Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
821 AM EDT Mon May 14 2018

Valid 00Z Tue May 15 2018 - 00Z Tue May 22 2018

The majority of model/ensemble guidance show Hawaii remaining in a
relatively benign weather pattern over the next week, with
gradually rising heights and increasing trades later in the week
as the subtropical ridge takes hold north of the state. A trough
is expected to pass well north of Hawaii Tue night into Wed, with
the associated surface cold front likely washing out well before
it reaches Hawaii. At this time, models show no major differences
with the handling of these features, with respect to any affects
on Hawaii. As the trough moves east, upper-level ridging is
expected to expand across the central Pacific, with a surface high
strengthening approximately 600 miles north of the state by Thu
night-Fri. Models continue to diverge in their solutions by
Sun-Mon, with the GFS/GEFS continuing to develop another trough
north of Hawaii, while the CMC/ECMWF and their respective
ensembles maintain a much stronger ridge. At this time, WPC
continues to prefer the solutions with a stronger/more persistent
ridge.

In terms of sensible weather, trades will initially be relatively
weak through mid-week as the pressure gradient remains weak and a
surface trough sets in the vicinity of Hawaii. By later in the
week as the subtropical ridge expands to the north, easterlies
should increase into the 15-25 kt range, and continuing into early
next week. Moisture will be rather limited in this pattern, and
would expect only isolated to scattered windward showers


Ryan