Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
333 AM EST Thu Dec 23 2021

Valid 00Z Fri Dec 24 2021 - 00Z Fri Dec 31 2021

Model guidance continues to indicate an anomalous warm core high to
remain anchored in the North Pacific between Hawaii and Alaska
through midweek next week.  A couple of vortices breaking away
from this omega block will be situated at some distance away from
either side of Hawaii.  An upper low breaking off from the
westerlies and dipping pass to the west and northwest of Hawaii
will likely interact with a stationary front to bring an
increasing chance of showers across the island chain later during
this holiday weekend.  The bulk of the heavy rainfall appears to
stay west of the island chain at this time but this system should
be monitored for any signs of further eastward nudge toward the
islands in future model runs.  Thereafter, models generally take
this low on a southwestward track, bringing it further away from
Hawaii by early next week.  Nevertheless, proximity of the
stationary front will likely slow the drying trend through midweek
next week.

Meanwhile, models are also indicating the possibility of another
vortex forming well to the east of Hawaii later in the holiday
weekend.  Models are not in agreement with the eventual track of
this feature.  The GFS tends to amplify this feature into a
compact low, with possible tropical characteristics, and take it
on a northeasterly track.  The ECMWF also shows a tendency to
develop this feature into a compact low.  But in contrast to the
GFS, the latest ECMWF brings it westward toward Hawaii by midweek
next week after being nearly stationary early in the week.  The
CMC solution was in between these two extremes.  The track,
structure, and intensity of this system should continue to be
monitored in future model runs.

Kong