Photo Credit: Braden Jarvis

West Kaua’i

Today: Partly sunny with scattered showers. Highs around 90 near the shore to around 78 above 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 72 near the shore to around 63 above 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 90 near the shore to around 78 above 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

South Kaua’i

Today: Mostly cloudy. Occasional showers in the morning, then numerous showers in the afternoon. Highs 82 to 89. East winds 10 to 15 mph. Chance of rain 90 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows around 74. East winds 15 to 20 mph. Chance of rain 70 percent.

Wednesday: Breezy. Partly sunny with scattered showers. Highs 82 to 90. East winds 15 to 20 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Breezy. Occasional showers in the morning, then numerous showers in the afternoon. Highs 74 to 86 in the valleys to around 66 above 4000 feet. East winds 10 to 20 mph. Chance of rain near 100 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then occasional showers after midnight. Lows 65 to 72 in the valleys to around 60 above 4000 feet. East winds 10 to 25 mph. Chance of rain 90 percent.

Wednesday: Mostly cloudy. Breezy. Occasional showers in the morning, then numerous showers in the afternoon. Highs 75 to 86 in the valleys to around 67 above 4000 feet. East winds 10 to 25 mph. Chance of rain 90 percent.

North Kaua’i

Today: Occasional showers in the morning, then numerous showers in the afternoon. Highs 77 to 91. East winds 10 to 15 mph. Chance of rain near 100 percent.

Tonight: Mostly cloudy with numerous showers. Lows 66 to 75. East winds 10 to 15 mph. Chance of rain 70 percent.

Wednesday: Partly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 77 to 91. East winds 10 to 20 mph. Chance of rain 70 percent.

East Kaua’i

Today: Occasional showers in the morning, then numerous showers in the afternoon. Highs 74 to 86. East winds 10 to 15 mph. Chance of rain near 100 percent.

Tonight: Mostly cloudy with numerous showers. Lows 66 to 77. East winds 10 to 15 mph. Chance of rain 70 percent.

Wednesday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 74 to 86. East winds 10 to 15 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

An area of higher moisture will will continue to spread westward across the state today, bringing an increase in windward shower activity through tonight. Moderate to breezy trade winds will continue through tonight as well, then increase to strong speeds Wednesday through Friday. Drier air will settle over the region during the second half of the week.

Discussion

Strong surface high pressure remains centered far north of the main Hawaiian Islands. However, with a surface trough to its south preventing the local trades from being as strong as they typically would with a 1035 mb high, speeds are currently in the breezy to locally strong range statewide. Meanwhile, mid- and upper- level troughing northwest of the islands is beginning to move away to the north, taking the enhanced showers over the northwest offshore waters and high clouds over the islands with it.
A band of higher moisture has moved into the islands from the east overnight, making it as far west as Oahu early this morning. The 12Z sounding from Hilo came in with 1.75 inches of precipitable water (PW), confirming the values indicated yesterday by the CIMSS MIMIC total PW. This moisture increased windward rainfall over much of the state. Despite the increase in shower coverage, rainfall amounts have been somewhat limited due to the presence of dry air in the mid-levels. Windward areas of the Big Island, Maui, Molokai, and Oahu have generally seen around a tenth to a third of an inch of rain over the last 6 hours, with a few isolated spots up to a half inch. This moisture will continue to spread westward to include Kauai through this morning. Additionally, the leeward slopes of the Big Island, and possibly Haleakala on Maui, will likely be more active this afternoon. Leeward areas elsewhere will experience a few passing showers carried over the mountains, but remain drier overall.
Models remain consistent that drier conditions and stronger trade winds will develop later Wednesday and Thursday as the surface trough moves away and the high to the north builds. Both high-res and global models appear to have backed off on wind speeds during the second half of this week, so have adjusted the forecast down a bit. A few of the windier spots on the Big Island and Maui may flirt with wind advisory criteria Wednesday and Thursday, but have kept everyone below for the time being. Overall, expect minimal windward rainfall and dry conditions over most leeward areas during the second half of the week, with trades easing this weekend.

Aviation

Moderate to locally breezy trades will continue today and then gradually strengthen into mid week. Showers and low clouds will favor windward and mountain areas. An area of enhanced moisture moving in from the east will bring enhanced windward shower activity today. In addition, clouds and showers will continue to build up on the Kona slopes of the Big Island during the afternoon hours. MVFR conditions will be possible with any shower activity. Otherwise, VFR should prevail.
AIRMET Sierra for mountain obscuration is in effect for all windward areas of the state due to enhanced shower activity this morning. This AIRMET may be needed on and off today as an area of enhanced moisture moves across the state.
AIRMET Tango for moderate low level turbulence is in effect for areas downwind of island terrain and will likely be needed for the next couple of days as low level wind speeds increase.

Marine

The forecast has been updated to extend the Small Craft Advisory for the windier areas through Wednesday night. The Wind grids have also been nudged upwards some some of the coastal waters through the week.
The 1035 mb high pressures far to the north, with fresh to locally strong winds remaining over the islands. Expect these winds to increase to near Gale levels in the windiest waters on Wednesday. As the winds trend upwards, additional coastal waters will be added to the SCA for the second half of the week. The high is expected to weaken some over the weekend which would allow the trades to ease back to fresh to locally strong speeds
With the current locally strong trade winds, and the increase expected over the next few days, surf will build along east facing shores throughout the work week. Rough and choppy surf should peak above the summer average (5 ft) Friday into Saturday then gradually ease early next week. Local windswell may wrap into select north and south facing shores. The current background south swell will continue its decline into the middle of the week. Otherwise, no significant swells are expected this week.
Local tide gauges are still showing water levels running about a half a foot above coastal flooding guidance at Hilo, Kahului, and Honolulu. The Coastal Flood Statement for isolated minor flooding remains in effect through this afternoon.

Fire weather

Moderate to breezy trade winds will prevail today, with wetter conditions expected as an area of higher moisture moves through. Beginning on Wednesday, trade winds will increase as somewhat dry and stable conditions develop. This could present some fire weather concerns Wednesday afternoon through Thursday, and potentially into Friday as well.

HFO Watches/Warnings/Advisories

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

Data Courtesy of NOAA.gov