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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
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