Photo Credit: Braden Jarvis

West Kaua’i

Today: Breezy. Mostly sunny with isolated showers. Highs around 85 near the shore to around 73 above 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 67 near the shore to around 57 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Saturday: Mostly sunny. Breezy. Scattered showers early in the morning, then isolated showers in the late morning and afternoon. Highs around 83 near the shore to around 70 above 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

South Kaua’i

Today: Breezy. Partly sunny with scattered showers. Highs 78 to 84. Northeast winds 15 to 25 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 68. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Saturday: Breezy. Mostly cloudy with numerous showers early in the morning, then partly sunny with scattered showers in the late morning and afternoon. Highs 77 to 83. East winds 10 to 20 mph. Chance of rain 70 percent.

Kaua’i Mountains

Today: Partly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 70 to 79 in the valleys to around 62 above 4000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Numerous showers in the evening, then occasional showers after midnight. Lows 60 to 65 in the valleys to around 55 above 4000 feet. East winds up to 15 mph. Chance of rain 80 percent.

Saturday: Mostly cloudy with numerous showers early in the morning, then partly sunny with scattered showers in the late morning and afternoon. Highs 70 to 77 in the valleys to around 61 above 4000 feet. East winds up to 15 mph. Chance of rain 70 percent.

North Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs 74 to 84. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 60 to 70. East winds up to 15 mph. Chance of rain 70 percent.

Saturday: Breezy. Partly sunny with numerous showers early in the morning, then mostly sunny with scattered showers in the late morning and afternoon. Highs 72 to 83. East winds up to 20 mph. Chance of rain 70 percent.

East Kaua’i

Today: Partly sunny with scattered showers. Highs 69 to 81. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 61 to 71. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Saturday: Mostly cloudy with numerous showers early in the morning, then partly sunny with scattered showers in the late morning and afternoon. Highs 69 to 80. East winds 10 to 15 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Windy easterly trade winds will gradually ease today into the weekend as a strong high pressure slowly drifts northeast and weakens. Showers will favor windward and mountain areas with some reaching the leeward areas. Drier and more stable conditions will return over the weekend, while the easterly trades become gentle to locally breezy. Rainfall chances could trend up again early next week as a disturbance moves through.

Discussion

The strong high north of the state has begun to gradually weaken and is slowly moving further northeast of the state. This has translated to winds easing slightly overnight based on recent observations. Breezy to locally windy winds are expected to continue to ease throughout the day today thus the Wind Advisory for the typically windier areas of Maui County and the Big Island has been cancelled. A band of clouds and showers is currently moving through Maui County and the Big Island. Showers will trend down this afternoon as an area of clear skies and isolated showers moves in. Chances of clouds and showers will pick up again tonight as another shallow band of moisture moves through. These showers will be moving through swiftly with minimal accumulations anticipated.
Drier and more stable conditions will briefly return over the weekend as upper heights rise and precipitable water dip to around an inch. Trade winds are expected to ease to a more gentle to locally breezy range by Sunday as the high weakens far northeast of the state and a front approaches the state from the far northwest.
Latest guidance from both the ECMWF and the GFS are now placing a surface trough between the state and very strong developing high (1050 mb) to the far north early next week. This setup may produce a weaker wind pattern than previously forecast and allow hybrid land/sea breeze pattern to develop over the western half of the state while trades veer out of the southeast over the eastern half of the state. Models continue to show an upper level trough digging southward over the region. These features may allow for precipitable water to gradually increase and provide enough instability to allow for an increased chance of heavier showers particularly along windward areas and perhaps interior areas each afternoon.
A return of breezy to strong trades is possible during the second half of next week as a low develops along the northern end of the trough and moves northwest of the area allowing a surface ridge to build in from the east. A more typical tradewind pattern may then return.

Aviation

Surface high pressure north of the state will maintain strong and gusty winds today, though winds are expected to be slightly weaker as compared to yesterday. Winds will continue to trend lighter through the weekend as the surface high moves off to the northeast. Low level moisture carried in on the trades will bring clouds and showers to windward and mauka areas, with the best chance of seeing periods of MVFR conditions during the overnight to mid morning hours when shower activity will be at its peak. Otherwise, VFR conditions will prevail.
AIRMET Sierra for tempo mountain obscuration is in effect for windward portions of the smaller islands. Ceilings and visibilities should improve by the afternoon.
AIRMET Tango remains in effect for tempo moderate turbulence lee of the island terrain. This AIRMET will likely be needed through this evening. AIRMET Tango is also in effect for 30 kt or greater winds from Molokai to the Big Island and will likely be dropped later today.

Marine

Fresh to strong easterly trades will continue through Saturday, then ease into the moderate to fresh range Sunday through Monday as the surface ridge weakens north of the state. This will support transitioning the gales in place over the Pailolo and Alenuihaha Channels back to a Small Craft Advisory (SCA) today, and reducing the coverage of the SCA to the typically windier zones from Oahu to the Big Island today through Saturday. For the extended forecast (Tuesday through midweek), confidence remains low due to model discrepancies and inconsistent solutions from cycle to cycle over the past few days. Although we would typically anticipate strong- to gale-force easterly trades with the ~1050 mb high setting up north of the state, the positioning of the tail-end of the aforementioned front between this high pressure system and the Hawaiian waters is making this challenging to predict at this time.
Surf along exposed north and west facing shores will remain small through early next week, with mainly overlapping small northwest medium- to long-period swells moving through. An upward trend is possible beginning Tuesday as a potential moderate sized, short- to medium-period north swell arrives from a decent sized area of north to northeast winds focused at the islands nearby to the north between the strong high pressure system and tail-end of the front. Again, confidence in the details for this setup remains low at this time.
Surf along east facing shores will remain rough and choppy due to the strong winds impacting the area locally and upstream. As the winds lower over the weekend, expect the surf to ease and remain small into Monday. Similar to north facing shores, an upward trend is possible by midweek depending on how the scenario evolves, particularly for shores exposed to north to northeast swells.
Surf along south facing shores will remain small with mainly a combination of background south-southwest swells and shorter period southeast trade wind energy moving through. For the extended (late next week/weekend), a small medium-period southeast swell can't be ruled out. Guidance continues to show a decent sized batch of strong southeast winds setting up southeast of the Tuamotu Islands late this weekend into early next week that is focused at the islands within the 150 deg directional band.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST this evening for Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters.
Small Craft Advisory until 6 PM HST Saturday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov