Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
812 AM EDT Tue Aug 20 2019

Valid 00Z Wed Aug 21 2019 - 00Z Wed Aug 28 2019

An upper-level ridge initially centered northwest of Hawaii will
keep moderate trades in place through late this week with showers
in typical windward/mountain areas. Models/ensembles show broad
agreement that an upper-level low will separate from the
westerlies near 40N/150W Tue night/Wed and drift southwestward
through the next few days, passing just north of Hawaii Fri-Sat.
Sensible weather impacts across the state should be relatively
minimal with limited moisture in place, but an associated weak
surface trough and strengthening surface high north of the state
in the wake of the feature may strengthen trades a bit (into the
20-25 kt range)by late Sat into early next week. By the middle of
next week ensembles suggest the surface high should move away from
Hawaii with the pressure gradient and trades weakening. Some
pieces of guidance and ensemble members show the potential for a
relatively weak system of tropical origin to pass near/south of
Hawaii by the middle of next week, although spread with respect to
this feature is quite high and confidence in any specific solution
very low at this time.


Ryan