Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
803 AM EDT Sun Oct 02 2016

Valid 00Z Mon Oct 03 2016 - 00Z Mon Oct 10 2016

Albeit with some differences in details that may have meaningful
influence, guidance offers similar ideas through the period. 
Expect a combination of moisture from the remnants Ulika, energy
aloft, and by midweek possibly a weak surface trough, to support a
period of enhanced rainfall from later today or tonight into
Wednesday or Thursday.  GFS/ECMWF runs agree that precipitable
water values should reach at least 2 inches and 3-4 standard
deviations above normal for a time over the Big Island.  In the
case of the 00z ECMWF such PWATs briefly extend farther
northwestward.  Guidance indicates a ridge aloft building eastward
along or just north of 30N latitude by Friday-Sunday, leading to
drier flow pushing in from the northeast during that time frame. 
Models differ in the extent of drying as the 00z ECMWF lowers
PWATs to a greater extent than 00z/06z GFS runs.

Evolution of trades appears fairly consistent with yesterday's
forecast.  High pressure initially northeast of the islands will
weaken slowly so initially brisk to moderate trades should trend
somewhat weaker with time and perhaps take on a more southeasterly
component heading into midweek.  A generally more east-west
elongated surface ridge near 30N will likely support moderate
trades from the east or east-northeast by Friday and next weekend.

Rausch