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Subtropical Storm JOYCE


Subtropical Storm Joyce Discussion Number   5
NWS National Hurricane Center Miami FL       AL102018
500 PM AST Thu Sep 13 2018

Joyce has an exposed center this afternoon with no substantial
deep convection anywhere nearby.  The initial intensity
remains 35 kt, consistent with the Hebert-Poteat ST2.5
classification from TAFB as well as the appearance of the very
tight low-level center as seen in the GOES-16 visible satellite
imagery.  As Joyce still remains embedded within an upper-level
trough, the system retains the subtropical storm label.

Joyce has now been devoid of deep convection for almost a day, due
to the dry stable air combined with strong tropospheric vertical
shear.  As the system is not expected to undergo extratropical
transition, without deep convection gradual weakening is
anticipated until dissipation in about four days.  The official
intensity forecast is a blend of the IVCN intensity consensus
scheme along with the GFS and ECMWF global model guidance.  This
new forecast indicates a reduction from the previous advisory, and
in fact, Joyce could become a post-tropical cyclone soon if deep
convection does not reappear shortly.

Joyce is moving toward the southwest at about 5 kt, as it is
situated slightly to the west of an upper-level low.  In a couple
days, a new short wave trough will dive equatorward west of Joyce
and begin advecting Joyce toward the northeast.  The new NHC track
forecast is a bit to the left (southwest) of the previous advisory
and is based upon a blend of the HWRF hurricane model and the GFS
and ECMWF global models.


INIT  13/2100Z 33.6N  44.2W   35 KT  40 MPH
 12H  14/0600Z 33.1N  44.6W   35 KT  40 MPH
 24H  14/1800Z 32.3N  44.7W   35 KT  40 MPH
 36H  15/0600Z 32.4N  44.0W   35 KT  40 MPH
 48H  15/1800Z 33.2N  43.1W   30 KT  35 MPH
 72H  16/1800Z 36.0N  39.5W   25 KT  30 MPH
 96H  17/1800Z...DISSIPATED

Forecaster Landsea