Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
732 AM EST Fri Dec 02 2016

Valid 00Z Sat Dec 03 2016 - 00Z Sat Dec 10 2016

...Heavy Rainfall Pattern for Hawai'i...

...Guidance and Uncertainty Assessment...

No large scale changes for the next few days as a very active
pattern will remain for the 50th state. An upper low currently
near the central islands will drift northwestward and weaken over
the next day or so. Longwave pattern across the central Pacific
next week supports another upper low dropping down from the
mid-latitudes to near 25N/165W by early Sunday before lifting out
to the northeast. Thereafter, yet another trough or upper low
around next Wednesday may dig around 170W. For the lead upper low
this weekend, the 00Z UKMET and 06Z GFS fell in the middle of the
spread between the faster 00Z GFS and the stronger/slower 00Z
ECMWF/Canadian (which were among the slowest 10% of the
ensembles). A solution near the 00Z UKMET/06Z GFS seems reasonable
as the 00Z parallel GFS was also in this cluster.

By next week, spread remains among the deterministic runs with the
next digging trough and perhaps closed low. Though the ensembles
have backed of on the possibility of closing of another upper low,
all forecast troughing to the northwest of the islands. The GFS
runs were still generally quicker than the ECMWF/Canadian. The 00Z
NAEFS mean (a compromise between the quicker 00Z GEFS mean and
slower 00Z Canadian mean) seems reasonable.


...Weather Highlights/Threats...

Moderate to brisk trades over the next day or so will subside a
bit and become disrupted as the cold front and inverted trough
push closer to the region from the northwest. Rainfall over the
next several days may be in excess of five inches over portions of
the Big Island as the best moisture plume should lift through this
region. Next week, more uncertainty in QPF is seen over the region
due to differences in the evolution of the upstream troughing.


Fracasso