Atlantic: Invest 92L

Invest 92L has been designated for a low pressure system off the northeastern coast of Florida. This system has consolidated quite a bit during the past day or so, and it has certain taken on a tropical-like look with a rather solid core of thunderstorms with bands of convection extending to the south and east. The main question is whether the system has a closed circulation - following the lines of low clouds on the visible satellite loop above suggests that there is a circulation trying to form, but it’s not quite there yet. In addition, surface pressures are fairly high (there are various observations of 1012-1014 mb in the area), which is another indication that there isn’t a closed circulation just yet.

The environment isn’t exactly favorable for tropical cyclone development - the low is situated underneath an upper-level circulation, and there is moderate westerly wind shear affecting it. Nonetheless, this system has an opportunity to become a short-lived subtropical or tropical depression as it moves up the coast during the next couple of days. If it manages to become a subtropical or tropical storm, it would be named Chantal. 92L will move inland over South Carolina on Sunday.

Whether 92L becomes Chantal or not, it’s going to trigger a pattern change for the mid-Atlantic and the Richmond area on Sunday evening. While today and tomorrow will be quite pleasant, 92L will bring very, very humid air (dew points in the upper 70s) into the region on Sunday night, and this soupy air will remain in place for several days. This will also increase the threat of scattered afternoon thunderstorms through the middle of next week, and just like the storms earlier this week, any storms that pop up will likely cause torrential rainfall and flash flooding. Keep an eye on products from the NWS for further information and possible warnings.