Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
303 AM EDT Sun Oct 18 2020

Valid 00Z Mon Oct 19 2020 - 00Z Mon Oct 26 2020

...Heavy Rainfall Threat for Hawaii...

An amplified upper low/trough is slated to remain to the northwest
of the state through early next week as a trailing front stalls
over the state. Disrupted trades/land-sea flow and deep moisture
pooling with axis of precipitable water values upwards of 1.75-2"
centered into the western islands will remain available to fuel a
multi-day period with a threat for locally heavy rains with
runoff/flooding potential. A flash flood watch has been issued.
Model and ensemble solutions remain well clustered, again
bolstering forecast confidence. Expected upper low/trough ejection
and the gradual diminishing of the front and moisture plume
starting next midweek would gradually weaken heavy rainfall
support. In this transition, trades may gradually return into
later next week and offer some potential to bring tropical
moisture into the islands from the southeast. 

Schichtel