Official Discussion issued by the National Hurricane Center

Florence (AL062018) DATA RELEASED: 9/2/2018 5:00:00 PM UTC

Copy of official data

Tropical Storm Florence Discussion Number  14
NWS National Hurricane Center Miami FL       AL062018
500 PM AST Sun Sep 02 2018

Florence's cloud pattern is characterized by a low-level center
partially displaced to the west of the coldest cloud tops, which
have expanded in coverage recently. A blend of the latest satellite
classifications supports maintaining an intensity of 45 kt for this
advisory package. Little change in strength is expected for much of
the forecast period, as Florence will be moving through an
environment characterized by moderate shear and marginal SSTs for
the next 3 days. By the end of the forecast period, the SSTs begin
to warm up, which should result in some restrengthening. The new NHC
intensity forecast is similar to the previous one and is closest to
the SHIPS model forecast.

The initial motion estimate is 285/15. Florence will be steered
west-northwestward or westward for the next several days by the
Atlantic subtropical ridge. There is a fair amount of north-south
spread in the guidance, with the GFS, GEFS ensemble mean and HWRF on
the right side of the envelope and the ECMWF, ECMWF mean and UKMET
on the left. This spread is likely due to large differences in the
vertical structure of the cyclone, with the ECMWF and UKMET having a
much weaker vortex at 500 mb compared to the GFS in 3-4 days. Given
the difficulty in forecasting these types of structural changes,
the NHC forecast lies in the middle of the guidance envelope and is
close to the multi-model consensus aids through the forecast period.
This forecast is largely an update of the previous NHC prediction.


INIT  02/2100Z 17.4N  34.6W   45 KT  50 MPH
12H  03/0600Z 17.7N  36.9W   45 KT  50 MPH
24H  03/1800Z 18.2N  39.6W   45 KT  50 MPH
36H  04/0600Z 18.6N  41.9W   45 KT  50 MPH
48H  04/1800Z 19.3N  44.0W   45 KT  50 MPH
72H  05/1800Z 21.1N  48.3W   45 KT  50 MPH
96H  06/1800Z 23.0N  52.0W   45 KT  50 MPH
120H  07/1800Z 25.5N  56.0W   55 KT  65 MPH

Forecaster Brennan