Hilo

Tonight: Mostly cloudy with frequent showers. Lows 65 to 72 near the shore to around 59 at 4000 feet. North winds up to 10 mph. Chance of rain 90 percent.

Wednesday: Partly sunny. Scattered showers in the morning, then numerous showers in the afternoon. Highs 79 to 88 near the shore to around 68 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 70 percent.

Wednesday Night: Mostly cloudy. Frequent showers in the evening, then numerous showers after midnight. Lows 65 to 73 near the shore to 57 to 62 at 4000 feet. Northeast winds up to 10 mph in the evening becoming light. Chance of rain 80 percent.

Kona

Tonight: Mostly clear. Lows around 75 near the shore to 50 to 56 near 5000 feet. North winds up to 10 mph.

Wednesday: Sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 83 to 89 near the shore to around 68 near 5000 feet. Light winds. Chance of rain 50 percent.

Wednesday Night: Mostly clear. Isolated showers in the evening. Lows around 76 near the shore to around 54 near 5000 feet. Light winds. Chance of rain 20 percent.

Waimea

Tonight: Mostly cloudy with numerous showers. Lows 65 to 73 near the shore to 58 to 65 near 3000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Wednesday: Breezy. Mostly cloudy with numerous showers. Highs 64 to 85. East winds up to 20 mph. Chance of rain 70 percent.

Wednesday Night: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows 65 to 73 near the shore to 58 to 66 near 3000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

Kohala

Tonight: Mostly cloudy with numerous showers. Lows 65 to 73 near the shore to 58 to 65 near 3000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Wednesday: Breezy. Mostly cloudy with numerous showers. Highs 64 to 85. East winds up to 20 mph. Chance of rain 70 percent.

Wednesday Night: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows 65 to 73 near the shore to 58 to 66 near 3000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

South Big Island

Tonight: Mostly clear. Breezy. Lows around 75 near the shore to around 55 near 5000 feet. Northeast winds up to 20 mph.

Wednesday: Breezy. Sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs around 87 near the shore to around 70 near 5000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Wednesday Night: Mostly clear. Isolated showers in the evening. Lows around 76 near the shore to around 56 near 5000 feet. East winds 10 to 15 mph shifting to the northeast after midnight. Chance of rain 20 percent.

Puna

Tonight: Mostly cloudy with frequent showers. Lows 65 to 72 near the shore to around 59 at 4000 feet. North winds up to 10 mph. Chance of rain 90 percent.

Wednesday: Partly sunny. Scattered showers in the morning, then numerous showers in the afternoon. Highs 79 to 88 near the shore to around 68 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 70 percent.

Wednesday Night: Mostly cloudy. Frequent showers in the evening, then numerous showers after midnight. Lows 65 to 73 near the shore to 57 to 62 at 4000 feet. Northeast winds up to 10 mph in the evening becoming light. Chance of rain 80 percent.

Waikoloa

Tonight: Mostly clear. Scattered showers in the evening. Lows around 76 near the shore to 54 to 59 above 4000 feet. North winds up to 10 mph in the evening becoming light. Chance of rain 50 percent.

Wednesday: Sunny in the morning then becoming partly sunny. Scattered showers. Highs 85 to 90 near the shore to 66 to 74 above 4000 feet. Northwest winds up to 10 mph. Chance of rain 50 percent.

Wednesday Night: Mostly clear. Scattered showers in the evening. Lows around 77 near the shore to around 57 above 4000 feet. North winds around 10 mph shifting to the east after midnight. Chance of rain 50 percent.

Detailed Forecast

Synopsis

High pressure far north of the state will maintain a more typical moderate to locally breezy trade wind pattern over the next several days, with an uptick in windward and mauka showers expected tonight through the rest of the week. Tropical Cyclone Gilma will weaken as it approaches later this week and bring the potential for more rain.

Discussion

Typical summertime trade wind weather returned today. Radar and satellite imagery show a few low clouds and isolated showers moving into windward and mauka areas on the trades this afternoon, along with some clouds building up over leeward areas on the Big Island and Maui. Trades will remain moderate to locally breezy through much of the week with high pressure centered over the northeast Pacific and extending down and across the Central Pacific.
This dry trade wind pattern won't last much longer. CIMSS MIMIC precipitable water satellite imagery shows a thin dry slot moving across the state this afternoon between moisture that's clearing out behind Hone and another moisture plume that's extending well out ahead of rapidly weakening Tropical Storm Gilma, now in the Central Pacific. This new batch of moisture will bring a wetter trade wind pattern starting tonight with heavier showers impacting mainly windward and mauka areas, especially during the overnight to early morning hours.
Gilma will continue to weaken and become a tropical depression as it approaches the main Hawaiian Islands and encounters a combination of cooler waters and increasing wind shear. Local impacts will depend on Gilma's track, but will likely be minimal. The strongest winds (around 30 kts or less) are expected to remain offshore as Gilma approaches the islands and winds will actually weaken and possibly take on a more southeasterly component across land areas Friday night into Saturday. A more southerly track would bring a greater probability of wet trade wind weather. Given the uncertainty in Gilma's track, timing of the heaviest rainfall is a little uncertain, but is currently looking like it will be Thursday evening through Saturday morning. Even so, rainfall totals are looking rather insignificant with windward areas currently expected to receive up to 1 to 3 inches of rain during the Thursday evening through Saturday morning period.
Finally for the last current tropical cyclone of interest in the eastern Pacific, remnants of Tropical Storm Hector will follow closely behind Gilma as a weak surface trough with a diffuse moisture plume sometime Saturday night into Sunday. Little to no impacts are expected from Hector at this time.
Heading into Sunday and early next week, moderate to breezy trades will return, with less moisture to work with compared to this week.

Aviation

Expect a trade wind distribution of clouds and showers across the islands, with both favoring windward areas. Brief MVFR conditions may occur in passing showers. TAF sites will be predominantly VFR. No AIRMETs are in effect and none are expected through tonight.

Marine

Trade winds will continue easing into the moderate to locally fresh category tonight as Tropical Storm Hone continues to move away from the region to the west. Based on an ASCAT pass from earlier today and observations this afternoon, the Small Craft Advisory that was previously in effect has been cancelled. These moderate to fresh winds will remain in place through Thursday. Attention will then turn to the remnants of what is currently Tropical Storm Gilma, which will approach the Hawaiian coastal waters by Thursday night. The latest advisory from the Central Pacific Hurricane Center depicts Gilma becoming post-tropical and passing just north of the islands Friday into the weekend. In this scenario, local winds could become light and variable near the end of the week. Note that any deviation in the forecast track could impact winds and waves across the Hawaiian nearshore waters this weekend.
Although easterly trades are weakening across the region, surf along east facing shores will trend upward by early Wednesday as a medium- period easterly swell from Gilma begins to fill in.
Surf along south facing shores will generally hold through tonight due to a combination of a small south swell and some residual short- to medium-period south-southeast swell that was generated by Hone that is quickly declining. A downward trend back to the summertime average is expected during the second half of the week.
Surf along north and west facing shores will remain near the seasonal average this week, but could slightly rise later this week for north facing shores as Gilma approaches the region and a small northwest swell fills in.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov