A break-away peice of energy left over from Isaac may be the source of a new tropical system. Currently located in the extreme northern Gulf of Mexico near Pensacola, Florida, this low pressure center may drift southwestward for the next 24 hours. The NHC currently has this storm assigned a 40% risk of developing into a tropical system within the next 48 hours.
I included the 850 millibar pressure lines here as well, which can clearly demonstrate the center of low pressure near Pensacola, FL. Most of the convection associated with this system is well to the southwest, so I do not anticipate any rapid strengthening or other imminent tropical developments just yet.
This low pressure did come from what was left over of Isaac a few days ago, but if this system did develop into a tropical system it would be given a new name. The National Hurricane Center provided a very detailed explanation why, which I will include below. In short, it is only a break-away piece of energy from Isaac, rather than the bulk of it’s energy. Thus it is designated as a new system, and would be given a new name should the time come.
There have been quite a few inquiries about whether the name “Isaac” would be given to the area of disturbed weather currently located along the northern coast of the Gulf of Mexico, if it were to develop into a tropical cyclone. The short answer is no, it would get a new name.
Our analysis of the satellite, surface, and lower-tropospheric radiosonde data suggested that the disturbance we’re currently following originated within Isaac’s broad circulation, but that it had its own surface pressure minimum distinct from Isaac’s. This was perhaps most apparent late in the day on Monday, when the residual surface center of Isaac was located over western Kentucky while a second weak low was located over northern Mississippi and Alabama. Isaac’s circulation continued to weaken after that and became difficult to track, while the new disturbance moved slowly toward the Gulf coast. So what basically happened here is that a little piece of Isaac broke away and moved south.
OK, now everybody get your lawyer and grammar hats on. The National Weather Service rule that applies here reads: “if the remnant of a tropical cyclone redevelops into a tropical cyclone, it is assigned its original number or name”.
Notice the rule says “the” remnant, and not “a” remnant. This means that the storm’s primary remnant (and not just any old part of it) has to re-develop in order for the name to be retained. Since the primary remnant of Isaac was still in Kentucky when the new low formed and broke away, the rule dictates that the new low is not entitled to the name Isaac.
This rule actually makes a lot of sense. If a storm died and each of two parts re-developed, we couldn’t give the same name to both parts. Only the primary remnant would retain the name, while a lesser remnant or part would get a new name.
As pictured above, tropical models generally expect this low to drift slowly southwestward, then reverse course and move ENE into the FL Panhandle or the big bend region of FL. Currently models only expect this to reach Tropical Storm strength at maximum, but like usual we need to keep a close eye on it.