West Side

Today: Mostly sunny with isolated showers. Highs 79 to 85. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 68 to 75. East winds up to 15 mph increasing to 10 to 15 mph after midnight. Chance of rain 20 percent.

Thursday: Mostly sunny with isolated showers. Highs 79 to 85. East winds 10 to 15 mph shifting to the northeast in the afternoon. Chance of rain 20 percent.

South Side

Today: Mostly sunny with isolated showers. Highs around 88. North winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Isolated showers in the evening. Lows 67 to 76. North winds up to 15 mph. Chance of rain 20 percent.

Thursday: Sunny with isolated showers. Highs around 88. North winds up to 15 mph. Chance of rain 20 percent.

North Shore

Today: Partly sunny with scattered showers. Highs around 82 near the shore to around 64 near 5000 feet. East winds 10 to 15 mph decreasing to up to 15 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows around 72 near the shore to around 52 near 5000 feet. East winds up to 15 mph increasing to 10 to 15 mph after midnight. Chance of rain 40 percent.

Thursday: Breezy. Partly sunny with scattered showers. Highs around 82 near the shore to around 65 near 5000 feet. East winds 10 to 20 mph decreasing to up to 20 mph in the afternoon. Chance of rain 50 percent.

Central Maui

Today: Mostly sunny with isolated showers. Highs 81 to 88. Northeast winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Isolated showers in the evening. Lows 68 to 73. Northeast winds up to 15 mph. Chance of rain 20 percent.

Thursday: Breezy. Mostly sunny with isolated showers. Highs 82 to 89. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Upcountry

Today: Partly sunny with scattered showers. Highs around 61 at the visitor center to around 66 at the summit. Light winds becoming east up to 10 mph in the afternoon. Chance of rain 50 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows 43 to 55. East winds up to 15 mph increasing to 10 to 20 mph after midnight. Chance of rain 20 percent.

Thursday: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 62 at the visitor center to around 67 at the summit. East winds up to 20 mph. Chance of rain 50 percent.

East Maui

Today: Partly sunny with scattered showers. Highs around 82 near the shore to around 64 near 5000 feet. East winds 10 to 15 mph decreasing to up to 15 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows around 72 near the shore to around 52 near 5000 feet. East winds up to 15 mph increasing to 10 to 15 mph after midnight. Chance of rain 40 percent.

Thursday: Breezy. Partly sunny with scattered showers. Highs around 82 near the shore to around 65 near 5000 feet. East winds 10 to 20 mph decreasing to up to 20 mph in the afternoon. Chance of rain 50 percent.

Lanai City

Today: Mostly sunny with isolated showers. Highs 73 to 81. Northeast winds 10 to 15 mph decreasing to up to 15 mph in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 63 to 68. Northeast winds up to 15 mph. Chance of rain 20 percent.

Thursday: Mostly sunny. Isolated showers in the afternoon. Highs 73 to 81. Northeast winds up to 15 mph. Chance of rain 20 percent.

Kaunakakai

Today: Mostly sunny with isolated showers. Highs 72 to 89. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Isolated showers in the evening. Lows 59 to 74. East winds 10 to 15 mph. Chance of rain 20 percent.

Thursday: Mostly sunny with isolated showers. Highs 72 to 89. East winds 10 to 15 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Partly cloudy conditions with scattered light showers under gentle to locally moderate trade winds the next couple of days. The weather pattern will undergo more significant change early next week as a result of a developing trough in the proximity of the Hawaiian Islands. There are increasing probabilities for a more overcast and wet start to November if a trough or subsequent cut- off low evolves over and or near the state.

Discussion

A fairly quiet morning with less precipitation than at this time a day ago. Most of the radar activity has been just south of Kona and points just offshore of southwest Big Island. A weakness in the height field between two ridges on either side of Hawaii, or weak troughing settling in over the region, has maintained this recently cloudier and showery behavior. There has been little to no impact from the occasional heavy downpour or isolated storm. Morning showers streaming onto windward Big Island may transition to towering afternoon cumulus leading up to an isolated storm or two along the leeward Kona slopes by sunset. Warming slopes in the midday sun may destabilize the atmosphere over the South Kona region just enough to allow the tallest cumulus to transform into cumulonimbus. The upper divergence produced by a passing subtropical jet (evidenced by the southwest-to-northeast plume of mid to high level cloudiness south of Big Island), along with a more moist air mass advecting in from the east, will pin the island of Hawaii as one that has the highest chances of picking up the highest rainfall accumulation today. Generally, most of the light rain of under a tenth of an inch will center along windward upslope mauka and within higher terrain the next few days.
Drier air will filter into the region through late week with only pockets of higher precipitable water producing widely-scattered showers and wetting the windward exposures of the island chain. The greatest rainfall will likely occur within a cooler, more shallow resident boundary layer during the nocturnal hours. The forecast going into the weekend is of a typical wash-rinse-repeat theme with very little fluctuation on the diurnal trends of trades, cloud cover and precipitation. Western-based upper ridging expanding east over the state will ensure agreeable weather for most in the state Thursday and Friday; partially cloudy skies while not to warm nor humid under gentle to light moderate trades. Weekend weather will begin pleasant but will doubtfully not end this way come Sunday. The reasoning stems from a deepening North Central Pacific trough that will dig down over the region Sunday and Monday. The backing northern air mass is forecast to be cold enough to force the associated lower level boundary into the local waters as a cold front late Sunday into Monday. This may be the first front to reach the area this season.
One deterministic model pinches off a cut-off low from the mid to upper level trough and settles it over the state Monday while the other has the trough remaining an open wave and slowly exiting off to the northeast. While ensemble guidance agrees with their deterministic siblings above, the general trend with the majority of the members is for a relatively sharp open wave trough passage across the area early next week. Higher QPF percentiles center on the higher rainfall being focused along and ahead of a cold front that will pass through sometime Monday. Instability indices do not look overly high but the highest (ensemble) CAPE will be located across the western half of the state, or in the vicinity of the front. Strengthened northerlies, with the highest early week POPs/QPF, will be over and around the islands of Oahu and Kauai. Troughing, or a generally weakness in western ridging, will maintain similar weather to what we are currently experiencing next Tuesday and Wednesday.

Aviation

Moderate trade winds through the week. Widely scattered light showers caught up within trade flow will quickly pass across windward-facing air fields. VFR should prevail in primarily dry conditions. Brief MVFR ceilings and vsbys are possible within any moderate intensity shower. There are very low chances for the development of an afternoon thunderstorm in the vicinity of HKO, east or south of the airport, along the leeward slopes of Mauka Kea and/or Mauna Loa.
Light icing may occur within FL150-250 mid layered clouds currently streaming up from the southwest, located southeast of the island chain, through Wednesday.

Marine

Weak high pressure anchored north of the Hawaiian Islands will maintain moderate to locally fresh trades into 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 Sunday into early next week. A Small Craft Advisory for winds and/or seas may be needed for portions of the area during this time.
Offshore NDBC 51001 and 51101 buoys have be picking up on the next small, short period NNW (330-350) swell overnight and is now filling in locally. This swell should peak today while veering to a more northerly direction before fading Thursday. A small, long period NNW swell (330) will fill in Thursday night and peak Friday, keeping surf along north and west facing shores elevated. Surf will then trend sharply upward late Friday 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 moderate, long period NNW (330) swell will arrive late Friday with swell peaking Saturday near or below the High Surf Advisory (HSA) threshold. The next small to moderate, medium period NNW (340) swell will arrive quickly late Saturday. This swell will likely peak above the HSA threshold. Messy forecast scenario unfolds during this time as model swells seems to be cross contaminated with an emerging strong NNE post-frontal wind swell, leading to 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 will remain small to moderate through the week. Strengthening post-frontal NNE trades may 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 will see a slight boost in surf today as a small, long period south swell fills in before slowly fading Thursday through the rest of the week.

Fire weather

Higher afternoon humidities with limited full sun under partly cloudy skies, along with moderate trades will maintain below critical fire weather thresholds the next few days. A more wet weather pattern early next week will keep the near future wildfire threat to a minimum.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov