Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Sunny. Isolated showers in the morning. Highs 78 to 85 near the shore to around 71 above 3000 feet. East winds up to 10 mph shifting to the southeast around 10 mph in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows around 66 near the shore to around 57 above 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Saturday: Sunny. Highs 78 to 85 near the shore to around 71 above 3000 feet. East winds up to 10 mph shifting to the southeast around 10 mph in the afternoon.

South Kaua’i

Today: Mostly sunny with isolated showers. Highs 77 to 84. East winds around 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows around 67. East winds around 10 mph. Chance of rain 30 percent.

Saturday: Mostly sunny with isolated showers. Highs 77 to 84. East winds around 10 mph. Chance of rain 20 percent.

Kaua’i Mountains

Today: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 72 to 79 in the valleys to around 63 above 4000 feet. Southeast winds up to 10 mph. Chance of rain 30 percent.

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 57 to 66 in the valleys to around 55 above 4000 feet. Southeast winds up to 10 mph in the evening becoming light. Chance of rain 40 percent.

Saturday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 72 to 78 in the valleys to around 63 above 4000 feet. East winds up to 10 mph. Chance of rain 30 percent.

North Kaua’i

Today: Mostly sunny with isolated showers. Highs 74 to 81. Southeast winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 60 to 68. Southeast winds up to 15 mph. Chance of rain 40 percent.

Saturday: Mostly sunny with isolated showers. Highs 73 to 80. Southeast winds up to 15 mph. Chance of rain 20 percent.

East Kaua’i

Today: Mostly sunny with isolated showers. Highs 71 to 82. East winds around 10 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with scattered showers. Lows 60 to 70. East winds up to 10 mph. Chance of rain 40 percent.

Saturday: Mostly sunny with isolated showers. Highs 71 to 82. East winds up to 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Drier weather under generally partly sunny skies with cloudier conditions along many windward mauka slopes. Gentle easterly trade winds today with more wind-sheltered areas experiencing diurnal land and sea breezes. East trades will better focus isolated showers over windward exposures and mauka slopes with the exception of leeward Big Island where the sea breeze will thicken clouds and generate showers. High pressure aloft, along with a dry air mass, should remain in place over the islands through the middle of next week. This will result in clearer skies and less frequent windward showers. Rain chances will increase from the west late next week.

Discussion

The weak upper trough passage yesterday that introduced better clustering pockets of rain over the central and eastern islands is now east of the islands this morning. Upper ridging will begin building in from the west and this will provide more stability to the area. This ridging, along with a drier air mass over the islands, will significantly limit shower activity the next several days. The radar has significantly quieted down overnight with the only pre-dawn activity being that of a few light showers moving south and west of Big Island. Primarily variable to gentle east trade winds will continue into the weekend. Statewide breezes will remain weak enough to allow the development of warmth-of-the-day sea breezes to kick in. These localized breezes will move up more leeward or trade wind-protected slopes and generate thicker cloud cover and trigger subsequent showers over further interior areas. Brief showers will produce low accumulations with the greater amounts being confined to the higher elevations.
Surface high pressure located approximately 1,600 miles northeast of the islands will create a tight enough pressure gradient back toward the islands to maintain these light to gentle east trades the next several days. Increasing stability from lower level ridging to the northeast and upper ridging moving in from the west, within a drying boundary layer, will restrict near term shower behavior into early next week. With the island chain remaining on the southwestern periphery of the surface high through early next week, gentle winds will generally come out of the east or southeast. Western island breezes will become more benign and variable…typically displaying more of a southerly component. Easterlies across the eastern end of the state will be slightly stronger. Weak or near calm interior winds will allow enhanced localized sea breezes to become more active once temperatures warm past 80 F. Sea breezes will promote thicker leeward clouds and increase light shower coverage over more interior communities. A better established east trade flow across the eastern half of the state will produce typical trade wind weather well into next week. Mid to upper level ridging will remain the dominate player in determining drier days heading into the second half of February. Next week's shower behavior will generally be infrequent and isolated in nature. Periodic thin bands of moisture advecting in from the east through the middle of the month will introduce brief episodes of greater shower activity over such spots as windward Big Island and Maui County.
The extended forecast may become more active during the later half of next week. An upper low a couple of thousand miles northwest of the islands will likely drag a weak cold front close to the island chain by Friday. The far distance of this low and the strength of the backing high will draw into question whether this boundary makes it here on Valentine's Day or not. Ensemble guidance is lacking any real consensus with all three ensembles (Euro, GFS and Canadian) depicting a third of their members pushing a thin line of rain through on Friday. The upper level dynamics seem to be absent but there should be enough mid layer moisture drawn up in the southerly flow to initiate a thin line of showers leading or along a shear line. As of now, the forecast leans towards moderate chances of Valentine's Day light showers with breezy southwesterlies veering more northeasterly from Oahu westward through Saturday (Day 8).

Aviation

Weak to moderate east or east southeast flow will prevail today and bring isolated showers along mainly windward facing slopes and coasts. Some of the heavier activity may allow for brief periods of MVFR ceilings and visibility. VFR conditions elsewhere.
There are currently no AIRMETs in effect.

Marine

A weak and nearly stationary surface ridge over the waters just N of Kauai will shift north today and become oriented E-W along 25N by late Saturday. The ridge will then hold along that latitude through the middle of next week. This will usher in moderate to fresh E winds over Maui and Big Island waters tonight. Elsewhere, light to moderate ESE winds will prevail.
A lingering medium period NE swell and a new long-period northwest swell have combined to bring high surf to most exposed Hawaiian shorelines. The NE swell will continue to decline today even as the NW swell reaches its peak. The most recent observations from the Hanalei buoy (51208) indicate that the NW swell is building in slightly above model guidance. A High Surf Advisory (HSA) is in effect for east, north, and west facing shores. The HSA for east facing shores will likely be canceled later today, but the HSA for north and west facing shores will likely be extended through Saturday.
The long-period northwest swell mentioned above is expected to generate surf heights of up to 15 to 20 feet along north shores of Niihau, Kauai, Oahu, Molokai, and Maui today. A slightly smaller NW swell is expected from Saturday night into Monday. A potentially larger WNW swell is looking increasingly likely from between Tuesday and Wednesday night of next week.
No significant surf is expected along south facing shores in the near term though a small south swell is possible around the middle of next week.
A Small Craft Advisory (SCA) for combined seas of 10 feet or greater remains in effect for zones exposed to the increasing NW swell and lingering NE swell. An SCA has also been issued for the typically windier areas surrounding Maui and the Big Island due to the moderate to fresh east winds that will develop tonight.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 AM HST Saturday for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kauai North, Molokai Windward, Molokai North, Molokai West, Windward Haleakala.
High Surf Advisory until 6 PM HST this evening for Olomana, Kauai East, East Honolulu, Koolau Windward, Molokai Southeast, Kipahulu, Big Island East, Big Island North.
Small Craft Advisory until 6 AM HST Saturday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters.
Small Craft Advisory from 6 PM this evening to 6 AM HST Saturday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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