Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
819 AM EDT Wed May 30 2018

Valid 00Z Thu May 31 2018 - 00Z Thu Jun 07 2018

Upper flow across the Central Pacific over the next week looks to
remain largely disconnected from the more active flow regime
across the North Pacific, with little change in the overall
pattern for Hawaii any time soon. Low-level easterlies are
expected to prevail across Hawaii over the next week, with shower
activity remaining relatively sparse. An upper low and surface
trough were initially located several hundred miles west of
Hawaii. Models/ensembles show consensus that the upper low should
weaken over the next few days and become absorbed into another
amplifying trough well north northwest of Hawaii. The upper
pattern looks to repeat, however, with the second trough likely to
amplify and once again cut off west of Hawaii by Sun. Some model
spread remains as to exactly where this second upper low will cut
off, but there is a general consensus among the GFS/ECMWF/UKMET
that the features will be centered west of Hawaii (the CMC was
much father east, with the low centered north of Hawaii by late
Sat). Nonetheless, this second low should be closer to the state
than the first. At the surface, the implications of this appear
somewhat minor, with a strong surface high remaining in place
north/northeast of Hawaii through the next week, keeping surface
easterlies in place, 15 to 20 kt through much of the next week.
The deepest moisture as shown by high PW values should generally
remain well south of Hawaii, and west of Hawaii in the vicinity of
the two troughs/upper lows. By early next week a slight increase
in moisture is possible across the western islands as the second
upper low will be a bit closer than the first, and the moisture
increase across Hawaii could be more widespread if the upper low
by this weekend cuts off farther east than the current model
consensus.


Ryan