Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
355 AM EDT Wed Oct 18 2023

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

After a period of light trades and land/sea breeze influence on
showers over some areas continuing into Wednesday, high pressure
behind a front arriving into the northwestern part of the state
Thursday-Friday should bring a brief rebound in trades and
windward rainfall focus.  The front's moisture band may serve to
enhance totals somewhat over the northwestern and possibly central
islands late this week.  This axis of moisture should begin to
dissipate or at least lift northward during the weekend as a
stronger front approaches from the northwest in response to an
amplifying central Pacific upper trough.  Guidance still agrees in
principle that the southeasterly/southerly flow ahead of the front
should draw up enhanced moisture from lower latitudes early next
week.  Current spread for alignment of the moisture axis, with
precipitable water values most likely peaking around Tuesday,
covers the central/eastern islands with the 00Z GFS a bit on the
eastern side of the envelope due to extending the upper trough a
little eastward of consensus.  Meanwhile the 00Z ECMWF continues
the recent tendency of that model to be somewhat deeper/sharper
than most other guidance with the upper trough early in the week,
leading to much heavier rainfall than what other models are
showing.  Current preference would be to lean away from the ECMWF
specifics until one or more models begin trending in that
direction, while expecting rain that could be somewhat heavier
than other models at least on a localized basis.  Even with the
differences aloft, the latest models and means are similar with
bringing the front into the main islands during Tuesday-Wednesday.

Rausch