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Tropical Storm Joyce Discussion Number  12
NWS National Hurricane Center Miami FL       AL102018
1100 AM AST Sat Sep 15 2018

Joyce is feeling the effects of shear this morning.  The low-level
center of the tropical storm has become exposed to the south of a
area of deep convection.  ASCAT data indicate the the maximum winds
have dropped to 35-40 kt, and 40 kt is chosen as the initial wind
speed since the resolution of ASCAT is likely causing an
undersampling of the small storm.

The environment isn't forecast to change much near Joyce during the
next day or so, with strong shear being offset by waters near 27C.
The NHC forecast is leveled off during that time, a bit lower than
the previous prediction mostly to account for the initial wind
speed.  Thereafter, while the shear is forecast to continue, the
mid-level air should become drier near the center, and SSTs cool off
gradually below 26C.  These conditions should cause Joyce to
slowly weaken early next week, and dissipate in 3 days or so.  This
is the solution provided by much of the guidance, and the NHC
forecast follows suit.

Joyce has accelerated overnight, now moving east-northeastward at
about 12 kt.  The storm remains embedded in the same trough as
Tropical Storm Helene and it should follow that tropical cyclone
east-northeastward to northeastward at increasing forward speeds
during the next day or two.  Beyond that time, as Joyce becomes a
shallow cyclone, it is forecast to turn southeastward due to
low-level flow around the eastern side of a building ridge over the
central Atlantic Ocean.  No significant changes were made to the
forecast, which lies on the southern side of the guidance envelope.


FORECAST POSITIONS AND MAX WINDS

INIT  15/1500Z 32.0N  41.0W   40 KT  45 MPH
 12H  16/0000Z 32.9N  39.2W   40 KT  45 MPH
 24H  16/1200Z 34.0N  35.9W   40 KT  45 MPH
 36H  17/0000Z 34.5N  32.2W   35 KT  40 MPH
 48H  17/1200Z 34.0N  29.0W   30 KT  35 MPH
 72H  18/1200Z 32.0N  25.5W   25 KT  30 MPH
 96H  19/1200Z...DISSIPATED

$$
Forecaster Blake

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