Photo Credit: Jason Weingardt

West Kaua’i

Today: Mostly sunny. Breezy. Highs around 89 near the shore to around 75 above 3000 feet. East winds 10 to 20 mph.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows around 72 near the shore to around 61 above 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Saturday: Mostly sunny with isolated showers. Highs around 89 near the shore to around 74 above 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

South Kaua’i

Today: Partly sunny. Windy. Isolated showers in the morning. Highs 80 to 87. Northeast winds 15 to 30 mph. Chance of rain 20 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 72. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Saturday: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 79 to 87. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

Kaua’i Mountains

Today: Mostly cloudy. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 73 to 87 in the valleys to 61 to 67 above 4000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Tonight: Cloudy and breezy. Numerous showers in the evening, then showers after midnight. Lows 66 to 72 in the valleys to around 58 above 4000 feet. East winds 10 to 25 mph. Chance of rain 90 percent.

Saturday: Cloudy and breezy. Showers in the morning, then scattered showers in the afternoon. Highs 73 to 87 in the valleys to 61 to 66 above 4000 feet. East winds 10 to 25 mph. Chance of rain 80 percent.

North Kaua’i

Today: Breezy. Partly sunny with isolated showers. Highs 76 to 90. East winds 10 to 25 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with scattered showers. Lows 65 to 74. East winds 10 to 15 mph. Chance of rain 50 percent.

Saturday: Partly sunny with scattered showers. Highs 77 to 90. East winds 10 to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Breezy. Mostly cloudy with isolated showers. Highs 74 to 86. Northeast winds 10 to 25 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 65 to 75. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Saturday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 74 to 85. East winds 10 to 15 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

A strong high pressure system north of the Hawaiian Islands will continue to produce breezy to locally windy trade winds across the region today with slight decreasing wind speed trends into the moderate to breezy range from Saturday to Sunday, and then wind speeds will decrease to moderate levels from Monday onward. Strong and stable subsidence aloft will limit shower potential for most days into next week. However, a slight increase in cloud and shower trends may develop later tonight through Saturday as a weak easterly wave moves from east to west down the island chain.

Discussion

Satellite imagery this morning shows an upper level cold core low is producing an area of thunderstorms roughly 500 to 600 miles northwest of Kauai. An upper level subtropical jet stream will continue to produce high cirrus clouds over the islands into the first half of next week, enhancing sunrise and sunset colors.
A strong high pressure system north of the Hawaiian Islands will continue to produce breezy to locally windy trade winds across the region today. The high center begins to weaken this weekend with decreasing wind speed trends into the moderate to breezy range from Saturday to Sunday, and then further weakening to more moderate levels from Monday onward. This change in the wind speed forecast for next week is consistent with the current blend of long range model solutions and represents a high confidence forecast for the next week time period. At most next week some of the more wind favored areas may see brief periods of locally breezy wind speeds.
Strong and stable subsidence under an upper level ridge will continue to limit vertical cloud heights and shower development into much of next week. Once wrinkle in this forecast will likely develop later tonight through Saturday as a weak easterly wave drifts from east to west down the island chain. Lower level forcing with this trough will lift trade wind temperature inversion heights enough for increasing shower trends, mainly over windward and mountain areas. Otherwise stable and mostly dry weather with trade wind thermal inversion heights in the 4,000 to 6,000 foot range will prevail for most of the smaller islands.

Aviation

Breezy to locally windy trades will persist through tomorrow with winds decreasing starting Saturday. SHRA and low cigs will favor windward and mauka locations and bring brief periods of MVFR conds.
AIRMET Sierra is in effect for mtn obsc for windward portions of all islands. Conds should improve later this morning.
AIRMET Tango remains in effect for mod low-level turb for areas downwind of island terrain and will likely be needed for the next few days.

Marine

Strong high pressure far northeast of the state will continue to produce strong to locally near gale force trade winds through today. As a result, a Small Craft Advisory (SCA) remains in effect for all Hawaiian waters through 6 pm HST today. The high will weaken a bit this weekend, resulting in a slight easing of the winds back to fresh to locally strong speeds. The SCA coverage will need to be trimmed potentially by tonight to just the typical windier areas around Maui County and the Big Island. Early next week trades continue to ease into the gentle to fresh range.
The enhanced trades will continue to produce rough and choppy surf for the east-facing shores through the weekend. Local wind swell may wrap into select north and south facing shores. Long period forerunners from a small south-southeast swell has filled in overnight providing small surf for south facing shores today. This will be followed by a background swell from the south- southwest on Saturday. Otherwise, no significant swells are expected for the rest of the week.

Fire weather

Gusty trade winds continue today under dry and stable conditions. This will keep elevated fire weather concerns for the windier trade wind areas and downslope leeward locations such as West Maui and leeward Kohala on the Big Island. Trade winds will gradually ease into the moderate to breezy range from Saturday to Sunday, and then down to moderate levels from Monday onward as the pressure gradient over the state relaxes.
Lower relative humidity will continue for the next several days as the relatively dry air mass upstream of the state remains in place. No significant changes in upstream moisture plumes are expected, these lower relative humidities will add to the elevated fire weather concerns, especially in areas with gusty winds. Most leeward areas will remain dry. Brief periods of showers will move into windward areas mainly in the overnight hours. Humidity levels will see good to excellent overnight recoveries.
Exceptions to this humidity rule will be for elevations in the 4,000 to 8,000 foot range, which may see periods of warmer temperatures with much drier conditions, within and above the subsidence inversion level.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST this evening for all Hawaiian waters,

Data Courtesy of NOAA.gov