Photo Credit: Jason Weingardt

West Kaua’i

Today: Mostly sunny with isolated showers in the morning, then partly sunny in the afternoon. Highs 83 to 89 near the shore to around 75 above 3000 feet. East winds around 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy in the evening, then mostly cloudy with isolated showers after midnight. Lows around 70 near the shore to around 60 above 3000 feet. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs around 84 near the shore to around 72 above 3000 feet. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

South Kaua’i

Today: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 82 to 88. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 70. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tuesday: Breezy. Partly sunny with scattered showers. Highs 80 to 86. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Partly sunny with scattered showers. Highs 76 to 81 in the valleys to around 67 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Breezy. Numerous showers in the evening, then occasional showers after midnight. Lows 62 to 68 in the valleys to around 58 above 4000 feet. Northeast winds 10 to 20 mph. Chance of rain near 100 percent.

Tuesday: Breezy. Scattered showers in the morning, then occasional showers in the afternoon. Highs 71 to 78 in the valleys to around 63 above 4000 feet. Northeast winds 10 to 25 mph. Chance of rain near 100 percent.

North Kaua’i

Today: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 77 to 86. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then occasional showers after midnight. Lows 64 to 72. Northeast winds 10 to 15 mph. Chance of rain 90 percent.

Tuesday: Partly sunny. Breezy. Scattered showers in the morning, then numerous showers in the afternoon. Highs 73 to 84. Northeast winds 10 to 25 mph. Chance of rain 70 percent.

East Kaua’i

Today: Partly sunny with scattered showers. Highs 75 to 85. East winds around 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 64 to 74. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Tuesday: Mostly cloudy. Breezy. Scattered showers in the morning, then numerous showers in the afternoon. Highs 71 to 82. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Ridging north of the islands will maintain moderate to locally breezy trade winds today, with isolated to scattered showers generally favoring windward and mauka areas. Stronger northeast trade winds are expected to build across the area Tuesday afternoon, and then persist through at least Thursday night. Shower chances will also increase across the islands from west to east Tuesday though Thursday morning before drier air returns statewide by Thursday afternoon. A return to more typical trade wind weather is expected from Friday through the weekend.

Discussion

No significant changes to the forecast this morning. High pressure remains far northeast of the islands with a ridge extending from the high to the northern boundary of the offshore waters. Moderate to locally breezy trade winds have spread across the region as a result. CIMSS MIMIC layer precipitable water (PW) shows precipitable water values have become more uniform across the islands. This correlates well with the overnight soundings which show Lihue at 1.40 inches, and Hilo 1.49 inches of PW. Much drier air is noted further northwest near Kauai closer to the ridge axis.
Moderate to locally breezy trade winds are expected to continue today, with showers favoring the windward and mauka areas. Expect drier air to spread over the eastern end of the state later today.
As a front passes north of the islands on Tuesday, moisture will once again increase over and upstream of the islands. Strong post- frontal high pressure will also begin to increase winds to locally strong levels by Tuesday afternoon, and these locally strong winds will persist through at least Thursday night. As the high pressure strengthens north of the state, moisture associated with another front will be pushed down the island chain, increasing shower chances from west to east Tuesday night through Thursday morning.
Much drier air will fill in across the state from west to east on Thursday. More typical trade wind weather with moderate to locally breezy trades and showers favoring windward and mauka locations will return from Friday through the weekend.

Aviation

Moderate to locally breezy trades will continue through the next 24 hours, with only a temporary diurnal weakening across the state during the overnight hours. Low clouds and showers will cause windward Big Island to continue to experience MVFR conditions early this morning, with only brief periods of MVFR conditions expected across other windward areas. Otherwise, VFR conditions will prevail.
AIRMET Sierra for mountain obscuration across windward Big Island remains in effect early this evening. However, drier air has filtered in and allowed conditions to improve slightly, so this AIRMET might be dropped later this morning. Satellite imagery, radar and surface observations show some low clouds and showers beginning to persist over windward Oahu this morning and if this activity becomes more extensive, windward Oahu may need to be included in the AIRMET Sierra for mountain obscuration.

Marine

A surface ridge sitting nearly 250 nm north of Kauai will maintain moderate to locally strong trade winds through today. A Small Craft Advisory (SCA) is in place for the typically windy waters around the Big Island and Maui. Winds should ease slightly and become northeasterly around Kauai this afternoon and evening as a front approaches from the northwest followed closely by a strong high pressure. As the weak front reaches Kauai late Tuesday or early Wednesday, the robust surface high to the northwest will drive increasing northeasterly trade winds and large rough seas. The SCA has been expanded to all waters Tuesday due to strengthening winds and building seas. This SCA may very well be expanded for most waters, if not all, as the high settles north of the area Friday and seas remain elevated. A decrease in trade winds is expected heading into next weekend, but SCA conditions could persist.
Latest near shore buoys show the 340-350 degree north-northwest swell of around 5 ft at 12 seconds has shifted to a more northerly (350-010 degrees) direction at around 4 ft 12 seconds and will continue to slowly decline through today. Since this swell is trending down, the threat of moderate surges in Kahului and Hilo harbors no longer posses a threat thus the Marine Weather Statement has been allowed to expire. Long- period forerunners from the next northwest swell will arrive early Tuesday, and the swell will peak at 9 to 10 ft Tuesday night and Wednesday. While the resulting surf will easily exceed High Surf Advisory levels on north and west facing shores, the peak of the swell will coincide with fresh to near gale northeasterly winds, leading to rough conditions and the potential for high surf along east facing shores due to large wind waves. On Thursday, the swell will shift out of the north- northwest and may be briefly reinforced, keeping surf elevated around advisory levels. The northerly swell is expected to decline late Friday into the weekend.
Small short-period wind waves and small wrapping northerly swell will produce moderate east shore surf through today, followed by a rise to around the advisory level Tuesday and Wednesday as strengthening northeasterly trade winds produce large wind waves. Above average east shore surf and rough conditions can be expected Thursday and Friday due to fresh to near gale trade winds and additional wrapping northerly swell. A small pulse of south- southwest swell will fill in late Monday into Tuesday.

HFO Watches/Warnings/Advisories

Small Craft Advisory from 6 AM Tuesday to 6 AM HST Wednesday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Big Island Windward Waters.
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