Official Discussion issued by the National Hurricane Center

Joyce (AL102018) DATA RELEASED: 9/13/2018 5:00:00 AM UTC

Copy of official data

Subtropical Storm Joyce Discussion Number   3
NWS National Hurricane Center Miami FL       AL102018
500 AM AST Thu Sep 13 2018

Joyce is still co-located with an upper-level low, and the most
recent TAFB intensity classification was still a subtropical type.
Furthermore, there has been no discernible increase of convection
near the center of the cyclone, and cloud tops have actually warmed
over the past few hours.  Therefore, Joyce is still classified as
subtropical for this advisory.  Since the cyclone hasn't changed
much in organization, the initial intensity has been held at 40 kt
based on the TAFB subtropical intensity estimate, but this is still
possibly generous.

Joyce's struggle to maintain deep convection bodes poorly for its
intensification prospects, considering that the shear is forecast
by the global models to increase considerably over the next few
days.  SHIPS, LGEM, and the global models continue to show Joyce
changing little in strength over the next few days until the
system dissipates by early next week.  The HWRF and HMON models are
still outliers in showing substantial intensification, but even
these models aren't quite as aggressive in strengthening Joyce as
they were previously.  The NHC forecast continues to favor the
statistical guidance and is just below the intensity consensus at
most forecast hours because it is frankly hard to believe that Joyce
will become a hurricane in 48 h based on its current appearance.

Joyce is still moving slowly southwestward with an initial motion
of 220/5 kt.  The global models remain in fairly good agreement
that Joyce will move slowly southwestward for the next day or
so as the storm remains in light steering flow.  A turn toward the
south will likely occur as Helene approaches from the southeast,
followed by a quick turn northeastward once the larger tropical
cyclone passes by.  Joyce should then accelerate quickly
northeastward ahead of a mid-latitude trough before dissipating
southwest of the Azores.  Little change was made to the official
track forecast which is near the middle of the various consensus


INIT  13/0900Z 33.8N  43.1W   40 KT  45 MPH
12H  13/1800Z 33.3N  43.8W   40 KT  45 MPH
24H  14/0600Z 32.6N  44.2W   45 KT  50 MPH
36H  14/1800Z 32.0N  44.0W   45 KT  50 MPH
48H  15/0600Z 32.1N  43.2W   45 KT  50 MPH
72H  16/0600Z 34.6N  39.4W   40 KT  45 MPH
96H  17/0600Z 37.0N  32.5W   40 KT  45 MPH
120H  18/0600Z...DISSIPATED

Forecaster Zelinsky