West Kaua’i

Today: Mostly clear then becoming partly sunny in the morning then becoming mostly sunny. Breezy. Isolated showers early in the morning, then scattered showers in the morning. Isolated showers in the afternoon. Highs 86 to 92 near the shore to around 78 above 3000 feet. East winds up to 25 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly clear with isolated showers. Lows 71 to 76 near the shore to around 63 above 3000 feet. Northeast winds up to 20 mph decreasing to up to 10 mph after midnight. Chance of rain 20 percent.

Monday: Sunny. Isolated showers in the morning. Highs 86 to 92 near the shore to around 79 above 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

South Kaua’i

Today: Breezy. Mostly cloudy with scattered showers. Highs 81 to 89. Northeast winds 15 to 25 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 72 to 77. Northeast winds 10 to 25 mph. Chance of rain 50 percent.

Monday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 83 to 91. East winds 10 to 15 mph. Chance of rain 40 percent.

Kaua’i Mountains

Today: Mostly cloudy. Breezy. Scattered showers early in the morning, then numerous showers in the morning. Scattered showers in the afternoon. Highs 74 to 85 in the valleys to around 67 above 4000 feet. East winds up to 20 mph increasing to 10 to 25 mph in the afternoon. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 66 to 71 in the valleys to around 60 above 4000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Monday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 76 to 85 in the valleys to around 68 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

North Kaua’i

Today: Partly cloudy early in the morning then becoming partly sunny. Breezy. Scattered showers early in the morning, then numerous showers in the morning. Scattered showers in the afternoon. Highs 76 to 88. East winds 10 to 20 mph. Chance of rain 70 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 66 to 75. East winds up to 15 mph. Chance of rain 50 percent.

Monday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 79 to 88. East winds up to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Mostly cloudy. Breezy. Scattered showers early in the morning, then numerous showers in the morning. Scattered showers in the afternoon. Highs 73 to 87. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows 66 to 78. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Monday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 74 to 88. East winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Breezy to locally windy trades will persist through this afternoon before slowly trending down into early Monday. Relatively dry and stable conditions will also continue into this evening. Light precipitation carried in on the trades will occasionally wetten windward and upslope mauka regions. The majority of leeward areas will remain dry the next few days. The remnants of Tropical Cyclone Gil will likely pass north of the islands during the middle of the week. This system will disrupt trade flow while increasing statewide rain chances.

Discussion

A 1030 mb high centered approximately 1,500 miles north of Oahu has maintained a tight enough downstream pressure gradient to drive strong winds across many eastern-facing windward exposures and through higher terrain. Last night's highest wind observations of sustained 30-plus mph winds with gusts approaching and exceeding 50 mph occurred across such notoriously windy areas as the northern Kohala Coast, the Central Maui Valley, eastern Molokai and atop Oahu's Koolau Range. A Wind Advisory will remain in effect for these areas (sans Oahu that expires at 6 AM) through the day. Interior dry conditions this afternoon with middle to upper 60 dew point temperatures will translate to sub-50% relative humidities (at the lowest) during the heat of the day. Thus, these windy and dry conditions will warrant the continuation of the Red Flag Warning through 6 PM this evening for all leeward areas.
12Z local soundings are still advertising the stout, relatively shallow 5k ft inversion that is assisting in these robust lower level trades. Near 850 mb winds will mix down with surface warming and, with occasional small just-above-the-surface wind bursts, surface winds will become gusty…especially in non (wind) sheltered areas and downwind of high terrain. Gusty winds can fall small trees or break tree branches so take heed if outside near or under larger trees. High profile vehicles may be suddenly buffeted within high wind. Also be prepared for power outages. Winds will trend down through the evening with breezy conditions expected through the first half of the week.
Lower clouds advancing into the state as verified by recent pre- dawn radar trends do show widely-scattered light east showers moving onshore and across windward locales. Any rain will be meager, at best, with the majority of the state staying dry the next few days. The majority of the GFS and EC ensemble (QPF) members show no appreciable rain accumulation through mid week. This will only exacerbate the (primarily leeward) moderate to severe drought.
Monday through Wednesday's weather will be one of breezy trades and dry conditions as high pressure north of the state drifts eastward and slackens the Central Pacific pressure gradient. Trades will likely become disrupted late Wednesday into Thursday as the remnants of Gil pass to our north. The latest National Hurricane Center forecast remains on track with Tropical Storm Gil weakening to a Tropical Depression by tomorrow. Although there is always some amount of uncertainty, the latest model guidance continues to show the highest moisture associated with Gil passing north of Hawaii. The threat for more moderate, persistent rain will remain low and focus across our northern offshore waters Thursday and Friday. With that being said, there will be an uptick in late week showers but scattered showers will produce the highest QPF in the normally more wet windward communities.

Aviation

Strong high pressure north of the region will help to generate breezy to locally windy northeasterly trades today with a strength similar to yesterday.
Scattered showers will mainly affect windward and mauka locations and bring MVFR ceilings and visibility on occasion. Elsewhere, VFR conditions prevail.
AIRMET Tango is in effect for moderate with isolated severe low level turbulence over and immediately S through W of the island mountains due to strong trade winds and gusts. This AIRMET will likely be needed through the afternoon.

Marine

High pressure north of the state will maintain fresh to locally near gale trade wind speeds across all coastal waters today. As the high weakens and slowly drifts east, trade winds look to ease Monday and Tuesday to the moderate to locally strong range. The current Small Craft Advisory has been extended for all coastal zones through this afternoon before scaling back to the windier waters and channels around Maui County and the Big Island tonight. Trade will continue to ease by the middle of the week as the remnants of Tropical Storm Gil passes to the northeast of the state.
Surf along south facing shores will continue to decline today before another moderate, long period south swell is expected to build in early Monday. This swell may peak just below High Surf Advisory (HSA) criteria late Monday and into Tuesday before declining Wednesday. Another swell is expected from a low formed south of New Zealand at the end of July, that measured seas of 35 to 40 feet aimed towards Hawaii. This swell is expected to build on Thursday and hold through the end of the week which could get near HSA criteria at its peak.
Short period trade wind swell will keep east facing shores elevated and choppy today due to strong trade winds. By late Monday into Tuesday, a moderate, medium to long period east swell is expected to fill in from the energy from Tropical System Gil in the eastern Pacific.
Surf along north facing shores will remain tiny through the afternoon. A small, medium period northwest swell originating from Typhoon Krosa in the western Pacific will bring a small bump up in surf along north facing shores this evening and hold through Monday. Another bump is expected as a small, medium to long period northwest swell looks to fill in Thursday and Friday.

Fire weather

A gusty, stable, and rather dry trades will remain in place through the day, producing critical fire weather conditions. Greater than 20 mph sustained winds and daytime relative humidities as low as the lower to middle 40 percentile are forecast through the day. A strong lower level inversion will ensure that the highest elevations of Big Island and portions of Haleakala on Maui will experience very low relative humidity. Winds will slowly ease from tonight into Tuesday which should result in winds falling below Red Flag criteria by tomorrow. Although winds will weaken, dry conditions will persist through mid week. An increase in moisture and shower activity will be possible going into the later half of the week as the remnants of TC Gil pass to our north.

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, Molokai North, Molokai West, Molokai Leeward South, Lanai Windward, Lanai Leeward, Lanai South, Lanai Mauka, Kahoolawe, 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, Maui Windward West, Maui Leeward West, Kohala, Molokai Southeast, Molokai North, Molokai West, Molokai Leeward South, Lanai Windward, Lanai Leeward, Maui Central Valley North, Maui Central Valley South, South Haleakala, Big Island Southeast, Big Island North.
Wind Advisory until 6 AM HST early this morning for Koolau Leeward.
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 AM HST Monday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.