Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
356 AM EDT Thu May 16 2024

Valid 00Z Fri May 17 2024 - 00Z Fri May 24 2024

...Heavy rain threat late week into the weekend...

Latest guidance continues to indicate that the deep upper low
initially north-northwest of the state and associated surface
boundary reaching the main islands will support a period of heavy
rainfall with flash flooding threats drifting from the central
islands into the western part of the state over the coming days. 
Around Sunday there is lingering uncertainty in exactly when the
band of heaviest rainfall will ultimately reach west of the main
islands.  From Monday onward expect light to moderate
east-southeasterly to southeasterly winds with a combination of
windward and sea breeze focus for showers.

As for details, there is fairly good consensus into the first part
of the weekend for the best moisture axis and focusing surface
boundary gradually shifting westward as the upper low drifts a
little farther away to the north.  Sunday is currently more of a
question mark as some guidance says the axis of heaviest rainfall
could already reach just west of the western islands, but
consensus still depicts fairly high precipitable water (PWAT)
anomalies over the area.  The 00Z ECMWF-initialized machine
learning models essentially split the difference, showing the axis
of highest QPF a little west but with some continued enhancement
into the state that would be consistent with the high moisture. 
Trade showers from Monday onward should produce lighter rainfall,
though the combination of PWATs staying somewhat above normal and
upper level impulses could still provide some localized
enhancement.

Rausch