Tropical Storm Francine Discussion Number   4
NWS National Hurricane Center Miami FL       AL062024
1000 AM CDT Mon Sep 09 2024

The structure of the system on satellite imagery has improved this 
morning, with a large circular region of cold convection between -70 
to -85 near the estimated center. An Air-Force Reconnaissance 
Aircraft is sampling the system this morning and earlier found a 
cyclonic wind shift from southeasterly to northwesterly flow near 
the center of the mass of deep convection. This data provides enough 
evidence that a well-defined circulation now exists, and thus PTC 
Six has become Tropical Storm Francine with sustained winds of    
45 kt this advisory.

The estimated motion is still tricky given the center only recently 
formed but is estimated still off to the north-northwest at    340/4 
kt. The system is expected to gradually turn northward and then 
north-northeastward as it moves between a mid-level ridge centered 
over Cuba and a broad mid- to upper-level trough located to its 
northwest over Texas. The guidance this cycle has shifted a little 
eastward and faster, and the NHC track forecast was once again 
nudged in that direction. The current track splits the difference 
between HCCA and TVCN and still shows Francine moving ashore of 
Louisiana sometime on Wednesday evening. There remains a decent 
amount of track uncertainty with the GEFS and EPS ensembles showing 
along-track spread implying some speed differences near landfall. 

While the system is now a tropical storm, the inner core wind field 
per reconnaissance observations is still broad and in the organizing 
stage, and initial intensification will be gradual. However, after 
an inner-core becomes established, and assuming the cyclone's 
vertical structure becomes aligned, a period of more significant 
intensification is possible while storm is embedded in a low shear, 
high mid-level moisture, and over very warm 30-31 C sea-surface 
temperatures.  The SHIPS rapid intensification (RI) indices are 
pretty elevated, and a period of RI could also occur between   24-48 
h. For now, the NHC intensity forecast will not explicitly forecast 
RI, but is higher than the previous cycle and shows a 75 kt peak in 
48 h, in good agreement with the intensity consensus aids. After 
that period, southwesterly vertical wind shear quickly increases 
from 10 kt to more than 30 kt and the intensity could plateau as it 
approaches the northwestern U.S. Gulf coastline, though the system 
is forecast to remain a hurricane at landfall. The NHC intensity 
forecast continues to be in good agreement with the consensus aids, 
but is a bit under the HAFS-A/B and COAMPS-TC models.

Given the latest forecast, a Hurricane Watch has been issued for
the Louisiana coastline from Cameron to Grand Isle, and a Storm 
Surge Watch has been issued from High Island, TX eastward to the 
Mississippi/Alabama Border.

With this advisory, the experimental cone graphic that includes 
inland Hurricane and Tropical Storm watches in the U.S. will be 
available on the NHC website. Due to the time needed to compile the 
inland watch information, the experimental cone graphic will not be 
available as quickly as the operational cone. The experimental cone 
graphic can be found from a link on the page with the operational 
cone graphic once it is available on hurricanes.gov. 

KEY MESSAGES:

1.  Francine is forecast to be a hurricane when it reaches the 
northwestern Gulf coast on Wednesday or Wednesday night and there is 
an increasing likelihood of life-threatening storm surge inundation 
for portions of the Upper Texas and Louisiana coastlines where a 
Storm Surge Watch is in effect.  Residents in the watch area should 
follow advice given by local officials. 

2. There is an increasing risk of damaging hurricane-force winds in 
portions of southern Louisiana beginning Wednesday, where a 
Hurricane Watch is now in effect. 

3. Francine is expected to bring heavy rainfall and the risk of 
considerable flash flooding along the coast of far northeast Mexico, 
portions of the southernmost Texas coast, the Upper Texas Coast, 
southern Louisiana, and southern Mississippi into Thursday morning.  
A risk of flash and urban flooding exists across portions of the 
Mid-South from Wednesday into Friday morning.



FORECAST POSITIONS AND MAX WINDS

INIT  09/1500Z 23.0N  94.9W   45 KT  50 MPH
12H  10/0000Z 24.0N  95.4W   50 KT  60 MPH
24H  10/1200Z 24.9N  95.7W   55 KT  65 MPH
36H  11/0000Z 26.3N  95.0W   65 KT  75 MPH
48H  11/1200Z 28.0N  93.5W   75 KT  85 MPH
60H  12/0000Z 29.7N  92.2W   75 KT  85 MPH...ON THE COAST
72H  12/1200Z 32.4N  90.7W   35 KT  40 MPH...INLAND
96H  13/1200Z 36.2N  89.6W   25 KT  30 MPH...POST-TROPICAL
120H  14/1200Z 37.5N  88.8W   20 KT  25 MPH...POST-TROPICAL

$$
Forecaster Papin