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Home News Hawaii Area Forecast Hawaii Area Forecast
Hawaii Area Forecast
Area Forecast Discussion for Hawaii
Area Forecast Discussion for Hawaii

Area Forecast Discussion for Hawaii
  • Synopsis
    A very humid and unstable air mass will support spotty, but locally heavy, showers and thunderstorms into the weekend. Weak trade winds and somewhat more stable conditions will spread from the east on Friday and Saturday, though the weather will remain hotter and more humid than usual. Prevailing winds will diminish into next week, leading to stagnant conditions and increased afternoon showers again.

  • Discussion
    Although precipitable water was down slightly from the insane amounts earlier in the week, especially over Kauai county, slight convergence in the weak southeast surface flow around the state continued to encourage convection. A shallow mid-level trough extending southeast over the islands from tropical cyclone Ignacio, and afternoon sea breezes, also contributed. Thunderstorms over the Big Island should diminish into the evening, and those over the Maui county windward waters may well move north out of the coastal waters, but showers likely will remain active more generally through the night. Another convective surge, followed by a gradual decrease into the evening, will occur as sea breezes become important again on Thursday. By Friday, a shift in the pattern of tropical cyclones driving regional weather may bring a noticeable change. Although tropical cyclone Jimena will remain far enough away not to affect the islands directly, a swath of northeast winds will extend past the north edge of the storm and over the state. Guidance predicted fairly modest wind speeds, but they stand a good chance of being stronger than the current prevailing flow. This period of trade winds will end by Sunday night once Jimena moves far enough north, leaving feeble northerlies in place, but a number of solutions predicted a slightly drier air mass to reach the islands in the meantime. Stagnant flow into next week will permit evaporation to moisten the air mass again, and diurnal effects will prevail. Conditions during the latter part of next week depended heavily on the precise track of Jimena.

  • Aviation
    See tc sigmet series tango for tropical cyclone Ignacio, located about 375 miles north of Lihue as of 5 pm Wednesday afternoon. A moist and unstable airmass will remain in place across Hawaii overnight and Thursday. Showers and thunderstorms are already diminishing with loss of daytime heating across the Big Island and Maui. However, the potential for locally heavy showers and isolated thunderstorms will linger overnight across Molokai and Oahu, shifting westward toward Kauai late tonight into Thursday, as a low level convergence band moves slowly west across the state. Any thunderstorms are likely to carry CB tops up to fl450, MVFR to isol IFR conditions, and the possibility of icing and turb. A seabreeze pattern will prevail across the state once again on Thursday, with scattered showers and isolated thunderstorms developing across the islands due to daytime heating. Mvfr and isolated IFR conditions will be possible. Airmet sierra for mountain obscuration remains for sections of the Big Island. This airmet will be cancelled later this evening as conditions improve. However, additional airmets for mountain obscuration may be needed across the central islands overnight.

  • Marine
    A high surf warning remained in effect for east-facing shores of most islands. The large surf was due to a mix of declining northerly swell from Ignacio, and a building east swell from distant hurricane Jimena. The Ignacio swell still was largest across Kauai and Oahu, but will be dropping off significantly. Surf along east-facing shores will approach warning levels tonight, and was expected to rise again on Thursday. Even if the swell drops slightly, east-shore surf will remain near warning levels through at least the weekend, and likely into early next week. The high surf warning probably will need extension beyond Thursday afternoon. A small craft advisory also remained in effect through Friday afternoon for hazardous seas produced by the swells from Ignacio and Jimena. Winds are expected to remain below advisory levels this week. Long-period swells from the south-southwest may produce advisory-level surf along south-facing shores this weekend. Please refer to the latest collaborative nearshore swell and wind forecast /srdhfo/ for more details on the swells.

  • HFO Watches/Warnings/Advisories
    High surf warning until 6 pm HST Thursday for Kauai windward, Oahu Koolau, olomana, Molokai, Maui windward west, Maui central valley, windward Haleakala, south Big Island, Big Island north and east. Small craft advisory until 6 pm HST Friday for Kauai northwest waters, Kauai windward waters, Kauai channel, Oahu windward waters, Kaiwi Channel, Maui county windward waters, Pailolo channel, Alenuihaha channel, Big Island windward waters, Big Island southeast waters.

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    DISCUSSION/MARINE...RYSHKO AVIATION...JACOBSON