Hilo

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Numerous showers. Lows around 70 near the shore to around 56 at 4000 feet. Northeast winds up to 10 mph shifting to the northwest after midnight. Chance of rain 70 percent.

Tuesday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 86 near the shore to 70 to 75 at 4000 feet. Northeast winds up to 15 mph shifting to the east in the afternoon. Chance of rain 70 percent.

Tuesday Night: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows around 70 near the shore to around 56 at 4000 feet. East winds up to 10 mph. Chance of rain 40 percent.

Kona

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 71 to 76 near the shore to around 57 near 5000 feet. Light winds. Chance of rain 20 percent.

Tuesday: Mostly sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 83 to 88 near the shore to around 70 near 5000 feet. Light winds. Chance of rain 40 percent.

Tuesday Night: Mostly cloudy in the evening then becoming partly cloudy. Lows 71 to 76 near the shore to around 57 near 5000 feet. Light winds.

Waimea

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows around 70 near the shore to 58 to 64 near 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tuesday: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs around 84 near the shore to 70 to 81 near 3000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Tuesday Night: Partly cloudy with scattered showers. Lows around 70 near the shore to 58 to 64 near 3000 feet. East winds 10 to 15 mph. Chance of rain 40 percent.

Kohala

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows around 70 near the shore to 58 to 64 near 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tuesday: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs around 84 near the shore to 70 to 81 near 3000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Tuesday Night: Partly cloudy with scattered showers. Lows around 70 near the shore to 58 to 64 near 3000 feet. East winds 10 to 15 mph. Chance of rain 40 percent.

South Big Island

Tonight: Breezy. Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Lows around 72 near the shore to around 55 near 5000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.

Tuesday: Breezy. Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 87 near the shore to around 74 near 5000 feet. East winds up to 25 mph. Chance of rain 20 percent.

Tuesday Night: Mostly cloudy in the evening then becoming mostly clear. Lows around 72 near the shore to around 55 near 5000 feet. East winds 10 to 15 mph.

Puna

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Numerous showers. Lows around 70 near the shore to around 56 at 4000 feet. Northeast winds up to 10 mph shifting to the northwest after midnight. Chance of rain 70 percent.

Tuesday: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 86 near the shore to 70 to 75 at 4000 feet. Northeast winds up to 15 mph shifting to the east in the afternoon. Chance of rain 70 percent.

Tuesday Night: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows around 70 near the shore to around 56 at 4000 feet. East winds up to 10 mph. Chance of rain 40 percent.

Waikoloa

Tonight: Mostly cloudy with isolated showers in the evening, then partly cloudy after midnight. Lows around 74 near the shore to 53 to 60 above 4000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 87 near the shore to 71 to 77 above 4000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Tuesday Night: Partly cloudy. Lows around 74 near the shore to 53 to 60 above 4000 feet. East winds up to 10 mph.

Detailed Forecast

Synopsis

Locally breezy trades will strengthen slightly during mid-week as they focus clouds and showers over windward and mauka areas. It could get particularly windy and wet across portions of the state over the weekend, depending on the track and development of Invest 90E, which currently resides well southeast of the island chain.

Discussion

Afternoon visible imagery shows a band of showery low clouds streaming onshore over windward portions of Oahu through Maui where mostly cloudy conditions and scattered showers have persisted into the afternoon. Similar to last night, this activity will expand in coverage and may see a slight boost in intensity with the onset of the favorable nocturnal period this evening. Showers have likewise developed over upslope portions of Leeward Big Island and will dissipate in the next couple of hours as diurnal heating is lost. Satellite trends support indications from the guidance that moisture will remain relatively deep through tonight leading to high confidence in rainfall over windward and mauka zones again overnight into Tuesday morning and little change overall through tomorrow.
Ridging downstream of the islands has generated an extensive dry mid- level airmass that will advect into the region during mid-week. This will cap deeper showers and cause the inversion to strengthen once more. Showers are therefore expected to decrease in coverage and intensity during this time. Trades become breezy during the latter half of the week as Invest 90E tracks west and surface high pressure settles along/north of 30N. Slightly deeper moisture north of Invest 90E is modeled to peel off in the trades and usher in a slightly wetter period Thursday night into Friday. The official forecast handles this brief uptick in trade wind showers well with no adjustments to the forecast needed.
Attention then turns to the track and evolution of Invest 90E, the center of which sits near 10N/138W at press time. A second circulation is noted just to its northeast, near 13N/131W. The interplay between these features is key to the current model solutions which remain highly uncertain given that an organized tropical system has yet to emerge from this rather broad area of interest. As such, it is reasonable to expect some fluctuation in modeling outcomes as the system takes shape in reality during the next few days. The potential does exist for conditions to be quite windy this weekend in addition to a concurrent flooding threat for a portion of the area – as alluded to above, this will be entirely dependent upon the eventual track. The Central Pacific Hurricane Center is closely monitoring Invest 90E, so stay tuned for updates during the next several days.

Aviation

This afternoon, moderate to locally breezy trade winds are prevailing across the island chain. Satellite and radar imagery shows that clouds and some light showers embedded within the trades are moving into windward slopes and coasts this afternoon, particularly for Maui where a band of clouds extends upstream. Additionally, afternoon convection across the leeward slopes of the Big Island have also been producing some localized showers there as well.
Tonight, expect that clouds and shower coverage will increase once again across the north through east sections of the islands. Winds will remain moderate to locally breezy, and will begin to increase a bit again on Tuesday.
There are currently no AIRMETs in effect, but AIRMET Sierra for tempo mountain obscuration will be possible this evening or tonight as windward showers and clouds increase. Additionally, AIRMET Tango may be needed to account for moderate low level turbulence downwind of the terrain of all islands by early Tuesday.

Marine

Fresh to strong easterly trade winds will continue through Tuesday, then become strong for most waters beginning around Wednesday as high pressure builds to the north. The Small Craft Advisory (SCA) in place for the typical windier waters/channels around Maui County and the Big Island will likely persist for much of the week, so have extended it out another 24 hours through Wednesday afternoon. The SCA will likely become expanded to most waters Wednesday through the second half as trades increase further. The National Hurricane Center in Miami, Florida is forecasting a high chance of tropical cyclone development in the eastern Pacific over the next couple of days, that could enter the Central Pacific well southeast of the Hawaiian waters later in the week. Upcoming forecasts across the Hawaiian waters will highly depend on how this development evolves over the next several days.
Surf along south facing shores will continue to climb tonight as a long-period south-southwest swell steadily builds. The nearshore buoys at Lanai and Barbers Point reflect this with 3 to 4 ft swell heights in the 15 to 19 second bands this afternoon. Based on the peak at the Samoa buoy back on Thursday, expect a local peak tonight and Tuesday, likely coming in just below the advisory level. A downward trend will follow through the second half of the week.
Surf along north and west facing shores will trend up Wednesday as a long-period west-northwest swell arrives from former Typhoon Ampil, now tracking northeastward over the far northwest Pacific. This should peak Wednesday through Thursday, then ease by next weekend.
Surf along east facing shores will remain small through Tuesday, then trend up Wednesday through the rest of the week as the trades increase locally and far east of the islands.
Due to the current water levels still running a half to three- quarters of a foot above predictions, minor tidal flooding is still possible again Tuesday afternoon despite the start of a slight downward trend. Therefore, the Coastal Flood Statement will be extended through Tuesday afternoon to cover the mid-afternoon high tide.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Tuesday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov