Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
830 AM EDT Wed Aug 02 2017

Valid 00Z Thu Aug 03 2017 - 00Z Thu Aug 10 2017

A general blocking regime across the central Pacific will feature
a compact upper low centered over the mid-latitudes. Eventually
this circulation is forecast to lift toward the Aleutians and be
of no consequence to the Hawai`ian island chain. Closer to the
region of interest, an upper low will spin off toward the
International Dateline while broad ridging extends to the east of
Hawai`i. By the early to middle part of next week, there is a hint
at some amplification in the mid-latitudes which could graze
Kauai. However, only the 06Z GFS/GEFS mean show this which appears
to be somewhat outlying based on ensemble spaghetti member
comparisons.

At the surface, ridging is forecast to continue to dominating
which supports the persistence of the climatological trade wind
regime. A strengthening in the dome of high pressure to the north
will lead to an uptick in the trades by Friday and into the
weekend. Recent model solutions show such an increase into the 20
to possibly 25 knot range at times. Eventually the strength of
these winds should come down a bit by early next week as the
surface pressure gradients begin to show some weakening. Regarding
threats for precipitation, the better moisture fluxes should stay
to the south of the islands based on the precipitable water
forecast. However, given the moderate trades noted in the
guidance, expect a potential increase in the coverage of windward
showers from Friday into the weekend.


Rubin-Oster