Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
823 AM EDT Fri Jul 11 2014

Valid 00Z Sat Jul 12 2014 - 00Z Sat Jul 19 2014

Fri through Sat will feature a modest weakening of trades and
mostly light windward showers as guidance shows PW values at or
slightly below 1.25 inches.  From late Sun through Tue there is
still meaningful spread as well as run to run variability in the
details of a surge of moisture reaching the islands from the
east/southeast.  The 00Z/06Z GFS runs have taken on a look similar
to yesterday's 00Z ECMWF in splitting highest PW's... 1.75-2.00
inches... to the north and south of the islands.  On the other
hand the 00Z ECMWF now keeps the band of moisture more intact with
some 2 inch or greater PW's reaching the islands.  Based on model
behavior thus far a blend of the two ideas appears best.  This
period of increased moisture will increase the potential for
locally heavy rainfall but moderately high heights aloft may tone
down the coverage of such activity.  Establishment of a fairly
strong eastern Pacific ridge at the surface and aloft should lead
to trades in the low-end moderate range by Wed-Fri.  PW values
will decrease somewhat from earlier in the week and progression of
low level flow should allow for lower values than maintained by
the 00Z ECMWF over the Big Island late in the week.  However
heights aloft are expected to fall during that time, allowing for
persistence of light to moderate windward showers.

Rausch