Photo Credit: Brendan Stephen

West Kaua’i

Today: Breezy. Partly sunny with scattered showers. Highs around 83 near the shore to around 71 above 3000 feet. Southwest winds 10 to 20 mph. Chance of rain 30 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 66 near the shore to around 55 above 3000 feet. Southwest winds 10 to 20 mph shifting to the west up to 20 mph after midnight. Chance of rain 30 percent.

Sunday: Breezy. Partly sunny with scattered showers. Highs around 83 near the shore to around 71 above 3000 feet. Southwest winds up to 15 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

South Kaua’i

Today: Breezy. Partly sunny with scattered showers. Highs around 82. West winds 10 to 20 mph. Chance of rain 30 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 62 to 67. West winds 10 to 20 mph. Chance of rain 30 percent.

Sunday: Breezy. Partly sunny with scattered showers. Highs around 82. Southwest winds 10 to 25 mph. Chance of rain 50 percent.

Kaua’i Mountains

Today: Breezy. Mostly sunny with scattered showers. Highs 70 to 78 in the valleys to around 65 above 4000 feet. Southwest winds up to 25 mph with gusts to 45 mph. Chance of rain 30 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 55 to 60 in the valleys to around 49 above 4000 feet. West winds 10 to 25 mph shifting to the southwest up to 25 mph after midnight. Chance of rain 30 percent.

Sunday: Breezy. Partly sunny with scattered showers. Highs 70 to 78 in the valleys to around 65 above 4000 feet. Southwest winds up to 25 mph increasing to 10 to 25 mph with gusts to 45 mph in the afternoon. Chance of rain 50 percent.

North Kaua’i

Today: Breezy. Mostly sunny with isolated showers. Highs 75 to 82. South winds up to 15 mph shifting to the west in the afternoon. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with scattered showers. Lows 58 to 67. Southwest winds 10 to 15 mph shifting to the south up to 20 mph after midnight. Chance of rain 30 percent.

Sunday: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs 75 to 82. Southwest winds up to 25 mph. Gusts up to 45 mph in the afternoon. Chance of rain 50 percent.

East Kaua’i

Today: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 75 to 82. Southwest winds up to 20 mph. Chance of rain 30 percent.

Tonight: Breezy. Partly cloudy with scattered showers. Lows 56 to 68. West winds 10 to 15 mph shifting to the southwest up to 20 mph after midnight. Chance of rain 30 percent.

Sunday: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs 75 to 82. Southwest winds up to 25 mph. Gusts up to 45 mph in the afternoon. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Light to moderate southwesterly winds are expected through tonight. A cold front will approach the western islands on Sunday with prefrontal convergence bands increasing shower activity over Kauai and Oahu. The cold front will bring clouds and showers into the western islands on Monday, then into Maui County on Tuesday and Wednesday, and then stalling out over the Big Island on Thursday and Friday. Trade winds will develop starting on Friday with drying trends expected to develop rapidly behind the front.

Discussion

Satellite and radar imagery this morning shows scattered showers riding into the islands on moderate southwesterly winds. Expect afternoon sea breezes to develop along terrain sheltered north and east slopes of all islands. This shower pattern will last through tonight. Upper air balloon soundings from 2 AM HST at Lihue, Kauai and Hilo, Hawaii continue to show the subsidence inversion height between 5,000 to 6,000 feet this morning. At this level cloud heights will grow deep enough to support isolated to scattered shower activity statewide. Strong southwesterly winds aloft are producing strong wind speeds over the summits of Mauna Kea and Mauna Loa on the Big Island this morning. A High Wind Warning remains in effect for the summits of both mountains.
The weather pattern begins to change for the western islands of Kauai, Niihau and Oahu starting on Sunday, as a cold front approaches the western islands from the northwest. Southwesterly winds will increase ahead of the front, and unstable prefrontal shower bands will develop in the warm sector over the western islands from Sunday afternoon through evening. Increasing southwesterly winds may be strong enough for some damaging wind gusts along north and east slopes of island mountains, wind speeds and gusts were increased in the forecast grids during this time period for areas along north and east mountain slopes from Kauai to Maui. A Wind Advisory for these lower elevations may be needed from Sunday night through early Tuesday morning.
The cold frontal band will move into the western half of the state on Monday with additional clouds and showers starting over Kauai by Monday morning, then spreading quickly into Oahu by Monday afternoon. The islands in Maui County will see showers spreading to all island areas from Tuesday to Wednesday, and the frontal band will then stall out near the Big Island and weaken from late Wednesday to Friday. Rainfall amounts with this passing frontal system are on the lower side and therefore the flooding threat remains low at this time.
More stable conditions are forecast with returning breezy trade winds as high pressure builds in behind the front. Expect rapidly decreasing shower trends as the front passes through each island from west to east. Improving weather trends will start on Friday near Kauai to next Saturday afternoon near the Big Island.

Aviation

A ridge to the east of the state and a front approaching from the northwest will allow moderate to breezy southwest winds to continue through the forecast period. A few showers embedded in the southwesterly flow continue to move over the smaller islands early this morning. Then, with diurnal heating, clouds and showers will increase slightly over interior areas this afternoon. While some brief periods of MVFR conditions will be possible in passing showers, VFR conditions will generally prevail over the next 24 hours.
AIRMET Tango is in effect for moderate low level turbulence lee of the terrain across the Hawaiian Islands early this morning. These conditions will likely continue through this afternoon.

Marine

A ridge south of the state will maintain moderate to fresh southwest winds over the western islands and light to moderate southwesterlies over the eastern end of the state through the weekend. The southwesterlies will strengthen in advance of a front late Sunday through Monday, with winds perhaps reaching Small Craft Advisory levels across portions of the marine area during this time. Winds will ease as the front moves into the islands Monday night and Tuesday, then become light and variable by the middle of next week as the front stalls out through the central portion of the state.
A new west-northwest swell is forecast to arrive Sunday and Monday, with surf building to advisory levels along exposed north and west facing shores Sunday night and Monday. The westerly component to the swell will likely bring advisory level surf to west facing shores of the Big Island as well. A reinforcing west- northwest swell is then forecast to build surf to warning levels along exposed north and west facing shores, including the Big Island, Tuesday. This swell is expected to slowly and steadily decline Wednesday through late next week. While the west- northwest swell declines, a moderate north swell is forecast to build Wednesday and hold through late next week.
Surf along east facing shores will remain small due to the lack of easterly trade winds. Surf along south facing shores will remain small except for areas exposed to the west wrap. Short- period choppy wind waves can also be expected Sunday through Tuesday as a front approaches and moves into western portions of the island chain.

HFO Watches/Warnings/Advisories

High Wind Warning until 6 PM HST this evening for Big Island Summits.

Data Courtesy of NOAA.gov