West Kaua’i

Today: Breezy. Mostly sunny with isolated showers. Highs around 89 near the shore to around 74 above 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with isolated showers in the evening, then cloudy with scattered showers after midnight. Lows around 73 near the shore to around 62 above 3000 feet. East winds up to 20 mph decreasing to up to 10 mph after midnight. Chance of rain 40 percent.

Sunday: Cloudy with scattered showers. Highs around 87 near the shore to around 73 above 3000 feet. East winds up to 15 mph. Chance of rain 40 percent.

South Kaua’i

Today: Breezy. Partly sunny with scattered showers. Highs 80 to 88. Northeast winds 15 to 25 mph. Chance of rain 50 percent.

Tonight: Breezy. Cloudy with scattered showers. Lows around 73. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Sunday: Cloudy with scattered showers. Highs 79 to 87. East winds 10 to 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Breezy. Partly sunny with scattered showers. Highs 73 to 85 in the valleys to around 64 above 4000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Tonight: Breezy. Cloudy with scattered showers. Lows 67 to 72 in the valleys to around 59 above 4000 feet. East winds 10 to 25 mph decreasing to 10 to 15 mph after midnight. Chance of rain 50 percent.

Sunday: Cloudy with scattered showers. Highs 72 to 85 in the valleys to around 64 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

North Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs 77 to 88. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 66 to 74. East winds up to 15 mph. Chance of rain 50 percent.

Sunday: Cloudy with scattered showers. Highs 77 to 87. East winds up to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Breezy. Mostly cloudy with scattered showers. Highs 74 to 85. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Cloudy with scattered showers. Lows 66 to 77. East winds 10 to 15 mph. Chance of rain 50 percent.

Sunday: Cloudy with scattered showers. Highs 73 to 85. East winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

An upper-level low will drift westward across the Big Island this morning, bringing enhanced shower activity and isolated thunderstorms across windward Big Island and the eastern coastal waters. This will increase humidity and help suppress fire weather concerns for much of the state. Trades will remain breezy through the morning, gradually decreasing this afternoon and persisting through the week. Another upper-level low moves into the vicinity of the islands by Wednesday, once again enhancing shower activity across the windward and mountain portions of the state through the remainder of the outlook period.

Discussion

Latest model guidance continues to support an upper-level low propagating west over the Big Island early this morning and meandering northwestward away from the islands later this weekend. This low will enhance shower activity and possible produce isolated thunderstorms this morning, especially along the windward and mauka areas of the Big Island, extending as far north as Maui. The heaviest shower activity developed last night, however, heavy showers remain possible along the Hamakua coastline of the Big Island throughout much of the day. A Winter Weather Advisory remains in affect for the Big Island summits to account for potential snow and ice accumulations through 6 AM HST Sunday.
The areal extent of the Red Flag Warning was trimmed to the leeward areas of Niihau, Kauai, and Oahu, and is in effect through 6 PM HST today to account for 45 percent or lower relative humidity within those areas. Latest model guidance continues to suggest enhanced moisture will begin to move into the eastern end of the state today, which will increase relative humidity above critical fire weather thresholds. Please refer to the Fire Weather section below for further details.
Observations from Mauna Kea, as well as the 600 mb wind profile from the Hilo balloon sounding, showed trade winds across the Hawaiian Islands have decreased below advisory levels. Therefore, have opted to cancel the Wind Advisory for Maui County, Big Island, and the Big Island summits.
Trade wind speeds continue to weaken to a more light to moderate pattern from Sunday night through much of next week as the ridge north of the islands weakens in response to a passing cold frontal system well north of the islands. More stable conditions move back into the islands with brief passing showers favoring predominately windward and mauka areas during the overnight to early morning hours through Tuesday.
Latest model guidance showcases another wet and unstable trade wind pattern by mid-week. This will enhance overnight to early morning shower coverage statewide, just in time to add a little more spooky ambiance right before Halloween weekend.

Aviation

Trade winds will slowly decrease into moderate to breezy levels today, then continue to trend lower from Sunday onward as the high pressure ridge north of the islands weakens. An upper level disturbance will continue to produce some moderate clear air turb near the islands today along with enhanced shower activity, favoring the overnight to early morning hours. Isolated thunderstorms may continue to develop over the Big Island today.
AIRMET Sierra for tempo mountain obscuration above 2500 feet will continue this morning for north and east sections of most islands. These conditions may decrease in coverage briefly during the daylight hours, before expanding once again in the overnight hours.
AIRMET Tango remains in effect for moderate turbulence below 9000 feet over and south through west of island mountains, and from FL250 to FL350 for the whole state.

Marine

Large surface high pressure north of the state maintaining a tight pressure gradient over the islands has and is resulting in fresh to locally strong trade winds. A Small Craft Advisory (SCA) remains in effect for all coastal waters through the day to account for these winds and for elevated seas near 10 feet. As the high drifts eastward through the weekend, fresh trades will drop off to more water-wide moderate magnitudes. SCA-level winds will hold through Sunday in Maui County's channels and bays as well as south of Big Island. Winds will significantly lower to gentle to moderate speeds from late Sunday through Monday as a cold front impinges on the high as it moves into the eastern Pacific. Moderate winds through the middle of the week may strengthen back to more fresh speeds over west waters as a cold front approaches the northwestern offshore waters.
A reinforcing north-northwest (330 degree) swell, similar in size to the swell that peaked Thursday morning, will be passing around the islands through the afternoon. This swell will provide a slight boost to north and west-facing shore surf but heights will remain under advisory criteria during its morning peak. This swell will fall from this evening through early Monday. A quick hitting moderate size, short period north (360-010 degree) swell Wednesday originating from post-frontal strong breezes over the far north offshore waters will hold head high north-facing shore surf.
Fresh to strong trades has kept near 7 foot short period easterly wind wave chop alive along most east-facing exposures. Moderate to fresh easterly fetch over and just upstream of the islands, in tandem with some northwest swell wrap, will hold elevated sub- advisory eastern shore surf through tonight. Despite some northerly swell wrap on Wednesday, weakening trades will allow rough surf to subside to more seasonable heights next week.

Fire weather

Enhanced shower activity associated with a passing upper-level low meandering across the Big Island this morning has resulted in an increase of humidity, suppressing the Red Flag Warning for much of the state. The Red Flag Warning continues for Niihau, and leeward areas of Kauai and Oahu through this afternoon and was canceled for all islands in Maui County and Big Island due to increased humidity. Trade winds across the state remain breezy today, however, will gradually trend lower tonight to a more light to moderate speeds through the remainder of the week. Increased humidity values and decreasing winds will help maintain below critical fire weather thresholds for the rest of the weekend and into next week. Temperature inversion heights near Maui and the Big Island will range from 6,500 to 7,500 feet elevation today.

HFO Watches/Warnings/Advisories

Red Flag Warning until 6 PM HST this evening for Niihau, Kauai South, Kauai Southwest, East Honolulu, Honolulu Metro, Ewa Plain, Waianae Coast, Oahu North Shore, Central Oahu, Waianae Mountains.
Winter Weather Advisory until 6 AM HST Sunday for Big Island Summits.
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.
Small Craft Advisory until 6 PM HST Sunday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.