Hilo

Tonight: Mostly cloudy. Scattered showers in the evening, then scattered showers and isolated thunderstorms after midnight. Lows 66 to 74 near the shore to around 60 at 4000 feet. Northwest winds up to 15 mph in the evening becoming light. Chance of rain 50 percent.

Friday: Partly sunny. Scattered showers and isolated thunderstorms early in the morning, then scattered showers in the late morning and afternoon. Highs 81 to 88 near the shore to around 70 at 4000 feet. South winds up to 10 mph shifting to the southeast in the afternoon. Chance of rain 50 percent.

Friday Night: Mostly cloudy with scattered showers. Lows 66 to 73 near the shore to around 59 at 4000 feet. South winds up to 10 mph in the evening becoming light. Chance of rain 50 percent.

Kona

Tonight: Partly cloudy. Numerous showers and slight chance of thunderstorms early in the evening. Lows around 75 near the shore to around 55 near 5000 feet. Light winds. Chance of rain 60 percent.

Friday: Mostly sunny in the morning then becoming partly sunny. Scattered showers until late afternoon. Isolated thunderstorms in the afternoon. Numerous showers late in the afternoon. Highs around 87 near the shore to around 69 near 5000 feet. Light winds. Chance of rain 70 percent.

Friday Night: Mostly clear. Numerous showers and isolated thunderstorms early in the evening. Lows around 75 near the shore to 51 to 56 near 5000 feet. Northeast winds up to 10 mph. Chance of rain 70 percent.

Waimea

Tonight: Slight chance of thunderstorms early in the evening. Showers through the night. Isolated thunderstorms after midnight. Lows 66 to 74 near the shore to 59 to 67 near 3000 feet. Northeast winds up to 10 mph shifting to the west after midnight. Chance of rain near 100 percent.

Friday: Showers and isolated thunderstorms early in the morning, then numerous showers in the late morning and afternoon. Isolated thunderstorms in the afternoon. Highs around 81 near the shore to 69 to 80 near 3000 feet. Southwest winds up to 10 mph in the morning becoming light. Chance of rain near 100 percent.

Friday Night: Mostly cloudy. Numerous showers and isolated thunderstorms early in the evening. Lows 66 to 74 near the shore to 59 to 65 near 3000 feet. Light winds becoming southeast up to 10 mph after midnight. Chance of rain 70 percent.

Kohala

Tonight: Slight chance of thunderstorms early in the evening. Showers through the night. Isolated thunderstorms after midnight. Lows 66 to 74 near the shore to 59 to 67 near 3000 feet. Northeast winds up to 10 mph shifting to the west after midnight. Chance of rain near 100 percent.

Friday: Showers and isolated thunderstorms early in the morning, then numerous showers in the late morning and afternoon. Isolated thunderstorms in the afternoon. Highs around 81 near the shore to 69 to 80 near 3000 feet. Southwest winds up to 10 mph in the morning becoming light. Chance of rain near 100 percent.

Friday Night: Mostly cloudy. Numerous showers and isolated thunderstorms early in the evening. Lows 66 to 74 near the shore to 59 to 65 near 3000 feet. Light winds becoming southeast up to 10 mph after midnight. Chance of rain 70 percent.

South Big Island

Tonight: Partly cloudy. Numerous showers and slight chance of thunderstorms early in the evening. Lows around 76 near the shore to around 57 near 5000 feet. West winds up to 10 mph. Chance of rain 60 percent.

Friday: Sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 86 near the shore to around 69 near 5000 feet. Light winds becoming southeast 10 to 15 mph in the afternoon. Chance of rain 70 percent.

Friday Night: Mostly clear. Scattered showers early in the evening. Lows around 76 near the shore to around 55 near 5000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Puna

Tonight: Mostly cloudy. Scattered showers in the evening, then scattered showers and isolated thunderstorms after midnight. Lows 66 to 74 near the shore to around 60 at 4000 feet. Northwest winds up to 15 mph in the evening becoming light. Chance of rain 50 percent.

Friday: Partly sunny. Scattered showers and isolated thunderstorms early in the morning, then scattered showers in the late morning and afternoon. Highs 81 to 88 near the shore to around 70 at 4000 feet. South winds up to 10 mph shifting to the southeast in the afternoon. Chance of rain 50 percent.

Friday Night: Mostly cloudy with scattered showers. Lows 66 to 73 near the shore to around 59 at 4000 feet. South winds up to 10 mph in the evening becoming light. Chance of rain 50 percent.

Waikoloa

Tonight: Partly cloudy. Numerous showers and slight chance of thunderstorms. Lows around 77 near the shore to around 59 above 4000 feet. East winds up to 10 mph in the evening becoming light. Chance of rain 70 percent.

Friday: Partly sunny. Numerous showers in the morning. Isolated thunderstorms through the day. Showers in the afternoon. Highs 84 to 90 near the shore to 67 to 74 above 4000 feet. West winds up to 10 mph. Chance of rain 80 percent.

Friday Night: Partly cloudy. Showers and isolated thunderstorms early in the evening. Lows around 77 near the shore to around 57 above 4000 feet. Light winds. Chance of rain 80 percent.

Detailed Forecast

Synopsis

Tropical Depression Gilma will bring a period of wet trades to the area tonight through Friday night. Moderate trades then fill in for the weekend.

Discussion

Muggy conditions across the state this afternoon as dewpoints range from around 70 in the driest leeward locales to the mid to upper 70s windward, including 77 at Hilo and 79 degrees at Hana earlier this afternoon. The airmass in place in advance of Tropical Depression Gilma has already demonstrated a tendency to support widespread showers, some locally heavy, courtesy of deep saturation and a weakened inversion. The approach of TD Gilma now adds to the tropical character of the island airmass, sending PWATs north of 2″ in some cases and pushing dewpoints in favored windward locations close to 80F at times. Cyclonic NE flow will continue through tonight in advance of TD Gilma, whose southern half will scrape the islands during the next 36 hours. During this time, saturation through at least the lowest 10kft will foster increasingly widespread trade wind showers, some of which will be locally heavy, mainly windward and mauka. The weakened inversion and relatively deep moisture field will also be favorable for allowing showers to penetrate leeward. At this time, the heaviest rainfall is expected over Windward Maui and the Hamakua Coast of the Big Island tonight, Oahu Friday into Friday night, and Lihue on Friday night. A general 1-3″, locally higher, is forecast. The highest amounts will focus over windward and mauka areas.
A corridor of moist S/SE flow will trail TD Gilma and is modeled to become established over central portions of the state on Friday night. In this scenario, scattered showers would lift northward over leeward areas throughout the night bringing additional pockets of locally heavy rainfall. However, this outcome will be highly dependent upon the track of Gilma. Any northward adjustment threatens to cut off winds altogether leading to a land breeze scenario and dry conditions on one or more islands. Finally, it is worth noting that the South Hilo and Puna Districts will remain rather dry throughout this time as increasingly NNE flow will focus orographic effects along the Hamakua Coast, leaving little opportunity for meaningful rainfall over the remainder of the Big Island's windward coastline.
Moderate ESE trades fill in behind Gilma and characterize the weekend weather. Breezy trades and a wetter variety of trades take shape late Sunday into Monday the remnant moisture field from former Tropical Cyclone Hector drifts over the area.&&
.AVIATION…
Gilma continues to weaken as it approaches the Hawaiian waters from the east. This system will be more of a low cloud and rain threat for aviation as it tracks just north of the Hawaiian Islands tonight through Friday. Isolated thunderstorms are also possible mainly near the low center and over interior Big Island.
Broad high pressure far north of the Hawaiian Islands will keep moderate to locally breezy trade winds blowing across the region through this evening. Weaker winds will fill in across the islands from east to west tonight through Friday as Gilma's weakening circulation center passes along the far northern edge of the coastal waters. Deeper moisture levels will enhance showers mainly over windward and mountain areas tonight through Friday as well. Periods of MVFR conditions are expected along with these showers. Otherwise, mostly VFR conditions will prevail.
There are currently no AIRMETs in effect. However, AIRMET Sierra for tempo mountain obscuration is likely later this evening through much of the day Friday as low clouds and showers increase from Gilma's moisture.

Marine

Tropical Depression Gilma, now centered roughly 150 nm east- northeast of Hilo, will weaken into a remnant low or trough as it passes just north of the islands late tonight through Friday night. A small area of fresh to strong easterly winds will persist along the northern portion of the circulation of Gilma and affect outer areas of windward waters. Elsewhere, trade winds will decline to gentle to moderate strength and turn northerly ahead of Gilma, then switch out of the southeast to south after the circulation passes by. Heavy showers and isolated thunderstorms may develop near Gilma as it moves through. Southeasterly winds will slowly build and become more easterly on Saturday, followed by moderate to locally strong easterly trade winds Sunday through Tuesday. Trades may diminish during the middle of next week.
Surf along east facing shores of Oahu and Kauai could remain slightly elevated for Oahu and Kauai into Friday as short to medium period swell from Gilma moves through. For the rest of the islands, surf along east facing shores will diminish late tonight and Friday. Returning trade winds will produce moderate east shore surf Sunday into early next week.
Generally small surf will prevail on other shores. A small south swell will fade tonight, followed by small background swells from the south and southeast through the rest of the week. A small northwest swell will arrive late tonight and Friday, then diminish during the weekend.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov