Photo Credit: Braden Jarvis

West Kaua’i

Today: Mostly sunny. Isolated showers in the morning. Highs around 82 near the shore to around 69 above 3000 feet. Southeast winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Lows around 69 near the shore to around 59 above 3000 feet. Southeast winds up to 15 mph.

Monday: Mostly sunny. Highs around 82 near the shore to around 70 above 3000 feet. Southeast winds up to 15 mph shifting to the south in the afternoon.

South Kaua’i

Today: Mostly sunny. Isolated showers in the morning. Highs 78 to 83. Southwest winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Lows around 67. Southwest winds around 10 mph.

Monday: Mostly sunny. Isolated showers in the afternoon. Highs 79 to 84. Southwest winds 10 to 15 mph. Chance of rain 20 percent.

Kaua’i Mountains

Today: Mostly sunny. Isolated showers in the morning. Highs 73 to 79 in the valleys to around 63 above 4000 feet. South winds up to 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Isolated showers after midnight. Lows 61 to 67 in the valleys to around 57 above 4000 feet. South winds up to 20 mph. Chance of rain 20 percent.

Monday: Breezy. Mostly sunny with isolated showers. Highs 73 to 79 in the valleys to around 63 above 4000 feet. Southwest winds up to 20 mph. Chance of rain 20 percent.

North Kaua’i

Today: Mostly sunny. Isolated showers in the morning. Highs 73 to 82. Southwest winds up to 10 mph shifting to the north in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Lows 62 to 69. South winds up to 20 mph.

Monday: Breezy. Mostly sunny with isolated showers. Highs 73 to 82. South winds up to 20 mph. Chance of rain 20 percent.

East Kaua’i

Today: Mostly sunny. Isolated showers in the morning. Highs 72 to 82. Southwest winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers after midnight. Lows 61 to 72. Southwest winds 10 to 15 mph. Chance of rain 20 percent.

Monday: Breezy. Mostly sunny with isolated showers. Highs 72 to 82. Southwest winds 10 to 20 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

The Hawaiian Islands remains under the influence of the subtropical ridge hovering over the region. Expect light to moderate southerly winds over the islands with hybrid sea breezes each day along terrain sheltered north slopes of each island through Tuesday. Stable conditions aloft will keep mostly dry weather in the forecast with scattered showers near Kauai this morning. A cold front will sweep from west to east across the smaller islands from Wednesday morning near Kauai to Maui County by Thursday. Drying trends and southerly flow will return with the subtropical ridge over the region from Friday to Saturday. The next round of rainfall will likely arrive by next Sunday as another cold front drifts into the western islands.

Discussion

Areas of mostly stable stratocumulus clouds continue to linger over most of the state this morning. Satellite imagery also shows a convergent band developing near Kauai on the early morning infra-red satellite imagery. Scattered showers may develop over Kauai and Niihau through the morning hours. Upper air balloon sounding from Lihue, Kauai this morning at 12 AM HST shows a deeper subsidence inversion height around 5,500 feet above sea level, supporting these slow moving scattered showers. The 2 AM HST sounding at Hilo, Hawaii remains low at a height of around 3,000 feet. Overall these stable and dry weather conditions will continue for most islands through Tuesday.
The large scale weather pattern remains unchanged with the subtropical ridge locked in place at the surface over the Hawaiian Islands and the upper level ridge stacks back towards the warm air near the equator. A cold front has stalled just north and west of the island of Kauai and will remain in place through Tuesday. Light to moderate southerly winds, from southeast to southwest directions, will continue to blow warm and humid air across all islands through Tuesday. Strong stability aloft due to subsidence, or downward atmospheric motions, under the ridge axis will continue to keep showers to a minimum.
By late Tuesday a cold frontal system will move across the International Date Line approaching the stalled cold front near Kauai. This next cold frontal system will pick up the stalled front near Kauai and then sweep the combined cloud and shower band through the islands from early Wednesday near Kauai through Thursday where it stalls out over Maui County. Widespread rainfall amounts are forecast as the frontal band moves across each island. The latest forecast guidance has this front stalling over the island of Maui and diminishing rapidly on Thursday, limiting rainfall potential for the Big Island to some scattered shower activity along the southern slopes. Storm total rainfall amounts for each island with this passing cold front should remain well below flood thresholds.
The stable subtropical ridge pattern returns on Friday and Saturday with light to moderate southerly winds, hybrid sea breezes along terrain sheltered northern slopes of each island, and limited rainfall. The next round of rainfall will likely arrive by next Sunday as another cold front drifts into the western islands. Stay tuned.

Aviation

A weak front northwest of Kauai combined with a ridge extending over the islands will maintain southerly winds across the state for the next several days. Expect mainly VFR conditions with local MVFR across southern portions of the islands. Will see an increase in clouds and isolated showers over Kauai and Oahu today as the front stalls west of state. However, eastern islands should remain mostly dry as a relatively dry air mass lingers over them.
No AIRMETs are currently in effect.

Marine

A series of large west to west-northwest (280-310 deg) swells associated with a cyclonic gyre that has evolved over the northern Pacific will persist through the week. The first swell (largest) is building down the island chain this morning and should peak today, driving the seas and surf up over exposed waters and beaches. Observations at the offshore buoys to the northwest have peaked near the predicted levels overnight, with the spectral peak centered around 16 seconds within the 285 degree directional band. Observations at the nearshore PacIOOS buoys have been building overnight and should peak later this morning. Provided the westerly direction, forecast confidence for seas and surf remains lower from Oahu to the Big Island due to the swell shadow from Kauai/Niihau. Observations coming in at the local beaches today will allow us to fine tune the surf/seas forecast numbers over the next day or two.
A Small Craft Advisory and High Surf Warning are in effect to account for the expected impacts over the exposed waters/beaches, which will continue through most of the first half of the upcoming week as these westerly pulses move through. The warning will likely ease to advisory levels for exposed beaches tonight through Monday, but will near warning levels once again as the next swell arrives Tuesday. With the westerly component, expect some wrap into southern exposures. This wrap combined with increasing south-southwest winds will support rising surf for southern shores.
Expect the local winds to hold out of the south to southwest direction over the smaller islands and out of the southeast around the Big Island through the first half of the week. Wind speeds will near advisory levels Tuesday night through Wednesday as a front approaches and begins to move through. Wind directions will shift out of the west to west-northwest following its passage late Wednesday through Thursday, with speeds easing into the light to moderate range.

HFO Watches/Warnings/Advisories

High Surf Warning until 6 PM HST this evening for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kona, Kohala, Kauai North, Molokai Windward, Molokai North, Molokai West, Maui Central Valley North, Windward Haleakala, Big Island South.
High Surf Advisory until 6 PM HST this evening for Lanai Leeward.
Small Craft Advisory until 6 AM HST Monday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Kaiwi Channel, Maui County Windward Waters, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov