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Tropical Storm John Discussion Number  19
NWS National Hurricane Center Miami FL       EP102024
900 AM CST Fri Sep 27 2024
 
John's satellite depiction has banding mainly concentrated on the 
southern semicircle. The center of the system is very near or just 
touching the coast of southwestern Mexico. There continues to be 
burst of convection within the curved bands to the south of the 
center, and GLM data depicts plenty of lightning within the bands. 
The various objective and subjective satellite intensity estimates 
range from 35 to 55 kt. Given the satellite presentation will lean 
to the higher side of these estimates, with an initial intensity for 
this advisory at 50 kt.
 
The center of John is right along the coast, and gradual weakening 
should continue as the storm moves inland or moves along the 
coastline. Later today, the high mountainous terrain will disrupt 
the low-level circulation and a faster rate of weakening should 
ensue. Beyond the next 24 h, the forecast is highly dependent if the 
center of John survives the interaction with land, and could 
dissipate sooner than what is currently forecast. If the surface 
center remains intact and doesn't dissipate, the remnants should 
re-emerge over the water in a few days, although models do not show 
regeneration and keep the system as a remnant low. The NHC intensity 
forecast lies near the HCCA and simple consensus aids.
 
John's initial motion is estimated to be northwestward, or 320/3
kt, and a turn to the west-northwest with a slight increase in
forward speed is forecast, provided John survives its interaction
with mountainous terrain.  The track forecast is similar to the
previous forecast and lies to the right of the previous forecast.
 
 
KEY MESSAGES:
 
1. Tropical Storm John will bring additional very heavy rainfall to
coastal portions of southwest Mexico through Friday. The additional
rainfall totals will be falling across areas that have received very
heavy rainfall amounts over the past few days.  This heavy rainfall
will likely cause significant and catastrophic life-threatening
flash flooding and mudslides to the Mexican States of Guerrero and
Michoacán.
 
2. John is forecast to continue bringing tropical storm conditions
across portions of the Tropical Storm Warnings area through today.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  27/1500Z 18.1N 103.0W   50 KT  60 MPH
 12H  28/0000Z 18.8N 103.8W   35 KT  40 MPH...INLAND
 24H  28/1200Z 19.4N 105.1W   30 KT  35 MPH...POST-TROP/REMNT LOW
 36H  29/0000Z 19.9N 106.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
 48H  29/1200Z 20.4N 108.3W   25 KT  30 MPH...POST-TROP/REMNT LOW
 60H  30/0000Z...DISSIPATED
 
$$
Forecaster Kelly
 
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