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Potential Tropical Cyclone SIX


Potential Tropical Cyclone Six Discussion Number   5
NWS National Hurricane Center Miami FL       AL062018
1100 AM AST Fri Aug 31 2018

The circulation is better defined this morning, but the associated
convection is rather weak.  In fact, Dvorak numbers have not
changed overall, and do not support classifying the system as a
tropical cyclone yet.  It seems like both NHC and the global models
predicted the development of a cyclone too soon.  Nevertheless, the
environmental conditions are favorable for both genesis and
strengthening, and a tropical depression or a storm is expected to
form later today or Saturday.  The shear does not appear to be a
problem at this time, but the cyclone should be moving over marginal
SSTs, limiting the amount of intensification.  The HWRF model
changed its tune to a more reasonable one, and it now shows more
modest strengthening.  The NHC forecast is similar to the previous
one, and continues to be very close to the intensity consensus.

The disturbance is moving toward the west-northwest or 285 degrees
at about 11 kt.  The subtropical high should continue to steer the
system toward the west-northwest with some increase in forward
speed for the next 2 to 3 days.  After that time, a weakness in the
ridge will induce a more northwestward track over the open Atlantic
Ocean.  This is supported by the track guidance which continues to
be in very good agreement for the next 3 days.  Thereafter, the
guidance envelope widens and becomes bounded by the westernmost
ECMWF and the easternmost GFS models decreasing the confidence
in the track forecast.


INIT  31/1500Z 13.7N  22.7W   30 KT  35 MPH...POTENTIAL TROP CYCLONE
 12H  01/0000Z 14.1N  24.5W   35 KT  40 MPH...TROPICAL STORM
 24H  01/1200Z 14.8N  27.0W   40 KT  45 MPH
 36H  02/0000Z 15.5N  29.5W   45 KT  50 MPH
 48H  02/1200Z 16.2N  32.1W   50 KT  60 MPH
 72H  03/1200Z 17.5N  37.5W   55 KT  65 MPH
 96H  04/1200Z 19.5N  42.0W   60 KT  70 MPH
120H  05/1200Z 22.0N  45.5W   65 KT  75 MPH

Forecaster Avila