Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
729 AM EST Thu Jan 18 2018

Valid 00Z Fri Jan 19 2018 - 00Z Fri Jan 26 2018

Models and ensembles agree that a strong surface high will bridge
to the north of the state over the next few days and pressure
gradients underneath support brisk island trades. A lingering
shearline further weakens over the state and the pattern remains
dry during this period under a stable upper ridge.

Weak shortwave trough and height fall approach from the west
weakens this ridge over the weekend into early next week as trade
flow decrease to moderate levels in response to the shift of the
supporting surface high into the eastern Pacific. This allows a
gradual return of moisture and a few showers statewide.

Guidance offers more variance and uncertainty at longer time
frames, but generally agrees to progress an amplified mid-upper
level trough and a deep surface low to the northwest of the state
into Wednesday/Thursday. A favored composite of best clustered
guidance from the latest GFS/ECMWF and GEFS/ECMWF ensembles offers
potential for a precipitation focusing trailing cold front to
reach the western islands as veering lead trades return moisture
over the state.

Schichtel