Photo Credit: Braden Jarvis

West Kaua’i

Today: Breezy. Partly sunny with scattered showers in the morning, then cloudy with showers in the afternoon. Highs around 82 near the shore to around 70 above 3000 feet. Southwest winds 10 to 20 mph. Chance of rain 90 percent.

Tonight: Breezy. Cloudy with showers. Lows around 65 near the shore to around 54 above 3000 feet. West winds 10 to 25 mph with gusts to 50 mph. Chance of rain 90 percent.

Wednesday: Windy. Partly sunny with scattered showers. Highs around 82 near the shore to around 71 above 3000 feet. West winds 20 to 30 mph with gusts to 50 mph. Chance of rain 40 percent.

South Kaua’i

Today: Partly sunny. Breezy. Scattered showers in the morning, then numerous showers in the afternoon. Highs around 81. West winds 10 to 25 mph. Chance of rain 70 percent.

Tonight: Breezy. Cloudy with showers. Lows 61 to 66. West winds 15 to 25 mph with gusts to 50 mph. Chance of rain 90 percent.

Wednesday: Windy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 81. West winds 15 to 30 mph with gusts to 50 mph. Chance of rain 40 percent.

Kaua’i Mountains

Today: Windy. Mostly sunny with scattered showers in the morning, then mostly cloudy with numerous showers in the afternoon. Highs 69 to 77 in the valleys to around 64 above 4000 feet. Southwest winds up to 20 mph increasing to 10 to 30 mph in the afternoon. Chance of rain 70 percent.

Tonight: Windy. Cloudy with showers. Lows 54 to 59 in the valleys to around 48 above 4000 feet. West winds 10 to 30 mph decreasing to up to 30 mph after midnight. Gusts up to 50 mph. Chance of rain 90 percent.

Wednesday: Partly sunny in the morning then becoming mostly sunny. Windy. Scattered showers. Highs 70 to 78 in the valleys to around 65 above 4000 feet. West winds 10 to 35 mph with gusts to 55 mph. Chance of rain 40 percent.

North Kaua’i

Today: Mostly sunny in the morning then becoming mostly cloudy. Breezy. Scattered showers. Highs 74 to 81. Southwest winds up to 15 mph increasing to up to 25 mph in the afternoon. Chance of rain 50 percent.

Tonight: Windy. Mostly cloudy with numerous showers. Lows 57 to 66. West winds 10 to 30 mph with gusts to 50 mph. Chance of rain 70 percent.

Wednesday: Windy. Mostly sunny with scattered showers. Highs 75 to 82. West winds 10 to 30 mph with gusts to 50 mph. Chance of rain 40 percent.

East Kaua’i

Today: Breezy. Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 74 to 81. Southwest winds 10 to 25 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers early in the evening, then numerous showers in the late evening and overnight. Lows 55 to 67. Southwest winds up to 25 mph with gusts to 50 mph. Chance of rain 70 percent.

Wednesday: Breezy. Mostly sunny with isolated showers. Highs 75 to 82. West winds 10 to 25 mph with gusts to 50 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A strong cold front will approach the state today, then sweep from west to east down the island chain tonight through Wednesday night, bringing showers and windy conditions to the state. Winds will ease with drier and cooler conditions filtering into the islands Thursday through the weekend, with warmer weather returning early next week.

Discussion

Currently at the surface, a weakening front is located over the Big Island, while a stronger cold front is located around 300 miles west-northwest of Kauai. Light to moderate west to southwest winds prevail across the island chain early this morning. Infrared satellite imagery shows partly to mostly cloudy conditions across the state, and radar imagery shows isolated to scattered showers moving into leeward areas. Main short term focus revolves around the approaching front and the potential for strong southwesterly winds across the island chain.
The front over the Big Island will continue to weaken and dissipate over the Big Island today. Light to moderate west- southwest winds will continue across the islands this morning, with the winds picking up to moderate and locally breezy levels in advance of the next cold front this afternoon. This front will sweep through Kauai tonight, through Oahu around daybreak Wednesday, through Maui County Wednesday afternoon, before finally clearing the Big Island late Wednesday night or early Thursday. Breezy southwesterly winds Tuesday evening, are expected to become windy prior to daybreak Wednesday, with windy west-southwesterly winds continuing through Wednesday evening. A Wind Advisory has been issued for the entire state from midnight tonight through midnight Wednesday night, with gusty downslope winds in excess of 50 mph likely over the windward areas northeast of the mountains. Due to the recent above normal rainfall and winds coming from the opposite direction from our normal trade winds, there will likely be a higher risk of tree falls.
Deep cyclonic flow will hold over the islands Thursday through Saturday, with moderate westerly winds Thursday becoming light for Friday and Saturday. Light winds are expected to prevail Sunday and Monday, as a weak ridge of high pressure slides eastward over the island chain.
On the summits of the Big Island, a High Wind Warning is now in effect through 6 PM Sunday. On the Haleakala summit, a High Wind Watch remains is now in effect tonight through Wednesday night.
As for the remaining weather details, scattered showers are expected to continue to affect leeward areas of the islands in the southwest flow today, with wet weather spreading into Kauai by late this afternoon in association with the approaching cold front. Fairly showery weather can be expected across much of the island chain tonight and Wednesday, particularly over leeward areas, with diminishing showers expected behind the front. Some showery weather will likely continue over the Big Island Wednesday night, with drier conditions overspreading the entire state Thursday through Monday. Noticeably cooler conditions are expected Thursday through Saturday as dewpoints drop into the 50s, highs struggle to reach 80 degrees, and lows bottom out in the upper 50s to lower 60s.

Aviation

West to southwest winds will continue today and will strengthen tonight as a front approaches the island chain from the northwest. Currently a cloud band associated with an old front continues to provide some showers and MVFR conditions to the western side of the Big Island and Maui. These showers are expected to decrease throughout the morning but remnant moisture could continue bringing some showers and low clouds to the eastern end of the state.
A stronger front is expected to approach the state today, then move into the western Islands tonight. Showers will increase across Kauai this afternoon, and over Oahu the rest of the state tonight. Widespread MVFR and isolated IFR conditions can be expected in the showers as the front moves through. Breezy to windy west-southwesterly winds will develop over Kauai by late this afternoon and spread to the rest of the state tonight
AIRMET Sierra is currently in effect for portions of the Big Island and may be removed if showers and clouds further decrease.

Marine

A weakening front appears to have slowed down as it moved over the Big Island early this morning. A second more potent cold front appears to be slightly less than 300 nm northwest of Kauai. Southwest winds will strengthen over portions of the state as this feature moves down toward the islands. Therefore, a Small Craft Advisory (SCA) has been issued starting this morning for the waters surrounding Kauai, as well as the Oahu Windward waters. In addition, the SCA is also in effect for strong southwest winds over the Alenuihaha Channel and the southeast Big Island waters, with strengthening winds expected over the Big Island Windward Waters by this afternoon.
The front will likely pass over Kauai this evening, and then move down the rest of the island chain on Wednesday. Strong to near gale force west winds are expected behind this front after it passes. In addition, a very large northwest swell combined with locally generated wind waves will likely produce elevated, hazardous seas over most of the marine area. A SCA has already been issued for the remaining Hawaiian waters starting tonight, and continuing through Wednesday night. The winds are expected to ease by Thursday, with much lighter winds expected Friday and Saturday. However, seas will likely remain above the SCA threshold into Friday for most waters exposed to the lingering northwest swell.
A small, medium period northwest swell (315 degrees) is expected to peak along most north and west facing shores this morning. The very large northwest swell (310-320 degrees) mentioned in the previous paragraph will likely build late tonight and Wednesday, peak Wednesday night, and then slowly decline Thursday and Friday. This swell may be in excess of 20 ft across Hawaiian waters from late Wednesday into early Thursday, and surf heights will exceed the High Surf Warning thresholds along most north and west facing shores, including the leeward Big Island. This could lead to significant overwash and coastal erosion, mainly Wednesday evening through Thursday morning along exposed north and west facing shores. Waves could also periodically overtop some vulnerable roads during the peak of this event, especially during high tide. The swell will gradually decline, and shift out of the north-northwest from late Thursday night through this weekend.
Minimal trade wind swell is expected this week, although there is some potential for localized wave wrap along east facing shores exposed to the large northwest swell from late Wednesday into Friday. Rough surf may briefly increase along south facing shores as the front moves down the island chain late tonight and Wednesday.

HFO Watches/Warnings/Advisories

Wind Advisory from midnight tonight to midnight HST Wednesday night for Niihau, Kauai Leeward, Kauai Mountains, Waianae Coast, Oahu North Shore, Olomana, Central Oahu, Waianae Mountains, Lanai Mauka, Kahoolawe, Maui Windward West, Maui Leeward West, Kona, Kohala, Big Island Interior, Kauai North, Kauai East, Kauai South, East Honolulu, Honolulu Metro, Ewa Plain, Koolau Windward, Koolau Leeward, Molokai, Lanai Windward, Lanai Leeward, Lanai South, Maui Central Valley North, Maui Central Valley South, Windward Haleakala, Kipahulu, South Maui/Upcountry, South Haleakala, Big Island South, Big Island Southeast, Big Island East, Big Island North.
High Wind Watch from this evening through late Wednesday night for Haleakala Summit.
High Wind Warning until 6 PM HST Sunday for Big Island Summits.
Small Craft Advisory from 6 AM this morning to 6 AM HST Thursday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Big Island Windward Waters.
Small Craft Advisory from 6 PM this evening to 6 AM HST Thursday for Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Maalaea Bay, Pailolo Channel, Big Island Leeward Waters.
Small Craft Advisory until 6 AM HST Thursday for Alenuihaha Channel, Big Island Southeast Waters.

Data Courtesy of NOAA.gov