Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
827 AM EDT Tue Jun 12 2018

Valid 00Z Wed Jun 13 2018 - 00Z Wed Jun 20 2018

With amplified flow remaining confined to the mid-latitudes, the
major influences will stay in the sub-tropics. A gradual eastward
expansion of an upper ridge is expected throughout the week while
a weakness in the flow drifts eastward across the Hawai`ian island
chain. Eventually this feature should become better defined once
east of the islands as most solutions depict a broad 582-dm
circulation around 140W longitude. Outside of the 00Z ECMWF, other
global models favor a slow retrogression of this upper low with
possible poleward adjustments depending on the level of
amplification across the mid-latitudes.

At the surface, a broad anticyclone is forecast to remain fixed
over the eastern Pacific which will allow light to moderate trade
winds to persist for much of the period. Models show the strength
of these trades should generally cap out in the 10 to 15 knot
range with occasional upticks. By Friday, the parent anticyclone
is expected to lift farther north although little change in the
surface winds are anticipated. By the end of the weekend,
solutions show a gradual slackening in the flow with overall wind
speeds reducing down to the 5 to 10 knot range which continues
into next week. Overall rain shower chances remain driven by the
climatological trades with expected precipitable water values on
the lower side, generally around 1 to possibly 1.25 inches. Some
increase in these numbers may take place by early next week as
higher moisture content drops down from the central Pacific.


Rubin-Oster