Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
255 AM EST Mon Jan 24 2022

Valid 00Z Tue Jan 25 2022 - 00Z Tue Feb 01 2022

The next several days should feature varying strength of trades
with a series of surface highs to the north, separated by fronts
that should stall before reaching the islands.  An area of
moisture reaching into the state from the east Tuesday-Wednesday
may help to increase windward/mountain-focused showers relative to
the drier conditions expected Monday.  Through the rest of the
week rainfall should be on the lighter side given forecast
below-average precipitable water values.  Some locations could see
trades weaken enough to allow for some sea/land breeze influence
on showers.

During the weekend and early next week the guidance increasingly
diverges.  GFS runs and to a fair degree the GEFS mean develop
more amplified upper troughing northwest of the state.  This
brings an associated front far enough east to support increased
potential for significant rainfall from a combination of frontal
moisture and additional moisture brought up from the south.  On
the other hand the ECMWF/CMC and UKMET (through the end of its run
at 144 hrs) as well as 00Z CMCens/12Z ECens members all suggest
that the upper troughing will be less amplified than the
GFS/GEFS--thus keeping the front farther west of the main islands
and maintaining more trade flow with moisture coming in from the
east.  Within the ECMWF cluster, the 00Z ECMWF is notable for
bringing in much more moisture in the easterly flow toward
Sunday-Monday versus the prior run or the 12Z ECMWF mean.  Based
on the proportion of guidance supporting each scenario for the
upper trough, would favor leaning two-thirds toward the ECMWF
cluster in principle but with somewhat less late-period moisture
arriving within trade flow versus the 00Z ECMWF.

Rausch