Photo Credit: Braden Jarvis

West Kaua’i

Today: Windy. Mostly sunny with isolated showers. Highs around 80 near the shore to around 68 above 3000 feet. East winds 10 to 30 mph. Chance of rain 20 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Windy. Scattered showers. Lows around 68 near the shore to around 57 above 3000 feet. East winds 10 to 30 mph. Chance of rain 50 percent.

Tuesday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 80 near the shore to around 68 above 3000 feet. East winds up to 25 mph increasing to 10 to 25 mph in the afternoon. Gusts up to 45 mph. Chance of rain 50 percent.

South Kaua’i

Today: Mostly cloudy. Windy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 79. Northeast winds 25 to 30 mph. Chance of rain 70 percent.

Tonight: Windy. Mostly cloudy with scattered showers. Lows 64 to 69. Northeast winds 25 to 30 mph. Chance of rain 50 percent.

Tuesday: Partly sunny. Windy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 79. Northeast winds 25 to 30 mph. Chance of rain 70 percent.

Kaua’i Mountains

Today: Mostly cloudy. Windy. Intermittent showers in the morning, then numerous showers in the afternoon. Highs 67 to 75 in the valleys to around 62 above 4000 feet. East winds 15 to 30 mph. Chance of rain 80 percent.

Tonight: Mostly cloudy. Windy. Numerous showers in the evening, then intermittent showers after midnight. Lows 57 to 62 in the valleys to around 51 above 4000 feet. East winds 15 to 30 mph with gusts to 50 mph. Chance of rain 90 percent.

Tuesday: Windy. Cloudy with intermittent showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 67 to 75 in the valleys to around 62 above 4000 feet. East winds 10 to 30 mph. Chance of rain 80 percent.

North Kaua’i

Today: Breezy. Partly sunny with scattered showers. Highs 72 to 79. East winds 10 to 25 mph with gusts to 45 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Numerous showers in the evening, then scattered showers after midnight. Lows 60 to 69. East winds 10 to 25 mph with gusts to 45 mph. Chance of rain 70 percent.

Tuesday: Breezy. Partly sunny with scattered showers. Highs 72 to 79. East winds up to 20 mph increasing to 10 to 25 mph in the afternoon. Chance of rain 50 percent.

East Kaua’i

Today: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 72 to 79. Northeast winds 15 to 25 mph. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with numerous showers. Lows 58 to 70. East winds 15 to 25 mph. Chance of rain 70 percent.

Tuesday: Partly sunny. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 72 to 79. Northeast winds 15 to 25 mph. Chance of rain 70 percent.

Detailed Forecast

Synopsis

A strong high pressure system located far north of the Hawaiian Islands will keep windy trade winds in the forecast at least into Thursday. An upper level disturbance will keep showers in the forecast over windward and mountain areas through the week with less shower activity over typically drier leeward areas of each island. The highest rainfall trends are expected over East Maui and the windward slopes of the Big Island as an unstable upper low lingers just east of Hilo. Wind speeds may trend lower into the moderate to breezy range from Friday to Saturday as a cold front approaches the region from the northwest.

Discussion

A very strong 1040 MB high pressure system located far north of the state will weaken slightly and remain nearly stationary over the next few days producing strong and gusty trade winds over the Hawaii region. A narrow upper level trough with embedded lows will linger over the Hawaii region through the week. Expect periods of wet trade winds affecting all island into Saturday.
Strong surface winds converging over island mountains will combine forces with instability under a narrow upper level trough. Trade wind temperature inversion heights will remain in the 7,000 to 10,000 foot range into Saturday allowing for periods of wet trade wind weather over all islands. The high pressure center far north of the islands will slowly weaken over the next few days. However, this high will remain strong enough to produce windy trade winds into Thursday with likely wind advisories over land, and small craft advisories to gale warnings over windier coastal waters. A Wind Advisory was expanded in coverage this morning to include the windier areas of most islands through Tuesday as trade winds strengthen today and tomorrow.
An upper level low will move in from the north, deepen, and dig in just east of the Big Island today through Wednesday. An upper level short wave trough rotating around this system will enhance shower activity over all islands through tonight. The best forcing and highest enhancement of shower activity is expected to develop over all islands during this time period. The highest rainfall amounts will likely fall over windward slopes of Maui and the Big Island, as these islands are closer to the cold core of this unstable low. Brief periods of icy conditions may reach the Maui and Big Island summits around the 10,000 foot elevation level tonight as temperatures hover near freezing. More typical breezy to windy trade winds will return from Tuesday night onward for the western and central islands with shower activity favoring the windward and mountain slopes of each island. Enhanced showers will remain in place over the windward slopes of East Maui and the Big Island with wet rainy weather lasting through Friday.
In the long range forecast for next weekend, wind speeds will decrease and veer more southeasterly as a cold front approaches the islands from the northwest. Shower activity will also trend lower over the smaller islands with continued higher rainfall activity over East Maui and the windward Big Island lasting into next weekend. Both the American (GFS) and the European (ECMWF) extended range guidance shows a cold front sweeping widespread rainfall from west to east across the island chain on Monday.

Aviation

Strong high pressure north of the islands will keep strong and gusty trade winds in place during the next couple days. Clouds and showers will favor windward and mauka areas, but a few will reach leeward communities at times. Some MVFR cigs/vsbys can be expected in the passing showers, with showers most prevalent over windward portions of Maui and the Big Island.
AIRMET Sierra remains in effect for mountain obscuration over windward sections most islands. Conditions will likely improve in many areas by mid morning.
AIRMET Tango remains in effect for moderate to isolated severe low level turbulence over and downwind of the terrain of all islands. AIRMET Tango is also in effect for strong surface winds from Molokai eastward to the Big Island.

Marine

Rough conditions out across the waters are here to stay this week as strong high pressure (1040-1045 mb) remains positioned to the north. Recent satellite data showed 20-30 kt winds with seas hovering around 10 ft, which line up well with buoy observations at the PacIOOS Mokapu station and a drifter buoy east of Hilo this morning. Guidance supports this and depicts a large belt of strong northeast to east trades over and upstream of the state. Seas are responding and will peak in the 10 to 15 ft range later today through midweek. Gales are expected over the windier waters and channels for Maui County and the Big Island through this period. For the extended, a pattern transition is possible next week as a cold front approaches, which means a potential break in the strong winds/seas.
Surf along east facing shores will build through the first half of the week, with heights hovering at/above the advisory level of 10 ft (faces) due to the aforementioned winds over and around the state and some mix added by a northeast groundswell from the west coast. As the seas peak by midweek, surf will near the 15 ft (faces) warning level. A downward trend is expected next weekend.
Surf along north facing shores will remain well below the seasonal average each day through next weekend. Storm-force low analyzed in the far northwest Pacific near the Kurils is forecast to track eastward toward the Date Line through Tuesday. A decent sized area of strong- to gale-force winds aimed at the islands down the 310 degree directional band associated with this feature should be enough to send a small west-northwest swell our way. This should fill in through the day Friday and linger into the weekend.
Surf along south facing shores will remain near the seasonal average each day, with mainly windswell wrapping into exposed areas.

HFO Watches/Warnings/Advisories

Wind Advisory until 6 PM HST Tuesday for most of the Hawaiian Islands.
High Surf Advisory until 6 PM HST Thursday for east facing shores of Kauai Oahu Molokai Maui and the Big Island.
Gale Warning until 6 PM HST Thursday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.
Small Craft Advisory until 6 PM HST Thursday for most Hawaiian waters.

Data Courtesy of NOAA.gov