Photo Credit: Braden Jarvis

West Kaua’i

Today: Mostly sunny with isolated light showers. Highs 86 to 91 near the shore to around 76 above 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 71 near the shore to around 62 above 3000 feet. East winds around 10 mph. Chance of rain 50 percent.

Thursday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 85 to 91 near the shore to around 76 above 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

South Kaua’i

Today: Partly sunny with scattered light showers. Highs 83 to 90. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

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

Thursday: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs 83 to 90. East winds around 15 mph. Chance of rain 70 percent.

Kaua’i Mountains

Today: Partly sunny. Breezy. Light showers likely in the morning, then scattered light showers in the afternoon. Highs 75 to 84 in the valleys to around 67 above 4000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Breezy. Showers likely in the evening, then occasional showers after midnight. Lows 64 to 70 in the valleys to around 59 above 4000 feet. East winds 10 to 20 mph. Chance of rain 90 percent.

Thursday: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs 75 to 84 in the valleys to around 67 above 4000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

North Kaua’i

Today: Mostly sunny with scattered light showers. Highs 77 to 87. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 66 to 73. East winds 10 to 15 mph. Chance of rain 50 percent.

Thursday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 78 to 87. East winds 10 to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Scattered light showers. Highs 75 to 87. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then showers likely after midnight. Lows 65 to 76. East winds 10 to 15 mph. Chance of rain 70 percent.

Thursday: Mostly cloudy with showers likely in the morning, then mostly sunny with scattered showers in the afternoon. Highs 75 to 86. East winds 10 to 15 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Moderate to locally breezy trade winds will focus low clouds and brief showers over windward and mauka areas, especially during nights and mornings. Leeward communities will be mostly dry, but afternoon clouds and a few showers will develop over leeward portions of the Big Island. High clouds will occasionally transit island skies.

Discussion

Morning soundings show a strong and low subsidence inversion based between 5 and 7 thousand feet, with PWAT a seasonable 1.2″. Regional satellite images show scattered to locally broken low clouds streaming westward at about 17 kt/20 mph, with increased low cloud coverage noted over waters E of Maui County. Surface high pressure to the distant NE is supporting a moderate to breezy trade wind flow. Radar shows widely scattered relatively light showers, while infrared imagery shows thin high clouds streaming ENE over the islands from Oahu to Maui, associated with a persistent TUTT (tropical upper-tropospheric trough) NW of Kauai.
Model guidance has been consistent in projecting little significant change to the current pattern into next week. At the surface, trade wind speeds look to remain remarkably consistent near their current levels. In the mid-levels, a strong ridge will remain over the islands, keeping the subsidence inversion low and strong. Brief showers will favor windward areas, especially during nights and mornings, with sensible weather highly dependent on the arrival of difficult-to-anticipate low cloud clusters. We do anticipate that an area of increased low-level moisture (PWAT currently near 1.9″), associated with the remnants of former Hurricane Adrian now near 20N 130W, will move through the area Monday into Tuesday. This would bring an increase in primarily windward showers if it were to verify. Leeward areas will remain mostly dry, except for the typical afternoon clouds and showers on the Big Island's leeward slopes, but even these should be limited.
There are some changes expected in the upper-level pattern, but impacts on sensible weather will likely be negligible. The nearly- stationary TUTT NW of Kauai will begin to move E later today, passing over the islands tonight and Thursday. This will bring periods of high clouds into Thursday, and some instability aloft, but it is highly unlikely that surface parcels tap into this. There could be some low-impact afternoon cloud/shower formation over the Big Island's summits and upper slopes Thursday. A new low developing within the TUTT this weekend may lead to more high clouds streaming over the islands within the associated subtropical jet.

Aviation

Moderate to locally breezy trade winds are expected to persist today and tonight. The atmosphere remains relatively dry and stable across the island chain early this morning. There are patches of scattered to broken low clouds with embedded isolated light showers being transported by the low-level trade wind flow into the windward sides of some of the islands. This may produce brief periods of MVFR conditions along some windward facing slopes and coastal areas, but VFR conditions will likely prevail across most of the state today.
No AIRMETs are currently in effect. We are monitoring observations from the VAD wind profiles in case we need to issue AIRMET Tango for moderate low-level mechanical turbulence later today.

Marine

A high pressure ridge will remain locked in place far north of the Hawaii region, producing moderate to locally strong trade winds over and upstream of the Hawaiian Islands lasting into early next week. A Small Craft Advisory (SCA) was extended in time through Thursday night for the typically windier waters around Maui County and the Big Island. This SCA will likely continue through the weekend.
Surf along all shores are expected to remain tiny through Friday. In the long range, a series of moderate period south-southeast (150 degree) to south (190-200 degree) swells are expected starting this weekend producing a good boost to south shore surf heights. Another long period south (180-190 degree) swell will move into the region from Monday to Tuesday of next week. North facing shores may see a slight pulses out of the north-northwest (330 degree) through the weekend keeping surf above flat levels starting on Friday.

HFO Watches/Warnings/Advisories

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

Data Courtesy of NOAA.gov