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WindNE 36 mph
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Hawaiian Islands Synoptic Discussion and Guidance

FXHW60 PHFO 260656

Area Forecast Discussion
National Weather Service Honolulu HI
856 PM HST Sat Mar 25 2017

A surface high to the north will move east through Monday, then
become nearly stationary far northeast of the islands. A ridge aloft
will remain over the islands through the middle of next week. By the
end of the week, a trough aloft and a front will approach from the


A 1026 MB high about 850 miles north of Honolulu near 34N 157W is
forecast to move east through the weekend, then become nearly
stationary early next week about 1500 miles northeast of Honolulu
near 35N 135W. A surface ridge extending west from the high will
remain north of the islands through the coming week. The high will
keep breezy trade winds blowing over the islands through the
weekend. A ridge aloft will remain over the main Hawaiian islands
through the weekend keeping the weather quite dry.

A trough aloft will move eastward to the north of the islands on
Monday. The surface high moving away to the east and the trough
aloft passing by will combine to weaken the trade winds Sunday night
through Monday. The trade winds will strengthen again on Tuesday,
but the trades won't get as breezy as they will be over the weekend.
The atmosphere will remain dry and stable through the middle of next
week, so rainfall will remain light.

Toward the end of next week a deep trough aloft and an associated
front will approach from the northwest. The surface ridge will shift
south closer to the islands and the atmosphere will become more
moist and less stable. Showers will likely become more active late
in the week.


Locally strong NE to E winds and a strong and low temperature
inversion will produce conditions favorable for low level
turbulence. AIRMET TANGO will remain up through at least Sunday for
OCNL MOD TURB southwest of the mountains of all island. Clouds and
showers will remain sparse, so VFR ceilings and visibilities will


Hazardous boating and beach conditions will continue into Monday
before trending down into mid week due to a combination of fresh to
strong trade winds and a large west-northwest (WNW; 310 deg) swell
that is currently building down the island chain this evening.
These conditions have led to a Small Craft Advisory for all Hawaiian
waters due to winds (25 to 30 kts, strongest in the channels) and/or
seas (10 ft or greater) through Sunday night. The large WNW swell
will generate life-threatening surf along exposed north and west
facing shores into Monday before slowly trending down into mid week.

A High Surf Warning remains in effect for Niihau, Kauai and the west
facing shores of the Big Island through Sunday night. A High Surf
Advisory remains in effect for exposed coasts on Oahu and the Maui
County islands through Sunday night. If heights climb above
predicted levels overnight, north facing shores of Oahu will need to
be included in the warning later tonight. Advisory-level surf will
likely continue through the day Monday along exposed north and west
facing shores before dipping below criteria.

For the building WNW swell, the latest PacIOOS nearshore buoy
observations are remaining in line with the latest wave model
guidance and are depicting swell heights ranging from seven to eight
feet at the Hanalei and Waimea buoys and down into the two to four
foot range at the Pauwela buoy. There was one random spike recorded
at the Waimea buoy up to 10 ft around 4 pm HST this afternoon, which
is the highest recorded thus far. The offshore buoys northwest of
Kauai are currently recording swell heights between 12 and 14 ft,
which is the predicted peak of this swell event.

Surf along east facing shores will remain small and choppy through
the upcoming week due to moderate to strong onshore winds

Surf along south facing shores could see a slight increase late
tonight through Sunday due to the previously discussed WNW swell
wrapping around the islands. A slight increase in surf along south
facing shores will also become a possibility Thursday through
Saturday due to a long-period swell (190 deg) associated with recent
activity across the southern Pacific.

For the outlook, another large long-period WNW (310 deg) swell will
be possible across the islands Thursday night through the weekend.
The latest deterministic and ensemble guidance remain in decent
agreement over the next few days and depict a storm-force low
developing off the coast of Japan Sunday night into Monday, then
tracking ENE to the Date Line Tuesday night into Wednesday while
intensifying (around 970 mb low). A large batch of gale-to-storm
force westerly winds focused toward the region through this time is
forecast with seas peaking within the 30 to 40 ft range.
Swell across the islands associated with this storm will likely lead
to another period of warning-level surf and advisory-level seas.
More details will follow in later packages this week as this system
evolves and confidence increases with regard to specifics on arrival
times and impacts.


High Surf Warning until 600 AM Monday for north and west facing
shores of Niihau and Kauai and west facing shores of the Big Island.

High Surf Advisory until 600 AM Monday for north and west facing
shores of Oahu and Molokai and north facing shores of Maui.

Small Craft Advisory through 600 AM Monday for all Hawaiian Waters.



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