973 
WTNT45 KNHC 122040
TCDAT5

Subtropical Storm Joyce Discussion Number   1
NWS National Hurricane Center Miami FL       AL102018
500 PM AST Wed Sep 12 2018

The strong low pressure system which the NHC has been monitoring in
the north Atlantic for a couple of days has developed a cyclonically
curved band of deep convection near the center, and scatterometer
data indicate that the winds are near 40 kt.  Since the system is
still vertically stacked with an upper-low, it is then classified
as a subtropical cyclone at this time.  However, the cyclone is
gaining organization while it is acquiring tropical characteristics.
The NHC forecast calls for Joyce to transform into a tropical system
in about 12 to 24 hours.  Since the ocean is warm, some slight
strengthening is possible during the next 3 days.  After that time,
Joyce will be over cooler waters and should then be absorbed by a
larger extratropical low.

Joyce has been moving southwestward or 225 degrees at 5 kt, steered
by the northerly flow around the subtropical high which has been
steering Florence and to west of the mid-latitude trough which
is forcing Helene to recurve. In a couple of days, global models
indicate that the steering pattern will change as the trough
amplifies, and Joyce should then turn toward the northeast with an
increase in forward speed.


FORECAST POSITIONS AND MAX WINDS

INIT  12/2100Z 34.3N  41.9W   40 KT  45 MPH
 12H  13/0600Z 33.7N  42.6W   40 KT  45 MPH...TROPICAL STORM
 24H  13/1800Z 33.0N  43.5W   40 KT  45 MPH
 36H  14/0600Z 32.5N  43.5W   45 KT  50 MPH
 48H  14/1800Z 32.5N  43.5W   50 KT  60 MPH
 72H  15/1800Z 34.0N  41.0W   50 KT  60 MPH
 96H  16/1800Z 37.0N  35.0W   40 KT  45 MPH
120H  17/1800Z...ABSORBED

$$
Forecaster Avila