Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
352 AM EDT Mon Apr 04 2022

Valid 00Z Tue Apr 05 2022 - 00Z Tue Apr 12 2022

Expect lighter trades and more shower activity during the first
half of the week as initial high pressure retreats northeastward
ahead of an approaching front and impulses aloft help to draw
moisture northward into the state.  Rainfall focus may vary
between windward/mountain areas and other locations depending on
the relative influence of background flow versus land/sea breeze
influence where the trades become sufficiently weak.  After
midweek the trades should return to brisk levels while showers
trend somewhat lighter, with the front stalled to the north of the
state and high pressure passing by to its north while the best
deep moisture is pushed to the south of the state.

From about Friday onward the guidance continues to show a
pronounced split for details aloft and precipitable water values
over the state.  Similar to yesterday, the GFS and GEFS mean hold
onto a deeper trough aloft over and just west of the main islands
versus the ECMWF/CMC and their ensemble means (plus the UKMET
through the end of its run).  As a result the GFS/GEFS bring back
some of the enhanced moisture south of the state northward into
the area, in contrast to other guidance that keeps it to the
south.  While the 00Z GEFS mean reflects the GFS in principle, at
least its precipitable water values do not reach as high as the
00Z GFS forecast.  Preference would be to lean more toward the
majority ECMWF cluster until any of those solutions start to trend
in the GFS/GEFS direction.  Consensus suggests that the deeper
upper trough farther to the northwest of the state should remain
far enough removed to keep its leading band of moisture to the
west of the main islands.  With high pressure settling into the
eastern Pacific, trades could take on somewhat of a southeasterly
component by Saturday-Monday while they may stay a little stronger
than indicated by the GFS as consensus maintains somewhat higher
surface pressures/tighter gradient over the area.   

Rausch