Photo Credit: Jason Weingardt

West Kaua’i

Today: Mostly sunny in the morning then becoming partly sunny. Breezy. Isolated showers. Highs around 90 near the shore to around 79 above 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Isolated showers after midnight. Lows around 72 near the shore to around 62 above 3000 feet. Northeast winds up to 20 mph becoming 10 to 15 mph after midnight. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers. Highs around 90 near the shore to around 78 above 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

South Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Breezy. Isolated showers. Highs 82 to 89. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows around 74. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Tuesday: Breezy. Mostly cloudy with numerous showers. Highs 82 to 89. East winds 15 to 20 mph. Chance of rain 70 percent.

Kaua’i Mountains

Today: Breezy. Partly sunny with scattered showers. Highs 76 to 86 in the valleys to around 67 above 4000 feet. East winds up to 15 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 65 to 72 in the valleys to around 59 above 4000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Tuesday: Breezy. Occasional showers. Highs 75 to 86 in the valleys to around 67 above 4000 feet. East winds 10 to 20 mph. Chance of rain near 100 percent.

North Kaua’i

Today: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 78 to 91. East winds up to 20 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 66 to 75. East winds up to 15 mph increasing to 10 to 15 mph after midnight. Chance of rain 70 percent.

Tuesday: Mostly cloudy with occasional showers. Highs 77 to 91. East winds 10 to 15 mph. Chance of rain 90 percent.

East Kaua’i

Today: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 75 to 87. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 66 to 76. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Tuesday: Numerous showers in the morning, then occasional showers in the afternoon. Highs 75 to 86. East winds 10 to 15 mph. Chance of rain near 100 percent.

Detailed Forecast

Synopsis

Moderate to locally breezy trade winds will focus showers over windward slopes today, and aside from afternoon and evening showers on the Kona slopes, leeward areas will be rather dry. An area of moisture will spread over the islands tonight and Tuesday, bringing an increase in shower activity into Wednesday. Trade winds will increase and showers will decrease late Wednesday and Thursday.

Discussion

Moderate to locally breezy trade winds and a typical pattern of mainly windward showers will prevail today. A rather strong 1034 mb high is centered about 1400 miles north of the state. A trough south of the high will keep the pressure gradient and associated trade winds slightly weaker than would be expected with a high of this strength. A weak upper-level trough just west of the islands is sending thin high clouds over the western end of the island chain and is enhancing a few heavy showers south and west of Kauai. However, the combination of stability from a mid-level ridge over the islands and a pocket of drier low-level air moving in from the east will produce modest windward rainfall today. Aside from scattered afternoon showers over leeward Big Island, leeward areas will be mostly dry.
An increase in shower activity is due tonight into Wednesday as a moisture pooled around a mid-level trough moves in on the trades. Precipitable water between 1.5 to 1.8 inches mainly below 12,000 feet will fuel an increase in windward rainfall, and leeward slopes of the Big Island, and possibly Haleakala, will likely be active each afternoon, while leeward areas elsewhere will experience a few passing showers.
Drier conditions and stronger trade winds will develop Wednesday and Thursday as the mid-level trough moves away and the high to the north builds. Expect minimal windward rainfall and dry conditions over most leeward areas. Trade winds will ease during the weekend.

Aviation

Moderate to locally breezy trades will continue and gradually strengthen through the next few days. Clouds and showers will favor windward and mountain areas, especially overnight into the early morning hours. In addition, clouds and showers will build up on the Kona slopes of the Big Island each afternoon. An area of enhanced moisture could bring a modest increase in clouds and shower coverage later tonight into tomorrow. MVFR conditions will be possible with any of this shower activity.
No AIRMETs are currently in effect although AIRMET Sierra could be needed later tonight for windward and mountain areas as increased moisture moves through.

Marine

A high pressure system far north of the Hawaiian Islands will keep trade winds in the fresh to locally strong range through much of this week. Trade wind speeds will remain strong enough to support Small Craft Advisory (SCA) conditions over the windier waters and channels near Maui and the Big Island through the end of the week. The current SCA was extended in time for these windier waters out through Tuesday night. Additional waters will likely be added later this week as wind speeds increase.
Background south swell energy pulses are forecast to continue, with surf remaining below average through much of this week. A small long period south swell may produce a slight increase in south shore surf heights on Thursday and Friday. Small, choppy surf will build along east facing shores as locally strong trade winds increase over the next few days.
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

A typical summer trade wind weather pattern will prevail today, followed by wetter conditions tonight into Wednesday. Late Wednesday and Thursday, trade winds will strengthen, and somewhat dry and stable conditions will develop. This could lead to some fire weather concerns Thursday and possibly Friday.

HFO Watches/Warnings/Advisories

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

Data Courtesy of NOAA.gov