Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
353 AM EDT Fri May 10 2024

Valid 00Z Sat May 11 2024 - 00Z Sat May 18 2024

...A wet pattern emerging for Hawaii...

Latest guidance agrees upon a compact upper low tracking near the
northwestern and central islands during Friday-Saturday before
continuing eastward and opening somewhat.  This upper low will
reflect as inverted troughing at the surface, yielding light
background flow and more sea/land breeze influence.  These
features along with sufficient moisture will promote the potential
for locally heavy rain including some thunderstorms from late this
week into the weekend.  Departure of the upper low should allow
for a return of light to moderate trades and more terrain focus
for rainfall by early next week.  Persistent moisture may continue
to support localized heavy rainfall.

Forecast details by mid-late next week will depend on how flow
within an early-week central Pacific upper trough may separate. 
Currently there are essentially two clusters.  One consists of the
ECMWF/CMC and their ensemble means, with separating energy forming
an upper low that settles to the northwest of the state.  This
would lead to an inverted surface trough west of the islands and a
northward surge of moisture, with the western islands possibly
seeing heavier rainfall.  On the other hand, the GFS/GEFS/ICON
cluster maintains a more open trough with the GFS/ICON eventually
forming a closed low to the north of the state along or north of
40N.  This pattern results in a front reaching at least as far
east as the main islands but with a less pronounced moisture feed.
 The 00Z ECMWF-initialized machine learning models strongly
support the ECMWF cluster in principle, so current preference
would lean to an average among the ECMWF/ECens and CMC/CMCens.

Rausch