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