Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Mostly sunny with scattered showers in the morning, then partly sunny with isolated showers in the afternoon. Highs 86 to 92 near the shore to around 77 above 3000 feet. East winds up to 15 mph shifting to the south in the afternoon. Chance of rain 40 percent.

Tonight: Partly cloudy with isolated showers. Lows around 72 near the shore to around 62 above 3000 feet. Northeast winds up to 15 mph increasing to 10 to 15 mph after midnight. Chance of rain 20 percent.

Monday: Sunny in the morning then becoming partly sunny. Highs 87 to 92 near the shore to around 78 above 3000 feet. East winds up to 10 mph shifting to the south in the afternoon.

South Kaua’i

Today: Partly sunny with scattered showers. Highs 85 to 92. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 71 to 76. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Monday: Mostly sunny. Isolated showers in the morning. Highs 85 to 92. East winds around 10 mph. Chance of rain 20 percent.

Kaua’i Mountains

Today: Partly sunny with scattered showers. Highs 75 to 86 in the valleys to around 67 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 66 to 71 in the valleys to around 59 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Monday: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 75 to 86 in the valleys to around 68 above 4000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

North Kaua’i

Today: Partly sunny with scattered showers. Highs 78 to 89. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 66 to 74. East winds around 10 mph. Chance of rain 50 percent.

Monday: Mostly sunny with isolated showers. Highs 78 to 89. East winds around 10 mph becoming up to 15 mph in the afternoon. Chance of rain 20 percent.

East Kaua’i

Today: Partly sunny with scattered showers. Highs 76 to 89. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 65 to 79. East winds around 10 mph. Chance of rain 50 percent.

Monday: Mostly sunny with isolated showers. Highs 76 to 89. East winds 10 to 15 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Expect light to moderate trade winds to persist through Monday. Low clouds and showers carried by the trade winds will continue to favor windward and mauka sections, especially during the nighttime and early morning hours. Spotty showers may also reach some leeward sections of the smaller islands into Monday. Clouds and isolated showers will develop over the upslope sections of the leeward Big Island each afternoon. Expect strengthening trade winds with dry and stable weather conditions from Tuesday through mid-week.

Discussion

A 1023 mb surface high pressure system centered near 36N 150W, or almost 1100 miles north-northeast of Honolulu, is moving slowly eastward. Aloft, a weak mid- and upper-tropospheric trough is evident just north the region according to loops of water vapor satellite imagery early this morning. As a result, the pressure gradient remains somewhat disrupted. This is producing light to moderate trade winds across most of the state. The background flow has been weak enough to allow local land breezes to become established over some sheltered leeward locations overnight.
The presence of the trough aloft just north of the area has produced some destabilization of the atmosphere over the island chain. The early morning balloon soundings at Hilo and Lihue show a low-level trade wind inversion around 8 thousand feet. Note that moisture remains somewhat limited, so showers are isolated to scattered over most windward facing sections. We expect low clouds with embedded isolated to scattered showers will persist mainly over windward and mauka sections this morning, with the potential for a few brief downpours through mid-morning.
The weak mid- and upper-tropospheric trough is expected to gradually lift northeast away from the area from later today through early Monday. At the same time, the surface high pressure system is expected to gradually weaken as it moves east to a position far northeast of the state. This will likely keep light to moderate trade winds across the state through Monday. The winds may be weak enough to allow local sea breezes to form over some leeward areas during the afternoon. This may produce some clouds and showers over leeward sections of the islands this afternoon (and possibly Monday afternoon). Otherwise, expect low clouds and showers to favor windward and mauka sections, especially during the nighttime and early morning hours early this week.
The forecast guidance shows high pressure building at the surface and aloft far north of the state starting Tuesday. This will likely bring a return to locally breezy trade winds through mid- week. In addition, the atmosphere will likely become more stable and drier. So, expect a rather typical dry trade wind weather regime with low clouds and brief showers favoring windward and mauka areas late at night and early each morning from Tuesday through mid-week. Leeward areas of the smaller islands can expect very dry weather, while clouds and spotty showers will develop over portions of the upslope sections of the leeward Big Island each afternoon.
Looking ahead, bulletins are now being issued by the National Hurricane Center in Miami, FL for east Pacific Tropical Depression Ten-E far east-southeast of the main Hawaiian Islands. We will monitor the future progress of this system as it tracks toward the west. Based on the latest forecast from 11 PM HST Sunday evening, Ten-E may be upgraded to a tropical storm later this morning (if so, it will be named Irwin). This system is forecast to eventually weaken to a post-tropical remnant low far east of the islands by Thursday. However, the remnant moisture from this system may eventually pass close by, or potentially over the islands later this week. Depending on the track this remnant system actually takes, there could be a period of wetter trade wind weather condition's over parts of the state. Due to the great uncertainty in the long-range forecast, please stay tuned for future updates.

Aviation

Light to moderate trade flow, along with weak upper troughing to the north of the state, will bring scattered moderate to occasionally heavier showers over windward portions of the islands through late this morning. Elsewhere, expect isolated showers to spill over onto leeward locations. Brief periods of MVFR ceilings and visibility may accompany some of the more robust showers, but not expecting anything widespread.
Sea breeze development may form along the leeward coasts by early this afternoon.
No AIRMETs are currently in effect.

Marine

High pressure north-northeast will continue to maintain moderate to fresh trades through Monday. Guidance shows high pressure restrengthening to the distant northeast Tuesday through the middle of the week, bringing trades back up into the fresh to locally strong range and possibly Small Craft Advisory conditions.
North and west facing shores will remain flat through this afternoon. The next small bump will fill in this evening through the next few days as a small medium period northwest swell traverses area waters. The northwest swell will then fade out during the middle of the week.
Surf along east facing shores will remain tiny through the beginning of the week as local winds weaken slightly. Surf then trends up toward the summer average by the middle of the week as trades restrengthen.
Surf along south facing shores will remain small into Monday, with mainly background southerly swells moving through. This will be followed by a modest bump mid-week as medium-sized, long-period energy reaches the area Monday, holds Tuesday then diminish through mid week.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov