Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
321 AM EDT Fri May 19 2023

Valid 00Z Sat May 20 2023 - 00Z Sat May 27 2023

...A wet pattern for Hawaii to linger into the weekend...

A favored guidance comosite indicates that a wet pattern for
Hawaii will linger into the weekend as an upper trough moves
slowly across the state. Anomalously high tropical moisture is
streaming in with the deep southerly flow with/ahead of this
feature, providing for widespread rain. This is quite evident in
latest blended precipitable water satellite loops and as per an
active ongoing radar loop signature. Some thunderstorms may be
possible as the trough aloft could lessen or or eliminate the
typical inversion and provide instability, but a limiting factor
for strong storms could be the widespread cloud cover reducing
surface heating. Regardless, enhanced rainfall totals that may
lead to local runoff issues are most likely today into Saturday.

Shower coverage should gradually decrease through the weekend into
early next week as the weakening upper trough moves away and is
increasingly replaced by upper ridging. This will shift the
moisture plume away from the state next week while surface highs
build to the northeast and the northwest over the islands across
the mid-latitudes of the Pacific, creating a more typical and
drier easterly trade wind pattern. Trades may increase to breezy
levels at times next week, and showers that do form should focus
across windward and mountain areas. There is a growing but still
uncertain guidance signal that favors slow carving of an upper
weakness of the state for mid-later next week that could again
pool shower fueling moisture.

Schichtel