Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
830 AM EDT Sun Sep 09 2018

Valid 00Z Mon Sep 10 2018 - 00Z Mon Sep 17 2018

The main player during the upcoming week will be Hurricane Olivia
although it is expected to lose some intensity as it approaches
the Hawai`ian island chain late Tuesday. The Central Pacific
Hurricane Center indicates it will likely be a strong tropical
storm with maximum winds of 55 knots, gusting to 65 knots at this
point. Before this occurs, the islands should be entrenched in
light northeasterly winds while gradually picking up early next
week in response to Olivia's wind field. Based on the
tropical-storm-force wind speed probabilities, there is a decent
chance of experiencing such winds across Maui and the Big Island,
particularly late Tuesday into Wednesday. The current track seems
to most closely resemble the 00Z ECMWF as the 06Z GFS/00Z UKMET
sit a bit to the south. In addition to the gusty winds and rough
surf, heavy rainfall is likely to impact the region. With the 00Z
ECMWF being a close proxy to the official track, storm totals on a
broader scale will sit around 1 to 3 inches while locally heavier
amounts in the 3 to 6 inch range are definitely possible.

Once Olivia passes to the west, a broad positively-tilted upper
trough sits well to the east of Hawai`i for the remainder of the
period while the mean ridge hangs back closer to the International
Dateline. Ultimately, the pattern is moving back toward a trade
wind regime given a broad surface anticyclone settles over the
central Pacific. Generally speeds of 15 to 20 knots are likely
from Thursday onward with trade driven showers possible each day.
This would fall on top of any heavy rainfall from Olivia which
could pose hydrologic threats depending on how saturated the soils
become.


Rubin-Oster