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Potential Tropical Cyclone Sixteen-E Discussion Number   1
NWS National Hurricane Center Miami FL       EP162023
1000 PM CDT Sat Oct 07 2023

A couple of SSMIS microwave overpasses this evening show that 
the disturbance (EP99) located a couple of hundred miles south of 
Acapulco, Mexico, is becoming better organized. There is evidence 
of some curved banding over the southwestern portion of the 
system.  While the disturbance does not have enough organization to 
be a classified as a tropical cyclone, it is expected to develop 
into one within the next day or so, and the forecast track brings it 
near the southern coast of Mexico within the next 36 to 48 hours.  
Therefore, Potential Tropical Cyclone advisories are being initiated 
in order to issue a Tropical Storm Watch for a portion of the 
southern coast of Mexico.  The initial intensity of the disturbance 
is set at 25 kt, which is supported by a couple of earlier ship 
observations. 

Since the system is still in its formative stage, the initial motion 
estimate is a somewhat uncertain 310 degrees at 6 kt.  The system 
is forecast to move northwestward overnight, but it should turn 
north-northwestward on Sunday between a mid-level ridge to its east 
and Tropical Storm Lidia to its west.  This motion should bring the 
center of the system near the southern coast of Mexico in about 48 
hours.  The GFS is much faster than the remainder of the global 
model guidance and takes the center ashore in a little more than 24 
hours, while the ECMWF and UKMET models are about 12 to 24 hours 
slower.  The NHC track forecast is near the various consensus aids, 
accounting for the variations in forward speed.

The disturbance is located within a moist atmosphere and over SSTs 
of 29-30 degrees C. However, the upper-level environment is not as 
conducive as there is currently moderate to strong vertical wind 
shear over the system.  The shear is forecast to relax during the 
next day or two, and this should allow the system to develop into a 
tropical cyclone and strengthen into a tropical storm before it 
reaches the southern coast of Mexico.  The NHC intensity forecast 
shows a peak that is similar to the latest HFIP corrected consensus 
aid.  After landfall, rapid weakening is expected, and the system 
is forecast to dissipate by 72 hours. 

Key Messages:

1. The disturbance is expected to become a tropical storm before it 
approaches the coast of southern Mexico on Monday.  A tropical storm 
watch has been issued for a portion of the southern coast of Mexico.

2. Heavy rains from this system will likely produce flash and urban 
flooding, along with possible mudslides in areas of higher terrain 
across the states of Guerrero and Michoacan.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  08/0300Z 13.9N 100.1W   25 KT  30 MPH...POTENTIAL TROP CYCLONE
 12H  08/1200Z 14.7N 100.7W   30 KT  35 MPH...TROPICAL CYCLONE
 24H  09/0000Z 15.6N 101.2W   35 KT  40 MPH
 36H  09/1200Z 16.4N 101.4W   40 KT  45 MPH
 48H  10/0000Z 17.3N 101.4W   45 KT  50 MPH
 60H  10/1200Z 18.5N 101.2W   30 KT  35 MPH...INLAND
 72H  11/0000Z...DISSIPATED
 
$$
Forecaster Brown
 
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