NHC 5-day outlook map showing the high chance of development for invest area 91L off the Southeast coast
The area of interest off the Southeast coast, now known as “invest 91L”, is slowly getting better organized. The NHC has increased the chances of development in to the high category as we head in to the big holiday weekend. But development in to what, exactly? That remains to be seen.
According to the latest statement put out this morning, a tropical or subtropical storm could form from the system as it approaches the coast this weekend. Let’s take a look at the differences between the two possible scenarios:
A tropical storm is what we are most used to hearing about. Winds are more or less concentrated around a well defined area of convection or thunderstorm activity close to the center.
A subtropical storm is more like a hybrid storm that has some tropical characteristics while also displaying some non-tropical signs as well – such as having winds and energy spread out over a larger area and more loosely defined convection. In other words, a subtropical storm hasn’t quite bundled all of its energy around a distinct, warm-core center like we are used to seeing with purely tropical systems, especially hurricanes. Subtropical storms usually transition completely in to classical tropical storms if they remain over warm water long enough.
In the case of 91L, right now, it remains spread out and not very concentrated, therefore, development has been slow. As long as this continues, we won’t see much more than a nuisance rain maker for the Carolina coast this weekend. However, water temps in the Gulf Stream, which is still to the west of the developing storm, are quite warm and it is possible that we will see a pure tropical storm form which would mean more wind, rain and rough surf conditions for the coastal areas that it impacts.
The good news is that none of the model guidance suggests anything too strong coming from this. After all, it is only late May, not September. That being said, we should never ignore a festering tropical feature that is so close to land. If you have plans along the beaches from Georgia to Cape Hatteras, keep them, but be aware of this feature and the potential for heavy rain and some gusty winds. The other hazard that would concern me is rough surf. Water temps along the beaches are still sub-80F but this will not keep people out of the water this weekend. Watch for local conditions to change including the chance of increased rip currents. Remember, tropical storms have the potential to be deadly if people don’t understand the local impacts. Keep an eye on the kids if they plan on heading in to the ocean in the affected area during the long holiday weekend.
I will post a video discussion concerning 91L later this afternoon followed by a blog post update here this evening.
M. Sudduth 9:50 AM ET May 26