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TROPICAL STORM IAN DISCUSSION NUMBER  15
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL102016
1100 PM AST THU SEP 15 2016

Ian has continued to accelerate northeastward within deep-layer
southwesterly flow ahead of an approaching cold front and strong
shortwave trough, and this general motion is expected for the next
2 days until the system becomes absorbed by a larger extratropical
low. The new track forecast is essentially just an update of the
previous advisory track and remains near the center of the tightly
clustered NHC model guidance, close to the GFS and ECMWF consensus.

The initial intensity remains at 45 kt based a 16/0034Z ASCAT-B
overpass that contained few 43-kt wind vectors southeast of the
well-defined low-level center. Ian is forecast to merge with
a baroclinic zone and undergo extratropical transition during the
next 12-36 hours, and in the process it is expected to strengthen to
at least storm-force before it is absorbed by another extratropical
low. The new intensity forecast is the same as the previous
advisory based on the global models and guidance from the Ocean
Prediction Center.

FORECAST POSITIONS AND MAX WINDS

INIT  16/0300Z 42.9N  44.9W   45 KT  50 MPH
 12H  16/1200Z 46.9N  39.5W   55 KT  65 MPH...POST-TROPICAL
 24H  17/0000Z 53.3N  31.4W   60 KT  70 MPH...POST-TROP/EXTRATROP
 36H  17/1200Z 58.9N  23.4W   55 KT  65 MPH...POST-TROP/EXTRATROP
 48H  18/0000Z 63.3N  15.6W   50 KT  60 MPH...POST-TROP/EXTRATROP
 72H  19/0000Z...ABSORBED

$$
Forecaster Stewart

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