Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
824 AM EDT Tue Sep 29 2015

Valid 00Z Wed Sep 30 2015 - 00Z Wed Oct 07 2015

...Widespread heavy rain possible this coming weekend...

Surface high pressure to the north of the state will keep trades
in place through much of the week with windward showers. By Friday
and into the weekend, a deep upper low is still forecast to dip
toward 34N/150W while tropical energy from the SW of Hawai'i is
forecast to lift northeastward. The combination is expected to
draw in moisture from the SW and SE over the 50th state starting
late Friday. PW values are forecast to rise over 2 inches
statewide which is well above climo (likely above 2-3 standard
deviations). The details of such tropical infusion are murky and
the ensembles are spread west-east from about 170W-155W with areas
of low pressure. The recent 06Z/00Z GFS runs align more with the
ensemble means but nothing can really be ruled out at this point.
Regardless, a very wet and windy pattern is likely for the weekend
into early next week.


Fracasso