Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
707 AM EST Sun Feb 08 2015

Valid 00Z Mon Feb 09 2015 - 00Z Mon Feb 16 2015

Through at least Thu there is reasonable model/ensemble agreement
with most aspects of the forecast.  Relatively light low level
winds will turn more southerly/southwesterly and strengthen,
perhaps considerably at some locations, with the approach of a
fairly strong cold front that should pass through the region
Mon-Tue.  As indicated in guidance over recent days there should
be two areas of potentially enhanced rainfall, one accompanying
the front and a second leading band that should lift northwestward
into the Big Island and vicinity.  In both bands precipitable
water values should reach 1.50 inches or greater.  Based on 06z
GFS trend toward the 00z ECMWF, the 00z GFS run may be a little
quick in lifting out the leading moisture band away from the Big
Island.  After frontal passage expect a brief drying trend around
midweek with brisk westerly to northwesterly winds that should
become lighter by Thu.

The uncertainty of northern and southern stream interaction
remains a significant forecast problem from late this week into
next weekend.  Prior to today the GFS/GEFS guidance has tended to
be on the strong side with a low latitude wave tracking northwest
of the islands around Fri while remaining guidance had favored
more northern stream emphasis and faster frontal passage over the
islands.  Currently the GFS is still on the strong side with the
low latitude wave, albeit with the 06z GFS trending weaker than
the 00z run.  However the 00z CMC/UKMET show a decent wave as well
and the 00z ECMWF/ECMWF mean are now suggesting more stream
interaction leading to slower frontal passage.  The 00z GEFS mean
actually has some similarities to the ECMWF mean aside from being
slower with the front.  Based on trends over the past day the 00z
ECMWF mean or some degree of compromise with the GEFS mean appears
most reasonable.  Regardless of specifics the return of
southerly/southwesterly low level flow ahead of the front should
bring an increase of deep moisture into the region around Fri-Sat.

Rausch