Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
253 AM EST Thu Jan 27 2022

Valid 00Z Fri Jan 28 2022 - 00Z Fri Feb 04 2022

Showers should be on the light side through late week into the the
weekend, with guidance continuing to show below-average
precipitable water values over most areas.  A trend to lighter
trades is likely by Friday with the approach and stalling of a
front just north of the state, with the northwestern islands
seeing the best potential for some sea/land breeze influence. 
Trades should rebound during the weekend as trailing high pressure
passes by to the north.

After Sunday the latest guidance shows significant spread as in
previous days, and in some cases continuity changes, for specifics
of flow aloft and what happens to a front that approaches the main
islands from the northwest early next week.  As has been the case
in recent days the GFS again shows the most extreme scenario with
a very sharply amplifying upper trough over the state by early
Tuesday, leading to an upper low just to the northeast of the
state soon thereafter.  This evolution corresponds to a
fast-moving front that crosses the state with some enhanced
rainfall, followed by drier air moving in from the west. 
Yesterday's 00Z ECMWF closed off a low a little farther to the
north and brought the front through, however the last two ECMWF
runs have gone back to having at most weak shortwave energy pass
through and the front reaching no farther east than the
northwestern islands.  The latest CMC/UKMET are fairly close in
principle to the latest ECMWF, and particularly notable is the
fact that are no 00Z GEFS/CMCens or 12Z ECens members that are as
extreme aloft as the 00Z/18Z GFS--yielding ensemble mean solutions
that are close to the ECMWF cluster as well.  This provides
significant support for a non-GFS evolution, with the front
reaching close to or just into the far northwestern islands before
weakening.  The associated band of moisture may increase rainfall
a bit in the northwest for a time, while trades could also weaken
before rebounding some after the front dissipates.  Another front
should approach from the northwest by Wednesday-Thursday. 

Rausch