856
WTNT41 KNHC 082100
TCDAT1

Potential Tropical Cyclone Six Discussion Number   1
NWS National Hurricane Center Miami FL       AL062024
400 PM CDT Sun Sep 08 2024

The area of disturbed weather located over the southwestern Gulf of
Mexico does not possess a well-defined circulation yet.  
Scatterometer and aircraft data indicate that it consists of an
elongated trough of low pressure oriented north-northwest to
south-southeast. However, there is a large area of 35-45 kt winds
located southwest of the trough axis. These tropical-storm-force
winds are also confirmed by an ongoing Air Force Reserve
reconnaissance mission, which found 975 mb flight-level winds up to
56 kt, with SFMR winds also quite high in the same vicinity. Some of
these high winds are likely enhanced in part due to a barrier jet
offshore of the Sierra Madre mountains of Mexico. Because the system
is expected to become a tropical storm over the next day or so, and
tropical-storm-force winds are forecast to be near the coast of
Mexico within 48 hours, advisories are being initiated on Potential
Tropical Cyclone Six. The initial intensity is set to 45 kt for this
advisory based on a blend of scatterometer and aircraft data.

The initial motion is highly uncertain given the fact that a
well-defined center does not yet exist, but our best estimate is
320/4 kt. The track guidance shows this slow northwest drift
continuing, though the center could reform or redevelop anywhere
along the current trough axis as the center becomes better defined.
Afterwards, the system is expected to turn northward and then
north-northeastward as it rounds the periphery of a mid-level ridge
centered over Cuba. The track guidance this cycle shifted east, with
the GFS and ECMWF models notably on the east side of the guidance
envelope. The initial NHC track forecast won't go quite that far
east, but splits the difference between the consensus aid TVCN and
these eastward model solutions. Future adjustments could be
necessary if these eastward trends continue. Given the current
structure, the track forecast is of lower confidence than usual.

Given that the current circulation is quite elongated, it will
likely take a day or even longer for intensification to begin, and
much of the wind enhancement on its southwestern side is more of a
reflection of a barrier jet rather than the true intensity of the
stretched out vorticity maxima. Both the global model and
hurricane-regional model guidance suggest the circulation will
become well-defined by tomorrow afternoon, and the NHC intensity
forecast shows the system becoming a tropical storm by that time.
Until then, the intensity guidance, especially the
statistical-dynamical guidance SHIPS and LGEM, likely show too much
short-term intensification because these tools are designed for
tropical cyclones and not elongated troughs. The hurricane-regional
models HAFS-A/B seem to have a fairly realistic depiction of the
system's current structure, and show little intensification for the
next 36 h or so. Afterwards, as they depict the center becoming
well-defined with contracting wind radii, they show more significant
intensification. Between 48-72 h, PTC Six could interact with an
upper-level trough centered over Texas, and its intensity as it
approaches the Texas and Louisiana Gulf Coast will be governed by
its inner-core structure and if it undergoes a favorable trough
interaction. This initial forecast shows the system becoming a
hurricane just before landfall.

KEY MESSAGES:

1. The system is forecast to become a tropical storm on Monday as
it moves northwestward to northward near or along the western Gulf
of Mexico coast. Tropical Storm Watches have been issued for a
portion of northeastern Mexico and additional watches may be needed
for the southern Texas coast tonight.

2. The system is forecast to become a hurricane before it reaches
the northwestern Gulf Coast by the middle of the week.  While it is
too soon to pinpoint the exact location and magnitude of impacts,
the potential for life-threatening storm surge and damaging winds
are increasing for portions of the Upper Texas and Louisiana
coastlines beginning Tuesday night.  Hurricane and Storm Surge
Watches will likely be issued for a portion of that area on Monday,
and residents should ensure they have their hurricane plan in
place.

3. Potential Tropical Cyclone Six is expected to bring heavy
rainfall and the risk of flash flooding from the coast of far
northeast Mexico into portions of coastal Texas and Louisiana
through Thursday.



FORECAST POSITIONS AND MAX WINDS

INIT  08/2100Z 21.6N  94.6W   45 KT  50 MPH...POTENTIAL TROP CYCLONE
12H  09/0600Z 22.3N  95.1W   45 KT  50 MPH...POTENTIAL TROP CYCLONE
24H  09/1800Z 23.2N  95.7W   45 KT  50 MPH...TROPICAL CYCLONE
36H  10/0600Z 24.3N  96.0W   45 KT  50 MPH
48H  10/1800Z 25.5N  96.1W   55 KT  65 MPH
60H  11/0600Z 27.0N  95.7W   60 KT  70 MPH
72H  11/1800Z 29.0N  94.1W   65 KT  75 MPH
96H  12/1800Z 33.6N  91.4W   30 KT  35 MPH...POST-TROP/INLAND
120H  13/1800Z 37.0N  89.9W   25 KT  30 MPH...POST-TROP/EXTRATROP

$$
Forecaster Papin