Photo Credit: Braden Jarvis

West Kaua’i

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 86 near the shore to around 74 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 71 near the shore to around 59 above 3000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Friday: Partly sunny with scattered showers. Highs around 86 near the shore to around 74 above 3000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

South Kaua’i

Today: Partly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 83. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 67 to 72. Northeast winds 10 to 15 mph. Chance of rain 60 percent.

Friday: Mostly cloudy. Scattered showers in the morning, then numerous showers in the afternoon. Highs around 83. Northeast winds 10 to 15 mph. Chance of rain 60 percent.

Kaua’i Mountains

Today: Mostly cloudy. Showers in the morning, then showers likely in the afternoon. Highs 73 to 80 in the valleys to around 64 above 4000 feet. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 90 percent.

Tonight: Cloudy with numerous showers. Lows 59 to 64 in the valleys to around 54 above 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Friday: Mostly cloudy. Scattered showers in the morning, then numerous showers in the afternoon. Highs 73 to 80 in the valleys to around 64 above 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

North Kaua’i

Today: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 76 to 85. East winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 70 percent.

Tonight: Mostly cloudy with numerous showers. Lows 62 to 71. East winds 10 to 15 mph. Chance of rain 70 percent.

Friday: Mostly cloudy. Scattered showers in the morning, then numerous showers in the afternoon. Highs 76 to 85. East winds around 10 mph. Chance of rain 70 percent.

East Kaua’i

Today: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 76 to 84. North winds 10 to 20 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with numerous showers. Lows 60 to 74. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Friday: Mostly cloudy. Scattered showers in the morning, then numerous showers in the afternoon. Highs 76 to 84. Northeast winds around 10 mph. Chance of rain 60 percent.

Detailed Forecast

Synopsis

A cold front far north of the islands will move south towards Hawaii today. An upper level disturbance is forming over the region this morning as the front stalls out north of the islands, creating continued unstable weather conditions with periods of enhanced showers for all islands through Saturday night. More stable conditions return for the western half of the state from Sunday into early next week. Windward Maui and the Big Island will continue to see enhanced shower trends through Monday. High pressure building back in north of the region will produce moderate to breezy trade winds from Tuesday onward in a more stable weather pattern.

Discussion

A cold front roughly 800 miles north of Oahu will continue to move south towards the Hawaiian Islands today. Water vapor satellite imagery shows an upper level low forming just north of the islands this morning. This upper low will drift slowly across the state into the weekend. Upper level soundings from 2 AM HST (12Z) at Hilo show this instability in the atmosphere, with trade wind temperature inversion height are hovering around the 13,000 foot level. This means cloud heights will build higher resulting in periods of enhanced shower activity.
The high pressure ridge north of the region will weaken over the next 24 hours as the cold front approaches the region from the north. Trade wind speeds will also decrease in strength for the next few days. Periods of unsettled weather conditions and showers will continue to develop across the state into the upcoming weekend. Periods of moderate to locally heavy showers are expected over all islands through Sunday night. The highest chances for rainfall amounts are forecast over windward and mountain sections of each island. These enhanced showers will also tend to favor the typical overnight to early morning hours. That said, some of the stronger showers that develop will bring brief periods of rainfall to the typically drier leeward areas. Isolated thunderstorms are possible over the Big Island on Friday and Saturday afternoon.
By Sunday the forecast guidance showers this upper low lifting slowly to the northeast as a strong high pressure system builds in north of the state. The combination of these two changes will produce a drying trend for the western half of the state starting on Monday. However, one wrinkle in the forecast remains from Sunday to Monday as a weak low level trough (700mb streamlines) drifts into the eastern islands as it passes just south of the island chain. This weak trough will extend enhanced shower activity over windward and eastern sections of Maui and the Big Island through Monday night.
Trade winds will strengthen back into the moderate to breezy range from next week Tuesday onward as a strong high pressure system builds in north of the region. A high pressure ridge aloft will produce stabilizing trends for all islands with only brief showers lingering over windward and mountain areas, mainly in the overnight to early morning hours.

Aviation

With high pressure persisting far north and northeast of the islands, trade winds will remain moderate to breezy across the area. Showers and accompanying MVFR conditions will mainly affect windward and mauka sections statewide. Also, an upper air disturbance in the region will likely enhance showers overall and marginally back surface winds toward the north and northeast.
AIRMETs are in effect for mountain obscuration over windward areas of the Big Island and Maui, and for low level turbulence downwind of higher elevations statewide.

Marine

Strong high pressure far northeast of the area will continue to produce moderate to locally strong trade winds across the area through this morning. The Small Craft Advisory has been extended for typically windy waters around Maui County and the Big Island through the afternoon today. Trade winds will gradually become a bit lighter throughout the day and remain on the lighter side into the early part of the weekend. Trade winds may begin to pick up on Sunday as the high tracks to our north.
A series of rather small short period northerly swells are expected through Tuesday. A slightly larger and longer period northwest swell may arrive Sunday night and Monday and linger into Tuesday. The current small long period south swell will linger through today with a slightly larger long period south swell expected to fill in later today, peak tomorrow and slowly subside through the weekend. Another similar size south swell may arrive Tuesday and Wednesday next week. Short period choppy surf will remain slightly elevated along east facing shores through today before diminishing a bit over the weekend. Strengthening trade winds early next week will likely boost east facing shores once again.

HFO Watches/Warnings/Advisories

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

Data Courtesy of NOAA.gov