Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
729 AM EST Thu Feb 15 2018

Valid 00Z Fri Feb 16 2018 - 00Z Fri Feb 23 2018

A series of vigorous closed upper lows will impact Hawaii over the
next week, according to the latest reliable global models. The
resultant from each feature will be moist unsettled weather with
the potential for heavy to excessive rains. Already a compact
closed 500mb feature is located about 26N 161-162W and keeping a
moist plume of tropical moisture with 1.50 inch precipitable water
values, especially near the Big Island and Maui. This feature will
begin to weaken slightly over the next day or two, while lifting
north and getting caught up in the westerlies. However, with the
blocking large scale pattern across the mid-latitudes across the
pacific, the continuous plume of tropical moisture will remain
especially for the eastern portion of the islands. The next set of
upper dynamics and lowering upper heights will arrive on Saturday
into Sunday. This time, upper dynamics will close off right over
the state, which may help in shoving the tropical moisture surge
east of the state but the Big Island could still be impacted.
Also, with the low closing off over the state, expect the
increasing chances of instability showers/perhaps thunderstorms
and maybe even snow for the highest peaks of the Big Island. This
low will begin to fill and weaken about Tuesday/Wednesday but once
again, another set of short wave upper dynamics dig southeast from
the central Pacific and close off northwest of the state. This may
allow the plume of tropical moisture to retrograde westward and
begin to encompass the entire state, just a little difficult to
pin down a week out. Another item, tough to peg exactly if these
features are true Kona lows. Based on the available guidance, the
most likely low is the initial one which contains the moist regime
locked in across the eastern portion of the state.

Musher