Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
256 AM EST Wed Jan 18 2023

Valid 00Z Thu Jan 19 2023 - 00Z Thu Jan 26 2023

Guidance is steadily coming into better agreement for the forecast
through early next week.  Initially expect fairly light winds with
land/sea breeze influence on showers, though perhaps with enough
easterly/southeasterly flow to promote some terrain focus over the
Big Island.  Meanwhile guidance has been consistent in showing a
weak front getting close to the far northwest islands around
Thursday, with that area possibly seeing some increase in rainfall
given the accompanying moisture.  A better defined front is still
on track to approach the northwestern islands during the weekend,
leading to stronger southeasterly/southerly flow by
Friday-Saturday.  Recent trends have gravitated toward keeping the
front in the western part of the earlier guidance spread,
corresponding to a stronger upper ridge building in from the
southwest.  This suggests that the front and its associated
rainfall may not reach quite as far eastward as the farthest east
GFS.  Given the stronger ridging aloft, the front is now
increasingly likely to weaken/retreat westward as more typical
trades become established from daytime Sunday onward.  Another
front may come in from the west by midweek, with winds possibly
shifting more northeasterly behind it.  Given that the GEFS/ECMWF
means from 24 hours ago were most amplified with upper troughing
forecast on Tuesday (now ridging per consensus), there is some
skepticism over the 00Z GEFS/12Z ECMWF means that are now most
amplified with troughing that develops by Wednesday.  Thus the
means could become a little too fast with the surface front.  This
front may provide some rainfall focus but with low confidence in
specifics at this time.

Rausch