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FXHW60 PHFO 280138

Area Forecast Discussion
National Weather Service Honolulu HI
338 PM HST Mon Mar 27 2017

A ridge will remain north of the state through Thursday night and
will drive moderate east to southeast flow across the state. A
trough aloft will dig east of the island chain Tuesday night and
will bring more windward showers to the state during the second
half of the work week. A prefrontal band of showers may impact the
state Thursday night and Friday, but the front is not expected to
reach the state. A strong high will set up northeast of the state
and bring windy conditions this weekend.


A 1031 mb surface high lies about 1750 miles northeast of
Honolulu, with a surface ridge extending southwest from the high
and passing 375 miles north of Honolulu. The ridge will remain
nearly in place through Thursday night and drive moderate east to
east southeast winds across the state through then.

A ridge aloft will remain over the main Hawaiian islands through
tomorrow night. The ridge will keep the atmosphere dry and stable,
so rainfall will remain light. Models show an increase in
precipitation arriving early Wednesday morning as an upper trough
digs in east of the state on Tuesday night. The trough will
enhance the moisture tracking in from upstream and will bring
relatively wetter trade wind weather during the second half of the
week. Winds will focus most of the precipitation over windward and
southeast facing slopes. Leeward areas may see a few passing
showers at times.

The ridge to our north will slide away to the east Thursday night
as a cold front approaches from the west. The front will stall out
Friday night and a building high to the north over us will force
the front away from us before impact. However, a prefrontal band
of showers will form out of the lingering moisture brought in with
the trade winds and set up over the state Thursday night and
Friday. A drier airmass will settle in over the state by midday

The aforementioned high pressure system to the north is forecast
to strengthen to about 1037 mb this weekend. Subtropical highs at
this strength typically produce some windy conditions across the
Hawaiian Islands. The atmosphere will stabilize this weekend with
typical windward and mauka showers moving in with the trades.


A stable trade wind flow will produce isolated MVFR ceilings along
windward terrain. VFR will dominate elsewhere. An inversion will
remain in place around 5000 ft with moderate E to ESE winds up to
20 kt at low levels. No AIRMETs in effect.


The current west-northwest swell continues to bring advisory
level surf to various north and west facing shores exposed to the
swell. The nearshore buoys have been a bit slow to decline, so
have extended the High Surf Advisory through tonight. Will monitor
the buoys overnight to see if the advisory can be dropped by
morning. However another bump is expected to arrive Wednesday,
which could bring surf back to advisory levels. 

The swell is keeping seas at or above 10 ft in many areas, and
some areas, particularly in the typically windier locations near
Maui and the Big Island, have winds in excess of 25 kts. The Small
Craft Advisory for many zones has been extended through the night.
Expect more areas to drop out of the SCA tomorrow as the seas and
winds subside.

Surf along east facing shores will remain small and choppy
through the week due to moderate trade winds. A long period south
swell is expected to bring a bump to south facing shores Thursday
through Saturday.

A new, potentially larger, west northwest swell is expected to arrive
Thursday night, peak Friday and then slowly ease over the weekend.
The swell is being generated by a strong low off the coast of
Japan with hurricane force winds. Will be monitoring model runs as
the system evolves.


High Surf Advisory until 6 AM HST Tuesday for north and west
facing shores of Niihau, Kauai, Oahu and Molokai, north facing
shores of Maui, and west facing shores of the Big Island.

Small Craft Advisory until 6 AM HST Tuesday for Oahu Windward 
Waters-Kaiwi Channel-Maui County Windward Waters-Alenuihaha 
Channel-Big Island Windward Waters-Big Island Leeward Waters-Big 
Island Southeast Waters.



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