ZCZC MIATCDEP2 ALL
TTAA00 KNHC DDHHMM

Tropical Storm Barbara Discussion Number   2
NWS National Hurricane Center Miami FL       EP022019
300 PM MDT Sun Jun 30 2019

The cloud pattern of Barbara is slowly becoming better organized,
with a curved convective band now forming in the southeastern
semicircle.  A recent ASCAT overpass indicates that maximum
sustained winds have increased to near 40 kt, and that a large area
of tropical-storm force winds now wraps more than halfway around the
center.  However, the wind data also show a significant trough
extending southwestward from the center into the Intertropical
Convergence Zone.

The initial motion is now 280/16.  A mid-level ridge to the north of
the cyclone should steer it westward to west-northwestward for the
next 48 h or so with a gradual decrease in forward speed. After
that, a weakness in the ridge should allow a west- northwesterly
motion for the rest of the forecast period.  The track guidance
remains fairly tightly clustered between the HWRF on the north side
of the envelope and the ECMWF on the south side. The new forecast,
which is similar to the previous forecast, lies near both the center
of the guidance envelope and the various consensus models.

Some northwesterly vertical wind shear continues to affect Barbara,
and this should persist for another 12 h or so.  After that, the
cyclone should be in an environment of light shear and over warm sea
surface temperatures through 72 h.  The intensity forecast thus
calls for slow development through 12 h and a faster rate of
development thereafter.  The various rapid intensification indices
suggest a 40-50 percent chance of rapid intensification from 12-72
h, and if this occurs Barbara could become a major hurricane. Beyond
72 h, the forecast track takes the center over decreasing water
temperatures and into renewed shear, which should cause some
weakening.  How much weakening, though, is going to be tied to how
far over the colder water the cyclone moves, with a more northerly
track resulting in a weaker storm then currently forecast.

FORECAST POSITIONS AND MAX WINDS

INIT  30/2100Z 10.9N 112.2W   40 KT  45 MPH
 12H  01/0600Z 11.4N 114.7W   45 KT  50 MPH
 24H  01/1800Z 11.9N 117.6W   55 KT  65 MPH
 36H  02/0600Z 12.2N 120.1W   65 KT  75 MPH
 48H  02/1800Z 12.6N 122.2W   75 KT  85 MPH
 72H  03/1800Z 14.0N 126.0W   95 KT 110 MPH
 96H  04/1800Z 15.5N 129.0W   90 KT 105 MPH
120H  05/1800Z 16.5N 133.0W   80 KT  90 MPH

$$
Forecaster Beven

NNNN