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Tropical Storm Barbara Discussion Number   4
NWS National Hurricane Center Miami FL       EP022019
200 AM PDT Mon Jul 01 2019

Although earlier microwave imagery indicated that Barbara was still
being affected by moderate northwesterly shear, the upper-level
outflow has expanded overnight and the center appears to be more
embedded within the area of very cold cloud tops.  A couple of
earlier ASCAT passes revealed peak winds of 50 kt, and a much larger
area of tropical-storm-force winds over the eastern semicircle of
the cyclone than previously analyzed.  Due to the typical
undersampling of peak winds in the ASCAT instrument, the initial
intensity has been increased to 55 kt, which is also in good
agreement with the latest TAFB Dvorak intensity estimate, and ADT
and SATCON estimates from UW/CIMSS.

As mentioned in the previous advisory, the global models continue
to forecast a reduction in the deep-layer vertical wind shear
during the next couple of days while Barbara moves over warm sea
surface temperatures.  These conditions are expected to allow steady
to perhaps rapid strengthening over the next couple of days.  The
SHIPS, FSSE, and HCCA models are quite aggressive and predict rapid
strengthening during the next 24 to 36 h, while the HWRF and HMON
models are somewhat lower.  Given the current structure of the
cyclone, the NHC forecast is a little below the more aggressive
models, but still predicts significant strengthening during the
next 24 to 48 hours.  After 72 hours, cooler waters and increasing
southwesterly shear are expected to cause gradual weakening.

The initial motion estimate is 275/18 kt.  A deep-layer ridge to
the north of the storm is forecast to gradually weaken over the
next several days.  This should cause Barbara to slow down and turn
west-northwestward within the next day or so.   By 96 h, the ridge
is forecast to build westward which should cause the cyclone to turn
back toward the west.  While the dynamical models generally
agree on the overall scenario there are some differences in the
predicted forward speed and how far north Barbara will move.  The
NHC forecast splits these differences and lies near the middle of
the guidance envelope, closest to the Florida State Superensemble.


FORECAST POSITIONS AND MAX WINDS

INIT  01/0900Z 11.2N 115.8W   55 KT  65 MPH
 12H  01/1800Z 11.5N 117.9W   65 KT  75 MPH
 24H  02/0600Z 11.9N 120.5W   80 KT  90 MPH
 36H  02/1800Z 12.4N 122.7W   95 KT 110 MPH
 48H  03/0600Z 13.0N 124.7W  105 KT 120 MPH
 72H  04/0600Z 14.5N 128.3W  105 KT 120 MPH
 96H  05/0600Z 16.3N 132.0W   85 KT 100 MPH
120H  06/0600Z 17.2N 136.2W   70 KT  80 MPH

$$
Forecaster Brown

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