Area Forecast Discussion
Issued by NWS Honolulu, HI

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000
FXHW60 PHFO 230653
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
855 PM HST Sun Jan 22 2017

.SYNOPSIS...
Winds over the islands will subside as a strong high northeast of
the area moves away to the east and weakens. A ridge extending west
from the high will maintain moderate trade winds through mid-week.
The trades will focus clouds and showers over mainly windward areas.
Later in the week the ridge will shift south near the islands as a
front approaches from the northwest. The ridge will bring light
winds and dry weather. A band of showers along a new front will move
across the islands next weekend. Trade winds will return early next
week as a new high moves east behind the front.

&&

.DISCUSSION...
An east to west band of showery low clouds associated with a
dissipating front is forecast to remain nearly stationary south of
the Big Island. A 1031 mb surface high 765 miles northeast of
Honolulu is forecast to move east at 15 to 20 mph over the next few
days. The high will maintain breezy trade winds over the islands
overnight. Rainfall will remain light over most areas, but clouds on
the north edge of the frontal band will keep the windward sides of
the Big Island and Maui rather showery overnight.

As the high moves east, a front about 1050 miles northwest of
Honolulu will move southeast toward the islands. Winds over the
islands will steadily subside as the high moves away and the front
approaches. Moderate trade winds will prevail through mid-week. The
trades will carry some showers over windward areas, especially on
the Big Island and Maui, but leeward areas will remain mostly dry.

The front will stall north of the islands and a surface ridge north
of the islands will shift south near the islands on Thursday. Winds
over the area will weaken and shift out of the southeast. The low-
level flow will be partly blocked by the Big Island and daytime sea
breezes and nighttime land breezes will prevail. A ridge aloft will
build eastward over the area and make the atmosphere quite stable,
so rainfall will be minimal.

A new front will move southeast over the islands next weekend,
reaching Kauai Saturday night and moving down to the big Island by
Monday morning. The front is expected to bring widespread showers,
but moisture along the front will likely be too shallow for heavy
rain. A new high will move east behind the front and produce breezy
trade winds early next week.

&&

.MARINE...
A strong high northeast of the area is maintaining strong to
gale force easterly trade winds across Hawaiian waters. While gale
force winds are likely no longer occurring across local waters,
combined seas above 10 ft and winds above 25 kt are. The Gale
Warning for traditionally windy waters will be replaced with a Small
Craft Advisory, which will then cover all Hawaiian waters through
Monday afternoon. Please refer to the latest Marine Weather Message,
MWWHFO, for further details. The Small Craft Advisory will likely
need to be extended in some areas beyond Monday.

The strong trade winds and a short-period north swell have been
producing surf above the High Surf Advisory (HSA) level on east
facing shores of all islands. With the winds and seas shifting out
of the east, surf will be dropping below the HSA threshold on Niihau
and Lanai, since the waves will be blocked by Kauai and Maui. The
HSA will likely stay up through Monday along east facing shores of
the other islands.

A large northwest swell will likely produce surf well above the
advisory threshold along north and west facing shores of the smaller
islands from Tuesday through Thursday morning. Another large
northwest swell may produce advisory-level surf along north and west
facing shores of the smaller islands starting Friday night and
continuing into next weekend.

&&

.AVIATION...
A strong surface high is maintaining strong easterly trade winds
over the main Hawaiian Islands. AIRMET TANGO remains in effect for
moderate turbulence downwind of all of the main Hawaiian Islands and
for STG SFC WIND. The part of the AIRMET for STG SFC WIND will
likely be dropped before midnight. The part of moderate turbulence
may stay up through the night.

A band of showery low clouds associated with a dissipating front
remains just southeast of the Big Island. Clouds on the fringe of
this band are moving over the east sides of Big Island and Maui.
AIRMET SIERRA for mountain obscuration over northern and eastern
slopes of Maui and the Big Island remains in effect. VFR will
prevail elsewhere.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...

High Surf Advisory until midnight HST tonight for east facing shores
of Niihau and Lanai.

High Surf Advisory until 600 PM Monday for east facing shores of
Kauai, Oahu, Molokai, Maui and the Big Island.

Wind Advisory until 1000 PM this evening for all islands except the
summits of Haleakala on Maui and Mauna Kea and Mauna Loa on the Big
Island.

Gale Warning until midnight tonight for the Pailolo and Alenuihaha
Channels, Maalaea Bay and waters south of the Big Island.

Small Craft Advisory until 600 PM Monday for Kauai Northwest Waters-
Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel-Oahu
Windward Waters-Big Island Windward Waters.

&&

$$
DISCUSSION and Aviation...Donaldson
MARINE...Powell



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