Official Discussion issued by the National Hurricane Center

Paulette (AL172020) DATA RELEASED: 9/8/2020 9:00:00 AM UTC

Copy of official data

Tropical Storm Paulette Discussion Number   6
NWS National Hurricane Center Miami FL       AL172020
500 AM AST Tue Sep 08 2020

GOES-16 Proxy-VIS and enhanced BD-curve infrared imagery reveals 
that Paulette's cloud pattern has continued to improve during the 
past several hours.  Specifically, the developing inner core is 
much more symmetric with new bursts of deep convection (-76C cloud 
tops) near the surface circulation center.  Subsequently, subjective 
and objective satellite intensity estimates support an initial 
intensity of 45 kt.

The global models and the statistical-dynamical intensity guidance 
indicate increasing southwesterly shear commencing later today. 
So, only modest strengthening is shown in the NHC foreast during 
next 24 hours.  On Friday, the shear stiffens and becomes less 
diffluent as the cyclone approaches the high amplitude mid-Atlantic 
TUTT.  Therefore, Gradual weakening is expected to occur at that 
time.  Beyond day 3, there are some mixed signals, specifically in 
the GFS/FV3 and ECMWF SHIPS output.  The GFS/FV3 continues to 
indicate strong southwesterly shear through day 5 further weakening 
Paulette to a depression around day 4.  The ECMWF SHIPS, however, 
shows a more southerly and diffluent upper wind pattern supporting 
reintensification after day 4.  The intensity forecast sides with 
that latter solution and also agrees with the HCCA intensity 
multi-model indicating the same intensity trend.   

The initial motion is estimated to be northwestward, or 325/5 kt.  
The rather weak synoptic steering pattern consists of a large mid-
to upper-level low just west of the Canary Islands and ridging to
the northwest of the cyclone.  During the next couple of days, the
large-scale models show the upper low filling and lifting
northeastward, allowing the subtropical ridge to build in behind
the departing upper low from the western Atlantic.  This change 
in the pattern should cause Paulette to turn west-northwestward on 
Wednesday and continue moving in this general motion through early 
Saturday.  Through the remaining portion of the period, the global 
models indicate a major shortwave trough moving off of the 
northeast coast of the U.S. and breaking down the western extent of 
the subtropical ridge/Bermuda high.  This growing weakness in the 
ridge should cause Paulette to turn toward the northwest early 
Sunday.  The official track forecast is a little bit slower and to 
the right of the previous forecast after day 3, and is close to the 
various consensus aids.


INIT  08/0900Z 18.1N  42.8W   45 KT  50 MPH
12H  08/1800Z 18.6N  43.6W   50 KT  60 MPH
24H  09/0600Z 19.5N  45.0W   55 KT  65 MPH
36H  09/1800Z 20.2N  46.9W   55 KT  65 MPH
48H  10/0600Z 20.5N  48.9W   55 KT  65 MPH
60H  10/1800Z 20.8N  50.4W   50 KT  60 MPH
72H  11/0600Z 21.3N  51.9W   50 KT  60 MPH
96H  12/0600Z 22.9N  54.9W   45 KT  50 MPH
120H  13/0600Z 25.4N  57.8W   50 KT  60 MPH

Forecaster Roberts