The tropical train is leaving the station as the disturbances we have been watching are finally making a move to the west. Two are already on track, and another will soon emerge off Africa. In addition, south of a Bermuda, there’s a disturbance to watch.
Disturbance #1 loosely formed from the moisture tail of defunct Tropical Storm Omar. It’s a swirl of clouds south of Bermuda, chugging off to the west toward the U.S. East Coast. Currently, it’s a mostly dry swirl, but up ahead is the moisture associated with a large upper-level low that has moved over Florida. It’s conceivable that the disturbance could use some of that moisture to turn into at least a tropical depression.
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There’s no sign it will become a strong storm, and it most likely won’t develop at all, but we’ll watch it since it’s not far from land. The system or its moisture surge is forecast to arrive at the Carolina coast late Wednesday or Thursday.
In the Eastern Atlantic, we have two new tropical depressions: #17 and #18. Both have well-established circulations, and both are forecast to fairly quickly develop into tropical storms. The next two names on the list are Paulette and Rene.
Dry air still covers the ocean to the north of the depressions and may temper their ability to strengthen a bit, although the larger size of Tropical Depression #18 should keep it more insulated from the surrounding air mass.
Disturbance #2, currently the third car in the African tropical train, will follow the depressions over the Atlantic in a few days.
The unusual factor in this scenario is that the steering current is quite weak, which means these systems will poke along to the west. Secondly, the steering currents aren’t uniform, so Depression #18 and Disturbance #2 might move more quickly than Depression #17. That means two or three of the systems could get close enough to affect each other’s track.
If that happens, random things can occur, but generally, the system at the front of the train gets deflected left (south-ish) and the trailing system gets deflected right (north-ish).
It will be an interesting dance to watch, if it happens, and we should have plenty of time to do it because all of these systems are going to crawl to the west.
Later in the week, a strong disturbance moving across Canada will temporarily weaken the blocking high-pressure system that holds tropical systems to the south, opening a path to the north. Currently, the long-range computer forecast models indicate that the systems will take that option, but the variabilities that come with storms interacting opens the door for one or more of them to miss the exit and continue farther west.
In any case, this is all going to happen in slow motion, so no threats to land, except the off chance of a little something with Disturbance #1 in or around the Carolinas, are expected this week.