Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
823 AM EDT Mon Oct 06 2014

Valid 00Z Tue Oct 07 2014 - 00Z Tue Oct 14 2014

An active mid-latitude flow should remain confined to regions
north of 30N throughout the forecast period. Eventually the upper
flow will become southwesterly across the mid-latitudes with a
broad ridge stretching across 20N-30N. There is some hint of
vorticity sliding westward underneath this ridge possibly headed
toward the Hawaiian island chain by the upcoming weekend. By
13/0000Z...the 06Z GFS and 00Z ECMWF/CMC all show a couple lobes
of energy along 20N, one in the vicinity of the islands and
another lurking east of 140W. The 06Z GFS/00Z ECMWF keep this
inverted trough over Hawaii through early next week with more
uncertainty with the possible closed low off to the east.

At the surface, trade winds will initially be on the lighter side
before strengthening by mid-week as a dome of high pressure builds
northeast of the state. By 10/0000Z, a majority of the guidance
depicts east-northeasterly trades around 15 to 20 knots impinging
on the islands. Models show the trades continuing to increase into
the weekend and early next week as the surface high further
strengthens thereby enhancing the pressure gradient. The 06Z GFS
in particular shows low-level winds in excess of 25 knots at
times. The outlier appears to be the 00Z CMC which carries a well
defined surface low toward the Big Island by 13/0000Z. With regard
to rainfall, the period should initially be relatively dry before
windward and terrain enhanced showers become more prevalent later
in the week as the trades increase in strength. This pattern
should continue through early next week as well. Again, the 00Z
CMC ends up incredibly wet across the Big Island in response to
the area of low pressure. But rejecting this model and favoring
something along the lines of the 06Z GFS/00Z ECMWF.


Rubin-Oster