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Tropical Depression Sixteen-E Discussion Number   4
NWS National Hurricane Center Miami FL       EP162023
400 PM CDT Sun Oct 08 2023
 
Since the prior advisory, 1-minute visible images from the GOES-18 
mesosector have been quite helpful in showing that the system we 
have been monitoring just south of Zihuatanejo has developed a 
well-defined circulation located a bit farther northwest of previous 
estimations. This circulation was farther supported by a 1702 UTC 
GMI pass which showed tightly curved bands wrapping most of the way 
around this apparent center on the 37 GHz channel. Thus, the system 
now can be considered a tropical depression, and the initial 
intensity is 30 kt for this advisory, which is in between the 
T1.5/25-kt estimates from TAFB and SAB versus 35-kt from the D-PRINT 
estimate from UW-CIMSS. 
 
Now that the center has become well-defined, it has formed farther 
northwest than earlier estimated. This should not be considered an 
acceleration in the short-term motion though, which still appears to 
be slowly off to the north-northwest at 340/4 kt. This slow motion 
is expected to continue with a gradual turn northward and then 
north-northeastward as the system is steered around mid-level 
ridging located east of it over the Caribbean Sea in addition to the 
outer circulation of Tropical Storm Lidia to its west. Given the 
farther northwestward initial position, the timing for landfall has 
moved up a bit to between 24-36 h, by tomorrow evening. There 
continues to be some spread in this landfall timing, with the GFS 
remaining on the faster end versus the slower CMC and ECMWF 
solutions. The latest NHC track forecast more or less splits the 
difference, which is close to both the TVCE and HCCA consensus aids, 
though most of the guidance now agrees the system should be inland 
after 36 hours. 

Intensification is still forecast up until the system moves inland 
over Mexico. With landfall now between 24-36 h, there might not be 
quite as much time for intensification as previously expected. With 
that said, both the raw model output from the ECMWF and CMC suggest 
significant intensification over the next 24 hours before the 
depression makes landfall, and out of respect of these models, a 
peak intensity of 45 kt continues to be shown just before landfall. 
This is on the higher end of the intensity guidance envelope. The 
system should quickly weaken after moving inland, ultimately 
dissipating over the higher rugged terrain of south-central Mexico 
by 48 hours. However, the significant up-slope flow that will result 
is anticipated to continue producing very heavy rainfall into 
Tuesday over coastal and inland Mexico as the cyclone and its 
remnants move farther inland.

 
Key Messages:
 
1. The depression is expected to become a tropical storm before it 
approaches the coast of southern Mexico on Monday.  A Tropical Storm 
Warning remains in effect for a portion of the coast of southern 
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, Michoacan and coastal sections of
western Oaxaca.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  08/2100Z 15.9N 101.7W   30 KT  35 MPH
 12H  09/0600Z 16.5N 101.8W   35 KT  40 MPH
 24H  09/1800Z 17.2N 101.7W   45 KT  50 MPH
 36H  10/0600Z 18.0N 101.4W   30 KT  35 MPH...INLAND
 48H  10/1800Z...DISSIPATED
 
$$
Forecaster Papin
 
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