Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
817 AM EDT Thu Aug 01 2019

Valid 00Z Fri Aug 02 2019 - 00Z Fri Aug 09 2019

...Erick forecast to move south of Hawai'i late this week...
...Flossie expected to move near/north of Hawai'i early next
week...

The general flow pattern features a deep layer cyclone dropping
south along the 150th meridian before turning southwest and then
westward along the 40th parallel.  The guidance is extremely well
clustered with this system so a compromise of the 00z UKMET, 00z
Canadian, 06z GFS, and 00z ECMWF should work nicely as they are
close to the ECMWF and NAEFS ensemble means solutions.  This
system will help guide and weaken the tropical cyclones near
Hawai'i over the next several days.

The Central Pacific Hurricane Center is issuing advisories for
Hurricane Erick.  Expect Erick to weaken over the coming days and
pass to the south of the main islands (on a west-northwest track)
as a tropical storm tonight.  This system should bring a period of
heavy rainfall as well as stronger winds, swells, and high surf. 
Guidance continues to show that highest rainfall totals should be
over the windward/eastern slopes of the Big Island, with some
enhanced activity possibly crossing the northwestern portion of
the main islands as well.  Local amounts of 4-6" are possible.

Upstream, the National Hurricane Center is providing advisories
for Hurricane Flossie.  Flossie is still forecast to approach the
main islands late Sunday and Monday, albeit in a somewhat weaker
form than it is currently.  There is still a reasonable consensus
that the track of Flossie will be farther north than Erick, with
guidance pointing northeast of Hawai'i.  There is ongoing
potential for another episode of heavy rainfall in a more Kona
trajectory (south to southwest flow) and enhanced winds/waves.

Away from the two tropical systems expect a moist trade wind
pattern with windward/mountain shower emphasis.  Mid-latitude high
pressure should weaken for a time in response to an east-central
Pacific low.  Eastern Pacific high pressure should expand toward
the middle of next week, supporting moderate trades immediately
behind Flossie.

Roth