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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
    High pressure far northeast of the state will maintain moderate to locally fresh trade winds across the islands. Showers carried by the trades will affect mainly windward and mauka areas for the next several days. A surge in moisture from the southeast could bring an increase in showers and more humid conditions late in the week.

  • Discussion
    Water vapor imagery shows an upper level trough north of the state, with a ridge to the southeast. At the surface, high pressure is located far northeast of the state, with a trough far to the north. 12Z soundings from Lihue and Hilo show inversions of 5-6kft and precipitable waters of 1.3-1.4 inches, which is normal for this time of year. Early morning mimic total precipitable water imagery shows drier air over 100 miles east of the Big Island extending well to the east and northeast. Rainfall amounts have been on the low side overnight. A few locations on windward Big Island received up to a tenth of an inch of rain in the last 12 hours, but most locations that saw rain only received a few hundredths. One more pocket of moisture is located east of the Big Island and Maui that will keep showers going into early afternoon, at least across the eastern islands. However drier low-level air will spread across the state during the afternoon/evening, leading to drier conditions later in the day. The surface high will remain nearly stationary far northeast of the state through much of the week. While the high does not strengthen, we are already starting to see a tightening of the pressure gradient across the islands due to low pressure well to our south. Overall we expect a typical trade wind setup with showers focused mainly across windward and mauka areas, at least for the first half of the week. Gfs forecast soundings show inversion heights dipping even lower for the next day or two. With no noticeable sources of moisture immediately upstream, this will help to limit rainfall chances for the next couple days. Winds may be locally breezy at times. By the end of the week, we may see a surge in tropical moisture from the southeast that could bring an increase in showers and muggy conditions. Extended models over the last few days have been back and forth with timing and how far north to bring the moisture, so it is difficult to nail down specifics at this point. However, they seem to be converging on a solution that would bring an increase in tropical moisture to Big Island late thursday/friday, and spread across the rest of the state through the weekend.

  • Aviation
    Morning showers linger over windward Big Island, bringing tempo MVFR cigs and isol MVFR vis to PHTO. Vfr should begin to prevail by this early this afternoon for windward Big Island. All other terminals continue with prevailing VFR conditions. Passing showers embedded within the trade wind flow may bring isol MVFR cigs throughout the day, mainly for windward and mauka areas. Early morning soundings from both sites show an inversion between 5.5-6.5 kft. With the moderate trades expected to increase slightly and the inversion, an airmet for turb in the lee of the terrain may be necessary later today. Otherwise, no other airmets are expected.

  • Marine
    An ascat pass last night showed a wide area of 25 knot winds through the Alenuihaha channel. Models show the gradient continuing to tighten over the next couple days as low pressure passes far south of the area. Therefore the current small craft advisory for the typically windier areas near Maui and the Big Island will likely remain in effect at least through Wednesday. A series of small southerly swells may bring minor bumps on south facing shores, with a slight increase on Thursday night. Short period trade wind swell will continue across east facing shores, possibly increasing a bit in the coming days as trades strengthen. No other significant swells are expected through the next several days.

  • HFO Watches/Warnings/Advisories
    Small craft advisory until 6 pm HST Wednesday for Maalaea Bay, Pailolo and Alenuihaha channels, Big Island leeward and southeast waters.

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