ZCZC MIATCDEP4 ALL
TTAA00 KNHC DDHHMM
 
Tropical Storm Sandra Discussion Number   2
NWS National Hurricane Center Miami FL       EP192021
100 PM PST Sun Nov 07 2021
 
This afternoon, deep-convective activity has decreased in coverage 
and intensity, shearing off to the east and revealing a well-defined 
low-level circulation. Even though the convection has waned, an 
earlier 1549 UTC ASCAT-A pass revealed a fairly large region of 
30-35 kt winds primarily to the east of the circulation. Based 
primarily on the scatterometer data, TD 19-E was upgraded to 
35-kt Tropical Storm Sandra at 1800 UTC and that will be the 
intensity for this advisory. It should be noted that the satellite 
presentation was better organized this morning, when both SAB and 
TAFB provided CI 2.5/35 kt estimates, and it is likely this system 
was already tropical storm earlier today.
 
The exposed low-level circulation has been moving left of the 
previous forecast track this afternoon, with the current estimated 
motion at 285/10 kt. The track guidance is insistent that a more 
poleward motion will resume soon, but its possible the storm's 
direction of motion is dependent on additional down-shear convective 
bursts helping to tug the center more poleward. As the system 
becomes more vertically shallow, the west-northwest motion should 
bend more westward and then west-southwestward as the circulation 
gradually decays. The track guidance this cycle is further to the 
left in the short-term, mainly based on the initial motion, but 
corrects to near the same place by the end of the forecast period. 
The latest NHC track forecast has also been shifted further south 
early on, but ends up near the previous one by 60 hours, close to 
the tightly clustered consensus aids.
 
Assuming that convection will redevelop near or east of the center, 
possibly during the diurnal convective maximum tonight, Sandra is 
expected to maintain its intensity for the next 12-24 hours. 
Thereafter, increasing vertical wind shear should help to import 
drier mid-level air that should finish off any additional 
convection. Forecast simulated IR imagery from the GFS and ECMWF 
suggests Sandra becoming devoid of convection by 48-60 h, and the 
latest NHC forecast still shows the cyclone becoming a post-tropical 
remnant low by this time frame. The NHC intensity forecast is in 
decent agreement with the intensity guidance and is quite similar to 
the latest SHIPS/LGEM, though remains lower than the HWRF/HMON runs.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  07/2100Z 14.0N 115.2W   35 KT  40 MPH
 12H  08/0600Z 14.5N 116.1W   35 KT  40 MPH
 24H  08/1800Z 15.3N 117.5W   35 KT  40 MPH
 36H  09/0600Z 15.7N 119.0W   30 KT  35 MPH
 48H  09/1800Z 15.5N 121.2W   30 KT  35 MPH...POST-TROP/REMNT LOW
 60H  10/0600Z 15.0N 124.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  10/1800Z...DISSIPATED
 
$$
Forecaster Papin
 
NNNN