Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
832 AM EDT Sat Oct 28 2017

Valid 00Z Sun Oct 29 2017 - 00Z Sun Nov 05 2017

Shortwave ridging will establish its presence over the island
chain in between a pair of systems which have been tracking
through the active mid-latitude flow. The lead system is forecast
to cut off just east of 150W but should generally remain out of
the picture when it relates to Hawai`ian impacts. Looking
upstream, a much more pronounced upper trough will be crossing the
International Dateline this weekend. Solid agreement exists in
cutting off this system as well, generally in the vicinity of
30N/170W on Tuesday. Gradually amplified flow within the
north-central Pacific will draw this mentioned system northward
which allows heights to build over the central Pacific. Toward the
end of next week, models show a broad 588-dm ridge settling over
the state as high-amplitude flow establishes its presence across
much of the oceanic basin. While solutions vary on details with
the upstream trough, they do not seem of significant consequence
to Hawai`i.

With a shearing frontal zone remaining over the Big Island, the
remnant axis of low-level convergence could foster the development
of some scattered showers. Eventually light warm advection will
take shape across the region which allows for a shift to a general
south-southeasterly flow. This ultimately allows for a nice surge
of tropical moisture as precipitable water values rise into the
1.50 to 2.00 inch range by early next week. By Tuesday/Wednesday,
wind speeds begin to pick up to around 10 to 15 knots as a frontal
zone approaches from the northwest. Most solutions favor the
enhanced showers to remain just offshore of Kauai. By Thursday
onward, a shift to a more climatological trade wind regime is
expected with speeds picking up toward next weekend given a robust
surface high setting up over the eastern Pacific. Windward showers
will be likely given the re-establishment of the trades.


Rubin-Oster