Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
258 AM EST Tue Nov 21 2023

Valid 00Z Wed Nov 22 2023 - 00Z Wed Nov 29 2023

A stalled front and moisture band initially over the state should
dissipate fairly quickly, leading to a lighter trend for recent
locally enhanced rainfall.  Guidance continues to show an area of
enhanced moisture just to the southeast of the state brushing at
least the Big Island and perhaps to some degree the rest of the
state during Tuesday-Wednesday.  This moisture could still help to
enhance rainfall to some degree.  Among latest models/means, the
00Z ECMWF shows slightly higher precipitable water values than
most other solutions.

Expect brisk northeasterly winds to transition to moderate trades
through Thursday, followed by a southeasterly trend as a front
approaches from the west.  Over the past day guidance has made a
notable change in the character of the supporting upper trough by
the weekend, pulling off energy in the southern part of the trough
while the rest of the trough passes by just to the north of the
state.  This latter part of the trough is somewhat more amplified
in the GFS/GEFS than most other solutions, so would initially
hedge away a bit from the GFS in particular that ultimately has a
nearly clear frontal passage before it stalls.  On the other hand,
the 12Z ECMWF mean is among the majority that brings the front
farther south/southeast than the 00Z ECMWF.  This change in upper
trough details has reduced some of the rainfall totals as the
front moves in.  By next Tuesday there is general agreement that
upstream energy should begin to develop additional troughing just
west of the state, leading to the potential for increasing
moisture to focus along the stalling front.  It will likely take a
while to resolve the details of this evolution but the pattern
does at least suggest the potential for increasing rainfall toward
next Tuesday.

Rausch