Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
244 AM EST Fri Nov 12 2021

Valid 00Z Sat Nov 13 2021 - 00Z Sat Nov 20 2021

...Potential for Locally Heavy Rainfall Early Next Week...

Guidance agrees that an amplifying upper trough northwest of the
state late this week through the weekend will push a surface front
toward the state.  This front will likely stall over the main
islands around Sunday and may persist at least in weaker form into
the first part of the next work week.  The best model/ensemble
consensus exists through Monday, with reasonable agreement for
increasing rainfall late Saturday or Sunday into Monday as
moisture lifts up from the south and interacts with the surface
front and shortwave energy aloft.  Models still vary for rainfall
specifics but the pattern does appear favorable for some locally
moderate to heavy rain.  By Tuesday there is a general signal that
upstream shortwave energy could keep the front and nearby moisture
over the area but most guidance thus far (including the 12Z ECMWF
mean) suggests that moisture should decrease somewhat compared to
Sunday-Monday with passage of the leading shortwave Monday--in
contrast to the 00Z ECMWF that brings a pronounced moisture surge
with heavy rainfall from southwest to northeast.  Most mid-late
week forecasts show enough high pressure northeast of the state to
support resumption of trades, with an easterly or southeasterly
component depending on location, along with a continued decrease
in moisture/rainfall (and earlier than seen in the 00Z ECMWF).  

Rausch