Photo Credit: Brendan Stephen

West Kaua’i

Today: Mostly sunny. Breezy. 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 20 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers. Lows around 71 near the shore to around 59 above 3000 feet. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Thursday: Mostly sunny with isolated showers. Highs around 86 near the shore to around 74 above 3000 feet. Northeast winds 10 to 15 mph decreasing to up to 15 mph in the afternoon. Chance of rain 20 percent.

South Kaua’i

Today: Breezy. Partly sunny with scattered showers. Highs around 84. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 67 to 72. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Thursday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 83. Northeast winds around 15 mph. Chance of rain 70 percent.

Kaua’i Mountains

Today: Breezy. Partly sunny with scattered showers. Highs 74 to 81 in the valleys to around 65 above 4000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with numerous showers. Lows 59 to 64 in the valleys to around 54 above 4000 feet. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

Thursday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 73 to 80 in the valleys to around 64 above 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

North Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 77 to 86. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 62 to 72. East winds 10 to 15 mph. Chance of rain 70 percent.

Thursday: Partly sunny with scattered showers. Highs 76 to 85. East winds 10 to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Breezy. Partly sunny with scattered showers. Highs 77 to 85. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 60 to 73. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Thursday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 76 to 84. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Moderate to locally breezy trade winds will continue across the state for the next several days. Showers will favor windward and mountain locations as periodic bands of enhanced moisture move into the state on the trades. The greatest coverage of showers will be during the overnight through early morning hours.

Discussion

As anticipated, not major changes to the forecast with the morning package. The main change was to lower PoPs this morning. Satellite shows little in the way of clouds over and immediately upstream of the islands.
A 1026mb high pressure system is far to the northeast of the islands early this morning, with a ridge extending to the southwest from the high. Water vapor imagery shows the mid to upper level trough axis is moving over the central islands early this morning, and is expected to continue to move southward today and tonight. High clouds being drawn to the north ahead of the upper level trough will continue, but otherwise not expecting this feature to have much of an impact in our weather.
The morning sounding from Lihue had precipitable water (PW) of 0.96 inches, on the dry side of normal, and Hilo had 1.21 inches, which is near normal. Satellite derived PW shows values on the dry side of normal upstream of the islands. Satellite imagery shows a few different showery low cloud bands upstream of the islands. We can expect to see some passing showers as these are carried in on the trade wind flow.
The high pressure to the northeast will move to the east, and a new high pressure system is expected to move in to the north of the islands Thursday. Winds may briefing weaken as the new high moves in, but otherwise expect moderate to locally breezy trade winds to dominate our weather for the week.
By early next week, a cold front will approach the islands from the northwest. This will weaken the ridge and moderate trade wind speeds from Sunday onward.

Aviation

Moderate to locally breezy trade winds will continue through Thursday. This will maintain a typical trade wind weather pattern, focusing a majority of showers and lower clouds across windward areas. A few showers may briefly reach leeward areas. Mainly VFR conditions are expected across TAF locations through the period, however brief MVFR conditions are expected across some windward locations, however the areal extent should remain below AIRMET criteria.
AIRMET Tango remains in effect for moderate low level turbulence over and downwind of terrain for all islands. This AIRMET will likely remain in place for the next few days.

Marine

The trade winds remain locally strong early this morning due to a surface high pressure system located far northeast of the state. The most recent scatterometer data from last evening showed areas with wind speeds of 25 kt or greater in the vicinity of the eastern islands. Therefore, a Small Craft Advisory (SCA) remains in effect through Thursday afternoon for the typically windier waters adjacent to the islands of Maui County and the Big Island. The trades are expected to become northeasterly starting late Thursday in response to a surface low pressure system, which will likely develop to the northeast of the islands. In addition, two high pressure systems passing by far north of the state from Thursday into this weekend are expected to maintain the locally strong trade winds. As a result, the SCA will likely be extended from Thursday night into this weekend for the typically windier waters based on the latest forecast.
The most recent observations from National Data Buoy Center buoy 51000 located northeast of the state, as well as the nearshore PacIOOS buoys, show the current small north-northeast swell appears to be gradually filling in early this morning with heights of 2 to 3 feet and wave periods of 12 to 13 seconds. Small to moderate north-northeast swells are expected to continue through Thursday night. The wave model guidance indicates the bulk of this swell energy is aimed just east of the islands, meaning that the largest surf may occur along north facing shores of the Big Island during the next couple of days. A shorter period north swell, which is related to the fetch around the surface low developing northeast of the islands, is due to arrive starting Friday. This will likely maintain moderate surf along most north facing shores through Friday night. The first sizable, long-period northwest swell of the season is expected this weekend. Surf produced by this swell may reach the High Surf Advisory criteria along most north and west facing shores of the smaller islands from Saturday into Sunday.
The gusty trade winds in the vicinity of, as well as upstream of, the state are generating rough, slightly elevated surf along east facing shores. In addition, the north-northeast swell may also provide a slight boost in surf along east facing shores with a northerly exposure during the next few days. Elsewhere, surf along south facing shores will likely remain small through early Friday. A small, long-period south-southwest swell arriving late Friday may provide a noticeable boost to surf heights along south facing shores this weekend.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Thursday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov