Invest 92L was upgraded to Potential Tropical Cyclone Nine (PTC 9) yesterday morning.
The PTC designation allows the National Hurricane Center to initiate advisories on a disturbance if they have high confidence in a disturbance becoming a TC and impacting land within 48 hours.
PTC 9 does not have a closed low-level center per data collected by a reconnaissance aircraft this morning, meaning a tropical depression or tropical storm has yet to form.
However, it is still likely that PTC 9 will develop sometime within the next 24 to 36 hours. The main thing that has prevented PTC 9 from closing off a center is the fast forward speed (currently 23 mph).
It is likely that PTC 9 will slow down soon. This should allow a tropical cyclone (TC) to form. Winds are already at 45 mph, so an upgrade straight to Tropical Storm Isaias is likely once a TC has developed.
PTC 9 is moving west-northwest. Interaction with Hispaniola is likely tomorrow. Because of this interaction, along with the current lack of a closed low-level center, the forecast PTC 9 is highly uncertain beyond the next 24 to 36 hours.
There is fairly good agreement the PTC 9 will track into the Bahamas Friday, and then turn north by Saturday or Sunday. However, where exactly this turn occurs is uncertain.
At this time a track into Florida, the eastern Gulf of Mexico, or up the East Coast are all possible. A track out to sea also can’t be ruled out, but is not suggested by any of the current model guidance.
Assuming PTC 9 develops and interacts with Hispaniola, the mountainous terrain of Hispaniola will almost certainty disrupt the center and cause weakening.
There could be some strengthening/restrengthening in the Bahamas, but this will partly be dependent on the extent of interaction with Hispaniola.
Latest model solutions range from a weakening system to a category 1 hurricane. Right now a tropical storm is most likely, but this could change depending on how PTC 9 evolves over the next 24 to 36 hours.
