Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
304 AM EST Mon Jan 06 2020

Valid 00Z Tue Jan 07 2020 - 00Z Tue Jan 14 2020

Between Monday and Tuesday eastern Pacific high pressure will
rebuild westward and then remain fairly close to 150W longitude
for the rest of the period, coincident with a strong east-central
Pacific upper ridge.  Flow around the surface high will support
strong trades for a majority of the period, with showers focusing
over windward/mountain terrain but at times straying to other
locales.  Meanwhile the upper ridge will encourage an upper low
initially east of the state to move into/across the region in the
late week-weekend time frame, continuing to the northwest by next
Monday.  The upper low/moisture should lead to a period of higher
rainfall totals.  Also the surface gradient and associated trades
may weaken for a time as the upper low passes through.

While all guidance shares the above theme, today's models and
ensemble means are no closer together regarding specifics of the
upper low energy and corresponding moisture.  Based on the full
range of guidance the 00Z GFS/GEFS mean may be a little too deep
with the upper low.  As has been the case in recent days the
ECMWF/ECMWF mean are considerably faster with the westward
movement of moisture.  In addition the GFS/GEFS mean ultimately
divert the axis of greatest moisture to the north of the islands
versus the ECMWF/ECMWF mean path of greatest moisture passing
directly across the islands--and with some plus 2-2.5 standardized
anomalies for precipitable water.  The CMC diverts the best
moisture a bit northward somewhat like the GEFS mean though its
upper low strength compares better to consensus.  Preference would
be to maintain continuity by way of a compromise between the
ECMWF/ECMWF mean and CMC/weaker version of the GEFS mean.

Rausch