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Temp8.5 C
RH7 %
WindNNE 19 mph
RoadOpen (4x4)
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Hawaiian Islands Synoptic Discussion and Guidance

FXHW60 PHFO 261933

Area Forecast Discussion
National Weather Service Honolulu HI
933 AM HST Thu May 26 2022

Stable and dry conditions prevail for the next week as trades
focus limited shower activity over windward slopes, mainly
overnight. Trades remain locally breezy through tonight, then
ease slightly during the weekend.



Strong mid-level subsidence and a very dry airmass above 7kft
contribute very stable conditions this morning and for the next
several days. For today, mostly sunny skies will prevail over
leeward zones while locally breezy trades focus shallow, stable
clouds containing little to no rainfall over windward slopes. As the
weekend progresses, the gradient will ease slightly allowing a
hybrid sea breeze pattern to emerge. While this will bring enhanced
cloud cover over the most sheltered leeward areas, high stability
will limit afternoon rainfall potential. At the same time, the band
of cirrus streaming from SW-NE south of the islands at press time
will gradually lift northward coincident a poleward migration of the
subtropical jet. This will in turn bring periods of filtered sun as
the coverage of high clouds expands this weekend. Global models
indicate the return of locally breezy trades early next week and
continuing into the extended. Continued stability will limit any
rainfall potential as the islands remain firmly under the influence
of strong mid-level ridging through the forecast period.



High pressure centered north of the islands, will maintain
moderate to locally breezy low-level trade winds through tonight.
Dry and stable conditions continue across the Hawaiian Islands
underneath a strong low lvl trade wind inversion. This pattern
will focus limited showers toward windward zones. Sea breeze
circulations developing this afternoon will enhance cloud cover
and chances for isolated showers over sheltered leeward interior
areas, especially across the Big Island. The greatest coverage of
lower clouds and trade wind showers, will trend toward late night
and early Friday morning. Mainly VFR conds are expected to
prevail through Friday, however an area of broken SC moving across
the state and trapped under the low lvl inversion, will briefly
generate a period of MVFR cigs today.

Low lvl mechanical turb meeting AIRMET criteria will increase
across portions of the islands today, as locally breezy easterly
trade winds continue through tonight. Additionally, we are
monitoring the possibility of moderate upper level turbulence
developing between FL280/350 over the eastern islands tonight, in
response to a weakly organized sub-tropical jet lifting up toward
the islands.



No changes to the swells and related grids with the morning
package, and not expecting to make any significant changes with
the afternoon package. The including swell is not expected to
reach the buoys until tonight, so will have little in the way of
ground truth until then.

A high pressure ridge north of the main Hawaiian islands will
continue to bring fresh to strong trade winds to the coastal
waters through Friday. A front to the northwest of the ridge is
expected to move to the east, pushing the ridge closer to the
islands, which will result in winds veering to a more east to
southeast direction, and weakening the pressure gradient over the
islands. A Small Craft Advisory (SCA) is in effect for the
typical windier areas near Maui County and the Big Island through
Friday afternoon. With winds expected to decrease this weekend,
the SCA will more than likely be dropped Friday night. The ridge
is expected retreat northward early next week, which will allow
the trades to return, so expect the SCA to be back next week.

An incoming south swell is expected to arrive tonight
(forerunners may show up later today), with another boost coming
Tuesday due to an active pattern near New Zealand. The initial
swell is expected to bring advisory level surf late Friday through
Saturday night. The next swell is currently looking to reach
warning levels late Tuesday through Wednesday.

A small north-northwest well moving through today will maintain
surf along north and west facing shores. Expect this swell to east
later tonight through Friday. A similar northwest swell is
expected by Sunday, which will linger into Monday before easing.

Surf along east facing shores will remain small and choppy through
Friday with the breezy trades in place. A downward trend is
anticipated over the weekend as the winds diminish and shift out
of the east to southeast. As trades rebound next week, expect an
uptick in the east facing surf.


Small Craft Advisory until 6 PM HST Friday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big
Island Southeast Waters.



MARINE...M Ballard

Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office