Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
828 AM EDT Thu Sep 12 2019

Valid 00Z Fri Sep 13 2019 - 00Z Fri Sep 20 2019

An upper low to the northeast of the region will slide westward
along 27N by early next week. Light trades may increase slightly
by next week as surface high pressure strengthens between Alaska
and Hawai'i. Models/ensembles remain in good agreement overall
with a trend toward a coherent area (or multiple areas) of low
pressure detaching from the ITCZ midweek next week. Initial areas
of low pressure may stay west of 165W but latest
guidance/ensembles indicate potential for another low nearer to
15N/160W by late Wed into next Thu. This would have the potential
to draw northward deep tropical moisture but confidence is low
given the spread in ensemble low positions and lead time. 00Z
ECMWF was a rather extreme example with >5" rainfall into the Big
Island by next Thu.

Prior to that, an area of increased moisture is forecast to move
through the region in tandem with the upper low (late Sat through
Mon) from east to west. An increase in showers is expected but
with generally light to locally modest amounts. Upper ridging may
attempt to nose into the area from the east next Tue-Wed but may
weaken thereafter as troughing slips southeastward to the north of
the area.


Fracasso