Tracking the Tropics: Potential Development in the Caribbean

An area of interest in the Caribbean has been highlighted by the NHC, with a 40% chance of development given in the next 7 days:

If this setup seems familiar, you're not wrong. It's essentially a redux of the same pattern that eventually spawned Helene in the Atlantic (and John in the EPAC). Check out this excellent article on central american gyre formation by Ryan Cedergren that further explains what a CAG is and how it forms. This is one of my favorite products to track these sort of CAG developments, where we essentially get some information from every level of the atmosphere. Wind barbs plotted are upper-level, the solid lines/dams are 500mb height (mid levels), and the shaded contours is 850mb vorticity (lower levels). Analyzed below we have our upper-level low like tropicwatch mentioned above highlighted in pink here (and moving quickly to the NW). Our tropical wave is also highlighted in teal:

Neither of these features will actually be catalysts for the GFS's solution on direct development, but it does play a role in preconditioning the environment out ahead of development. In 24 hours, we should see a new upper-level feature enter the Caribbean that I've also outlined here in pink:

A common area of low-level vorticity development due to the terrain is located near Columbia/Panama (highlighted in teal below). Essentially the orientation of the mountain range and valley in this region provides a topographical lift that assists in low-level vorticity forming here. Some of this vorticity in 48 hours will begin to interact with the new upper-level feature entering the Caribbean:

Full loop through 120 hours showing this evolution:

While the dynamic models have picked up on development of this feature, it's important to understand impacts to the United States are highly uncertain at this time. Given the longer lead time (120+ hours), I would advise following ensemble products for now until we have a consolidated system to track. One such product is the GFS ensembles:

The above product shows solutions are spread across multiple states in the Gulf of Mexico, so it's not prudent to focus on just one model/solution at this point in time. However, climatology can give us some clues on where such a system may track. Below is a plot of tracks from 1850-2023 that show all systems that have formed in this area from October 1st-10th and their eventual track:

As we can see, October becomes a very favorable month for tropical landfalls on the western coast of Florida and the panhandle for systems that form in this region.

- Matthew Weiberg