Photo Credit: Brendan Stephen

West Kaua’i

Today: Breezy. Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 90 near the shore to around 78 above 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Breezy. Scattered showers after midnight. Lows around 72 near the shore to around 62 above 3000 feet. Northeast winds up to 20 mph. Chance of rain 40 percent.

Monday: Mostly sunny. Breezy. Highs around 90 near the shore to around 79 above 3000 feet. East winds up to 20 mph.

South Kaua’i

Today: Breezy. Mostly sunny with isolated showers. Highs 83 to 90. East 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 10 to 20 mph. Chance of rain 50 percent.

Monday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 82 to 89. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs 76 to 86 in the valleys to around 68 above 4000 feet. East winds up to 15 mph. Chance of rain 40 percent.

Tonight: Partly cloudy with scattered showers in the evening, then mostly cloudy with numerous showers after midnight. Lows 65 to 71 in the valleys to around 59 above 4000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Monday: 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.

North Kaua’i

Today: Mostly sunny with isolated showers. Highs 79 to 91. Southeast winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 66 to 74. Southeast winds up to 15 mph. Chance of rain 50 percent.

Monday: Breezy. Partly sunny with scattered showers. Highs 78 to 91. East winds up to 20 mph. Chance of rain 50 percent.

East Kaua’i

Today: Mostly sunny with isolated showers. Highs 76 to 88. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 66 to 77. East winds up to 15 mph. Chance of rain 50 percent.

Monday: Partly sunny with scattered showers. Highs 75 to 87. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Trade winds will gradually strengthen over the next couple of days as a stable pattern of mainly windward showers prevails. A batch of moisture moving in the trade wind flow will produce an increase in showers Monday night and Tuesday. Trade winds are expected to strengthen Wednesday and Thursday, bringing drier weather.

Discussion

A stable, moderate to locally breezy trade wind flow will prevail through tomorrow. A rather strong 1033 mb high is sitting about 1300 miles north of the state. A trough south of the high is keeping the pressure gradient and associated trade winds slightly weaker than would be expected with a high of this strength. As the trough fills, trade winds will gradually strengthen. A mid- level ridge over the islands will maintain stable conditions, and as a shallow batch of moisture moves westward today, drier air will slowly move over the region from the east. Modest rainfall will be focused over windward slopes, and mostly dry conditions are expected leeward. Exceptions will be on the Kona slopes of the Big Island, where clouds and showers will develop each afternoon, and leeward Kauai, which could see a couple of brief showers this afternoon.
An increase in shower activity is due Monday night and Tuesday as another batch of moisture moves in on the trades. This area will be deeper than the one that passed through yesterday, which suggests that shower chances will be higher, especially for windward areas. Leeward slopes of the Big Island, and possibly Haleakala, will likely be active Tuesday afternoon, while leeward areas elsewhere will experience a few passing showers. A mid-level trough will accompany the moisture, but generally stable conditions will remain aloft, minimizing chances for any heavy rainfall.
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.

Aviation

Moderate trades will remain in place through the next few days. Clouds and showers will favor windward and mountain areas and night time hours. In addition, clouds and showers will build up on the Kona slopes of the Big Island each afternoon. A few of the showers could bring brief MVFR conditions. Otherwise, VFR should prevail.
No AIRMETs are currently in effect.

Marine

A strengthening 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 be strong enough to support Small Craft Advisory (SCA) conditions over the windier waters and channels near Maui and the Big Island. The SCA was extended in time for these waters out through Tuesday. 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. Small, choppy surf will increase along east facing shores as locally strong trade winds increase over the next few days.
Spring tides will peak this afternoon, with local tide gauges showing water levels are still running about a half a foot above guidance and at least 1 foot higher than the Mean Higher High Water (MHHW) threshold at Hilo, Kahului, and Honolulu. The Coastal Flood Statement for isolated minor flooding remains in effect through Monday evening.

Fire weather

A typical summer trade wind weather pattern will prevail into Monday, followed by wetter conditions Monday night and Tuesday. On Wednesday and Thursday, trade winds will strengthen, and somewhat dry and stable conditions will develop. This could lead to some fire weather concerns.

HFO Watches/Warnings/Advisories

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

Data Courtesy of NOAA.gov