Floridians must be scratching their head this weekend, after seeing “Alberto” named, while the more vigorous-more weather producing storm on Oct 10, 2011 that crashed into central Florida was not. This is an objective look at why that October storm was not named, yet this weekend’s swirl was.
First of all, there is a definitive closed circulation with Alberto, unassociated with cold air aloft. The system that hit Florida in Oct. 2011 never attained a closed circulation and was purely associated with upper-level cold air. The key distinction between the two cases is the cold air aloft.
I attended a tropical meteorology conference this past April, and this Florida gale was the topic of much debate. Certainly it was much more vigorous than Alberto has become. Again, that is due to cold-air forcing aloft, as the cold air fueled very strong thunderstorms. The storms produced thousands of lightning strikes, some hail and damaging wind gusts. It was almost akin to a winter low pressure system with cold fronts. And, as the storms around the low intensified in the colder upper air, a brief low-level swirl did actually take place on radar, just prior to landfall.
Key points to keep in mind: purely tropical systems actually have warmer air aloft, do not produce hail and almost have no lightning activity associated with them. It’s a backwards way of thinking, but the physical process of warming aloft actually forces air down on the perimeter of a tropical cyclone, where it is then returned vertically in the center of circulation.
Let me point out that there is quite a bit of subjectivity that goes into naming a tropical cyclone. It is not up to the discretion of just one person at the National Hurricane Center, rather their entire team of meteorologists, to examine the data and make a decision. They spend many hours pouring over radar and satellites to make a very informed and complete decision.
After seeing the data first-hand at that tropical conference, I think the Hurricane Center indeed got the call right in “not naming” the October 2011 gale.