Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
828 AM EDT Wed Apr 15 2015

Valid 00Z Thu Apr 16 2015 - 00Z Thu Apr 23 2015

Mid-upper level trough passage will interrupt trades and allow an
increase in instability/moisture that offers the potential to fuel
some locally heavy convective downpours into Thursday. This seems
well supported by water vapor imagery and latest blended
precipitable water loops show deeper moisture poised southwest of
the islands that is roughly 175-200% of normal values.

A favored composite of reasonably compatable models and ensembles
suggests that moderate to brisk trades will return in the wake of
system passage leading into transition to a drier pattern with
limited windward terrain based showers extending into next week.

Forecast spread and uncertainty increases significantly next week
to the northwest of the state with respect to the extent of
mid-latitude energy digging southeastward to the lee of a west
Pacific mean ridge. A modest compromise of the more amplified
GFS/GEFS/CMC and flatter ECMWF/ECMWF ensemble mean, and
consideration of the overall larger scale flow, may suggest
digging could begin to effect trades and induce some lead moisture
and shower return into Hawaii by next midweek.

Schichtel