Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Honolulu HI
1000 am HST Sat Jan 31 2015
light winds today will give way to gentle trades Sunday as a weak
surface ridge builds north of the area. Clouds and showers over the
interior of the islands today will give way to more typical windward
and Mauka showers Sunday. A front approaching from the northwest
Monday will turn the winds to the southwest ahead of the front and
to the northwest behind the front. Expect showers associated with
the front to spread across the islands.
a weak ridge north of the islands will bring light to gentle trades
to the islands through Sunday night. The models are in fair
agreement with the winds and weather over the islands through Sunday
night or Monday. With light winds expected today...some locations
will see afternoon sea breezes...so expect more clouds and showers
over the interior of the islands this afternoon.
Heading into Monday...the ridge gives way to a front approaching
from the northwest. As a result...winds are expected to becoming
southeasterly ahead of the front...with an increase in speeds in
particular over the Western Islands for Monday night through
Tuesday. Little change has been made with regards to the forecast
through this time period.
More significant changes have been made from Wednesday onwards. The
GFS and European model (ecmwf) have varied significantly on the placement and
strength of lows passing to the north of the islands during the
second half of the week. This discontinuity persists...with the GFS
continuing to show stronger and stronger systems moving north of
the islands through the end of the week. While it is still possible
for the GFS solution to pan out...it seems unlikely. Consensus today
with collaboration with the weather prediction center is to follow
the European model (ecmwf) solution.
The last few runs of the European model (ecmwf) have shown more defined features
passing over the islands during the second half of the week. Winds
will turn to the northwest after a frontal system moves down the
island chain Wednesday/Wednesday night. Winds remain westerly
Thursday/Friday as another system begins to develop just northwest
of the islands...before turning northerly again Saturday behind this
system. A new surface ridge begins to build in over the islands
Saturday night...bringing light trades by Sunday.
With these frontal systems...periods of increased low level moisture
will increase shower activity over the islands. At least that/S the
consensus over the last few runs of the European model (ecmwf). Its still several
days out...so timing and refinement of the forecast will come with
light winds will allow for onshore sea breezes today...with clouds
and light showers focused across interior portions of the islands.
Conditions will be primarily VFR...with brief MVFR ceilings possible
in showers near Kauai/Oahu. MVFR conditions are more likely across
Maui County/Big Island...where greater low-level moisture is
located. No airmets are currently in effect...but we may need one
during the afternoon depending on how active and anchored showers
become over the terrain.
the current northwest swell continues to produce elevated surf of
the smaller islands this morning. The high surf advisory for north
and west facing shores remains posted...but may need to be extended
beyond 6 am Sunday morning if buoy readings show the swell remains
elevated later tonight. This north northwest swell should start to
gradually subside starting Sunday afternoon.
The current swell is also producing combined seas in excess of 10
feet...so a Small Craft Advisory /sca/ remains posted for areas
exposed to the swell. While winds are expected to remain below Small Craft Advisory
levels this weekend...ahead of the next front...winds may reach Small Craft Advisory
late Monday particularly near Kauai...Oahu and Molokai.
high surf advisory until 6 am HST Sunday for north and west facing
shores of Niihau...Kauai...Oahu...and Molokai...and for north
facing shores of Maui.
Small Craft Advisory until 6 am HST Sunday for the waters
surrounding Kauai...the Oahu windward waters...the Kaiwi Channel and
the Maui County windward waters.