Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
750 AM EDT Fri Apr 14 2017

Valid 00Z Sat Apr 15 2017 - 00Z Sat Apr 22 2017

Expect shower activity today focused on the eastern islands as an
upper trough approaches and then for activity to wane as the upper
trough moves east of the islands Saturday and areas of ascent
switch to areas of descent. Drying aloft occurs this weekend
through early next week with layer relative humidity dropping to
below 50 percent.  With a low level ridge north of the islands,
showers are focused primarily in windward locations with moderate
trades.

On next Thu and Fri the next deep layer trough is forecast to
approach from the west, with a surface cold front gradually
weakening as it approaches. Both the GFS and ECMWF show pockets of
enhanced precipitable water around 1.5 inches in the western
islands.  Pre-frontal convergence should produce an uptick in
shower coverage and amounts.  The models have come into better
agreement with good clustering of forecasts among the gfs/gefs
mean along with the ECMWF and ECMWF ensemble mean regarding the
evolution of the early week ridge and later week approach of the
front. 

Petersen