Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Mostly sunny with isolated showers. Highs around 83 near the shore to around 70 above 3000 feet. Southeast winds up to 10 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Lows around 66 near the shore to around 56 above 3000 feet. East winds up to 10 mph.

Sunday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs around 82 near the shore to around 70 above 3000 feet. Southeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 40 percent.

South Kaua’i

Today: Mostly sunny with isolated showers. Highs around 81. Light winds. Chance of rain 20 percent.

Tonight: Partly cloudy. Lows around 65. Northeast winds up to 10 mph.

Sunday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs around 81. Southeast winds up to 10 mph. Chance of rain 30 percent.

Kaua’i Mountains

Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 71 to 78 in the valleys to around 64 above 4000 feet. Light winds. Chance of rain 30 percent.

Tonight: Mostly clear with isolated showers. Lows 57 to 62 in the valleys to around 52 above 4000 feet. Light winds. Chance of rain 20 percent.

Sunday: Sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 70 to 77 in the valleys to around 63 above 4000 feet. South winds up to 15 mph. Chance of rain 50 percent.

North Kaua’i

Today: Mostly sunny with isolated showers. Highs 74 to 82. Light winds becoming east up to 10 mph in the afternoon. Chance of rain 20 percent.

Tonight: Mostly clear. Lows 59 to 68. Southeast winds up to 10 mph.

Sunday: Sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 74 to 81. South winds up to 10 mph. Chance of rain 50 percent.

East Kaua’i

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 73 to 82. Light winds becoming southeast up to 10 mph in the afternoon. Chance of rain 30 percent.

Tonight: Partly cloudy with isolated showers. Lows 58 to 69. Light winds. Chance of rain 20 percent.

Sunday: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 73 to 81. South winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Locally breezy east-southeasterly flow will prevail over the eastern half of the state, and light land/sea breeze pattern will be present over the western half of the state through today before weakening slightly tonight. A period of active weather will begin Sunday night as a front approaches and moves through, bringing the potential for heavy rainfall, thunderstorms, and gusty southerly winds. Another system looks to continue unsettled weather across the islands during the second half of next week.

Discussion

A 1034 mb surface high pressure remains centered about 1350 miles northeast of Honolulu with a surface ridge axis extending southwestward from the high over the central Hawaiian Islands. This will maintain light southeasterly winds over the western half of the state and breezy east to southeast winds over the eastern half of the state through today. Satellite and radar imagery shows low level clouds moving along exposed windward areas of Maui and the Big Island with less clouds and showers over areas blocked by terrain upstream. Less than half an inch of rainfall was recorded overnight for these exposed areas and little to no rainfall was recorded elsewhere. A mid- upper level trough has eroded the inversion over Hilo as indicated in this morning's sounding. This trough will continue to provide some instability today and provide some enhancement to clouds and showers along exposed windward areas with some clouds and showers developing inland in the afternoon hours as seabreeze picks up. The trough is expected to move east of the state later today but will then eventually develop into a negatively tilted trough. This will likely support the development of a surface low along an approaching front far northwest of the state over the next day or so.
The main weather concern over the next several days will be associated with the surface low and cold front that will bring a period of wet weather, including the potential for widespread rainfall that could be heavy at times, and a few thunderstorms Sunday night into mid week next week. The surface high will shift east as the front and parent low far northwest of the state moves closer. Winds will respond by weakening slightly tonight then veering out of the south Sunday. Winds will strengthen to locally breezy south- southwest winds by Monday as the low moves 300 miles north- northwest of the state and the front swings through the state. Models showing winds at 850 mb reaching near 40 kts or so that could cause damaging downslope winds. The front will gradually dissipate in the vicinity of Maui County Tuesday night into Wednesday. Winds will continue to veer out of the west- southwest and ease slightly during this time. While flooding potential is still being evaluated, it is possible that a Flood Watch will eventually be needed for at least portions of the state. Lingering shower activity will continue into Wednesday, but rainfall intensity should be decreasing during the day as the front dissipates.
Models suggest that another cold front and its associated deep low/trough aloft could bring another round of heavy showers, thunderstorms, and perhaps even stronger winds to the islands Thursday. This still remains quite far out in time, but an overall wet pattern looks to persist throughout much of next week.

Aviation

The Big Island will continue to block southeasterly winds from reaching the smaller islands through most of the weekend. Expect local land and sea breezes to impact sheltered leeward areas. A dry and stable airmass will limit cloud and shower activity, with isolated showers favoring windward and southeast slopes. VFR conditions will prevail with brief periods of MVFR possible under passing showers. Wet and unstable weather is on tap late Sunday into next week.
AIRMET Tango remains in effect for moderate lee turbulence below 8000 feet over and downstream of the terrain on Maui and the Big Island.

Marine

Moderate to strong east to east-southeast trades will prevail over the eastern waters, while light to moderate east-southeast trades hold over the western waters today. Winds will ease tonight then become more southerly on Sunday as a front shifts closer to the state. The winds will ramp up out of the south and southwest at fresh to strong speeds Monday through Tuesday as the front moves into the islands, then ease back to light to moderate levels and shift more westerly on Wednesday as the front stalls out in the vicinity of Maui County. A Small Craft Advisory remains in effect for most waters due to strong winds and/or 10 foot seas through 6 PM this evening.
The current northwest swell has dropped below advisory levels this morning, therefore the High Surf Advisory for north and west facing shores of most of the smaller islands has been cancelled. This swell will continue to slowly decline through the weekend. A new moderate sized long-period northwest swell will build Monday, peak below advisory levels Monday night and Tuesday, then gradually decline through Wednesday. A medium period northwest swell reinforcement will give north and west shore surf a boost on Thursday. A new long-period northwest swell will then build Thursday night, potentially building surf to warning levels on Friday.
Surf along east facing shores will remain elevated today then gradually decline Sunday through late next week. Surf along south facing shores will remain small through the weekend, with only background southerly swells. South shore surf could get rough and choppy Monday through much of next week as south to southwest winds ramp up ahead of a couple passing cold fronts.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST this evening for Kauai Windward Waters, Oahu Windward Waters, Kaiwi Channel, Maui County Windward Waters, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov