000
WTPZ44 KNHC 051437
TCDEP4
 
Tropical Storm Jimena Discussion Number  11
NWS National Hurricane Center Miami FL       EP092021
500 AM HST Thu Aug 05 2021
 
Conventional satellite imagery indicates that Jimena's cloud pattern 
has changed little during the past several hours, although most 
recently, enhanced infrared images show some warming of the cloud 
tops just west of the center.  Timely AMSR-2 and GMI passive 
microwave color composite images revealed a well-developed banding 
feature wrapping around the surface center from the north and west 
portions of the cyclone.  The initial intensity is held at 35 kt and 
is in agreement with the Dvorak satellite intensity estimates from 
TAFB and SAB.

The large-scale models and the statistical-dynamical SHIPS intensity 
guidance (GFS/ECMWF) show that the previously noted period of 
conducive atmospheric and oceanic conditions should be ending soon.  
By the 36-hour period, sub-25C sea-surface temperatures and a 
gradually stabilizing/drier surrounding air mass should cause Jimena 
to weaken.  Guidance also shows increasing west-northwesterly shear 
beyond 48 hours.  Accordingly, the NHC forecast calls for Jimena to 
weaken to a depression by mid-period, and degenerate into a remnant 
low in 60 hours.
 
Based on the aforementioned microwave images, the initial motion is 
estimated to be northwestward, or 315/6 kt.  A subtropical ridge 
anchored to the northeast of the cyclone is forecast to steer Jimena 
toward the northwest through the 48 period.  Afterward, a turn 
toward the west-northwest is expected as the vertically shallow 
system is influenced more by the easterly tradewinds.  The official 
forecast is basically an update of the previous one and lies near 
the multi-model consensus (TVCN) aid.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  05/1500Z 16.1N 137.2W   35 KT  40 MPH
 12H  06/0000Z 16.5N 137.7W   35 KT  40 MPH
 24H  06/1200Z 17.5N 138.9W   35 KT  40 MPH
 36H  07/0000Z 18.5N 140.2W   30 KT  35 MPH
 48H  07/1200Z 19.5N 141.5W   30 KT  35 MPH
 60H  08/0000Z 20.3N 142.9W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  08/1200Z 20.9N 144.3W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  09/1200Z...DISSIPATED
 
$$
Forecaster Roberts