Official Discussion issued by the National Hurricane Center

Rene (AL182020) DATA RELEASED: 9/10/2020 3:00:00 AM UTC

Copy of official data

Tropical Storm Rene Discussion Number  12
NWS National Hurricane Center Miami FL       AL182020
1100 PM AST Wed Sep 09 2020

Rene remains a sheared tropical cyclone, with modest 
mid-/upper-level easterly vertical wind shear of 12-15 kt 
undercutting the otherwise favorable outflow layer. The combination 
of the shear and intrusions of dry mid-level air have caused the 
convective pattern to continue to fluctuate since the previous 
advisory. Although a recent burst of deep convection has again 
pulsed near and to he west of the center, the intensity is being 
maintained at 35 kt based on a 09/2305Z ASCAT-A overpass indicating 
barely 34 kt winds in the northwest quadrant. The 34-kt wind radius 
was also expanded in that quadrant based on the ASCAT wind data.

The initial motion remains west-northwestward motion or 285/11 kt. 
Under the influence of a mid-level ridge, Rene is expected to 
continue moving west-northward over the eastern Atlantic for the 
next few days. A weakness in the ridge is forecast to develop around 
40W-45W longitude, which will be partly induced by Tropical Storm 
Paulette's circulation, causing Rene to slow down and turn toward 
the northwest and then north-northwest on 3-4 days. By day 5, Rene's 
northward motion is forecast to be blocked significantly by a 
building ridge to the north of the cyclone as TS Paulette moves 
farther away. It is possible that Rene could stall or even make a 
small looping motion if the storm gets trapped within the much 
larger ridge. The new NHC forecast is to the left or south of the 
previous advisory track, but not as far left as the consensus models 
or the preponderance of the remaining guidance.

Rene's upper-level outflow is forecast to remain intact for the 
next 60 h or so, which would should allow for at least gradual 
strengthening during that time. The shear is forecast by both the 
GFS and the ECMWF models to decrease to near zero in the 36-48 h 
time frame, and that is when Rene should be able to take advantage 
of marginal sea-surface temperatures (SST) of 26.5C and modest 
mid-level humidity conditions, and obtain hurricane status in 48-60 
h. Thereafter, strong west-northwesterly shear is expected to induce 
gradual weakening despite the cyclone moving over warmer SSTs of 
27-28C. The official intensity forecast is similar to the GFS 
model intensity forecast, and lies below the simple consensus model 
IVCN and the corrected-consensus models HCCA and FSSE. 


INIT  10/0300Z 18.0N  34.0W   35 KT  40 MPH
12H  10/1200Z 18.4N  35.5W   40 KT  45 MPH
24H  11/0000Z 18.9N  37.4W   45 KT  50 MPH
36H  11/1200Z 19.4N  39.3W   50 KT  60 MPH
48H  12/0000Z 20.5N  41.4W   60 KT  70 MPH
60H  12/1200Z 21.8N  43.2W   65 KT  75 MPH
72H  13/0000Z 23.5N  45.1W   60 KT  70 MPH
96H  14/0000Z 26.8N  46.5W   50 KT  60 MPH
120H  15/0000Z 28.3N  47.6W   40 KT  45 MPH

Forecaster Stewart