Tropical Storm Elsa has formed out of the disturbance we’ve been tracking in the middle of the Atlantic. This is the earliest in the season that an “E” storm has been named, beating Edouard by 4 days – which formed late on July 5th last year.
And yes. This is super unusual to have a storm form in this part of the tropical Atlantic on July 1st. It’s only happened one other time in the record book. That was in 1933.
Elsa is being swept toward the Caribbean by a strong high pressure that is sprawled across the Atlantic. This is the same high that is spreading the plume of storm-killing dust over the ocean as well. But this disturbance started far enough south that it wasn’t engulfed by the plume and could pull clear, moist air from the south to hold off the dust. It will move into the Caribbean Sea wrapped in moisture.
The strong flow around the high will propel Elsa across the eastern Caribbean islands tomorrow. Tropical Storm Watches and Warnings have been issued for the affected islands by the local governments there. The expectation is that Elsa will continue to strengthen as it approaches the islands. The big question is, what happens after that.
Fast-moving storms often have a hard time intensifying because the upper-level winds have to move the top of the storm at the same speed as the bottom to keep the storm from tilting over and weakening. Lots of times, the winds don’t sync up. Also, the track Elsa takes is critical to how strong it can be.
The nose of the steering high-pressure system will be clipped over the weekend by an unseasonably strong dip in the jet stream over the eastern U.S. This dip is responsible for the cold and rainy first half of the weekend in the Northeast.
Without the influence of the high, Elsa will slow down and turn toward the north. But exactly where it does that is critical to its future strength. If Elsa turns early and runs over Haiti and the Dominican Republic, the mountains could weaken it significantly. If it runs over Cuba, that land mass could affect it as well, but perhaps less so.
The current expectation is that Elsa will be in the general vicinity of Florida early next week. The details are unknowable at this time. Remember, forecasts for developing storms always have greater errors than for strong hurricanes. So don’t read too much into the cone or any specific forecasts.
The end of the cone is over South Florida at this point, but remember that the cone is the same size for all storms – ones with fairly certain forecasts and ones with a high fuzziness factor like this one.
Right now, the computer forecast models are all over the place both in terms of where the storm will track and how strong it will be when it crosses the big Caribbean islands. The National Hurricane Center smartly averages the various computer projections when they make their forecast and publish the cone.
In an ideal world, the cone for this one would be much wider to show the high uncertainty.
How strong Elsa will be when it’s in the vicinity of South Florida is also an open question, so don’t get committed to the idea that it will be “only” a tropical storm. It’s easy to imagine how it could be stronger, and some computer forecast models predict it will be. But, as I noted, if it runs into big mountains, it could be a lot weaker.
The most useful information we have at this point is Elsa’s timing. Unfortunately, we’re going to have to pay close attention to Elsa over the holiday weekend in case action is required the first of the week.
Ahead of Elsa, the other tropical disturbance we were following is just a moisture surge moving across the Caribbean. Some of that moisture is forecast to move across the southern Florida peninsula over the weekend before any affects from Elsa would be felt, if they are.