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Hurricane Barbara Discussion Number  12
NWS National Hurricane Center Miami FL       EP022019
1100 PM HST Tue Jul 02 2019

Barbara appears to have reached its peak intensity.  The solid
white ring that had surrounded the eye in the Dvorak enhancement at
the time of the previous advisory has eroded, and the eye is not
quite as warm.  Although Dvorak T-numbers have fallen as a result,
Barbara's winds would likely take some time to respond, and the
initial intensity is held at 135 kt as a blend of subjective and
objective Dvorak CI numbers.

There are a couple of factors, internal and external, that should
lead to gradual weakening in the short term.  First, the layer of
warm water at the ocean's surface ahead of Barbara is becoming
shallower, with oceanic heat content values falling to zero in the
next 48 hours. Second, a very recent GPM microwave overpass suggests
that Barbara is developing a concentric eyewall structure, which
tends to precede an eyewall replacement and associated weakening.
Once weakening is underway due to these circumstances, deep-layer
southwesterly shear is then expected to increase over 20 kt from 48
hours and beyond.  The intensity models on this cycle are
suggesting that Barbara's weakening rate could be a little faster
than shown previously after 48 hours, and this is reflected in the
new NHC official forecast, which lies close to the HCCA model and
the intensity consensus.  Barbara could lose its deep convection,
and thus become post tropical, around the time it is forecast to
cross 140W into the central Pacific basin.

Barbara continues to move west-northwestward, or 285/12 kt, along
the southwestern periphery of the subtropical ridge.  There has
been no change in the track forecast reasoning, with the hurricane
expected to turn northwestward and slow down during the next 36
hours as it approaches a large break in the ridge near and east of
the Hawaiian Islands.  Once Barbara weakens and becomes a shallower
system, it should then turn back to the west and accelerate on days
3 through 5.  The new NHC forecast has been adjusted slightly
southward for much of the forecast period in order to fall closer
to the model consensus solutions.


FORECAST POSITIONS AND MAX WINDS

INIT  03/0900Z 13.5N 125.6W  135 KT 155 MPH
 12H  03/1800Z 14.1N 127.0W  125 KT 145 MPH
 24H  04/0600Z 15.1N 128.8W  115 KT 130 MPH
 36H  04/1800Z 16.3N 130.5W  100 KT 115 MPH
 48H  05/0600Z 17.4N 132.3W   85 KT 100 MPH
 72H  06/0600Z 18.9N 136.4W   50 KT  60 MPH
 96H  07/0600Z 19.0N 142.0W   35 KT  40 MPH...POST-TROPICAL
120H  08/0600Z 18.5N 149.0W   30 KT  35 MPH...POST-TROP/REMNT LOW

$$
Forecaster Berg

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