Official Discussion issued by the National Hurricane Center

Oscar (AL162018) DATA RELEASED: 10/27/2018 11:00:00 PM UTC

Copy of official data

Tropical Storm Oscar Discussion Number   5
NWS National Hurricane Center Miami FL       AL162018
1100 PM AST Sat Oct 27 2018

Satellite imagery shows that convection associated with Oscar has
become better organized, with increased banding around the low-
level center.  In addition, recent scatterometer data indicate that
the system now has a relatively small wind field with a radius of
maximum winds of about 25 n mi.  Although the cyclone is still
tangled up with the upper-level low to the point where it has not
yet developed the anticyclonic outflow of a tropical cyclone, the
convection and the wind field now justify calling the system a
tropical storm.  The initial intensity has been raised to 55 kt
based on the scatterometer data, and it is possible this is a little
conservative.

The initial motion is a somewhat uncertain 240/17, as the
short-term motion has been more toward the southwest or south.  For
the next several hours, Oscar should continue to pivot around the
upper-level low to its east.   Thereafter, it should turn more
westward with a decrease in forward speed on the south side of a
large ridge over the North Atlantic.  After about 36 h, a large
deep-layer trough moving eastward across the western Atlantic
should cause Oscar to turn northwestward and northward, followed by
recurvature into the westerlies and acceleration.  The track
guidance is generally in good agreement with this scenario,
although by 120 h there is some spread in both the direction and
forward speed after recurvature.  The new forecast track is near
the various consensus models, and the early part of it is shifted a
little to the south of the previous forecast due to the current
location and motion.

The global models suggest that the core of Oscar should mostly avoid
nearby strong upper-level winds through 24-36 h, and then encounter
strong upper-level divergence associated with the deep-layer trough.
While the environment is not ideal for a tropical cyclone,
conditions appear favorable for additional intensification, and the
intensity forecast now calls for Oscar to reach hurricane strength
in about 24 h. Interaction with the trough after 72 h should start
extratropical transition, which should be complete between 96-120 h.


FORECAST POSITIONS AND MAX WINDS

INIT  28/0300Z 25.7N  51.4W   55 KT  65 MPH
12H  28/1200Z 25.2N  54.1W   60 KT  70 MPH
24H  29/0000Z 25.1N  56.5W   65 KT  75 MPH
36H  29/1200Z 25.8N  58.2W   70 KT  80 MPH
48H  30/0000Z 27.2N  58.6W   75 KT  85 MPH
72H  31/0000Z 32.5N  55.5W   75 KT  85 MPH
96H  01/0000Z 41.0N  47.0W   70 KT  80 MPH
120H  02/0000Z 48.5N  32.0W   60 KT  70 MPH...POST-TROP/EXTRATROP

$$
Forecaster Beven