Area Forecast Discussion
Issued by NWS Honolulu, HI

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FXHW60 PHFO 221949

Area Forecast Discussion
National Weather Service Honolulu HI
949 AM HST Wed Mar 22 2017

A stable and rather dry trade wind weather pattern will prevail
through early Friday, with low clouds and brief trade showers
confined primarily to windward facing slopes of some of the
islands. A slight increase in trade wind speeds and windward
rainfall is expected from late Friday through this weekend.


A 1026 mb high remains to the northeast of the islands, with trade
winds expected through tonight. There is good agreement between
the models with high pressure remaining the dominant feature over
much of the upcoming week.

A relatively dry and stable airmass currently over the islands is
resulting in few showers, and this pattern is expected to continue
over the next few days. Satellite derived precipitable water (PW)
values are around 1 inch over and near the islands, which matches
well with the overnight soundings. The satellite PW does show a
band of increased moisture to the north of the islands, associated
with a cold front. The models are in good agreement with the front
passing north of the islands over the next couple of days.

As the front passes north of the islands, the ridge will shift
closer to the islands, resulting in some east-southeast to
southeast flow. Some increased low moisture is expected to ride
in on these winds, so we could see a few more showers,
particularly over Maui County and the Big Island for the end of
the week, although rainfall totals are expected to remain low.

A new high replaces the current on by Saturday, with another high
moving north of the islands Sunday. This high will help to
bring some trade winds for the start of the new week. That high
will move to the northeast with winds once again becoming a bit
east-southeast to southeast with some increase in showers.


A front passing far north of the state will push the trade wind
driving high pressure system temporarily away from our area. The
result will be east southeast flow over the western end of the
state and easterly winds across Maui County and Big Island. VFR
conditions expected today, with possibly some clouds and showers
moving onto windward Big Island and Maui tonight. MVFR conditions
may be possible over these windward sections tonight within

No AIRMETs are in effect at this time.


A 1026MB surface high is located 1000NM northeast of Hilo with a
surface ridge trailing west from the high to about 235NM north of
Kauai. The pressure gradient south of the ridge has been producing
winds reaching the Small Craft Advisory (SCA) threshold of 25Kt over
the windier areas around the Big Island and Maui. The high will move
east at 5Kt and the ridge will weaken over the next couple of days
as two fronts pass north of the area. Winds are expected to drop
below SCA strength this afternoon.

The surface ridge will strengthen again north of the area starting
Friday. Winds are expected to reach SCA strength by Saturday and may
reach near-gale strength around the Big Island and Maui over the
weekend as a new high builds north of the area. Surf along east
facing shores will increase as the trade winds strengthen.

A large storm east of Japan will produce a large west northwest
swell reaching the islands starting Saturday. Surf from this swell
will be well above the advisory threshold through early next week
and may reach warning levels. As this swell subsides next Tuesday,
a new northwest swell is expected to arrive.


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



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