Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
711 AM EST Thu Dec 27 2018

Valid 00Z Fri Dec 28 2018 - 00Z Fri Jan 04 2019

A cold front evident in satellite imagery early this morning
several hundred miles west-northwest of Hawaii is expected to
reach the islands on Friday, and then potentially stall, lingering
into the weekend as it washes out. As a result, expect deeper
moisture to focus across Hawaii in the vicinity of the front, with
an increase in convective activity likely. While locally heavy
rainfall is possible, ECENS and GEFS members show general
agreement that the focus for more widespread heavy rains should
remain just to the southwest of Hawaii. As upper ridging begins to
build across/north of Hawaii by early next week, drier air should
begin to spread across Hawaii, with both the ECMWF and the GFS
showing PWs dropping well below one inch by Mon night. Building
high pressure at the surface by this time will bring a return of
moderate trades in the 20-25 kt range. Ensembles show broad
agreement that Hawaii the upper ridge will persist or even
strengthen through the end of next week, bringing a continuation
of relatively dry conditions and only very isolated showers in
favored terrain locations.


Ryan