Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
155 AM EST Sun Dec 7 2025

Valid 00Z Mon 08 Dec 2025 - 00Z Mon 15 Dec 2025

Easterly trades start out the period with the usual windward 
shower paradigm expected. A compact cut off low will meander east 
and northeast of the state as late as Wednesday but is forecast to
have minimal, if any, impact on precipitation amounts across 
Hawai'i before it moves northeast, out of the picture. 

Another cold front moves into the western main islands late Wednesday
at the leading edge of a positively tilted trough. While timing 
is no longer a factor, the guidance now allows the front to
generally through the main Hawaiian Islands by Saturday. While 
there is decreased spread concerning where the occluded cyclone 
north of the islands sets up shop, the 00z GFS remains south of 
the other guidance while the 00z ECMWF appears to anomalously 
allow another cold low to its west to force retrogression on 
Friday. This is an error the guidance sometimes displays, so will 
side against the 00z ECMWF and prefer a non-ECMWF consensus. In 
any event, moderate to heavy showers/thunderstorms are expected to
accompany the frontal passage, though expected rainfall doesn't 
appear to be excessive at the present time as the front is 
forecast to be progressive. For the moment, the 00z GFS heavy 
rainfall signal heading towards the main islands from the west 
next Sunday onward is non-preferred, but it bears watching.

Roth