Hurricane John Forecast Discussion

000
WTPZ45 KNHC 261439
TCDEP5

Hurricane John Discussion Number  15
NWS National Hurricane Center Miami FL       EP102024
900 AM CST Thu Sep 26 2024

John continues to depict a small inner core, with earlier microwave 
images depicting a small eye feature. Since that microwave pass, the 
eye feature has become more prevalent on infrared imagery. The 
UW-CIMSS objective intensity guidance ranges from 65 to 75 kt. The 
subjective satellite estimates from TAFB and SAB are both 65 kt, 
respectively. Using a blend of the intensity estimates and the 
continued improved satellite depiction, the intensity is set at 65 
kt for this advisory.

The hurricane is estimated to be moving northwestward at 310/5 kt.
The official forecast is shifted slightly to the right in the near
term, which follows recent satellite trends and lies near the latest
HCCA consensus aid. On the forecast track, the center of John is
forecast to approach and move along the coast of southwestern Mexico
or just inland later today. However, some of the global model fields
do linger the system offshore near the coast a little longer,
particularly the ECMWF global model. In the long term, a turn back
to the west-northwest is anticipated as the system weakens and is
steered by the ridge over northern Mexico.

The overall environment remains favorable for John to continue to 
strengthen until landfall with very warm sea surface temperatures, 
low wind shear, abundant moisture throughout all levels of the 
atmosphere. The latest NHC intensity forecast continues to call for 
strengthening up until landfall and shows a peak intensity of 75 kt, 
which is slightly lower than previous intensity peak due to the 
latest forecast showing the system moving inland a little faster 
than the previous forecast.

John has very large rain shield and flooding impacts will extend
well outside where the system makes landfall. It cannot be
emphasized enough that catastrophic life-threatening flash flooding
and mudslides are expected to continue through the end of the week
for portions of the Mexican States of Guerrero, Oaxaca and
Michoacan.


KEY MESSAGES:

1. Hurricane 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 strengthening up until landfall, and
a Hurricane Warning is in effect along the coastline of southwestern
Mexico, where tropical storm conditions are imminent.  Tropical
Storm Warnings are also in effect for portions of the area and
tropical storm are ongoing.


FORECAST POSITIONS AND MAX WINDS

INIT  26/1500Z 17.5N 102.7W   65 KT  75 MPH
 12H  27/0000Z 18.0N 102.9W   75 KT  85 MPH...NEAR COAST
 24H  27/1200Z 18.6N 103.4W   45 KT  50 MPH...INLAND
 36H  28/0000Z 19.2N 104.2W   30 KT  35 MPH...INLAND
 48H  28/1200Z 19.8N 105.4W   30 KT  35 MPH...POST-TROP/REMNT LOW
 60H  29/0000Z 20.5N 107.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  29/1200Z...DISSIPATED

$$
Forecaster Kelly