Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Mostly sunny with isolated showers. Highs around 83 near the shore to around 73 above 3000 feet. Northeast winds up to 10 mph shifting to the west in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy with scattered showers. Lows 62 to 67 near the shore to around 53 above 3000 feet. Light winds. Chance of rain 50 percent.

Wednesday: Partly sunny with scattered showers. Highs around 83 near the shore to around 73 above 3000 feet. Northeast winds around 10 mph. Chance of rain 40 percent.

South Kaua’i

Today: Mostly sunny in the morning then becoming partly sunny. Breezy. Isolated showers. Highs around 81. Northeast winds 15 to 20 mph. Chance of rain 20 percent.

Tonight: Breezy. Mostly cloudy with numerous showers. Lows 60 to 66. Northeast winds 15 to 20 mph. Chance of rain 70 percent.

Wednesday: Partly sunny with scattered showers. Highs around 81. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Partly sunny. Scattered showers in the morning, then numerous showers in the afternoon. Highs around 76 in the valleys to around 65 above 4000 feet. Northeast winds up to 10 mph. Chance of rain 60 percent.

Tonight: Mostly cloudy with numerous showers. Lows around 56 in the valleys to around 48 above 4000 feet. Light winds becoming east up to 10 mph after midnight. Chance of rain 70 percent.

Wednesday: Partly sunny with scattered showers. Highs around 76 in the valleys to around 65 above 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

North Kaua’i

Today: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs 76 to 82. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with numerous showers. Lows 56 to 65. East winds up to 15 mph. Chance of rain 70 percent.

Wednesday: Partly sunny with scattered showers. Highs 76 to 82. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Partly sunny with scattered showers. Highs 74 to 80. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with numerous showers. Lows 54 to 67. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Wednesday: Partly sunny with scattered showers. Highs 74 to 80. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Light to moderate trades will build over Kauai and Oahu today through Wednesday after a weakening front passes by. A sea breeze pattern will increase afternoon showers across Maui County and the Big Island from Wednesday onward. A few locally heavy showers are possible.

Discussion

A ragged 150 mile wide band of broken showery low clouds, marking a weakening front, lies across Oahu and Molokai this morning. Satellite loop shows this band continues moving toward the southeast slowly, with models indicating the front will stall near Maui on Wednesday. Radar shows that associated showers have formed a ragged 30 mile wide band extending northeast from Oahu. Other showers are noted across waters lee of Oahu and Molokai. Cold cloud tops are noted within the frontal cloud band, mostly southwest and outside Hawaiian coastal waters. However, one or two cold convective tops lie within our coastal waters just southwest and west of Molokai. Isolated thunderstorms have been added to the grids for these affected coastal waters through this afternoon.
North northeast trades will continue building eastward behind the front until it stalls over Maui County and/or the Big Island Wednesday through the end of the week. A hybrid sea breeze/trade wind pattern will prevail over Kauai and Oahu, with light trades giving way to enhanced convergence over leeward areas each afternoon. For Maui County and the Big Island, expect a continued land breeze/sea breeze pattern. While isolated thunderstorms are possible over the eastern end of the state Wednesday afternoon, confidence is too low to add them to the gridded database. Models suggest moderate trades may briefly return over the weekend.

Aviation

A weak cold front will move east of Oahu and over Molokai today, then stall and weaken over Maui County Wednesday into the latter half of the week. Clouds and showers will accompany the front, as well as strengthening winds out of the north-northeast behind it through tonight. Light and variable winds will continue across most of Maui County and the Big Island today, where sea breezes will again result in some inland clouds and a few showers.
AIRMET Sierra for tempo mountain obscuration has been dropped for Kauai, but remains in effect for Oahu. Molokai may need to be added to AIRMET Sierra later this morning if showers and low clouds become more widespread. VFR conditions will prevail elsewhere.

Marine

A weak frontal boundary near Molokai is moving slowly southeast. A poorly defined band of broken to locally overcast low clouds with embedded towering cumulus clouds and scattered heavy showers is along and ahead of this feature. In addition, some thunderstorms are popping near the coastal waters far south of Kauai. Elsewhere, the tail end of a weak northeast to southwest oriented surface ridge is located just east-northeast of the Big Island early this morning. To the northwest of the frontal boundary, light to moderate north to northeast winds are evident near Kauai and Oahu. This is due to a surface high pressure system building far northwest of the state. The winds remain light and variable near Maui County, while light southeast winds are in the vicinity of the Big Island.
The forecast guidance continues to show the weak surface ridge will linger just east-northeast of the Big Island into mid-week. This will keep light east to southeast winds near the Big Island. The weak frontal boundary will continue to push southeast over Molokai and Lanai, and transition into a surface trough. The high building northwest of the area will keep moderate northeast winds west of this feature. Expect little change to this flow pattern into Wednesday. However, by late Wednesday the trough will likely dissipate, and the surface high will dissipate by Thursday. By Friday, the forecast models continue to show a new surface high pressure system building far north of the area, which will produce strengthening trade winds heading into next weekend. The latest forecast indicates winds over the typically windier waters adjacent to the islands of Maui County and the Big Island may reach the Small Craft Advisory criteria on Saturday.
The current medium-period northwest (320 degrees) swell continues to slowly subside. As a result, the High Surf Advisory has been cancelled this morning for exposed north and west facing shores of the smaller islands. This swell will continue to gradually subside today, and will likely fade out on Wednesday. A small northwest (310 degrees) swell is expected Thursday / Friday, while a small north-northwest (330-340 degrees) swell may spread over the area this weekend. The current small, medium-period south (190 degrees) swell will gradually subside today. The wave model guidance suggests there may be a small, reinforcing south (180-190 degrees) swell arriving late Wednesday. Elsewhere, the lack of significant trade winds in the vicinity of, or upstream of, the islands will keep minimal surf along most east facing shores this week.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov