Hilo

Tonight: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows 64 to 72 near the shore to 52 to 58 at 4000 feet. Light winds. Chance of rain 70 percent.

Wednesday: Mostly cloudy. Scattered showers in the morning, then numerous showers and isolated thunderstorms in the afternoon. Highs 79 to 85 near the shore to around 66 at 4000 feet. North winds up to 10 mph shifting to the east in the afternoon. Chance of rain 70 percent.

Wednesday Night: Mostly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 63 to 71 near the shore to 52 to 58 at 4000 feet. Light winds becoming northeast up to 10 mph after midnight. Chance of rain 50 percent.

Kona

Tonight: Mostly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows around 73 near the shore to 50 to 55 near 5000 feet. Light winds. Chance of rain 50 percent.

Wednesday: Mostly cloudy. Scattered showers in the afternoon. Highs 84 to 89 near the shore to around 67 near 5000 feet. Light winds. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy. Scattered showers in the evening. Lows around 73 near the shore to 50 to 55 near 5000 feet. Light winds. Chance of rain 30 percent.

Waimea

Tonight: Mostly cloudy with scattered showers. Lows 63 to 73 near the shore to 56 to 63 near 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Wednesday: Partly sunny. Scattered showers in the morning, then scattered showers and isolated thunderstorms in the afternoon. Highs around 80 near the shore to 68 to 79 near 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy with isolated showers. Lows 63 to 72 near the shore to 55 to 63 near 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Kohala

Tonight: Mostly cloudy with scattered showers. Lows 63 to 73 near the shore to 56 to 63 near 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Wednesday: Partly sunny. Scattered showers in the morning, then scattered showers and isolated thunderstorms in the afternoon. Highs around 80 near the shore to 68 to 79 near 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy with isolated showers. Lows 63 to 72 near the shore to 55 to 63 near 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

South Big Island

Tonight: Mostly cloudy. Isolated showers in the evening. Lows around 75 near the shore to around 56 near 5000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Wednesday: Mostly cloudy. Breezy. Scattered showers in the afternoon. Highs around 86 near the shore to around 66 near 5000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy. Isolated showers in the evening. Lows around 74 near the shore to around 55 near 5000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Puna

Tonight: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows 64 to 72 near the shore to 52 to 58 at 4000 feet. Light winds. Chance of rain 70 percent.

Wednesday: Mostly cloudy. Scattered showers in the morning, then numerous showers and isolated thunderstorms in the afternoon. Highs 79 to 85 near the shore to around 66 at 4000 feet. North winds up to 10 mph shifting to the east in the afternoon. Chance of rain 70 percent.

Wednesday Night: Mostly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 63 to 71 near the shore to 52 to 58 at 4000 feet. Light winds becoming northeast up to 10 mph after midnight. Chance of rain 50 percent.

Waikoloa

Tonight: Mostly cloudy with scattered showers. Lows around 74 near the shore to 52 to 57 above 4000 feet. Northeast winds up to 10 mph in the evening becoming light. Chance of rain 50 percent.

Wednesday: Partly sunny. Scattered showers and isolated thunderstorms in the afternoon. Highs around 86 near the shore to 65 to 72 above 4000 feet. Northeast winds up to 10 mph shifting to the north in the afternoon. Chance of rain 50 percent.

Wednesday Night: Mostly cloudy. Isolated showers in the evening. Lows around 74 near the shore to around 54 above 4000 feet. Light winds. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Light to moderate trades are expected over the next few days with showers favoring windward and mauka areas, particularly near both the eastern and western ends of the state. A brief period of drier weather Friday into the first half of the weekend will be followed by more overcast and wet weather early next week in response to an early November upper trough near the state.

Discussion

This afternoon, a weakening surface front is making its way eastward across the North Pacific, situated between two areas of high pressure far north and far northeast of the main Hawaiian Islands. This frontal boundary extends into the northern offshore waters this afternoon, but is expected to weaken over the next 12 to 24 hours. Meanwhile, troughing aloft stretches over the western end of the island chain, but latest regional satellite imagery shows that most showers and more extensive clouds associated with this feature are located well to the northeast, where much more instability exists aloft. Locally, CIMSS precipitable water imagery shows that a pocket of drier air is currently working its way over the smaller islands, while greater available moisture is located near developing troughs near both the far eastern and western ends of the state. Latest satellite and radar imagery supports this, with afternoon cloud buildups and a few showers over the Big Island, while low clouds and showers across the remaining islands have have been few and far between. Some towering cumulus have been noted on satellite imagery over the Big Island, where the afternoon 00z Hilo sounding indicated slightly higher CAPE when compared with the previous couple of afternoons. While the probability is low, isolated thunder has been introduced for the Big Island interior through the remainder of the afternoon. Meanwhile, surface observations and a late morning scatterometer pass show moderate trade winds prevailing across the state.
Guidance suggests that the trough aloft will pinch off into a cutoff upper low, located southwest of the islands by Thursday. As a result, more organized thunder potential and chances of heavy rain will shift far south/southwest of the state. For the islands, showers will favor windward and mauka areas, particularly in the overnight through morning periods. Isolated thunderstorms cannot be ruled out again on Wednesday afternoon for the Big Island, though increasing stability should mitigate these chances by Thursday.
Drier air begins to work into the area late in the week, with typical trade wind showers expected Friday into the first half of the weekend and light to moderate easterly trades.
An early November cold front may reach the northern coastal waters this weekend, with winds backing to become more northerly by Sunday. Beyond the weekend, there are significant differences amongst the various global models regarding the strength of an assoicated upper trough or potential low aloft. The development of this feature and its evolution would have significant impacts on the rain forecast and thunderstorm chances for early next week. For now, the forecast has been trended wetter to account for the possibility of a lower level trough/front hanging up north of the state, but have removed isolated thunderstorm chances in the extended forecast for now since it is too early to determine specifics based on the spread of model solutions at this time.

Aviation

Moderate trade wind regime continues with typical windward isolated showers over the islands becoming more scattered overnight.
Light icing impacts have decreased due to mostly clear conditions in the mid and upper levels.

Marine

Weak high pressure anchored north of the Hawaiian Islands will maintain moderate to locally fresh trades through the first half of the weekend. The potential then exists for trades to back to a more NEly direction and become strong over the western waters in the wake of a cold front that is forecast to advance through part or all of the island chain early next week. A Small Craft Advisory for winds and/or seas may be needed for portions of the area by early next week.
Energy out of the NW (330-350) remains small and rather short period through Friday. Surf will then trend sharply upward late Friday through through Monday in response to a couple of swells sent toward the islands by an active pattern across the N Pac. Forerunners of the first swell in the sequence, a small, moderate period NNW (330) swell are modeled to arrive on Friday with swell peaking Saturday below the High Surf Advisory (HSA) threshold. The next swell, small to moderate and medium period out of the NNW (340), arrives quickly on its heels late Saturday likely peaking above the HSA threshold. Messy forecast scenario during this time as modeling seems to contaminate this second swell with emerging strong NNE post-frontal winds leading to explicit output reflecting a larger and more N swell than anticipated. However, even a conservative approach suggests HSA-criteria surf for N and W facing shores for the Sunday-Monday period.
Surf along E shores remains small to moderate as trades slightly weaken. Strengthening post-frontal NNE trades potentially bring a rapid increase in wind waves and short period fresh swell for favored exposures early next week, particularly over the western end of the state. South facing shores see small background swells through the week.

Fire weather

Increased relative humidity values and moderate trade wind speeds will keep fire weather conditions below critical thresholds for the next several days.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov