Photo Credit: Braden Jarvis

West Kaua’i

Today: Partly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 86 near the shore to around 71 above 3000 feet. East winds up to 25 mph increasing to 10 to 25 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with isolated showers. Lows around 69 near the shore to around 58 above 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Sunday: Mostly cloudy with isolated showers. Highs around 86 near the shore to around 71 above 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

South Kaua’i

Today: Breezy. Cloudy with numerous showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 76 to 84. East winds 15 to 20 mph. Chance of rain 70 percent.

Tonight: Cloudy and breezy. Scattered showers in the evening, then numerous showers after midnight. Lows around 68. East winds 15 to 20 mph. Chance of rain 70 percent.

Sunday: Cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 77 to 84. East winds around 15 mph. Chance of rain 70 percent.

Kaua’i Mountains

Today: Cloudy and breezy. Showers in the morning, then scattered showers in the afternoon. Highs 71 to 82 in the valleys to around 61 above 4000 feet. East winds 10 to 25 mph. Chance of rain 90 percent.

Tonight: Breezy and showers. Lows around 66 in the valleys to around 55 above 4000 feet. East winds 15 to 20 mph. Chance of rain near 100 percent.

Sunday: Cloudy and breezy. Showers in the morning, then scattered showers in the afternoon. Highs 71 to 82 in the valleys to around 62 above 4000 feet. East winds 10 to 20 mph. Chance of rain 80 percent.

North Kaua’i

Today: Breezy. Mostly cloudy with scattered showers. Highs 75 to 86. East winds up to 20 mph. Chance of rain 50 percent.

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

Sunday: Cloudy with scattered showers. Highs 75 to 86. East winds 10 to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 71 to 81. East winds 10 to 20 mph. Chance of rain 70 percent.

Tonight: Cloudy. Numerous showers in the evening, then showers after midnight. Lows 63 to 72. East winds around 15 mph. Chance of rain 90 percent.

Sunday: Cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 71 to 82. East winds 10 to 15 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Breezy trade winds will continue into Monday as a high pressure system remains anchored far north of the state. An upper level low northwest of Kauai will slowly drift across the island chain through Monday enhancing shower activity mainly over windward and mountain areas of each island. By Tuesday the disturbance aloft weakens and drifts northeast of the state, briefly decreasing shower activity. A low level cloud band will ride into the islands on the trade winds with support from an upper level trough from Wednesday to Thursday, increasing shower trends over all islands.

Discussion

Satellite imagery water vapor channel continues to show an upper level low roughly 700 miles to the west-northwest of Kauai this morning. An upper level trough is also evident over the islands enhancing trade wind showers as shown on island radar. The subtropical jet stream flows from west to east over the Big Island this morning, and this jet stream will slowly drift north over the next few days.
A 1030 mb high pressure center and subtropical ridge will remain anchored over the Central Pacific basin, far north of the Hawaiian islands through the weekend. This system will produce breezy easterly trade winds across the Hawaii region into Monday. Trade wind speeds will slowly decrease to moderate levels from Monday into Tuesday as the high pressure center drifts eastward away from the island chain and a long wave trough moves into the Central Pacific. Easterly trade winds will continue to blow at moderate levels through Friday.
Expect continued enhanced showers across the state as the unstable upper level disturbance slowly drifts eastward across the island chain. Most of the rainfall amounts will favor windward and mountain areas as breezy trade winds build clouds up and over the windward mountain slopes. Down sloping trade wind flow over the leeward sides of island mountain ranges will tend to decrease shower activity for leeward areas of each island. Shower trends will tend to increase during our typical diurnal rainfall maximum in the overnight to early morning hours.
In the extended forecast we continue to see a long band of unsettled shallow clouds, remnants of an old Eastern Pacific cold front, drifts into the islands on the moderate trade winds from Wednesday morning into Thursday. This cloud band may produce wet weather over all islands for an 18 to 24 hour time period. The highest rainfall amounts will tend to favor windward and mountain areas, however many leeward sites may also see measurable rainfall totals with this next system. This fairly shallow cloud band will likely not be deep enough to produce heavy rainfall, rather more beneficial rain is forecast for all islands.

Aviation

Breezy easterly trade winds will persist through the weekend, with clouds and showers favoring windward and mauka locations. MVFR CIGs/VSBYs in showers are possible over windward areas, especially overnight through the early morning periods. Elsewhere, VFR conditions will prevail with an occasional shower making it to leeward sections of the smaller islands.
AIRMET Sierra is in effect for tempo mountain obscuration for windward portions of each island. This may persist through the early morning hours before conditions improve.
AIRMET Tango is in effect for mod turb below 9000 feet downwind of island terrain, which will continue through the weekend.

Marine

Consolidating high pressure far N of the islands will support strong E trade winds into Monday, with island terrain accelerating winds to near-gale force in the windier channels. The high will move E thereafter, leading to a gradual easing in trade wind speeds by the middle of next week. A Small Craft Advisory (SCA) for all waters will remain posted through at least Sunday. A disturbance aloft will allow for the development of a few heavier showers the next couple of days, producing periods of gusty winds and reduced visibility.
Combined seas increased to near 10 feet at several of the near- shore PacIOOS buoys overnight, mostly due to an increase in short- period wind waves. These wind waves arriving along E facing shores will result in rough and choppy surf for at least the next several days. Also, a new medium- to long-period NNW swell will peak near 4 feet today. This swell will gradually diminish Sunday, but another relatively small, moderate-period NW swell is expected Monday and Tuesday.
Elsewhere, the storm track in the S hemisphere recently became favorable for the generation of Hawaii-bound S swell, with pulses of swell arriving on-and-off for at least the next week. The first of these long-period S swells is expected to arrive later this weekend and early next week, with peak surf heights remaining below High Surf Advisory (HSA) heights, although later swells may be large enough to warrant a HSA.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Monday for all Hawaiian waters,

Data Courtesy of NOAA.gov