Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 89 near the shore to around 77 above 3000 feet. Light winds. Chance of rain 30 percent.

Tonight: Partly cloudy. Scattered showers early in the evening, then isolated showers in the late evening and overnight. Lows 69 to 74 near the shore to around 60 above 3000 feet. Light winds. Chance of rain 30 percent.

Saturday: Mostly sunny with isolated showers. Highs around 90 near the shore to around 78 above 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

South Kaua’i

Today: Mostly sunny with isolated showers. Highs around 86. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with scattered showers. Lows 67 to 73. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Saturday: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 87. Northeast winds 10 to 15 mph. Chance of rain 40 percent.

Kaua’i Mountains

Today: Partly sunny with scattered showers. Highs 76 to 83 in the valleys to around 67 above 4000 feet. Light winds becoming east up to 10 mph in the afternoon. Chance of rain 50 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 60 to 65 in the valleys to around 55 above 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Saturday: Partly sunny with scattered showers. Highs 77 to 84 in the valleys to around 68 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

North Kaua’i

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 79 to 88. East winds up to 15 mph. Chance of rain 30 percent.

Tonight: Mostly cloudy with scattered showers. Lows 63 to 73. East winds up to 10 mph in the evening becoming light. Chance of rain 40 percent.

Saturday: Partly sunny with scattered showers. Highs 80 to 89. East winds up to 15 mph. Chance of rain 40 percent.

East Kaua’i

Today: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 79 to 87. Northeast winds up to 10 mph. Chance of rain 30 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 61 to 74. Northeast winds around 10 mph in the evening becoming light. Chance of rain 40 percent.

Saturday: Partly sunny with scattered showers. Highs 80 to 88. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 40 percent.

Detailed Forecast

Synopsis

Fairly typical trade wind weather featuring mainly windward and mauka showers is expected through the middle next week, although we could see a few leeward showers this afternoon as the trades remain rather light. The trades will be on the increase late Saturday and Saturday night as a high builds to the distant northwest, with moderate to breezy conditions then expected Sunday through the middle of next week. The trades could weaken for the tail end of the next work week as a front approaches from the northwest, with the potential for an increase in showers as some deeper moisture moves in from the east.

Discussion

Currently at the surface, a weak trough of low pressure is positioned around 600 miles north-northeast of Honolulu, while a 1020 mb high is centered around 1400-1500 miles northeast of the island chain. The trough to the north continues to cut off the stronger gradient associated with the high, keeping the trades weaker and in the light to moderate range, with localized land breezes in the more sheltered locales. Infrared satellite imagery shows partly to mostly cloudy skies in windward areas, with mostly clear to partly cloudy conditions in leeward sections. Main short term focus revolves around trade wind trends and rain chances.
The trough north of the islands will gradually weaken and merge with a front during the the next day or so. This will keep the trade winds fairly steady in the light to moderate range, with localized land and sea breezes developing in some of the more sheltered leeward areas. A new building high to the distant northwest will begin to strengthen the trades late Saturday and Saturday night, with moderate to breezy conditions then expected Sunday through Wednesday. A front approaching from the northwest may weaken the trades back into the light to moderate range for the tail end of the upcoming work week.
As for the remaining weather details, a broken band of low clouds seen in satellite imagery will keep scattered showers moving into windward areas early this morning, with a few of these showers making the trip over the mountains into leeward communities. A typical diurnal decrease in trade wind showers is expected this afternoon, with a few showers expected to develop over interior and leeward sections of the islands with the assistance of localized sea breezes. Fairly typical trade wind weather will then prevail tonight through the middle of next week, with bands of clouds and showers moving through the islands from time to time, favoring primarily windward and mauka locations. We could see an increase in trade wind showers toward the tail end of the upcoming work week as some moisture associated with the remnant trough of tropical cyclone Jova may break off and move through the island chain.

Aviation

Light to moderate easterly trade winds will continue over the next 24 hours with clouds and showers favoring windward and mauka locations. However, in protected leeward areas with lighter winds, land and sea breezes can be expected. VFR conditions will generally prevail, but brief periods of MVFR will be possible in any showers that move through.
No AIRMETs are in effect.

Marine

A trough far north-northeast of the Hawaiian Islands will continue to weaken the high pressure ridge north of the state today with gradual building trends in the ridge this weekend. Expect gentle to fresh trade winds today with near shore land and sea breeze winds along terrain sheltered western areas close to the coastline. Trade winds will strengthen through the weekend into the fresh to locally strong range by Sunday and continue to blow at these levels through the first half of next week. A Small Craft Advisory may be issued for the windier coastal waters near Maui and the Big Island by Saturday.
The current south swell will continue to decline today with decreasing surf height trends along south facing shores. A smaller long period south swell will arrive by Saturday night. No other significant swells are expected through the rest of the week. Extended range models suggest the next long period south swell may arrive the following weekend starting around Saturday or Sunday September 16th and 17th.
East facing shores remain small into Saturday as winds remain on the weaker side. Strengthening trade winds will help to boost wind wave driven choppy surf heights by Sunday. A moderate long period east swell from Hurricane Jova in the East Pacific will arrive early next week, with the forerunners reaching east facing shores as early as Sunday morning for exposed shores of the Big Island and possibly Maui. Surf heights may approach High Surf Advisory criteria for exposed east facing shores as the swell energy peaks on Monday.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov