Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
237 AM EST Thu Dec 19 2019

Valid 00Z Fri Dec 20 2019 - 00Z Fri Dec 27 2019

...Very strong trades Friday into Saturday...

...Heavy rain possible next week...

A cold front will move into the region and perhaps stall over or
just south of the islands by Sunday, enhancing windward/mauka
showers with some locally modest amounts and leeward spillover. At
the same time, strong surface high pressure (1033-1035mb, which is
much stronger than average for late December) will bring in windy
trades (20-35kts with higher gusts) Friday into Saturday before
slackening late Sunday into Monday.

To the west, the models/ensembles show an upper trough or closed
low with developing surface low pressure passing north of 20N by
12Z Sat. The models diverge after that, with the 00Z GFS/UKMET
stronger and a bit farther east than the 00Z ECMWF/Canadian with
the low. This would bring an area of heavy rain into at least
Kauai by about Monday-Tuesday should the moisture plume push east
of 160W. However, the 00Z ECMWF ensembles have trended
slower/weaker (like its deterministic model) and kept the moisture
plume west of the islands through next Thursday. With the
increased uncertainty, heavy rainfall is still a threat but will
need to wait some more model cycles to gain confidence.


Fracasso