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Potential Tropical Cyclone SEVEN

Potential Tropical Cyclone Seven Discussion Number   2
NWS National Hurricane Center Miami FL       AL072018
1100 PM EDT Sun Sep 02 2018
There has been little change in the organization of the disturbance
since the previous advisory.  Satellite imagery shows that some new
convective bands have formed to the northeast of the trough axis,
but there is still no evidence of a closed surface circulation at
this time.  The initial intensity remains 25 kt, which is in
agreement with the earlier ASCAT data and recent surface
observations.  An Air Force Reserve Unit reconnaissance aircraft is
scheduled to investigate the disturbance on Monday to give a better
assessment of the structure and intensity of the system.
The disturbance will be moving over warm waters and within
an area of generally low vertical wind shear.  These conditions
should allow gradual development of the system over the next day or
so.  The global model guidance indicates that the surface trough
will sharpen and that a closed surface circulation is likely to
develop in association with the system over the Gulf of Mexico
within the next 24-36 hours.  Once this occurs, the system is
expected to continue to gradually strengthen until it reaches the
north-central Gulf coast Tuesday night or early Wednesday.  The
intensity guidance did not change much this cycle and neither has
the latest official forecast.
The initial motion estimate is 300/13 kt.  The disturbance is
forecast to move west-northwestward to northwestward around the
southwestern portion of a deep-layer ridge that is centered over the
Mid-Atlantic states.  On this heading, the disturbance is
expected to pass over the Florida Keys or the southern Florida
peninsula tomorrow morning, then cross the eastern Gulf of Mexico
Monday night before approaching the north-central Gulf coast late
Tuesday or Tuesday night.  The dynamical model guidance is in good
agreement on this scenario, however, since the system is still in
the pre-genesis phase future changes regarding the exact track
and timing of the onset of hazards are possible.
Key Messages:
1. Potential Tropical Cyclone Seven will bring heavy rainfall and
gusty winds to portions of the Bahamas, South Florida, and the
Florida Keys tonight and Monday, and interests in those areas should
monitor the progress of this system.
2. A Tropical Storm Watch has been issued for portions of the
central Gulf Coast, and tropical storm conditions are possible in
those areas Tuesday night and Wednesday. Heavy rainfall from this
system will affect portions of the central Gulf Coast later this
week, including areas that are currently receiving heavy rainfall
from a different weather system. Interests in these areas should
monitor products from their local National Weather Service office.
3. Users should be aware that forecast uncertainty for potential
tropical cyclones is generally larger than that for tropical
cyclones, especially beyond 48-72 hours.
INIT  03/0300Z 23.4N  78.7W   25 KT  30 MPH...POTENTIAL TROP CYCLONE
 12H  03/1200Z 24.5N  80.7W   30 KT  35 MPH
 24H  04/0000Z 25.9N  83.4W   35 KT  40 MPH
 36H  04/1200Z 27.5N  86.2W   40 KT  45 MPH
 48H  05/0000Z 28.8N  88.6W   50 KT  60 MPH
 72H  06/0000Z 31.7N  92.5W   30 KT  35 MPH...INLAND
 96H  07/0000Z 33.2N  94.4W   25 KT  30 MPH...INLAND
120H  08/0000Z 34.2N  95.7W   20 KT  25 MPH...POST-TROP/REMNT LOW
Forecaster Brown