Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
322 AM EDT Mon Oct 26 2020

Valid 00Z Tue Oct 27 2020 - 00Z Tue Nov 03 2020

...Heavy rain increasingly likely this week...

An upper low forming to the northwest of the area today will drop
southward toward Hawai'i into Wednesday. The guidance has come
into much better agreement with the 00Z runs, taking it to about
27N. The UKMET/Canadian were just east of 160W while the GFS/ECMWF
were just west of 160W by late Wed into early Thu and formed the
preferred solution. Upper ridging to the north is expected to pass
by, leaving the upper low nearly stationary until about Saturday.
Thereafter, troughing south of the Aleutians should help tug it
eastward with uncertainty if heights rise or another upper
low/trough fill in from the NNW. Ensembles were split about 1/4
(additional troughing) to 3/4 (heights rise at least a bit).
Prefer to side with the larger consensus for now.

Deep tropical moisture over the island chain (precipitable water
values over 2 inches) will spread across much of the region around
Tuesday on southerly flow as a surface boundary stalls across the
area. Should the upper low indeed meander just to the NW of Kauai
through the rest of the week, several inches of rain are possible
each day in this scenario which may result in flooding.

Fracasso