Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Mostly sunny. Highs 85 to 92 near the shore to around 77 above 3000 feet. East winds up to 10 mph.

Tonight: Partly cloudy. Lows around 72 near the shore to around 62 above 3000 feet. East winds up to 10 mph.

Wednesday: Mostly sunny. Highs 86 to 91 near the shore to around 77 above 3000 feet. East winds up to 10 mph.

South Kaua’i

Today: Mostly sunny. Isolated showers in the morning. Highs 84 to 91. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows around 73. East winds 10 to 15 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny. Highs 85 to 91. Northeast winds 10 to 15 mph.

Kaua’i Mountains

Today: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 76 to 84 in the valleys to around 68 above 4000 feet. East winds 10 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 65 to 70 in the valleys to around 59 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday: Mostly sunny with isolated showers. Highs 76 to 85 in the valleys to around 67 above 4000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

North Kaua’i

Today: Mostly sunny with isolated showers. Highs 78 to 88. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 65 to 74. East winds 10 to 15 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny with isolated showers. Highs 78 to 88. East winds 10 to 15 mph. Chance of rain 20 percent.

East Kaua’i

Today: Mostly sunny with isolated showers. Highs 76 to 88. East winds around 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 65 to 77. East winds around 10 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny with isolated showers. Highs 76 to 88. Northeast winds around 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

The high pressure ridge north of the islands will weaken over the next few days as a cold frontal system passes from west to east across the Central Pacific basin. Trade winds will weaken into the light to moderate range through Thursday. Lighter trade winds are in the forecast from Friday through the first half of next week, allowing afternoon sea breezes to expand in coverage. Brief passing trade wind showers are forecast from the overnight through the early morning hours through Friday morning, mainly over windward and mountain areas. Cloud bands associated with a cold front that dissipated far north to northeast of the state will drift into the Hawaiian weather picture from Thursday through Friday, briefly increasing shower activity over the island chain.

Discussion

Regional satellite imagery this morning continues to show a subtropical jet stream over the islands producing a large band of high level cirrus clouds spreading from southwest to northeast across the state. A few low level cumulus cloud bands are just upstream of the state riding in on the trade winds. Expect brief showers through the early morning hours mainly over windward and mountain areas. Upper air balloon soundings from 2 AM HST (12Z) this morning continue to show a stable environment with trade wind temperature inversion heights at Lihue and Hilo remaining around 5,000 and 6,000 feet above the surface respectively. At these levels upper level large scale subsidence is strong enough to limit shower coverage within the isolated to scattered range, favoring windward and mountain areas.
The subtropical ridge far north of the Hawaiian Islands will weaken over the next few days as a high center within the ridge drifts farther eastward and a cold frontal system moves from west to east across the northern Central Pacific basin. Cold air advection with the cold front will weaken the ridge, decrease local area pressure gradients, and decrease trade winds speeds across the region. Moderate trade winds are forecast from Wednesday through Thursday, then becoming lighter trades from Friday through the first half of next week. Cloud bands associated with a different cold front that dissipated far north to northeast of the state will drift into the Hawaiian weather picture from Thursday through Friday, briefly increasing shower activity across the island chain.
Lighter large scale trade winds will allow afternoon sea breezes to expand in coverage over all islands, especially from Friday onward. This means less windward and mountain overnight shower activity with a transition to a few interior sea breeze showers during the late afternoon to early evening hours. Land/mountain breezes each night with a high pressure ridge aloft will trend the weather pattern towards less overnight shower activity.
Little changes are expected in the long range forecast and only slight decreasing precipitation trends were added to the morning forecast grids. No significant changes in weather impacts are expected over the next seven days.

Aviation

Trade winds will relax slightly into the moderate range today as high pressure over the area moves to the east and the local pressure gradient weakens. Some shallow moisture in the relatively stable trade wind flow will bring isolated to scattered showers and brief MVFR conditions to mainly the windward side of the islands today and tonight. Otherwise, besides any showers that may develop in sheltered areas over some leeward areas this afternoon, VFR conditions will prevail.
A weak subtropical jet stream will continue to drift northward this morning and bring TEMPO moderate turbulence aloft. AIRMET Tango is currently in place over the state between FL300 and FL400 and model guidance suggests that it will likely be able to be dropped later this morning.

Marine

No significant changes to the forecast this morning. High pressure to the north will continue to maintain a moderate to locally fresh trades over the coastal waters. Winds are expected to remain below Small Craft Advisory levels. The high will continue to move to the east tonight, and a series of fronts will pass to the north over the next several days. This will keep winds on the weaker side into the weekend.
A series of overlapping small, medium to long period northwest swells will fill in through Friday, keeping surf heights steady. Forecast guidance Friday into early next week shows a moderate, long period northwest swell, from a still yet to develop system, to impact north and west facing shores. Surf heights may reach just below High Surf Advisory criteria. More details can be expected as the low develops in the far northwest pacific over the next few days.
Small surf along south facing shores is expected through the week as a series of medium to long period background southerly swells move through. Long range models suggest the potential for surf to pick up over the weekend and persist through much of next week as a series of small long period south swells move through, boosting surf near to above average. Surf along east facing shores look to remain small and choppy due to weaker than normal local trade winds and will gradually ease to tiny to nearly flat during the second half of the week into early next week as winds weaken.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov