Photo Credit: Jason Weingardt

West Kaua’i

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 87 near the shore to around 75 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 73 near the shore to around 61 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Thursday: Mostly sunny with scattered showers in the morning, then partly sunny with isolated showers in the afternoon. Highs around 86 near the shore to around 74 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

South Kaua’i

Today: Mostly cloudy. Breezy. Showers likely in the morning, then scattered showers in the afternoon. Highs around 84. Northeast winds 15 to 20 mph. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 69 to 74. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Thursday: Breezy. Partly sunny with scattered showers. Highs around 83. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Breezy. Frequent showers in the morning, then scattered showers in the afternoon. Highs 74 to 81 in the valleys to around 65 above 4000 feet. East winds up to 20 mph. Chance of rain near 100 percent.

Tonight: Mostly cloudy. Breezy. Showers likely in the evening, then frequent showers after midnight. Lows 61 to 67 in the valleys to around 57 above 4000 feet. Northeast winds up to 20 mph. Chance of rain 80 percent.

Thursday: Cloudy and breezy. Frequent showers in the morning, then showers likely in the afternoon. Highs 73 to 80 in the valleys to around 64 above 4000 feet. Northeast winds 10 to 20 mph decreasing to up to 15 mph in the afternoon. Chance of rain 80 percent.

North Kaua’i

Today: Mostly cloudy. Frequent showers in the morning, then scattered showers in the afternoon. Highs 77 to 86. East winds up to 15 mph. Chance of rain 90 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then showers likely after midnight. Lows 65 to 74. East winds 10 to 15 mph decreasing to up to 10 mph after midnight. Chance of rain 70 percent.

Thursday: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs 76 to 85. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

East Kaua’i

Today: Frequent showers in the morning, then scattered showers in the afternoon. Highs 77 to 85. Northeast winds 10 to 15 mph. Chance of rain near 100 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then showers likely after midnight. Lows 62 to 76. North winds 10 to 15 mph. Chance of rain 70 percent.

Thursday: Mostly cloudy. Breezy. Showers likely in the morning, then scattered showers in the afternoon. Highs 76 to 84. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Breezy easterly trades will continue today, then ease slightly and shift out of the northeast Thursday into the weekend as an upper disturbance moves over the region. Pockets of moisture combined with the upper disturbance moving through will lead to periods of showery conditions, especially overnight through the morning periods. A return of a more stable pattern with moderate easterly trades is possible by the end of the weekend through early next week.

Discussion

Guidance remains in decent agreement and depicts the breezy easterly trades holding today as strong high pressure remains anchored to the north. A band of low clouds moving through has led to better windward shower coverage this morning, with some making it into leeward areas periodically. Morning upper air soundings reflect this with very moist low-level profiles beneath elevated inversions positioned around 10,000 feet. Peak rainfall totals have ranged from half of an inch to around an inch overnight, and similar amounts can be expected through the day today as this band of moisture moves through.
A transition is anticipated Thursday as upper heights lower in response to an upper trough digging southward into the area. A weakness within the surface ridge will result and lead to our local winds backing out of the northeast and weakening slightly. Added instability (decent mid-level lapse rates) associated with the cooler temperatures aloft accompanying the upper trough combined with the trade wind inversion eroding should be enough to support locally heavy showers Thursday into the weekend for portions of the state. The best chance for thunderstorms will favor the Big Island slopes through these afternoon periods.
Despite some model differences shown, rising upper heights along with the surface ridge strengthening to the north should translate to a return of a more stable trade wind pattern Sunday through early next week.

Aviation

Surface high pressure far north of the state will continue to produce strong trade winds today. A band of broken low clouds with embedded scattered showers is being transported into the islands by the strong low-level trade wind flow. This cloud cover and precipitation is producing periods of MVFR conditions along many windward facing sections this morning. Otherwise, VFR conditions will likely prevail for most leeward areas today. By this afternoon. this band of clouds and showers may eventually push west of the islands. The forecast guidance appears to indicate a new band of clouds and showers may move into the islands later tonight or early Thursday morning.
AIRMET Tango remains in effect for Tempo moderate low-level mechanical turbulence below 9 thousand feet downwind of the higher terrain on all islands. This AIRMET will likely be needed through this evening. In addition, AIRMET Sierra is in effect for mountain obscuration above 2500 feet over windward facing slopes of the smaller islands from Kauai to Maui. We may also need this AIRMET on the windward Big Island later this morning if clouds and showers increase in coverage.

Marine

Strong to moderate trade winds will hold through this afternoon as a strong high pressure far north of state weakens as it tracks east. A Small Craft Advisory (SCA) is in effect for all Hawaiian Waters through this afternoon. The SCA will then be scaled back to typically windy waters around Maui County and the Big Island this evening through early morning Thursday as the trade winds ease and shift out of the northeast. Another high will build northwest of the state Thursday and stall north of the area over the weekend into early next week producing fresh to moderate trades.
A recent gale north of the region will be sending a series of small northwest to north swells over the next couple days. Offshore buoys are still showing some swell energy in the 10 to 12 second range which should translate to the swell peaking this afternoon and the swell direction should gradually veer toward the north. A small north swell is possible next Sunday into Monday. Otherwise, no significant swells are expected along north facing shores for the foreseeable future.
South facing shores will remain small through today with mainly background energy and windswell wrapping in. A small long- period south swell is expected to start filling in Thursday and likely peak Friday before slowly dropping over the weekend into early next week. A series of small south swells will keep the surf from going flat along south facing shores through next week. Choppy, elevate surf along east facing shores will hold through today before gradually declining Thursday through Saturday. East shore surf will gradually build Sunday into early next week as trades return.

HFO Watches/Warnings/Advisories

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 Thursday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov