Photo Credit: Jeni Ji Cousins

West Side

Today: Windy. Mostly sunny with isolated showers. Highs 74 to 80. Northeast winds 15 to 30 mph with gusts to 50 mph. Chance of rain 20 percent.

Tonight: Windy. Mostly cloudy with scattered showers. Lows around 68. East winds 15 to 30 mph with gusts to 50 mph. Chance of rain 50 percent.

Tuesday: Windy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 74 to 80. Northeast winds 20 to 30 mph with gusts to 50 mph. Chance of rain 40 percent.

South Side

Today: Windy. Mostly sunny with isolated showers. Highs around 80. North winds 20 to 35 mph with gusts to 55 mph. Chance of rain 20 percent.

Tonight: Windy. Partly cloudy with scattered showers. Lows around 67. North winds 20 to 35 mph with gusts to 55 mph. Chance of rain 30 percent.

Tuesday: Mostly sunny. Windy. Scattered showers in the morning. Highs around 80. North winds 25 to 35 mph with gusts to 55 mph. Chance of rain 30 percent.

North Shore

Today: Mostly cloudy. Breezy. Intermittent showers in the morning, then numerous showers in the afternoon. Highs 72 to 77 near the shore to around 58 near 5000 feet. East winds 20 to 25 mph with gusts to 45 mph. Chance of rain 90 percent.

Tonight: Windy. Intermittent showers. Lows 64 to 70 near the shore to 45 to 51 near 5000 feet. East winds 20 to 30 mph with gusts to 50 mph. Chance of rain near 100 percent.

Tuesday: Mostly cloudy. Windy. Intermittent showers in the morning, then numerous showers in the afternoon. Highs 72 to 77 near the shore to around 58 near 5000 feet. East winds 20 to 30 mph with gusts to 50 mph. Chance of rain 90 percent.

Central Maui

Today: Windy. Mostly sunny with isolated showers. Highs 76 to 81. Northeast winds 20 to 30 mph with gusts to 55 mph. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows 65 to 70. Northeast winds 20 to 25 mph with gusts to 45 mph. Chance of rain 20 percent.

Tuesday: Windy. Mostly sunny with isolated showers. Highs 76 to 81. Northeast winds 20 to 30 mph with gusts to 50 mph. Chance of rain 20 percent.

Upcountry

Today: Windy. Mostly sunny with scattered showers. Highs around 53 at the visitor center to around 49 at the summit. East winds around 30 mph. Chance of rain 50 percent.

Tonight: Windy. Partly cloudy with scattered rain showers. Lows around 42 at the visitor center to around 35 at the summit. East winds 30 to 35 mph. Chance of rain 50 percent.

Tuesday: Very windy. Mostly sunny with scattered rain showers. Highs around 52 at the visitor center to around 48 at the summit. East winds 30 to 40 mph. Chance of rain 50 percent.

East Maui

Today: Mostly cloudy. Breezy. Intermittent showers in the morning, then numerous showers in the afternoon. Highs 72 to 77 near the shore to around 58 near 5000 feet. East winds 20 to 25 mph with gusts to 45 mph. Chance of rain 90 percent.

Tonight: Windy. Intermittent showers. Lows 64 to 70 near the shore to 45 to 51 near 5000 feet. East winds 20 to 30 mph with gusts to 50 mph. Chance of rain near 100 percent.

Tuesday: Mostly cloudy. Windy. Intermittent showers in the morning, then numerous showers in the afternoon. Highs 72 to 77 near the shore to around 58 near 5000 feet. East winds 20 to 30 mph with gusts to 50 mph. Chance of rain 90 percent.

Lanai City

Today: Windy. Mostly sunny with isolated showers. Highs 69 to 76. East winds around 30 mph with gusts to 55 mph. Chance of rain 20 percent.

Tonight: Windy. Partly cloudy with isolated showers. Lows around 63. East winds 25 to 35 mph with gusts to 55 mph. Chance of rain 20 percent.

Tuesday: Windy. Mostly sunny with isolated showers. Highs 68 to 75. Northeast winds 25 to 30 mph with gusts to 50 mph. Chance of rain 20 percent.

Kaunakakai

Today: Windy. Mostly sunny with isolated showers. Highs 69 to 79. East winds 25 to 30 mph with gusts to 55 mph. Chance of rain 20 percent.

Tonight: Windy. Partly cloudy with scattered showers. Lows 58 to 70. East winds 25 to 30 mph with gusts to 55 mph. Chance of rain 40 percent.

Tuesday: Mostly sunny. Windy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 69 to 79. East winds 25 to 30 mph with gusts to 50 mph. Chance of rain 40 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.

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Data Courtesy of NOAA.gov