Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
716 AM EST Sun Feb 03 2019

Valid 00Z Mon Feb 04 2019 - 00Z Mon Feb 11 2019

A transient mid/upper-level ridge will build across Hawaii through
Mon as a broad 500 hPa weakness which has been across Hawaii for
several days moves east. This will allow drier air to filter
across the state bringing a reduction in shower activity and a
resumption of 10-20 kt surface easterlies. Models continue to
suggest significant flow amplification developing across the
north/central Pacific by mid-week as shortwave energy separates
from digging northern stream flow and continues to amplify north
of Hawaii. While there is general agreement among the guidance on
this general scenario, solutions differ as to the specifics of the
evolution. The ECMWF/CMC continue to cut off a low at 500 hPa
several hundred miles north of Hawaii by Thu, then the low drifts
south toward Hawaii. The GFS shows a similar solution, but delays
the feature cutting off until Sat. Most solutions show an eventual
surface low reflection as well. Given the range of possible
scenarios, will recommend an ensemble approach by late week into
next weekend, as ensemble means show a bit more consistency.
Nonetheless, would expect PWs to increase across Hawaii by
mid-week as moisture advects north into the developing low
pressure system, with a significant increase in shower activity
and disruption in trades. Given the degree of amplification
expected, there seems to be consensus that a cold front may push
through Hawaii by Fri, bringing drier air across Hawaii and
perhaps a period of brisk northwesterly flow at the surface.
Confidence in these details by next weekend is modest at best,
however.


Ryan