Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
715 AM EST Sun Feb 19 2017

Valid 00Z Mon Feb 20 2017 - 00Z Mon Feb 27 2017

Weakening cold front moving through Hawai'i as of 12Z will usher
in gusty winds from the north and then northeast for the next few
days as a 1030mb surface high slides eastward along 30N. Ensembles
show another shortwave late Monday that should dig and deepen to
the north and then northeast of the state on Tuesday, closing off
about 900 miles to the NNE. Models/ensembles have trended a bit
farther west over the past few days but mostly in unison. The
upper low is forecast to sink southward to near 30N but then pull
eastward which should keep the tropical moisture plume (mostly
associated with the leftover front in the near term) to the
southeast of the area.

Thereafter, the ensembles show yet another shortwave to drop
southward from the mid-latitudes on Friday into Saturday around
165W which looks to sink southward toward 30N. The deterministic
00Z ECMWF/Canadian and UKMET (through the end of its run at 00Z
Sat) were clustered together with a stronger upper low than the
GFS runs. This affects how the previous upper low evolves, with
the GFS lingering it near 30N/150W allowing it to become the more
dominant upper feature. Pattern is also complicated by another
upper low moving southward off the British Columbia coast which
may or may not get pulled into the first upper low. Altogether,
the Canadian fits in best with the multi-center ensembles by next
weekend with the ECMWF second best. Still, moisture with the
system to the northwest may still stay to the northwest by next
Sunday but tropical moisture from the lower latitudes may try to
lift northward. This could leave Hawai'i in between the two in a
drier pattern but it may be a close call.


Fracasso