Good Saturday evening, everyone! So, let’s jump right into talking about Florence. The storm remains quite a distance to the southeast of Bermuda, and unlike what I was expecting a few days ago, Florence should track well to Bermuda’s south before making its approach towards the East Coast. Given Florence’s current location and previous track, it’s remarkable that this system isn’t going to curve out to sea a safe distance away from the East Coast, and although I included the East Coast impact scenario in my previous article, I previous leaned towards an out-to-sea scenario. While it physically made sense that Florence could approach the coast, it’s become apparent that I relied too strongly on how other tropical systems behaved in the same vicinity as Florence. Although it’s never a bad idea to take this approach, it must be understood that every storm and situation is different. Last winter when parts of Georgia received over a foot of snow, Firsthand Weather produced a highly-accurate forecast by going against climatology. Sometimes, that’s what has to be done, and it should have been done in this case, too!
Florence is currently only a tropical storm with maximum sustained winds of 70 mph as of Saturday evening. Remarkably, Florence was previously able to intensify into a major hurricane despite being in an environment of moderate to strong vertical wind shear, which gives me yet another reason to point out why we have a lot to learn about tropical cyclone rapid intensity changes. Eventually though, wind shear and drier air began to take its toll on the storm, but don’t let that fool you! Florence will once again strengthen into a major hurricane. The first graphic below shows the National Hurricane Center’s current projected track for Florence, which I overlaid with current sea surface temperatures. Florence is currently located in a region where sea surface temperatures (SSTs) are around 27.5°C/81.5°F but is moving into a region where those waters are much warmer (around 29.5°C/85.1°F). With the combination of warming SSTs and lighter wind shear, the environmental conditions are going to become increasingly conducive from rapid intensification. This is why NHC now forecasts Florence becoming a 145 mph hurricane in 96 hours!
So, there continues to remain a bit of uncertainty about exact track, which I know is the last thing most of you want to hear since many of you are trying to make preparations. Let me walk you through the forecast, and then I’ll share my thoughts on how everyone should be making preparations. The NHC has Florence approaching the Carolina coast, shown on the first image below. Now remember, the cone is simply a projection of where the center of the storm could go. That has nothing to do with impacts, which always occur outside of the cone. Anyway, the NHC forecast generally agrees with what most of the operational guidance has been indicating, along with the ensemble means. But take a look at the spread in the European ensembles (courtesy of Ben Noll’s website). Each red line represents a member of the group of ensembles, and those members have Florence making landfall anywhere from northern Florida to the Mid-Atlantic. Some even have Florence skirting along the coast/curving out to sea, something that cannot be entirely ruled out.
Two main factors are at play here. First, we must continue to monitor how far to the south Florence remains this weekend. That alone could determine how far to the south Florence will be as it approaches the coast. But here’s another key factor. . .the strength of the developing ridge that will build to Florence’s northeast and then attempt to strengthen to Florence’s north. This is the feature that is currently expected to steer Florence towards the coast. IF the ridge were to be weaker than currently projected and if Florence could gain a decent amount of latitude this weekend, that would put Florence very close to the East Coast, but it’d possibly curve along the coast instead of making landfall. Given these two uncertain factors, residents from the northern Florida coast to North Carolina need to go ahead and begin making preparations, keeping in mind that all of those locations won’t be getting the brunt of the storm. On the map below, I only circled regions near the coast that could be heavily impacted by Florence, but impacts will extend beyond that boundary farther inland, if a landfall does occur.
Although I understand that my outlined boundary covers a lot of real estate, I encourage anyone in those areas to begin making some preliminary preparations over the rest of this weekend. On Monday or Tuesday evening, I will produce a follow-up post with an updated map that will be a lot more narrowed down at that point. Please continue to Firsthand Weather on Facebook for future announcements on when the latest updates and articles will be published.