Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
727 AM EST Mon Feb 05 2018

Valid 00Z Tue Feb 06 2018 - 00Z Tue Feb 13 2018

...Locally heavy rain possible in the short range...

As of 12Z Monday, a surface cold front is currently moving through
the northwest islands with scattered showers and embedded
heavier/steadier rain and some thunderstorms. Waves of low
pressure will ride along the front as it slowly makes is way down
the island chain over the next couple of days. With available
moisture well above average (1.50-1.75" precipitable water or
about +2 standard deviations) flash flooding is possible in some
locations. Cold air aloft will support snow at the Big Island
summits.

Models/ensembles show the cold front exiting past the Big Island
late Wednesday or early Thursday as the upper trough finally
swings through. Timing will depend on the evolution of the
embedded surface waves. Northwesterly upper flow will follow in
the wake of the FROPA as surface winds veer to northwesterly
behind the front then quickly to northerly/northeasterly. A
showery and breezy pattern for the islands will follow later in
the week into the weekend with precipitable water values generally
under one inch. 00Z GFS/ECMWF blended solution should suffice
through the period, which would be near the 00Z ECMWF ensemble
mean. By next Monday, some models/ensembles show a moisture plume
from the east to push westward into the region. This may help to
expand precipitation ahead of another significant trough near 165W
by 00Z Tue Feb 13, per the ensembles.


Fracasso