Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
712 AM EST Mon Nov 11 2019

Valid 00Z Tue Nov 12 2019 - 00Z Tue Nov 19 2019

A surface frontal boundary is forecast to dissipate in the
vicinity of Hawaii over the next couple days. Surface high
pressure north of the state will bring relatively weak trades
along with windward and mauka showers through much of the week.
Models have been consistent in showing an upper trough amplifying
northwest of Hawaii by Thu night/Fri, with a cold front
approaching Hawaii from the northwest by Fri night/Sat and
potentially stalling across the state over the weekend. In general
model solutions show relatively good consensus on the amplitude of
the trough and the timing of the cold front. Solutions also agree
on the potential for moisture from an easterly wave to potentially
be drawn northward into the frontal zone, with both the GFS and
ECMWF showing PWs rising to over 2.00 inches by next weekend. This
setup should support the potential for more widespread and at
least locally heavy rainfall across Hawaii by next weekend. As the
easterly wave drifts westward by early next week (solutions differ
on exactly how quickly this well occur), guidance shows the front
eventually dissipating, and the resumption of moderate trades
along with a push of drier air across the state. The ECMWF would
bring the push of drier air across Hawaii more quickly than the
GFS. At this point, a compromise between the two scenarios seems
reasonable, and this is supported by the ensemble means.

Ryan