Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
302 AM EST Sat Jan 04 2020

Valid 00Z Sun Jan 05 2020 - 00Z Sun Jan 12 2020

The forecast pattern continues to be favorable for strong trades
during the period as one surface high to the northeast of the
state moves into the eastern Pacific by Sunday-Monday followed
immediately by another high rebuilding to the west (supported by a
strong ridge aloft) and persisting for the remainder of the
period.  Rainfall should focus over windward/mountain areas but
with some activity possibly extending into other locations at
times.  Guidance is consistent in showing an upper low developing
to the east of the state this weekend and some westward
progression of associated energy and moisture during the latter
half of next week.  However there is still considerable spread in
timing the arrival of this energy/moisture (and a possible surface
trough) over the islands.  The 00Z ECMWF remains the fastest model
while the 12Z ECMWF mean is about a day slower with the westward
progression of 1.50 inch and greater precipitable water values,
and the GFS/GEFS mean are slowest.  Combination of a faster GFS
trend in the past 24 hours and 12Z ECMWF mean being a bit slower
than recent operational runs would favor an even compromise timing
for a single specific forecast.  Once this moisture arrives,
expect a noticeable increase in rainfall compared to the lighter
activity that should prevail through the first half of the week.

Rausch