For the past several days now, we have been watching two tropical disturbances out in the open Atlantic that came off the coast of Africa last week and over the weekend. The lead system is now crossing the Lesser Antilles and moving into the eastern Caribbean. It is currently running into higher wind shear and has been battling dry and dusty air. This is cutting off the window of potential this first system had for development into an official tropical system.
The system behind it is quickly becoming the one to watch. The lead system is acting kind of like a "sacrificial lamb" in that it is helping erode the dry air in place, starting to pave the way for the second system to have better conditions as it approaches the Caribbean. Already, satellite data today shows that this second system is getting increasingly healthy. Outflow is improving, as evidenced by the outward fanning upper-level high clouds. We are also getting increasing convection around the mid-level center of circulation, and satellite-derived surface wind data suggests that a surface low pressure system is in the process of closing off and getting vertically stacked with the mid-level circulation. These are all classic signs that the system is in the process of forming into a tropical depression, and it would not shock me one bit if this becomes Tropical Depression 5 or even Tropical Storm Elsa within the next 24 to 36 hours. The National Hurricane Center gives the system a 90% chance of developing into at least a tropical depression, and a 70% chance of that happening within the next 48 hours.
As what is likely to become Elsa continues westward over the next few days, conditions will become increasingly favorable for tropical development and storm intensification. The Baron Hurricane Index shows that conditions are already favorable for development where the system is now, but as we head into the weekend and the system is moving through the Caribbean, conditions will become very favorable for development ahead of the system. Shear will be lessening with time, and the lead disturbance is working to erode the dry air. The waters of the Caribbean are also very warm, and that warm water is very deep, leading to high levels of oceanic heat content, especially in the west and northwest Caribbean. That is high octane fuel for tropical systems.
Computer models are in strong agreement that the system will be moving into the eastern Caribbean by Friday and then moving west-northwestward through the Caribbean through the weekend. As we get to Sunday and Monday, naturally, the models diverge on the eventual path of the system. Some models take the system close to Hispaniola and Cuba before recurving northward over the Bahamas. A large number of models take the system mostly south of Hispaniola, toward Jamaica and western Cuba, and then potentially into the Gulf of Mexico by early next week. This far out, and with the system not even fully formed yet, there is a LOT of uncertainty in both the track and the future intensity of this system. It is possible that the system tracks into the Gulf by next week, or curves north across Cuba toward Florida, but it is just as possible that it curves north earlier and misses the United States. We also have a substantial amount of uncertainty because of what any land interaction with those mountainous islands may do to both the track and the intensity of the system. It is simply too early to know right now, and if anyone tells you any differently, they do not deserve your trust.
One important thing that we are highly confident in is that this poses NO THREAT to the United States through the holiday weekend. If you're headed toward the Gulf Coast for the 4th of July weekend, there will be showers and storms, but you will NOT be threatened by this tropical system. At EARLIEST, this would not become a possible problem to the United States until sometime next week.
As always, we will be watching vigilantly and will be passing along new information as it becomes available.