Hurricane Florence Likely To Be Catastrophic For Parts of the Carolina Coast

After Florence’s recent eyewall replacement cycle, it has re-strengthened into a 140 mph hurricane. Strengthening is expected to continue, given that vertical wind shear will be weak, sea surface temperatures will be more than sufficiently warm, and little dry air will be present to mix into Florence’s core. In an effort to answer many unanswered questions, I’ve made a couple of maps. Let me briefly explain what they mean.

The first map includes where I believe Florence will be making its (first) landfall. Some southern shifts in track could occur; thus, I’ve included the northern South Carolina coast as a potential landfall location. Given the fairly good consistency amongst the models on landfall location, I decided not to shift the landfall threat farther south. I’ll decide tomorrow if I need to make any additional shifts southward. Locations in and around the circled region is where I am currently anticipating damage to reach catastrophic levels.

Hurricane Florence landfall

The second map includes the regions that could be impacted by Florence, whether that’s from wind, flooding, or coastal storm-surge. Most of the forecast model guidance today made a noteworthy shift westward (and even southwestward) in Florence’s track once it reaches the southern North Carolina and northern South Carolina coasts. Some of the guidance even brings the center back over water and has a second landfall occurring farther southward into South Carolina. Weak steering flow is making this a particular challenging forecast. A high pressure ridge to Florence’s east/northeast and also to its west will result in Florence slowing significantly near the coast. The pink zone is where I’m currently most concerned about; while some parts of the red zone could experience significant impacts as well. At the least, I expect those in the red zone to experience some impacts from wind and rain. If the southward trend continues, I may end up chopping parts of northern Virginia out of the red zone, but in this update, I mainly included them due to potential flooding. I’m sure modifications will have to be made to the forecast, since we’re now getting down to the county-level.

Hurricane Florence impact zones

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What Impacts Should You Expect From Hurricane Florence?

Hurricane Florence underwent rapid intensification last night and today and currently has maximum sustained winds of 140 mph. This puts Florence at category 4 strength, and expectations are that further strengthening will occur, given the favorable environmental conditions. It appears that Florence’s strength has currently leveled off for the time being, and with hurricanes of this strength, it is not uncommon for an eyewall replacement cycle to occur. This occurs when an outer eyewall begins to form around the original eyewall. Over time, the new eyewall eventually replaces the old one. Although this can result in temporary weakening, the storm can later strengthen further, and the wind field usually increases in diameter. We will have to see if that occurs overnight tonight or tomorrow.

In this article, I want to focus mostly on impacts, instead of going into a lot of detailed meteorology as I often do in my discussions. Below, I have included several questions that many of you have asked, and I am going to do my best to answer those.

Where is Hurricane Florence going to make landfall?

We’ve managed to get a better handle on where Florence is going, even though there are still some disagreements in the forecast model guidance. That’s normal though! Previously, we outlined a region from the northern Florida coast through the Carolinas. That zone can now be narrowed down a bit further. The region that should watch for a potential landfall extends from Charleston, SC to the northern coast of North Carolina. The latest several runs of the operational European model have consistently projected a landfall around the South Carolina/North Carolina border, and the ensemble means have shown a similar picture, maybe a hair farther south. Even though locations as far south as Charleston is out of the National Hurricane Center’s cone of uncertainty, I want to watch this storm for another 12 hours before taking that location out of the threat zone, especially since Florence has continued to maintain a westward to west northwestward trajectory. As ridging begins to build and strengthen to Florence’s north, we’ll see if it begins on a more northwest trajectory tomorrow.

Hurricane Florence forecast

Hurricane-force winds will extend well-inland from the center of the storm and along areas to the east of the center. Florence is going to slow down significantly as it approaches land; meaning, this may put somewhat of a limit on just how far inland hurricane-force wind gusts will extend. If the storm were booking it, it would cover a lot of real estate before weakening. In this case, hurricane-force winds may ultimately occur over less real estate, compared to a Hugo-type storm, BUT the wind damage that occurs within the first 24-hours of Florence’s landfall could very well reach catastrophic levels. Given that even a small margin of error in track could change the region that will have those kinds of winds, I recommend erring on the side of caution and preparing, especially if you’re on the Carolina coastline and within 100 miles of the coast.

Hurricane Florence winds

How much flooding will Florence produce, and how widespread will it be?

If Florence makes landfall where it is currently projected, flooding could be widespread and deadly, well away from the storm’s center. Air will be forced upward by the mountainous terrain on the eastern side of Florence, something referred to as orographic lift. This means that rainfall rates could be a bit higher compared to a region that has a hurricane moving over flat terrain. Remember, Harvey was a prolific rain producer because it stalled for days. There will be other factors at play that could enhance Florence’s total rainfall amounts; thus less time will be needed for heavy rainfall totals to occur.

In no way do I want to undermine the wind threat. It’s going to be bad! But, I always take flooding very seriously on Firsthand Weather, especially when I see that it’s going to be a widespread event such as this one. Below, I included an image that shows the Weather Prediction Center’s current projected rainfall totals that will be associated with Florence. As you can see, widespread areas of 10 to 15 inches of rain is expected across North Carolina and Virginia. Many of those locations have already received a lot of rainfall this summer, even recently. I think these totals could be a bit underdone in some places, so assume that there will be regions that could well-exceed above 10 to 15 inch rainfall totals.

Hurricane Florence rainfall

Will Storm Surge Be A Big Threat?

The short answer is. . .yes!! For residents along and near the coast, storm surge will be a major issue on the east side of Florence. This is a deadly threat that is often not taken seriously. Even a very small change in track could alter the regions that will get the highest storm surge.

Hurricane Florence storm surge

Some Advice:

If you are under mandatory evacuations, I strongly urge you to evacuate. There will be some of you who will evacuate and may come to realize by the end of all of this that it wasn’t necessary. However, you don’t want to find yourself in a situation wishing that you had left. You may be putting yourself and your family at risk. It’s generally a good idea to expect the unexpected. When do meteorologists ever get a forecast completely accurate, especially one like this? Never. That’s not a criticism of the science, but instead, it’s something that you should take into consideration. It’s best to plan for unexpected changes in track and intensity that weren’t necessary predicted by professional meteorologists. It’s the nature of the science, and it’s one you should be aware of, especially if you are tempted to believe your area may not be a high-impact area.

If you are unable to evacuate, whether that’s due to financial reasons or whatever else, try to reach out to those who are willing to help. Many of our followers on Firsthand Weather have been providing tips, making others aware of resources that they weren’t aware of, and even offering their homes for free for others to stay. Please go to the Firsthand Weather Facebook page, and we will do our best to guide you to the great amount of information that many of our followers have already provided.

Hurricane Florence Could Directly Hit The East Coast But Uncertainty Still Remains

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!

Hurricane Florence track and warm waters

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.

NHC Hurricane Florence Track

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.

Hurricane Florence impact zone

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.