Area Forecast Discussion
Issued by NWS Honolulu, HI

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FXHW60 PHFO 311406

Area Forecast Discussion
National Weather Service Honolulu HI
406 AM HST TUE MAY 31 2016

A somewhat wet trade wind regime will continue for another day or
so  in wake of a front that is now near northern Big Island. This
front that is in a stationary stance now, is expected to continue
moving east this afternoon, and exit the big island late Wednesday
night. Moderate trades will be strengthening this morning reaching
moderate strength this afternoon and continuing through tonight.
The trades will then turn light and variable by Saturday as a
surface trough close in on the islands from the northeast .


There were signs the front that was over Maui early Monday
evening was starting to advance eastward at a faster pace,
threatening to move onto northern Big Island overnight.
Although difficult to locate after the clouds along its leading
edge dissipated, we placed the stalled front in the Alenuihaha
Channel. Within the past half hour however, a band of low clouds
is taking shape off Hamakua coast. Is this the actual position of
the front? We are not sure. Both the ECMWF and GFS models have it
in the Alenuihaha. However, the EC is still the faster of the two
in dealing with this front by advancing it eastward to the Big
Island this later this morning. The GFS solution does not begin
this process until late this afternoon. The faster movement of the
ECMWF is our preferred choice especially now that clouds are
present off the Hamakua coast. The EC goes on to edging the front
down Puna coast of the Big Island tonight and finally breaking it
up over the Kau coast Wednesday evening.

It appears the showers have diminished slightly in the past few
hours, and they are not as heavy as earlier in the evening. In
fact, the clouds and showers around windward Maui have diminished
quite a bit since early Monday evening. This a good sign where
flooding will be less of a threat. The POPS and SKY grids have
been adjusted lower but still has a wet trade flavor through
Wednesday morning. A drier trade wind regime should rule the
islands for the rest of the work week.

As for the trade winds, they will be gaining strength today
behind the front. Their speeds will max out at moderate levels
this afternoon and continue through tonight. The trades should
start weakening Wednesday when the surface high is passing north
of the islands.

A surface low is expected to form along the front northeast of the
islands near 29n143w tonight. It is forecast to drift west
southwestward - opening up to a trough late in the week. Our trade
winds will disappear for the upcoming weekend as this trough
enters our windward waters. The trough gets filled late Sunday
over our windward waters. Higher pressure moves in resulting in
strengthening trades for the first half of next week.


With a weak front in the vicinity of the Aloha State, TEMPO MVFR
is likely over all the isles; especially in northern, windward,
and mauka sections; as broken lower cloudiness and showers move
toward the south and southwest. However, VFR will predominate

No AIRMETs are currently in effect


Peak spectral densities associated with the lingering south-
southwest swell have shifted from the 14-16 sec band to the 12-14
sec band with swell heights holding steady in the 2-3 ft range at
the nearshore Lanai PACIOOS buoy. This should correspond to slightly
smaller surf along south facing shores today when compared to
yesterday, which will be reflected in the latest surf forecast. Surf
along north facing shores associated with the small northwest swell
that peaked yesterday will also steadily ease through tonight. The
latest nearshore wave model guidance remains in decent agreement
with the current conditions and depicts the southerly source in
place becoming reinforced later tonight through the mid-week period
out of the south-southwest (220 deg). This new southerly source
should continue to generate small surf along south facing shores
Wednesday and Wednesday night before easing Thursday. Small and
choppy surf will continue through mid week along east facing shores
as moderate to fresh trade winds associated with high pressure north
of the state continue.

Out across the marine areas, moderate to fresh trade winds will
continue to fill in through tonight with high pressure located
some 700 miles north of Kauai. The weak frontal boundary in the
Alenuihaha Channel will slowly shift east and southeast over the
Big Island and dissipate tonight through Wednesday. Although the
winds are forecast to remain below advisory levels, the waters
around Kauai will need to be monitored closely today. Earlier
model run showed some 25 kt winds in the Kauai Channel but has
since backed off. High pressure is forecast to weaken during the
second half of the week while a surface troughs drifts into our
windward waters over the upcoming week end pretty much shutting
down the cooling trades in the process.




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