Hilo

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Haze through the night. Lows 58 to 67 near the shore to 48 to 54 at 4000 feet. South winds up to 10 mph. Chance of rain 40 percent.

Friday: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Haze. Highs 76 to 82 near the shore to 64 to 70 at 4000 feet. Southeast winds up to 10 mph. Chance of rain 20 percent.

Friday Night: Mostly cloudy. Haze through the night. Scattered showers after midnight. Lows 59 to 68 near the shore to 47 to 55 at 4000 feet. Light winds becoming north around 10 mph after midnight. Chance of rain 40 percent.

Kona

Tonight: Mostly clear. Haze. Lows around 69 near the shore to 41 to 49 near 5000 feet. North winds around 10 mph in the evening becoming light.

Friday: Mostly sunny. Haze through the day. Isolated showers in the afternoon. Highs 81 to 86 near the shore to around 66 near 5000 feet. Northeast winds up to 10 mph shifting to the northwest around 10 mph in the afternoon. Chance of rain 20 percent.

Friday Night: Mostly clear. Haze. Lows around 69 near the shore to 41 to 49 near 5000 feet. Light winds.

Waimea

Tonight: Partly cloudy. Haze. Lows 59 to 68 near the shore to 51 to 58 near 3000 feet. South winds around 10 mph in the evening becoming light.

Friday: Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Haze through the day. Highs around 77 near the shore to 68 to 74 near 3000 feet. South winds up to 10 mph shifting to the northeast around 10 mph in the afternoon. Chance of rain 20 percent.

Friday Night: Partly cloudy. Haze. Lows 59 to 69 near the shore to 51 to 59 near 3000 feet. East winds 10 to 15 mph.

Kohala

Tonight: Partly cloudy. Haze. Lows 59 to 68 near the shore to 51 to 58 near 3000 feet. South winds around 10 mph in the evening becoming light.

Friday: Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Haze through the day. Highs around 77 near the shore to 68 to 74 near 3000 feet. South winds up to 10 mph shifting to the northeast around 10 mph in the afternoon. Chance of rain 20 percent.

Friday Night: Partly cloudy. Haze. Lows 59 to 69 near the shore to 51 to 59 near 3000 feet. East winds 10 to 15 mph.

South Big Island

Tonight: Mostly clear. Haze. Lows around 70 near the shore to around 49 near 5000 feet. Northeast winds 10 to 15 mph.

Friday: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Haze through the day. Highs around 83 near the shore to around 67 near 5000 feet. East winds 10 to 15 mph shifting to the southeast in the afternoon. Chance of rain 40 percent.

Friday Night: Mostly clear. Haze. Lows around 71 near the shore to around 49 near 5000 feet. East winds 10 to 15 mph.

Puna

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Haze through the night. Lows 58 to 67 near the shore to 48 to 54 at 4000 feet. South winds up to 10 mph. Chance of rain 40 percent.

Friday: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Haze. Highs 76 to 82 near the shore to 64 to 70 at 4000 feet. Southeast winds up to 10 mph. Chance of rain 20 percent.

Friday Night: Mostly cloudy. Haze through the night. Scattered showers after midnight. Lows 59 to 68 near the shore to 47 to 55 at 4000 feet. Light winds becoming north around 10 mph after midnight. Chance of rain 40 percent.

Waikoloa

Tonight: Mostly clear. Haze. Lows 67 to 72 near the shore to 45 to 51 above 4000 feet. South winds around 10 mph shifting to the southeast after midnight.

Friday: Mostly sunny. Haze. Highs 80 to 85 near the shore to 63 to 69 above 4000 feet. Southeast winds around 10 mph shifting to the northwest in the afternoon.

Friday Night: Mostly clear. Haze. Lows 67 to 72 near the shore to 45 to 51 above 4000 feet. East winds 10 to 15 mph.

Detailed Forecast

Synopsis

A ridge over the islands will maintain light winds and dry conditions through Friday. A new ridge building north of the islands this weekend will bring a return of trade winds, while a weakening front and its associated upper level feature will help to enhance trade wind showers this weekend, mainly during the overnight and early morning hours along windward and mountain slopes of each island.

Discussion

The forecast was updated with the afternoon package to bring it in-line with the latest information from the National Blend of Models (NBM) and the latest data from the University of Hawaii's vog model. Overall the philosophy remains the same, but the fine tuning did result in lower PoPs through Friday night, and then boosting PoPs particularly over the smaller islands for the weekend. Additional changes were made to the areas of vog, identified as haze, in the forecast based on the latest model data.
The latest surface analysis shows the surface ridge just north of Kauai where it will remain for the next 24 hours or so. A cold front to the northwest will advance towards the islands, and is expected to be just northwest of Kauai tomorrow night. The afternoon soundings from Hilo and Lihue reported 0.98 and 0.91 inches of precipitable water (PW), so up a touch from last night, but continuing to match the satellite derived PW. The satellite derived PW shows the moisture associated with the front to be about 600 miles to the northwest. The surface front is expected to weaken as it approaches the islands, but the global models continue to show the upper level trough remaining intact as it moves down the island chain through the weekend. The GFS remains the locked in on the possibility of thunderstorms Sunday and Sunday night, but the latest couple of runs have a trend downward in that possibility. The ECMWF and NBM were marginal before and have continued to slowly back off. As such, confidence is low and therefore leaving that out of the forecast at this time.
Behind the front, high pressure building north of the islands will bring trades to the islands as early as Saturday. Even with the weakening front and upper level trough overhead, we can expect trades to filter in at the surface. The front and upper level trough will help to enhance trade wind showers. By Sunday night the upper level trough is expected to be east of the Big Island, which should allow a more typical trade wind pattern to set up to end the year and start the new.
The hot spot over Halemaumau Crater on the Big Island continues to be seen on infrared satellite imagery. Some of the emissions are seen at times on the various satellite bands reaching over the waters near the smaller islands, but its harder to determine the extent over the islands. The University of Hawaii (UH) Vog Model show SO2 emissions reaching the smaller islands through Friday night, and the forecast has been updated to reflect the areas and times based on the model data. The model data currently only extends through Friday night, however based on trades returning Saturday, we would expect the vog to clear the smaller islands at that time.

Aviation

Light winds will allow development of a land/sea breeze regime for the next few days. Low cigs and SHRA may develop across mauka areas each afternoon, then decrease overnight. While SHRA should be light, ISOL MVFR conds may occur within them. However, VFR should prevail. Due to the continuing eruption of Kilauea, leeward portions of the Big Island may see MVFR vsbys due to vog.
No AIRMETs are in effect and none are expected through tonight.

Marine

An extra large west-northwest to northwest (290-315 degrees) swell will continue to build across the island chain this afternoon and evening with peak swell heights expected this evening through tonight. Latest swell observations at the offshore buoys northwest of Kauai continues to come in well above guidance with peak swell heights of up to 21 feet 16 seconds seen on buoy 51001 at around noon today. Surf heights as of this afternoon on Oahu is well above warning thresholds and will continue to build through this evening. This swell is expected to gradually taper off on Friday but will hold above warning thresholds for exposed north and west-facing shores of the smaller islands and for west facing shores of the Big Island.
Following a series of extra-large northwest swells last week, this event is expected to worsen ongoing erosion issues, including the potential for periodic overwash onto low-lying properties and roadways, particularly during high tide cycles. In addition to the coastal impacts associated with the surf, a Small Craft Advisory has been issued to account for seas exceeding 10 feet over exposed waters. This swell will slowly lower over the weekend and into early next week. An upward trend is possible Monday through midweek, as a couple of smaller northwest swells arrive.
Surf along south and east facing shores will remain small through early next week. The exception could be for south facing shores exposed to more westerly swells, which could see a slight rise this evening through Friday as the aforementioned west-northwest builds down the island chain.
A surface ridge just north of the state will continue to produce light winds across the area through Friday with sea breezes developing near the coast during the day and land breezes at night. A front approaching the state late Friday will likely bring a brief period of moderate northerly winds to the western half of the state. As the front moves over the state, it is expected to stall over the state this weekend and dissipate. Meanwhile, a ridge of high pressure will build north of the state and we should see the return of fresh to strong northeast trade winds this weekend. Showery weather conditions will also be possible especially windward waters this weekend.

Fire weather

No critical fire weather conditions are expected for the next seven days. Dry weather with light winds through Friday will give way to trade winds with increased shower activity for the weekend, followed by a more typical trade wind pattern Monday onwards.

HFO Watches/Warnings/Advisories

High Surf Warning until 6 PM HST Friday for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kona, Kohala, Kauai North, Molokai Windward, Molokai North, Molokai West, Maui Central Valley North, Windward Haleakala, Big Island South.
Small Craft Advisory until 6 PM HST Friday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov