359 FXHW60 PHFO 231951 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 951 AM HST Sun Feb 23 2020 .SYNOPSIS... Winds will be generally light today as a front approaches from the northwest. The front will stall and dissipate early this week just north and west of Kauai while a new high passes by far to our north resulting in moderate trade winds returning. Mostly dry weather today will transition into a typical shower pattern favoring windward and mauka areas. A new strong high will build in north of the area toward the end of the week and on into next weekend with trade winds becoming rather windy. An upper trough will also move over the area resulting in a wetter trade wind pattern. && .DISCUSSION... High pressure is centered far northeast of the area with a ridge extending west southwest to a position just north of the state. Meanwhile, a weakening cold front is approaching the area from the northwest. Winds a rather light with sea breeze circulations expected to prevail today across most areas. The airmass is rather dry and stable so just a few showers are expected today mainly over interior areas. The front is forecast to stall just to the north and west of Kauai on Monday, then gradually dissipate on Tuesday. A new high will be passing by far north of the area during that time with light to moderate trade winds returning. Moisture embedded in the trades will provide for some passing showers over windward and mauka areas with a few showers possible over select leeward locations. By Wednesday and Thursday, surface high pressure will be centered far northeast of the area. Aloft, an upper low is expected to be centered several hundred miles east of the Big Island while an upper level ridge axis lies just west of Kauai. Moisture embedded in the trades will provide for passing showers over windward and mauka areas with the trade winds sufficiently strong enough to blow some brief passing showers over leeward areas at times. Models are in good agreement with some changes occurring as we head into next weekend. A new strong high will build in to our north while an upper level trough develops across the area. Trade winds will pick up and become rather windy across some areas. The upper trough will destabilize the airmass especially over the east end of the state. The upper trough is forecast to cut off near the Big Island over the weekend. Thus a windy and rather wet trade wind pattern is setting up for next weekend. Details will be fine tuned as we get closer to the event. && .AVIATION... Most of the area has variable low level winds due to the weakening front to the north of the state. The winds are weak enough to where a daytime sea breeze/nighttime land breeze scenario will be in place through tonight. As the front washes out and high pressure begins to nudge in, expect northerly winds to pick up through the day on Monday, starting with Kauai, then moving southeast. Therefore, the winds are not much of a factor. Due to the sea breezes, there is a chance of interior showers and some areas of MVFR conditions, especially up against the mountains, but most of the state will have VFR a majority of the time through this forecast period. There are no AIRMETs currently in effect. && .MARINE... Have cancelled the Small Craft Advisory (SCA) for the remaining waters with the morning package. An overnight ASCAT pass showed winds below SCA levels over the area, and the small area of 10 ft seas to the northeast of the Big Island early should be on the decline. SCA level winds are expected once again Monday night, with SCA level seas filling in on Tuesday. The ridge to the north of the islands this morning will be pushed closer or over the islands later today as a front to the northwest moves to the east. The front is expected to stay north of the islands, but light winds will continue through tonight. High pressure will strengthen north of the islands starting Monday, allowing trade winds to increase. As mentioned above, SCA level winds are expected to enter the typically windier areas near Maui County and the Big Island, as well as some additional nearby waters, as early as Monday night. Winds are expected to strengthen further through the week, so expect additional coastal waters to be under a SCA by the end of the week. The current northwest swell will gradually lower through Monday. A large northwest swell is expected to arrive Monday night, with seas reaching SCA levels filling in on Tuesday. The surf from this swell is expected to peak Tuesday well above advisory levels, and could reach warning levels for north and west facing shores. It will then gradually subside through Thursday, with a new northwest swell arriving. This new swell will peak Thursday night and Friday near advisory levels, before gradually decreasing next weekend. Surf along the east showers will be trending up this week as the trades increase, and may reach advisory levels by the end of the week. && .HFO WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Burke AVIATION...Chevalier MARINE...M Ballard |