Photo Credit: Brendan Stephen

West Kaua’i

Today: Mostly sunny with isolated showers. Highs around 84 near the shore to around 74 above 3000 feet. Northwest winds up to 10 mph shifting to the southwest in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy. Lows around 72 near the shore to around 61 above 3000 feet. Light winds becoming northeast up to 10 mph after midnight.

Sunday: Mostly sunny. Highs around 85 near the shore to around 75 above 3000 feet. Northeast winds up to 15 mph shifting to the southeast in the afternoon.

South Kaua’i

Today: Mostly sunny with isolated showers. Highs around 83. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows around 72. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Sunday: Breezy. Mostly sunny with isolated showers. Highs around 84. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Kaua’i Mountains

Today: Mostly sunny with isolated showers. Highs 72 to 78 in the valleys to around 67 above 4000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows around 65 in the valleys to around 57 above 4000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Sunday: Mostly sunny with isolated showers. Highs 73 to 79 in the valleys to around 68 above 4000 feet. East winds up to 15 mph. Chance of rain 20 percent.

North Kaua’i

Today: Mostly sunny with isolated showers. Highs 74 to 83. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 65 to 73. Southeast winds up to 10 mph. Chance of rain 20 percent.

Sunday: Mostly sunny with isolated showers. Highs 75 to 84. East winds up to 15 mph. Chance of rain 20 percent.

East Kaua’i

Today: Mostly sunny with isolated showers. Highs 74 to 84. Northeast winds up to 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 63 to 74. Northeast winds up to 10 mph. Chance of rain 20 percent.

Sunday: Mostly sunny with isolated showers. Highs 75 to 85. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

Detailed Forecast

Synopsis

The subtropical ridge will slowly build in north of the island chain this weekend as a weak surface trough northwest of Kauai diminishes. Trade wind speeds will increase a bit starting today, with decreasing afternoon sea breeze coverage. Mostly brief passing showers remain in the forecast in through Sunday afternoon. An easterly wave passing from east to west across the Hawaii Region will increase overnight trade wind shower activity from Sunday night through Tuesday morning. Otherwise more stable conditions return for the second half of next week.

Discussion

The forecast continues to show moderate trade winds blowing through much of next week. Afternoon sea breezes will be limited to terrain sheltered western slopes of each island. Local radar and infra-red satellite imagery this morning continues to show limited clouds and showers upstream of the Hawaiian Islands in a fairly stable weather pattern. Water vapor imagery shows a narrow trough (also known as the TUTT) in the upper levels with the axis just southeast of the Big Island. This upper trough will add some extra subsidence and stability forcing through Sunday afternoon. Upper air balloon soundings from 2 AM HST (12Z) this morning show trade wind temperature inversion heights are measured at 5,000 and 6,500 feet above the surface at Lihue and Hilo respectively. These low inversion heights will continue to limit vertical cloud development and limit shower activity across the state. Therefore we expect brief passing windward and mountain showers, favoring the overnight to early morning hours into Sunday morning.
Trade winds will strengthen today into the moderate range as the ridge north of Hawaii builds in and the surface trough to the northwest of the state diminishes. Model streamlines at 700 mb (around 10,000 feet) also show an easterly wave feature moving into the Hawaii Region from the east enhancing shower activity from Sunday night through Tuesday morning. The upward low level forcing with this trough will push back on the upper level subsidence, increasing the trade wind temperature inversion heights into the 7,000 to 9,000 foot range. This added lift will boost vertical cloud heights and increase rainfall coverage, once again favoring the overnight to early morning hours. More stable conditions return from next week Wednesday to Thursday as the upper level ridge builds back in over the region, increasing stability aloft and limiting shower activity.

Aviation

The transition to trade flow will continue today. Expect isolated to scattered showers across windward portions of the islands. Sea breezes may still develop, bringing the potential for increased afternoon clouds and showers across sheltered leeward locations. While isolated MVFR conditions may occur in showers, TAF sites will be predominantly VFR. AIRMET Tango is in effect for moderate turbulence from FL320 to FL420 and will likely remain in effect through the day. No other AIRMETS are in effect.

Marine

Surface high pressure to the far northwest of the islands is expected to track east and allow a more typical trade wind pattern to set up over the region through the middle of next week. Wind speeds are expected to remain moderate to locally fresh, just below Small Craft Advisory levels for the next several days.
Surf along north facing shores will decline through the weekend as the current north swell continues to drop. A small long period west northwest swell is expected for north and west facing shorelines around the middle of next week. Surf along south facing shores will stay elevated as a small long period swell fills in across the state today. East facing shores will remain small to moderate as the trade winds fill in this weekend.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov