Weather Service Report


989 
FXHW60 PHFO 162019
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
1019 AM HST Mon Jan 16 2017

.SYNOPSIS...
Trade winds will build from east to west across the state through
Tuesday as a ridge of high pressure pushes slowly north away from
the islands. Limited showers are expected with showers favoring
windward and mountain areas. A change is expected this weekend as
a weak front ushers in strong trade winds and increasing showers.

&&

.DISCUSSION...
Sunny skies prevail across the aloha state this morning with
gentle trade winds blowing over the Big Island and Maui county,
and variable winds over Oahu and Kauai. A ridge of high pressure
sits just north of Kauai and it stretches into the East Pacific.
The ridge is expected to push north slowly over the next few days,
and that movement will allow gentle trade winds to reach Oahu and
Kauai Tuesday and Wednesday. Things will be more breezy over Maui
County and the Big Island with the exiting ridge allowing for
increasing winds. The returning trades will also bring a return
to windward and mauka showers Tuesday and through the week, though
only limited rainfall is expected.

A front will approach the islands from the northwest late in the
week, and it is expected to reach the smaller islands over the
weekend. There will be an uptick in rainfall with the passing of
the front but the most noticeable change will be increasing trade
winds behind the front. A healthy high pressure will drive strong trade
winds across the state Saturday and Sunday with the winds pushing
clouds and showers into windward areas and up the mountain slopes.
Some showers will blow over to leeward locations as well. 

Winds at the Big Island summits increased last night and this
morning, prompting the issuance of a wind advisory. A building
ridge in the mid atmosphere located north of the islands is
responsible for the increasing winds at the summits. The advisory
has been issued through Tuesday, but may need to be extended as
the midlevel ridge remains in place through midweek.

&&

.AVIATION...
Weak trade wind flow this morning will give way to light sea
breezes most areas this afternoon. Patchy clouds and scattered
light showers will favor eastern slopes and coasts through midday
then refocus over island interiors in the afternoon and early
evening hours. Isolated MVFR CIGS expected in passing -shra.
Otherwise, VFR conditions will prevail all areas.

Reports of moderate turbulence have ceased as the subtropical jet
stream aloft has weakened. Expect to cancel AIRMET Tango for upper
level turbulence with the noon issuance.

&&

.MARINE...
A surface ridge currently located about 150 nm N of Kauai will
move slowly north during the next couple of days. Under very
stable conditions, E to ESE trade winds are being accelerated
around the high terrain around the Big Island, where a Small Craft
Advisory (SCA) is in effect near South Point and in the Alenuihaha
Channel. Gentle to moderate ESE winds will continue across the
western half of the state today, followed by increasing E winds on
Tuesday. As the ridge retreats northward on Wednesday, E trade
winds will briefly build over the island chain, which will likely
require an expansion of the SCA. On Thursday and Friday, winds
will decrease as the ridge is weakened by an approaching front.
The front is expected to produce strong NE winds and large, rough,
short-period seas during the weekend, leading to SCA conditions
over all waters.

Moderate WNW swell will continue for the next couple of days. The
next large WNW swell will build late Tuesday night, peak late
Wednesday, then drop to moderate levels by Thursday night. This
swell is expected to be similar to the last large WNW swell from
a couple of days ago. As a result, expect warning level surf on
Wednesday and Wednesday night for most N and W facing shores of
the smaller islands. The Kona coast of the Big Island will also
experience surf near or at the warning level late Wednesday night
and early Thursday. A front expected to move down the island
chain next weekend will likely produce large, rough, short-period
seas from the NE. A High Surf Advisory could be needed for E
facing shores.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 PM HST Tuesday for Alenuihaha 
Channel-Big Island Leeward Waters-Big Island Southeast Waters.

Wind advisory for the Big Island Summits through Tuesday. 

&&

$$

Morrison...Discussion
Wroe...Marine 
Bedal...Aviation

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Western Regional Climate Center, wrcc@dri.edu