Photo Credit: Brendan Stephen

West Kaua’i

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 89 near the shore to around 79 above 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 67 to 72 near the shore to around 58 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Thursday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 89 near the shore to around 78 above 3000 feet. Northeast winds up to 10 mph shifting to the southwest in the afternoon. Chance of rain 50 percent.

South Kaua’i

Today: Breezy. Partly sunny with scattered showers. Highs 86 to 91. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows 65 to 71. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

Thursday: Partly sunny with scattered showers. Highs 86 to 91. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 76 to 87 in the valleys to around 68 above 4000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 60 percent.

Tonight: Mostly cloudy. Numerous showers in the evening, then showers after midnight. Lows 58 to 63 in the valleys to around 53 above 4000 feet. East winds 10 to 15 mph decreasing to up to 15 mph after midnight. Chance of rain 80 percent.

Thursday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 75 to 86 in the valleys to around 68 above 4000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 60 percent.

North Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 78 to 89. East winds up 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. East winds up to 15 mph. Chance of rain 70 percent.

Thursday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 78 to 89. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

East Kaua’i

Today: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 77 to 90. Northeast winds 10 to 15 mph. Chance of rain 60 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 59 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 89. Northeast winds 10 to 15 mph. Chance of rain 60 percent.

Detailed Forecast

Synopsis

A high pressure ridge north of the Hawaiian Islands will produce moderate to locally breezy trade winds today, wind speeds will weaken to more moderate levels this evening due to a weakening ridge north of the state. Weaker trade winds will produce a hybrid trade wind and sea breeze weather pattern each afternoon through the weekend. Passing showers to continue mainly over windward and mountain areas in the overnight to early morning hours. Shower trends will increase through the weekend as three disturbances drift through the Hawaii Region. Increasing shower activity will continue to favor the windward and mountain areas in the overnight to early morning hours, a few of the stronger showers may reach drier island interior and leeward areas.

Discussion

Satellite infra-red imagery this morning continues to show three weak troughs over and upstream of the islands. These weak troughs will pass through the islands in succession today through the weekend, lifting trade wind temperatures inversion heights, and producing increasing rainfall coverage through the weekend. High level cirrus clouds from the subtropical jet stream are also passing over the islands, likely enhancing sunrise and sunset colors though the weekend.
The high pressure ridge north of the Hawaiian Islands will begin to weaken today as a cold front moves through the northern Central Pacific basin starts to break down the northern ridge. A combination of the weakening ridge and three weak passing easterly waves (troughs) will decreasing trade winds into the moderate range through Monday. As large scale trade wind speeds weaken, land and sea breezes will expand in coverage, and a hybrid trade wind sea breeze pattern will develop through Sunday and possibly lasting into Monday.
Three weak low level troughs will pass over the islands through the weekend as shown on the 700 mb streamlines. Trade wind temperature inversion heights, shown on model cross sections, will rise into the 8,000 to 10,000 foot range. Most of the dynamics with these systems will pass just north of the state with lingering instability along the southern tail of the first two troughs drifting across each island. Kauai and Oahu may see a larger increase in shower trends as both islands are farther north, and closer to the highest instability. The third trough associated with the remnants of former Tropical Cyclone Jova will reach the island chain on Saturday and Sunday. Sea breeze and trade wind convergence zones may briefly enhance interior and leeward showers in the afternoon hours this weekend.

Aviation

Moderate to locally breezy trade winds will persist through today and then trend weaker heading into Thursday. Clouds and showers will generally favor windward and mauka areas during the overnight through mid morning period, with a few spillover showers possible in leeward areas. Expect brief periods of MVFR ceilings and visibility associated with this activity. Then shower activity will become more isolated late morning into the afternoon.
AIRMET TANGO for tempo moderate low-level turbulence remains in effect.

Marine

A ridge of high pressure far north of the state will maintain moderate to locally strong trade winds through the day. The Small Craft Advisory (SCA) will be in effect through this afternoon across the normally windier areas surrounding Big Island and Maui County. As this ridging to the north weakens into Thursday, trade winds will slightly ease back to more gentle to low-end moderate speeds. Winds will remain gentle to moderate until late Friday or early Saturday when the remnants of Tropical Cyclone Jova pass through the waters as a weak surface trough. Early week moderate to fresh winds will veer more southeast as this trough axis travels west across the island chain.
A relatively small, medium period east (80-90 degree) swell that originated from former Tropical Cyclone Jova has been moving through the local waters over the past day or so. Recent buoy data has shown that this swell has peaked and will be declining through Thursday. This fading swell, combined with the lighter winds, will produce lowering east-facing shore surf that will come in below seasonal averages the second half of the week. A small, medium period south (180-190 degree) swell continues to move through the area. This swell will also begin to decline late today into early Thursday. Another very small, medium to short period south swell now passing through American Samoa is forecast to arrive this weekend. No significant swells are expected to affect north-facing shores the next several days.

HFO Watches/Warnings/Advisories

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

Data Courtesy of NOAA.gov