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Tropical Storm Jimena Discussion Number  15
NWS National Hurricane Center Miami FL       EP092021
500 AM HST Fri Aug 06 2021
 
A convective mass continues to persist over the center of Jimena, 
although coldest cloud tops have warmed over the past few hours. 
A fortuitous 1105 UTC AMSR-2 pass shows the center a bit west of 
the earlier estimates, which places it beneath the coldest 
remaining cloud tops. The intensity is held at 35 kt based on a 
blend of Final-T and CI numbers from TAFB, SAB and ADT.  This 
intensity is also supported by overnight ASCAT data and a more 
recent ship observation.  Jimena is currently moving over SSTs near 
24C.  Going forward, westerly shear will increase along the 
cyclone's path during the next 12-24 hr.  These factors should cause 
the tropical cyclone to weaken, and Jimena is expected to degenerate 
into a remnant low by Saturday morning.  The NHC intensity forecast 
is in good agreement with the SHIPS and HCCA guidance. 

The initial motion estimate is 300/8 kt.  As Jimena weakens, the 
increasingly shallow system is expected to be steered by the 
low-level trade-wind flow, which should cause it to gradually turn 
toward the west in about 48 hours.  The ECMWF is a little faster and 
lies on the southwest side of the guidance envelope, while the GFS 
is slower and northeast of the consensus.  The NHC forecast was
adjusted to the southwest of the previous forecast during the
first 12-24 hours based on the farther west initial position.  
Thereafter, the track is close to the previous forecast, and in 
best agreement with the HCCA and TVCN consensus models.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  06/1500Z 17.5N 139.3W   35 KT  40 MPH
 12H  07/0000Z 18.0N 140.4W   30 KT  35 MPH
 24H  07/1200Z 18.7N 141.8W   25 KT  30 MPH...POST-TROP/REMNT LOW
 36H  08/0000Z 19.2N 143.3W   25 KT  30 MPH...POST-TROP/REMNT LOW
 48H  08/1200Z 19.5N 144.9W   20 KT  25 MPH...POST-TROP/REMNT LOW
 60H  09/0000Z 19.6N 146.7W   20 KT  25 MPH...POST-TROP/REMNT LOW
 72H  09/1200Z...DISSIPATED
 
$$
Forecaster Hagen/Brown
 
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