Potential Tropical Cyclone One Discussion Number   5
NWS National Hurricane Center Miami FL       AL012024
400 PM CDT Tue Jun 18 2024

Air Force Reserve and scatterometer data show that the disturbance
consists of a large northwest-to-southeast-oriented circulation 
with a 150-250-n mi wide area of light winds and a broad minimum in
pressure.  The scatterometer data also revealed that the strongest
winds--30 to 35 kt--are located about 360 n mi north of the
estimated center.  With the continued lack of a well-defined center
and little central convection, the system is still being designated
as a potential tropical cyclone at this time.

The system is moving generally northward, or 360/5 kt.  A mid-level
ridge over the eastern United States is forecast to build
southwestward, forcing the disturbance to turn westward and
accelerate toward the coast of Mexico tonight and on Wednesday.
The model trackers appear to be too fast relative to the model
fields themselves.  As a result, the NHC official track forecast is 
slower than deterministic and consensus trackers, and brings the 
center of the system to the coast of Mexico in about 36 hours.  
This could still be a little fast since the global models have the 
center just offshore of Mexico at that time.

Global model fields suggest that the circulation will gradually 
consolidate over the next 24 hours, and the center could be well 
defined enough by then to designate the system as a tropical 
cyclone.  Even if that occurs, only modest intensification is 
forecast before the center reaches land due to the continued broad 
nature of the circulation.  The most aggressive intensity models 
peak the intensity between 40-45 kt, and the NHC forecast is within 
that range.

Regardless of the exact track of the low, this system will have a 
large area of heavy rains, moderate coastal flooding and 
tropical-storm-force winds well north of the center.  Importantly, 
the official wind speed probabilities are likely underestimating the 
chances of tropical-storm-force winds along the Texas coast because 
of the unusually large and asymmetric area of strong winds on the 
northern side of the circulation.


Key Messages:

1. Users are reminded not to focus on the exact forecast track of
this system.  The disturbance is very large with rainfall, coastal
flooding, and wind impacts likely to occur far from the center
along the coasts of Texas and northeastern Mexico.

2. Rainfall associated with Potential Tropical Cyclone One will 
impact large regions of Central America, north across northeastern 
Mexico and into South Texas. This rainfall will likely produce 
considerable flash and urban flooding along with new and renewed 
river flooding. Life-threatening flooding and mudslides are likely 
in areas of higher terrain across the Mexican states of Coahuila and 
Nuevo Leon, including the city of Monterrey.

3. Moderate coastal flooding is likely along much of the Texas
Coast through midweek.

4. Tropical storm conditions are expected to begin tonight or
Wednesday along portions of the Texas coast south of San Luis Pass
and along portions of the coast of northeastern Mexico within the
Tropical Storm Warning area.


FORECAST POSITIONS AND MAX WINDS

INIT  18/2100Z 22.1N  92.7W   35 KT  40 MPH...POTENTIAL TROP CYCLONE
12H  19/0600Z 22.7N  93.9W   35 KT  40 MPH...POTENTIAL TROP CYCLONE
24H  19/1800Z 23.0N  95.7W   40 KT  45 MPH...TROPICAL CYCLONE
36H  20/0600Z 23.3N  97.8W   40 KT  45 MPH...NEAR THE MEXICO COAST
48H  20/1800Z 23.3N 100.2W   30 KT  35 MPH...INLAND
60H  21/0600Z...DISSIPATED

$$
Forecaster Berg