Photo Credit: Brendan Stephen

West Kaua’i

Today: Mostly sunny with isolated showers. Highs around 87 near the shore to around 74 above 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Breezy. Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows around 72 near the shore to around 62 above 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Monday: Mostly sunny in the morning then becoming partly sunny. Breezy. Isolated showers. Highs around 87 near the shore to around 74 above 3000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

South Kaua’i

Today: Partly sunny. Breezy. Showers likely in the morning, then scattered showers in the afternoon. Highs 82 to 89. East winds 15 to 25 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Breezy. Numerous showers in the evening, then scattered showers after midnight. Lows around 72. East winds 15 to 20 mph. Chance of rain 70 percent.

Monday: Breezy. Partly sunny with scattered showers. Highs 82 to 88. East winds 15 to 20 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Breezy. Occasional showers in the morning, then showers likely in the afternoon. Highs 73 to 82 in the valleys to around 65 above 4000 feet. East winds 15 to 25 mph. Chance of rain near 100 percent.

Tonight: Breezy. Occasional showers in the evening, then numerous showers after midnight. Lows 64 to 70 in the valleys to around 60 above 4000 feet. East winds 15 to 25 mph. Chance of rain near 100 percent.

Monday: Breezy. Mostly cloudy with numerous showers. Highs 73 to 82 in the valleys to around 65 above 4000 feet. East winds 15 to 25 mph. Chance of rain 70 percent.

North Kaua’i

Today: Partly sunny. Breezy. Showers likely in the morning, then scattered showers in the afternoon. Highs 76 to 87. East winds 10 to 20 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Breezy. Numerous showers in the evening, then scattered showers after midnight. Lows 65 to 73. East winds 10 to 20 mph. Chance of rain 70 percent.

Monday: Breezy. Partly sunny with scattered showers. Highs 76 to 87. East winds 10 to 20 mph. Chance of rain 50 percent.

East Kaua’i

Today: Breezy. Occasional showers in the morning, then scattered showers in the afternoon. Highs 73 to 85. East winds 10 to 20 mph. Chance of rain near 100 percent.

Tonight: Mostly cloudy. Breezy. Numerous showers in the evening, then scattered showers after midnight. Lows 65 to 76. East winds 15 to 20 mph. Chance of rain 70 percent.

Monday: Breezy. Mostly cloudy with scattered showers. Highs 73 to 85. East winds 15 to 20 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Breezy trade winds will prevail into Monday, delivering a few brief windward showers. A surge of strong northeasterly trade winds Monday night and Tuesday will push a cold front down the island chain. The front will move over the islands from the northeast, bringing a period of increased clouds and showers, especially over windward areas. A cool and relatively dry air mass will move over the islands after the front passes. Lighter winds and warming conditions are expected by the end of the week.

Discussion

In the short term, moderate to locally breezy trade wind pattern will trend a little stronger today as a strong high NW of the islands slowly moves closer to the area. As the high moves into a position due N of the islands on Monday, it will bring a surge in NE winds while also pushing a shallow cold front over the islands. Winds could get strong enough to warrant a Wind Advisory for many areas. Guidance indicates this will occur Monday night/Tuesday, with a band of showery low clouds moving quickly through the island chain. While the strong trades may deliver a few showers to leeward areas, most of the frontal moisture will focus over windward areas. Limited upper- level support will accompany the front, thus significant rainfall totals are not expected.
Immediately after the passage of the front, very windy and relatively dry conditions are expected to develop for a day or two, with lowering dew points making it feel seasonably cool. Wind gusts near 50 mph will likely necessitate the issuance of a Wind Advisory for many locations, if not the entire chain. Leeward areas are not expected to receive significant rainfall, with the strong winds and dry air mass combining to bring the potential for an increased risk of fire danger. Some uncertainty exists as to how dry it will get after the front passes. Recent model runs indicate that a shortwave passing just NE of the islands will lead to an increase in trade wind showers Thursday, otherwise just a few windward showers are expected. The high will weaken NE of the islands Thursday and Friday, allowing trade winds to diminish in speed while veering to the E.
The preponderance of long range guidance indicates a deep trough will develop NW of the islands by next weekend. While differences remain as to how progressive this feature will be, initial expectations are for winds to veer to the S Saturday, which could lead to increased rainfall chances, especially for leeward areas. A frontal passage may occur next Sunday.

Aviation

Moderate to locally breezy trade winds will continue to push clouds and showers across the islands. Showers will favor windward areas. Expect predominantly VFR conditions at the terminals. AIRMET Tango remains posted for occasional moderate turbulence over and to the lee of mountains for all islands due to breezy trade winds. No other AIRMETS are in effect now, but AIRMET Sierra may be issued later today if cloud cover increases across windward Maui and Big Island slopes.

Marine

Strong surface high pressure far north northwest of the area will drift east due north of the islands over the next few days. A surge of strong to near gale force east trade winds will increase winds across all local waters as a cold front will push down the island chain Monday night into Tuesday. A Small Craft Advisory (SCA) remains in effect for typical windy waters around Maui County and the Big Island before all zones will be added into the SCA starting at 6 AM this morning through Tuesday afternoon. The SCA will likely be extended through at least the middle of the week for the increasing wind and seas greater than 10 feet.
A small, medium period northwest swells will build in today across north and west facing shores and hold through Monday. This swell will decline Monday and no significant swells are expected until a small long period northwest swell is expected late Friday.
Surf along east facing shores will remain choppy through the forecast period. Strengthening trades, coinciding with a large, short period northeast swell will likely push east shore surf to High Surf Advisory levels from late Monday through Wednesday. The trade wind swell will also wrap into exposed north facing shores.
Small mainly background south swell energy is expected through middle of next week. A small long period south swell could boost south shore surf up from Thursday night through Friday.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Tuesday 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 Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov