Photo Credit: Jason Weingardt

West Kaua’i

Today: Mostly cloudy. Breezy. Numerous showers and isolated thunderstorms in the morning, then scattered showers and isolated thunderstorms in the afternoon. Highs around 88 near the shore to around 76 above 3000 feet. East winds up to 20 mph. Chance of rain 70 percent.

Tonight: Partly cloudy with isolated showers. Lows around 72 near the shore to around 62 above 3000 feet. East winds up to 15 mph shifting to the northeast after midnight. Chance of rain 20 percent.

Wednesday: Breezy. Mostly sunny with isolated showers. Highs around 87 near the shore to around 75 above 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

South Kaua’i

Today: Breezy. Mostly cloudy with numerous showers and isolated thunderstorms. Highs 80 to 89. Northeast winds 15 to 20 mph. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows around 74. Northeast winds 15 to 20 mph. Chance of rain 40 percent.

Wednesday: Breezy. Partly sunny with scattered showers. Highs 79 to 87. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Breezy. Cloudy with showers and isolated thunderstorms. Highs 74 to 85 in the valleys to around 65 above 4000 feet. East winds 10 to 20 mph. Chance of rain 90 percent.

Tonight: Mostly cloudy. Breezy. Numerous showers in the evening, then scattered showers after midnight. Lows 63 to 70 in the valleys to around 59 above 4000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Wednesday: Mostly cloudy. Breezy. Showers in the morning, then scattered showers in the afternoon. Highs 74 to 84 in the valleys to around 64 above 4000 feet. East winds 10 to 20 mph. Chance of rain 80 percent.

North Kaua’i

Today: Mostly cloudy with numerous showers and isolated thunderstorms. Highs 76 to 89. East winds up to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 65 to 73. East winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday: Partly sunny with scattered showers. Highs 75 to 88. East winds 10 to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Mostly cloudy with numerous showers and isolated thunderstorms. Highs 73 to 86. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows 66 to 77. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday: Partly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 72 to 85. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Unsettled and breezy trade wind weather will continue through the early morning hours as a weak upper low drifts slowly westward across the state. More stable air will move in from the east today, decreasing local shower activity through Wednesday. Another increase in rainfall activity remains in the forecast from late Wednesday into Friday. Drier conditions with lighter winds return just in time for the upcoming weekend.

Discussion

The satellite water vapor picture this morning continues to show a weakening upper level low over the western half of the state. This low will continue drifting westward keeping unsettled shower activity and isolated thunderstorms in the forecast over the western islands through the morning hours. Periods of wet weather conditions will persist this morning.
More stable conditions with drier trends remain in the short range forecast. Increasing large scale subsidence (downward vertical motions) will spread drier air aloft from east to west across the state today, as the upper low moves farther westward away from the islands. These drier trends will last through Wednesday across much of the state.
By Wednesday afternoon deeper tropical moisture and instability, associated with the remnants of former Hurricane Kristy, will move into the windward slopes of the Big Island. This band of unstable moisture will then spread numerous showers westward across the smaller islands through Friday. There remains a fair chance for a few heavy showers in this pattern, although not enough to support a Flood Watch at this time.
The forecast for this weekend continues to trend drier and weaker trade winds are favored due a weaker high pressure ridge north of the island chain. Lighter large scale winds will allow sea breeze winds to expand in coverage along western terrain sheltered slopes of each island.

Aviation

Breezy easterly trades will continue today, with moderate to heavy showers favoring windward slopes and scattered showers over the leeward areas. The instability associated with an upper low will hang over Kauai through the morning as it continues to drift west. Breezy to locally strong trades should persist through the forecast period.
AIRMET Sierra for mountain obscuration has been updated for N thru E sections of Kauai as conditions have improved over Maui, Molokai, and Oahu.
AIRMET Tango remains in effect for tempo moderate low-level turbulence downstream of island terrain below 8000 feet and is expected to continue today.
AIRMET Zulu is in effect for the potential for moderate icing associated with the deep layered clouds over Maui, Molokai, Oahu, and Kauai. The potential for icing will be greatest between 130 and FL220. The threat for moderate icing should decrease over the eastern half of through the morning hours.

Marine

Fresh to strong easterly trades will continue through Friday, then potentially ease over the weekend as a weakness forms in the ridge to the north. Expect the strongest winds and roughest conditions over the windier waters and channels from Oahu to the Big Island, where a Small Craft Advisory is posted. In addition to the winds and seas, heavy showers and a few thunderstorms remain possible today as an upper low continues to influence the local weather. Conditions will gradually improve from east to west through midweek as drier conditions return.
Surf along north facing shores will hold today, then slowly ease through midweek as a north-northeast swell lingers. An upward trend is possible this coming weekend due to a storm-force low centered over the far northwest Pacific near Kamchatka. Guidance shows small, long-period forerunners arriving out of the north- northwest from this system by the end of the day Friday, then peaking near the advisory level Saturday.
Surf along east facing shores will remain rough through the week due to the strong trades locally and upstream across the eastern Pacific. A small, medium-period easterly swell mixed in will hold today, then fade through midweek.
Surf along south facing shores will gradually lower through midweek as a small, south-southwest moves out. Expect a mix of short-period southeast and background, long-period south swell energy to return by midweek.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Wednesday for Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters.
Small Craft Advisory until 6 AM HST Thursday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov