Photo Credit: Jason Weingardt

West Kaua’i

Today: Mostly sunny. Isolated showers in the morning. Highs around 82 near the shore to around 70 above 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Lows around 68 near the shore to around 57 above 3000 feet. East winds up to 15 mph becoming around 10 mph after midnight.

Saturday: Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 83 near the shore to around 71 above 3000 feet. East winds up to 15 mph shifting to the south in the afternoon. Chance of rain 20 percent.

South Kaua’i

Today: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 81. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Partly cloudy. Lows 64 to 69. Northeast winds 10 to 15 mph decreasing to up to 10 mph after midnight.

Saturday: Mostly sunny. Isolated showers in the afternoon. Highs around 82. Light winds becoming south around 10 mph in the afternoon. Chance of rain 20 percent.

Kaua’i Mountains

Today: Mostly cloudy with numerous showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 69 to 77 in the valleys to around 64 above 4000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 70 percent.

Tonight: Partly cloudy. Lows 57 to 62 in the valleys to around 51 above 4000 feet. East winds up to 15 mph.

Saturday: Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 70 to 78 in the valleys to around 65 above 4000 feet. South winds up to 15 mph. Chance of rain 20 percent.

North Kaua’i

Today: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 74 to 81. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy. Lows 60 to 69. Southeast winds up to 10 mph.

Saturday: Mostly sunny. Isolated showers in the afternoon. Highs 75 to 82. South winds up to 10 mph shifting to the southwest in the afternoon. Chance of rain 20 percent.

East Kaua’i

Today: Mostly cloudy with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 74 to 81. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy. Lows 58 to 70. Northeast winds up to 15 mph.

Saturday: Partly sunny in the morning, then mostly sunny with isolated showers in the afternoon. Highs 75 to 82. South winds up to 10 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Trade winds will hold at moderate to locally breezy levels today, then ease tonight as a weakening high settles southward and closer to the islands. After a shower start in windward areas early this morning, rather dry conditions will develop across the state and prevail through Saturday, with only minimal chances for rain. Winds will shift southerly over the weekend as a front approaches from the west. The front will bring some showery weather as it pushes down the island chain Sunday and Sunday night, with winds shifting around to the north and northeast in its wake. The front appears to stall out in the vicinity of Maui County on Monday, then dissipate Monday night. A weak ridge north of the state will keep light to moderate trades and typical windward and mauka showers in place Tuesday through Thursday.

Discussion

Currently at the surface, a 1023 mb high centered around 575 miles north of Honolulu, is driving moderate trade winds across the island chain early this morning. Infrared satellite imagery shows mostly cloudy conditions in most windward areas and partly cloudy conditions in most leeward locales. Radar imagery shows scattered trade showers moving into windward slopes and coasts, with a few showers spilling into leeward communities at times. Main short term focus revolves around trade wind trends and rain chances.
High pressure will weaken as it settles southward and closer to state today, with the trades generally holding at moderate to locally breezy levels. An approaching front will ease the trades tonight into early Saturday, with winds shifting southerly and southwesterly Saturday afternoon into Sunday at moderate levels. The front will push southeastward down the island chain Sunday through Monday, with moderate to breezy north shifting to northeast winds developing following the frontal passage. The front should dissipate by Tuesday, with moderate trades easing into the light to moderate range Wednesday and Thursday as some weak troughing develops in the vicinity of the islands.
As for the remaining weather details, after a showery start in windward areas early this morning, we should see things dry out quickly by late morning and early this afternoon. Rather dry weather will then prevail tonight and Saturday with limited shower activity statewide. Increasing south to southwest flow will bring some showers into leeward areas Saturday night and Sunday, with a band of moisture associated with the front bringing some showery weather as it pushes through the islands, with the shower focus shifting back over to windward areas following its passage. The latest model guidance disagrees on how far this front makes it before stalling out, with the GFS similar to previous runs showing the front making it into the eastern islands. The ECMWF on the other hand shows the front stalling out over the western end of the state, a change from 24 hours ago when it was in good agreement with the GFS. For now we will keep the forecast unchanged, showing the front hanging up in the vicinity of Maui County early next week, which is a decent compromise between the two model solutions. The remnant moisture band from the dissipated front appears to get caught up in the trades by Tuesday, bringing a more typical trade wind pattern featuring mainly windward and mauka showers which should continue through Thursday.

Aviation

Moderate to locally breezy trades will persist through this morning and bring scattered to numerous showers to the windward coasts and slopes. Some spill over may lead to isolated showers along leeward locations. Periods of MVFR ceilings and visibility will likely accompany these showers, especially along north through east sections of the islands. Expect a decrease in shower activity by this afternoon as drier air filters in from the north.
AIRMET SIERRA for extensive mountain obscuration above 2500 feet is in effect for north through east sections of the Big Island due to clouds and showers.

Marine

Fresh to locally strong trade winds will continue to blow across the Hawaii Region today. A cold front approaching the islands from the northwest will break down the ridge north of the state with wind speeds diminishing and veering out of the southeast to south direction from tonight into Saturday with land and sea breezes developing along the near shore coastal waters. The cold front will march down the island chain late Sunday into early next week producing numerous showers with wind directions shifting out of the north behind the frontal boundary. Small Craft Advisory conditions are forecast through tonight across the typical windier waters around Maui and the Big Island.
Surf along east facing shores will remain elevated and rough at the High Surf Advisory (HSA) levels today. As the trade wind winds weaken over the next few days expect the northeast swell to decline with surf heights falling just below HSA levels by tonight. A rapid downward trend will develop this weekend as the wind direction shifts out of the south.
Sunday night through early next week the gale low around 1000 NM to the north will generate a large, medium-period north-northwest (340-350 deg) swell. Advisory level surf is expected at a minimum, but swells from these nearby northerly sources typically come in much larger than predicted, which could produce heights climbing well above advisory levels during the peak of the swell energy forecast to arrive on Monday. This swell energy will persist through Wednesday from a more northerly direction. In the longer range forecast, an even larger northwest swell is brewing late next week with surf heights possibly exceeding warning levels along north facing shores.
An out of season south swell will build through the day today, peaking this weekend, and then declining early next week.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST this evening for Olomana, Maui Windward West, Kauai East, Kauai South, East Honolulu, Koolau Windward, Molokai Windward, Molokai Southeast, Windward Haleakala, Kipahulu, Big Island Southeast, Big Island East, Big Island North.
Small Craft Advisory until 6 AM HST Saturday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov