Photo Credit: James Grenz

Hilo

Rest Of Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 76 to 82 near the shore to 64 to 70 at 4000 feet. West winds up to 10 mph shifting to the east in the afternoon. Chance of rain 50 percent.

Tonight: Partly cloudy with a 20 percent chance of showers. Lows 61 to 69 near the shore to 52 to 57 at 4000 feet. Light winds becoming northwest up to 10 mph after midnight.

Tuesday: Mostly sunny with a 20 percent chance of showers. Highs 76 to 82 near the shore to 64 to 71 at 4000 feet. Northeast winds up to 10 mph.

Kona

Rest Of Today: Sunny with isolated showers. Highs around 81 near the shore to around 67 near 5000 feet. Light winds. Chance of rain 20 percent.

Tonight: Mostly clear. A 20 percent chance of showers after midnight. Lows around 68 near the shore to 47 to 54 near 5000 feet. Light winds.

Tuesday: Mostly sunny. A 20 percent chance of showers in the afternoon. Highs around 82 near the shore to around 68 near 5000 feet. Light winds.

Waimea

Rest Of Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 63 to 81. Light winds becoming northwest up to 10 mph in the afternoon. Chance of rain 40 percent.

Tonight: Partly cloudy with a 20 percent chance of showers. Lows 60 to 65 near the shore to 52 to 60 near 3000 feet. Light winds.

Tuesday: Mostly sunny. Slight chance of showers in the morning, then chance of showers in the afternoon. Highs 63 to 82. Northeast winds up to 15 mph. Chance of rain 40 percent.

Kohala

Rest Of Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 63 to 81. Light winds becoming northwest up to 10 mph in the afternoon. Chance of rain 40 percent.

Tonight: Partly cloudy with a 20 percent chance of showers. Lows 60 to 65 near the shore to 52 to 60 near 3000 feet. Light winds.

Tuesday: Mostly sunny. Slight chance of showers in the morning, then chance of showers in the afternoon. Highs 63 to 82. Northeast winds up to 15 mph. Chance of rain 40 percent.

South Big Island

Rest Of Today: Mostly sunny with isolated showers. Highs around 80 near the shore to around 66 near 5000 feet. East winds around 10 mph shifting to the southwest in the afternoon. Chance of rain 20 percent.

Tonight: Mostly clear. Lows around 69 near the shore to around 51 near 5000 feet. Light winds.

Tuesday: Mostly sunny. Highs around 81 near the shore to around 67 near 5000 feet. Southeast winds up to 15 mph.

Puna

Rest Of Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 76 to 82 near the shore to 64 to 70 at 4000 feet. West winds up to 10 mph shifting to the east in the afternoon. Chance of rain 50 percent.

Tonight: Partly cloudy with a 20 percent chance of showers. Lows 61 to 69 near the shore to 52 to 57 at 4000 feet. Light winds becoming northwest up to 10 mph after midnight.

Tuesday: Mostly sunny with a 20 percent chance of showers. Highs 76 to 82 near the shore to 64 to 71 at 4000 feet. Northeast winds up to 10 mph.

Waikoloa

Rest Of Today: Sunny. Isolated showers in the late morning and afternoon. Highs around 81 near the shore to 64 to 70 above 4000 feet. Light winds becoming west up to 10 mph in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy. A 20 percent chance of showers after midnight. Lows around 69 near the shore to 47 to 53 above 4000 feet. Southeast winds up to 10 mph.

Tuesday: Mostly sunny. Highs around 81 near the shore to 65 to 71 above 4000 feet. North winds up to 15 mph.

Detailed Forecast

Synopsis

Southwest winds will increase some today as a weak front approaches from the northwest. This front will move down the island chain tonight and Tuesday, briefly boosting winds and shower activity. Behind the front, expect a short period of cool trade winds. A mainly light wind pattern will lead to land and sea breezes Wednesday through Friday, followed by a possible return of trade winds next weekend.

Discussion

Made a couple tweaks to the forecast for the first 24 to 36 hours to boost some PoPs and associated grids. In the very near term, have boosted near Maui County to account for increased clouds based on recent satellite imagery. Radar is showing a few more showers popping up in this area as well. Other changes were to nudge the PoPs forecast towards the blend of models just a bit.
The surface ridge is edging closer to the Big Island, as a front pushes in from the northwest. The front remains to the northwest of the coastal waters, but as it pushes in, it will erode the ridging aloft, allowing for showers to be a bit heavier than the last couple of days. Kauai and Oahu will see an increase in southwest winds today as the front edges closer. The moisture band that had been over the Big Island is moving closer to Maui County perhaps a bit faster than expected, thus the tweaks to the forecast mentioned above. The models have been pretty consistent over the last several runs with the prefrontal convergence bands settings up over Maui County, so still expecting scattered showers there before the front arrives.
The weakening front will move across Kauai and Oahu tonight and fall apart near the Big Island late Tuesday. The front will be shallow and will deliver modest rainfall to mainly northwest to northeast slopes of Kauai this evening and Oahu late tonight or early tomorrow morning. High pressure passing north of the state will push what is remaining of the dissipating front to windward slopes Maui on tomorrow and the Big Island tomorrow night. This high will produce a brief period of moderate northeasterly trade winds and a shot of cooler air. Dew points should drop back into the mid to upper 50s across the northern half of the island chain, leading to a cool feel.
The surface ridge will move back near or over the state late Wednesday through Friday, leading to light and variable winds and a dominant land and sea breeze pattern. A persistent, zonal west Pacific jet stream could send a disturbance aloft over the state and trigger an increase in spotty showers on Thursday. Otherwise, little significant rainfall is expected.
The GFS and ECMWF are showing another front stalling and dissipating just north of Kauai on Saturday, signaling a return of trade winds as a surface ridge builds to the north.

Aviation

Latest surface analysis reveals a cold front north of the state that will weaken as it approaches Kauai and Oahu later today, eventually reaching the Big Island late Tuesday. As it approaches, pre-frontal southwest winds will reach moderate levels across the northern half of the state by this afternoon. Behind the front, winds will switch to become more northerly across Kauai and Oahu tonight as speeds reach breezy levels.
Early morning satellite imagery depicts cloud bands across northwest sections of the Big Island and Maui County, though shower activity has remained minimal for now. However, pre-frontal convergence is expected to increase clouds and shower coverage across Maui County ahead of the front today.
There are currently no AIRMETs in effect. Although mountain obscuration cannot be ruled out later this morning for portions of Maui County and northwest Big Island, VFR conditions are expected to prevail for most locations.

Marine

A cold front approaching from the northwest will continue to weaken the high pressure ridge over the islands. Wind speeds will slowly increase as the cold front moves into the area later today into Tuesday. Shower trends will increase along the frontal band as it passes into the northwest waters before dissipating over the central waters near Maui on Tuesday morning. A high pressure system will then pass by north of the state from Tuesday to Wednesday, producing a brief period of moderate trade winds. Light winds return from Thursday into the weekend as another cold front approaches the region from the northwest.
A large northwest swell, from a 300 direction, will slowly decrease today. However, a larger northwest swell will arrive later tonight, from a 320 degree direction, peaking on Tuesday, then slowly lowering Tuesday night and into Wednesday. A third northwest swell, also from a 320 degree direction, will likely arrive by Wednesday night, peaking on Thursday, then lowering slowly from late Thursday to Friday.
A High Surf Warning (HSW) remains in effect for exposed north and west facing shores due to the large northwest swell currently moving through the area. The next large northwest swell, arriving Monday night, will easily produce warning level surf. While the surf heights will briefly drop below warning levels on Monday between these two swells, the HSW is being kept up for the north and west facing shores from Kauai to Maui to cover both large swell events. The HSW for the west facing shores of the Big Island has been dropped to a High Surf Advisory as surf heights decrease a bit. The third swell, arriving Wednesday night, now appears to produce advisory level surf. However, confidence on the swell heights with this third northwest swell remains less certain as long range swell guidance continues to evolve over time.
Winds will remain below Small Craft Advisory (SCA) levels throughout the forecast period. However, seas will reach or exceed SCA levels across exposed waters as the above mentioned northwest swells move across the area.

HFO Watches/Warnings/Advisories

High Surf Warning until 6 PM HST Tuesday for north and west facing shores of Niihau, Kauai, Oahu, and Molokai, and for north facing shores of Maui.
High Surf Advisory until 6 PM HST Tuesday for west facing shores of the Big island.
Small Craft Advisory until 6 PM HST Tuesday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Alenuihaha Channel, Big Island Windward Waters.

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Data Courtesy of NOAA.gov