect a trough at the surface. This surface trough will combine forces with a moderate strength subtropical ridge just north of the state, tightening local pressure gradients and producing stronger trade winds across the region. These strong trade winds will continue to blow at advisory thresholds over and downstream of wind favored mountain regions over the eastern half of the state. The Wind Advisory for lower elevations was extended through the afternoon hours, and the Wind Advisory for the Big Island summits was cancelled as wind speeds at summit level are forecast to remain below advisory thresholds today. Expect decreasing wind speeds into the weekend. Light and variable winds return by next week, from late Monday into Wednesday, as two passing cold fronts break down the ridge north of the island chain.
Rainfall into the first half of next week will be limited with dry conditions likely persisting into Wednesday. Two exceptions to this dry pattern will be enhanced showers along the eastern slopes of the Big Island lasting into Friday morning, and a slight boost in trade wind showers for windward and mountain areas of all islands, due to a passing short wave trough, from Saturday night to Sunday morning. There are some early signs of a weakening cold front drifting into the Hawaii region by the end of next week, possibly bringing our next best chance for rainfall coverage. The forecast impacts and the track of the frontal cloud band this far out remains challenging, and at this point we can say the western islands have higher chances to pick up enhanced showers. Global model solutions unsurprisingly remain inconsistent on the track and timing of this weakening front. Stay tuned.

Aviation

Strong trade winds will continue, delivering randomly distributed low cloud clusters that will briefly drop a few showers windward, producing ISOL MVFR VIS/CIG. AIRMET Tango will continue to highlight the ongoing likelihood for low-level turbulence to the lee of the terrain, and sustained surface winds near 30 kt for portions of the area today.

Marine

High pressure centered far northeast of the Hawaiian Islands will maintain a tight enough downstream pressure gradient across the state to hold sustained fresh to strong trades through the day. The Gale Warning for the notoriously windier waters around Maui County and Big Island…with a Small Craft Advisory for the remaining waters…remains in effect through this afternoon to account for both strong winds and elevated seas. Trades will gradually ease back to moderate to locally strong magnitudes by Friday and these speeds will persist this weekend.
Near head high north-facing surf, with waist to chest level surf along the west shores, will hold through tonight with only a subtle fall Friday. The ongoing near 3 to 4 foot, 12 second north northwest swell will significantly decline this weekend. A much larger, long period north northwest swell originating from a deep hurricane force low over the northwest Pacific later this week is scheduled to reach the islands sometime around the middle of next week. This swell will likely lift surf along northern and western exposures to high surf warning heights late next week. Rough, choppy surf will occur along east-facing shores through Friday in response to recently fresh to strong trades. East wind wave surf will subside this weekend once trades fall off.

Fire weather

A borderline Red Flag Warning (RFW) remains in effect until 6 PM HST today, as RFW conditions are expected to be met for a few hours from late morning through afternoon. Humidity levels will be the borderline factor during this RFW event, which are forecast to fall slightly below critical thresholds during this time period.

HFO Watches/Warnings/Advisories

Red Flag Warning until 6 PM HST this evening for Niihau, Kauai South, Kauai Southwest, Honolulu Metro, Ewa Plain, Waianae Coast, Oahu North Shore, Central Oahu, Waianae Mountains, Molokai West, Molokai Leeward South, Lanai Windward, Lanai Leeward, Lanai South, Lanai Mauka, Maui Leeward West, Maui Central Valley North, Maui Central Valley South, South Maui/Upcountry, South Haleakala, Big Island South, Big Island Southeast, Kohala, Big Island Interior.
Wind Advisory until 6 PM HST this evening for Lanai Mauka, Kahoolawe, Maui Windward West, Maui Leeward West, Kohala, Big Island Interior, Lanai Windward, Lanai Leeward, Lanai South, Maui Central Valley North, Maui Central Valley South, South Haleakala, Big Island South, Big Island Southeast, Big Island North.
Small Craft Advisory until 6 PM HST this evening 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.
Gale Warning until 6 PM HST this evening for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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