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Hawaiian Islands Synoptic Discussion and Guidance |
FXHW60 PHFO 240152
Area Forecast Discussion
National Weather Service Honolulu HI
352 PM HST Sun Feb 23 2020
Winds will be light through tonight as a front approaches from
the northwest. The front will stall and dissipate Monday and
Tuesday just northwest of Kauai while a new high system passes by
far to our north, resulting in moderate trade winds returning.
Mostly dry weather today will transition into a typical trade wind
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.
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 are rather light with sea breeze circulations
expected to transition to land breezes across most areas
overnight. The airmass is rather dry and stable so just a few
light showers are expected through tonight.
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
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 some 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.
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 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.
The morning ASCAT pass continued to show winds below Small Craft
Advisory (SCA) around the islands. Some minor changes were made to
the swells and related grids to be in line with the latest NWPS
A front is expected to stall northwest of Kauai tonight, with
light winds remaining over the region. High pressure will
strengthen north of the islands starting Monday, allowing trade
winds to increase. 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 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
Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office