Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Mostly sunny with isolated showers. Highs 83 to 88 near the shore to around 75 above 3000 feet. East winds 10 to 15 mph decreasing to up to 15 mph in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 69 near the shore to around 60 above 3000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Wednesday: Mostly sunny with isolated showers. Highs 83 to 88 near the shore to around 75 above 3000 feet. Northeast winds up to 10 mph shifting to the southeast in the afternoon. Chance of rain 20 percent.

South Kaua’i

Today: Partly sunny with scattered showers. Highs 78 to 86. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 71. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday: Mostly sunny with isolated showers. Highs 78 to 86. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Kaua’i Mountains

Today: Partly sunny. Scattered showers in the morning, then numerous showers in the afternoon. Highs 73 to 83 in the valleys to around 64 above 4000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 61 to 68 in the valleys to around 57 above 4000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

Wednesday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 72 to 82 in the valleys to around 65 above 4000 feet. East winds up to 15 mph. Chance of rain 40 percent.

North Kaua’i

Today: Partly sunny with scattered showers. Highs 75 to 86. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 63 to 71. East winds 10 to 15 mph decreasing to up to 15 mph after midnight. Chance of rain 50 percent.

Wednesday: Mostly sunny with isolated showers. Highs 74 to 86. East winds up to 15 mph. Chance of rain 20 percent.

East Kaua’i

Today: Partly sunny with scattered showers. Highs 72 to 84. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 63 to 75. Northeast winds around 10 mph. Chance of rain 70 percent.

Wednesday: Mostly sunny with isolated showers. Highs 71 to 83. Northeast winds around 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Breezy trade winds will gradually ease through tonight and become light and variable Wednesday. Widely scattered showers caught up in today's trade flow will primarily focus along windward exposures and higher terrain with a few showers reaching leeward communities. Drier, more stable weather will commence Wednesday. Mainly dry conditions and light winds will occur from Thursday into the weekend. A weak front moving into the far northern offshore waters early next week will disrupt trade flow while increasing more widespread shower activity.

Discussion

The pressure gradient back toward Hawaii from a 1026 mb surface high located approximately 700 miles north northeast of the state will support breezy trade winds through the day. Early morning IR satellite imagery indicates the next ribbon of higher moisture a few hundred miles east of Oahu heading west, mid to upper level clouds streaming northeast over the eastern third of the state within the stronger upper level winds around the southern periphery of a weakening low. Isolated morning showers will transition to latter day scattered showers initiated from this higher slug of mid level moisture passing across from the east. The upper low just south of the island chain and its associated cooler air will destabilize the regional atmosphere just enough to maintain widely scattered west-moving showers through this evening. Despite the modest instability, evening shower coverage may be somewhat limited, with a diurnal increase in windward showers expected later tonight into early Wednesday morning. Short term model guidance initialized fairly well as it jives with satellite trends in relation to this next round of higher moisture a few hundred miles east of Oahu…progs the moisture to arrive through the morning hours and lasting through a good part of the day, fueling an increase in today's windward mauka shower activity.
The surface high northeast of the islands will weaken as it moves south and closer to Hawaii through mid week. This scenario will weaken today's trades to more region-wide gentle to locally breezy magnitudes. Trades will continue to drop off through Wednesday evening in response to weak surface ridging as increasing upper heights envelop the region from the west. Winds will become light Thursday on into the weekend as resident ridging is pushed south and further weakened by an approaching cold front from the north. This situation will lend itself to local land and sea breezes becoming the dominant late week wind patterns. The ongoing forecast still leans more toward the EC solution of advancing the surface ridge axis over the islands this weekend, or a little quicker than the GFS's frontal timing. The weak front's arrival may introduce increased northwest-to-southeast advancing rain across northern zones and waters around Monday, but forecast confidence is low due to the differences in model timing. The associated upper low far north of the area will linger through Tuesday before moving southeast and weakening as ridging rebuilds in from the west. As the resident atmosphere re-stabilizes in response to the departing broad upper low/trough next Tuesday, there may be lessened trade shower behavior within a shallower boundary layer.

Aviation

Trade winds will diminish gradually through Wednesday. Expect brief MVFR ceilings and visibilities within showers across windward and mauka areas, with showers reaching leeward areas at times where VFR conditions should prevail.
AIRMET Tango remains in effect for moderate low-level turbulence over and downwind of island terrain. This AIRMET will likely remain in effect through tonight. No other AIRMETS are in effect or expected.

Marine

High pressure northeast of the Hawaiian Islands will move south and weaken over the next several days. Trade winds will remain moderate to locally strong through much of today and then decrease tonight through the remainder of the week. Winds could then become light and variable by the end of the week as weak ridging moves just north of the islands. Buoy observations this morning show wave heights lowering below 9 ft. Therefore, the Small Craft Advisory (SCA) has been scaled back to the typically windy waters and channels of Maui County and the Big Island through today.
Surf along east-facing shores is on the decline, but will remain rough and choppy through today, then decrease further over the next few days as the trade winds decrease. Surf along south facing shores will remain small through the forecast period.
The current small, medium period northwest (320 degree) swell will continue to decline today. However, a similar pulse from the northwest is possible late Wednesday night into Thursday, providing a small boost in north shore surf. A larger medium- period northwest swell is expected this weekend, as well as a moderate northeast swell.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST this evening for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov