Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
716 AM EST Thu Mar 01 2018

Valid 00Z Fri Mar 02 2018 - 00Z Fri Mar 09 2018

While there are some detail differences at the surface and aloft,
current models and ensembles agree in principle on a noticeable
retrogression of the large scale pattern aloft.  This adjustment
of the mean pattern will ultimately lead to a drier trend for the
state next week.

From now into the weekend expect areas of rainfall with varying
intensity.  Multiple ingredients will play a role in this
activity.  These include relatively high precipitable water values
(maximum just to the south/west of the islands), shortwaves
embedded within flow ahead of an upper trough/embedded low to the
west of the state, and moist low level east-southeasterly flow. 
By the start of next week an amplifying Pacific upper trough on
either side of 140W longitude--with some elongation southwest
toward/over Hawai'i--will replace a west coast CONUS trough, while
the upstream mean ridge likewise sets up farther westward.  This
pattern change will bring much drier flow aloft with PWATs
trending to below normal values.  Meanwhile surface high pressure
becoming oriented north-south along 160-170W longitude will
encourage brisk low level flow from the east-northeast.  Expect
some lingering windward precipitation next week but with
relatively light amounts given the lower moisture levels.  Toward
the end of the period next Thursday the 06z GFS represents one
notable guidance difference within the upper trough, bringing an
upper low center farther southwest than other solutions with some
effect on the surface pattern over/east of the region.  Thus at
this time would recommend an average of other guidance.

Rausch