Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
344 AM EDT Fri Apr 14 2023

Valid 00Z Sat Apr 15 2023 - 00Z Sat Apr 22 2023

Guidance agrees upon a drier trend from late this week through the
weekend along with moderate trades, as upper ridging
approaches/reaches the state behind a departing upper low/trough
and initial North Pacific high pressure drops southeastward to
replace a leading surface high well north of the islands.  Then
consensus shows a system northwest of the islands pushing a front
toward the region early next week, turning the winds more
southerly.  Guidance appears to have improved its clustering for
the general forecast Tuesday onward.  Most solutions indicate the
front will reach far enough east to bring increasing moisture and
potentially heavy rainfall into the western islands around
Tuesday, followed by progression of the rain into the central and
eastern islands during mid-late week.  The weakening front and
associated moisture band should stall over the eastern/central
islands into Friday as the supporting dynamics lift away and upper
heights rise.  Sufficient weakening of the front could allow for a
return of trades to some degree around next Friday or so.  There
are some differences in exact position of the front/moisture late
in the week but they are well within typical spread for days 6-7
forecasts, so a model/ensemble mean average appears to be a good
starting point at this time.  Such an approach would also help to
balance out possible model inconsistency, such as the 00Z ECMWF
ultimately bringing the band of highest moisture a little east of
the GFS even though the ECMWF shows higher heights aloft than the
GFS or most other guidance.

Rausch