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Hawaii Extended Forecast Discussion
(Latest Discussion - Issued 1230Z Sep 24, 2018)
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Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
830 AM EDT Mon Sep 24 2018

Valid 00Z Tue Sep 25 2018 - 00Z Tue Oct 02 2018

A favored composite of well clustered models and ensembles agree
that an upper low now northwest of Hawaii will eject slowly
northeast and weaken as strong reinforcing energy digs upstream to
form a potent new closed trough/low. This seems reasonable
considering the high amplitude of the upstream ridge over the
subtropical west-central Pacific. In this pattern, a trailing low
level front now west of the islands will tend to shift gradually
eastward toward the state. Confluent flow east of the front sets
up deep return moisture advection, as the models indicate
potential for a high 2-2.25 inch precipitable water plume to feed
into the islands. This will fuel a risk of enhanced showers and
potential for locally heavy rainfall extending into mid-late week.
In the wake of this system, expect a return to a modest trade and
rainfall pattern by next weekend as upper ridging returns over
Hawaii. However, we'll need to keep an eye on deep moisture
wrapping on the north side of a potential tropical disturbance to
pass south of the state.