Photo Credit: Sebastien Gabriel

West Kaua’i

Today: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 83 near the shore to around 70 above 3000 feet. Northeast winds up to 20 mph. Chance of rain 40 percent.

Tonight: Breezy. Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows around 68 near the shore to around 57 above 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Wednesday: Mostly sunny with isolated showers. Highs around 83 near the shore to around 70 above 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

South Kaua’i

Today: Partly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 79 to 84. Northeast winds 15 to 25 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows 64 to 69. Northeast winds 10 to 20 mph. Chance of rain 70 percent.

Wednesday: Breezy. Cloudy with showers in the morning, then mostly sunny with scattered showers in the afternoon. Highs 79 to 84. East winds 10 to 20 mph. Chance of rain 80 percent.

Kaua’i Mountains

Today: Breezy. Cloudy with numerous showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 70 to 77 in the valleys to around 64 above 4000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 70 percent.

Tonight: Mostly cloudy. Breezy. Numerous showers in the evening, then showers after midnight. Lows 57 to 62 in the valleys to around 52 above 4000 feet. East winds 10 to 20 mph decreasing to up to 20 mph after midnight. Chance of rain 80 percent.

Wednesday: Cloudy with showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 70 to 77 in the valleys to around 64 above 4000 feet. East winds up to 15 mph. Chance of rain 80 percent.

North Kaua’i

Today: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 74 to 82. East winds up to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Numerous showers in the evening, then showers after midnight. Lows 60 to 69. East winds 10 to 15 mph decreasing to up to 15 mph after midnight. Chance of rain 80 percent.

Wednesday: Mostly cloudy with showers in the morning, then mostly sunny with scattered showers in the afternoon. Highs 75 to 82. Southeast winds up to 15 mph. Chance of rain 80 percent.

East Kaua’i

Today: Cloudy with numerous showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 74 to 81. Northeast winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Cloudy. Numerous showers in the evening, then showers after midnight. Lows 59 to 70. Northeast winds 10 to 15 mph decreasing to up to 15 mph after midnight. Chance of rain 80 percent.

Wednesday: Cloudy with showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 74 to 81. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 80 percent.

Detailed Forecast

Synopsis

A weak disturbance moving through the islands will produce showers over all windward and mountain areas through the early morning hours. Otherwise a high pressure system, northwest of the state will track eastward, build the ridge north of the Hawaii region and keep moderate to breezy trade winds in place through Wednesday. A weak cold front will approach the islands from the northwest on Thursday, this frontal trough will break down the ridge north of the state and produce light southeasterly winds across the region into Friday. The frontal shower band will stall out over Kauai and possibly Oahu from Friday through Saturday, diminishing by Sunday. Another weak cold front approaches the islands from the northwest early next week.

Discussion

Local radar imagery shows bands of showers moving into most windward and mountain areas this morning. The satellite picture shows a weak disturbance moving through the central islands, this system will enhance showers through the early morning hours, then showers will diminish through the day, then showers will increase once again over Kauai during the overnight hours. Elsewhere, a weak cold front just north of Kauai will stall out before reaching the islands with little short range impacts to island weather. A stronger low pressure system and cold front approaching the International Date Line, will likely move into the western islands from late Friday into Saturday, increasing rainfall potential for Kauai and Oahu.
A migratory high pressure system, currently northwest of the state, will drift eastward over the next 36 hours. This system will build the ridge north of the island chain and keep moderate to breezy trade winds in place through Wednesday. The next weak cold front will then approach the islands from the northwest on Thursday, weakening the ridge north of the region and causing the trade winds to weaken and veer from a more southeasterly direction from Thursday through Friday. This wind direction will keep the smaller islands in the lee rain shadow of the Big Island and leave most of the state in a drier weather pattern. The exception to this drier forecast will be for east and southeastern slopes of the Big Island, where southeasterly winds will drive clouds and showers up the southeast slopes of Mauna Loa increasing shower trends over the Ka'u and Puna Districts.
The latest medium range models show the next weak cold front moving into and stalling out over the western islands of Kauai and Oahu from late Friday through Saturday. Expect increasing clouds and showers during this time period mainly for Kauai and to a lesser extent Oahu. Global weather models differ a bit on how far east the frontal cloud band will drift into the islands. The American (GFS) model stalls the frontal clouds and showers over Kauai by Saturday morning with abundant showers for the Garden Isle. While the European (ECMWF) model lifts the frontal shower band farther north and brings more showers into Oahu and Molokai. We've used a blended model approach to increase shower coverage over the western half of the state during this time period with the highest rainfall chances expected to develop over Kauai from Friday evening through Saturday afternoon.
This frontal trough diminishes by Sunday as the trade winds return and lift the remnant clouds towards the northwest, away from the state. A brief stable and dry weather pattern returns with light to moderate easterly trade winds from Sunday to Monday. Another weak cold front approaches the islands from the northwest from next week Tuesday into Wednesday. Low forecast confidence on enhanced shower trends with higher confidence on breezy trade winds with this next weather system. Stay tuned.

Aviation

High pressure north of the state will keep breezy trade winds in place during the next 24 hours. A band of moisture caught up in the trades will bring some showery weather along with MVFR cigs/vsbys to windward sections of Maui County and Oahu early this morning, likely spreading to Kauai late this morning or this afternoon. Some showery weather may continue into the evening over windward Kauai, while improving conditions are expected over Oahu and Maui County by late this morning. Rather dry VFR conditions are expected over the Big Island during the next 24 hours.
AIRMET Sierra remains in effect for mountain obscuration across windward sections of Oahu, Molokai and Maui. These conditions are expected to remain in place through at least daybreak. AIRMET Sierra may need to be expanded to windward Kauai later today.
AIRMET Tango remains in effect for moderate low level turbulence over and downwind of the terrain. This AIRMET will likely remain in place through early Wednesday.

Marine

Fresh to strong northeast to easterly trades associated with high pressure building north of the area trailing a passing front will persist into Wednesday. A combination of a large north-northwest swell building down the island chain and the strong winds will support Small Craft Advisory (SCA) conditions for all Hawaiian waters through Wednesday. For the second half of the week, the winds will diminish and shift out of the south to southeast as a weakening front approaches and moves into the area. Seas will respond and lower due to the lighter winds and the large north- northwest swell moving out.
Surf along exposed north and west facing shores is rising quickly this morning as a large north-northwest (330 deg) swell builds down the island chain. Early morning swell observations at the offshore buoys to the northwest appear to be peaking around the predicted levels. As a result, the surf will peak through the day at warning levels, then lower to advisory levels tonight through Wednesday. Daily water levels are slowly dropping (smaller daily tidal range for the month), which will lower the chances for coastal impacts or overwash onto roadways during the high tide cycle. For the long range, guidance shows a medium-period north- northwest swell arriving Friday night through the weekend from a broad gale passing far north of the area later this week. Surf heights may reach advisory levels for north and west facing shores as this swell peaks Saturday.
Surf along east facing shores will become rough and choppy through Wednesday due to the strong trades. A downward trend is anticipated through the second half of the week as the winds diminish and the front moves in.

HFO Watches/Warnings/Advisories

High Surf Warning until 6 PM HST this evening for north and west facing shores of Niihau, Kauai, Oahu, Molokai, and north facing shores of Maui.
Small Craft Advisory until 6 PM HST Wednesday for all Hawaiian waters,

Data Courtesy of NOAA.gov