Photo Credit: Braden Jarvis

West Kaua’i

Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs around 91 near the shore to around 79 above 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 74 near the shore to around 64 above 3000 feet. East winds around 10 mph. Chance of rain 50 percent.

Thursday: Partly sunny with scattered showers. Highs around 91 near the shore to around 79 above 3000 feet. East winds around 10 mph. Chance of rain 50 percent.

South Kaua’i

Today: Partly sunny with scattered showers. Highs 82 to 90. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Numerous showers in the evening, then showers after midnight. Lows around 74. Northeast winds 10 to 15 mph. Chance of rain near 100 percent.

Thursday: Mostly cloudy with numerous showers. Highs 83 to 91. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Kaua’i Mountains

Today: Mostly cloudy with numerous showers. Highs 76 to 88 in the valleys to around 68 above 4000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Tonight: Breezy and showers. Lows 67 to 74 in the valleys to around 61 above 4000 feet. East winds 10 to 20 mph. Chance of rain near 100 percent.

Thursday: Cloudy and breezy. Showers in the morning, then numerous showers in the afternoon. Highs 76 to 88 in the valleys to around 68 above 4000 feet. East winds 10 to 20 mph. Chance of rain 90 percent.

North Kaua’i

Today: Partly sunny with scattered showers. Highs 78 to 91. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Showers. Lows 68 to 76. East winds 10 to 15 mph decreasing to up to 10 mph after midnight. Chance of rain near 100 percent.

Thursday: Mostly cloudy with numerous showers. Highs 78 to 92. East winds 10 to 15 mph. Chance of rain 70 percent.

East Kaua’i

Today: Mostly cloudy with scattered showers. Highs 75 to 87. Northeast winds up to 15 mph shifting to the east in the afternoon. Chance of rain 50 percent.

Tonight: Showers. Lows 67 to 78. East winds around 10 mph. Chance of rain near 100 percent.

Thursday: Cloudy with numerous showers. Highs 75 to 87. East winds 10 to 15 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

A high pressure ridge far north of the Hawaiian Islands will keep moderate to locally breezy trade winds in the forecast through Thursday. A weak disturbance currently passing through the islands will bring deeper moisture levels to the state with increasing wet trade wind showers to all islands. Two tropical cyclones are on approach, Gilma and Hector are located far east of the state and are on a westward track. Both systems show significant weakening over the next few days. Weather impacts from these systems are favoring additional periods of wet weather for the islands from Friday through Sunday.

Discussion

The satellite picture this morning continues to show two tropical cyclones approaching Hawaii from the far east, Gilma and Hector. Both of these systems will weaken as they approach the state, in part due to increasing westerly wind shear aloft. A weak 700 mb trough passing through the islands today and deepening tropical moisture running ahead of Tropical Storm Gilma will enhance trade wind showers in the short range forecast through Thursday.
A broad high pressure ridge remains locked in place far north of the Hawaiian Islands this week. This ridge will keep moderate to locally breezy trade winds in place over the islands through Thursday and help to steer the weakening tropical cyclones Gilma and Hector on a high confidence westward track. Wind speeds will likely decrease from Friday through Sunday morning, as these systems weaken and move into the Hawaii region. Expect more variable wind directions, and an expansion to the typical leeward sea breeze areas lasting through the weekend.
According to the latest forecasts from the hurricane center both tropical cyclones Gilma and Hector continue to weaken as they approach, which means the main impacts to the islands will more likely from rain, not wind. That said, there remains some uncertainty in how long these systems can hold together, which plays a role in forecasting rainfall totals for each island. The good news for the Big Island is the rainfall totals from each of these systems will probably feel more like a wet trade wind weather with a only a slight risk for flash flooding. More or less rain will fall based on slight deviations in the track of these post-tropical low centers. A slight shift in forecast track to the north will mean less rainfall for the islands, and a slight shift to the south will bring higher rainfall totals across the state. Stay tuned for more wet weather details as rainfall impacts evolve over time.
High pressure will build in across the state starting early next week. Expect a return to breezy trade winds by Sunday night, with drying trends limiting rainfall to brief passing showers favoring overnight to early morning hours along windward and mountain slopes.

Aviation

Trade winds, locally brisk at times, will continue through Thursday and possibly beyond. Bands of showers moving in off the North Pacific will impact mainly east and northeast facing slopes and coasts and be most active in the late night and morning hours. Brief MVFR conditions may occur in passing showers.
On the Big Island, lee-side sea breezes will encourage moderate cumulus development along south and west facing slopes in the afternoon and early evening hours. After sunset, land breezes will encourage overnight clearing along those same leeward slopes.
No AIRMETs are in effect and none are anticipated at this time.

Marine

Moderate to locally fresh category trades will hold through Thursday. Tropical Storm Gilma is forecast to weaken to a remnant low as it approaches the coastal waters late Thursday into Friday. This will further help weaken the gradient over the state allowing winds to ease to moderate levels over the western half of the state and possibly gentle southerly winds over the eastern half of the state. Note that any deviation in the forecast track could impact winds and waves across the Hawaiian nearshore waters this weekend.
Surf along east facing shores are trending upward by early Wednesday as a medium- period easterly swell from Gilma begins to fill in.
Surf along south facing shores will trend down today as small medium period south-southwest swell fades. Below average surf is then expected Thursday through the weekend as tiny background south swells move through. Summertime average surf may return next week as a series of small, long period southerly swells begin to fill.
Surf along north and west facing shores will remain near the seasonal average this week, but could slightly rise Thursday into Friday due to a gale low currently tracking east over the Aleutian islands.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov