Visualization of Florence, at hurricane strength, on Wednesday. (earth.nullschool.net)

(This story, initially published midday, was updated just after 5 p.m. and 11 p.m. to incorporate new information from computer models and the National Hurricane Center.)

The odds of a major hurricane making landfall along the East Coast next week keep growing. Forecast models paint an increasingly grim picture, converging on a track that would have what is currently Tropical Storm Florence making a direct hit as a powerful hurricane somewhere along the Southeast coast.

The National Hurricane Center predicts “a dangerous major hurricane” near the Southeast coast by late in the week. Its official forecast places Florence right along the coast of southeast North Carolina at 11 p.m. Thursday as a Category 4 hurricane – although that placement is within a large cone of uncertainty.

Rick Knabb, The Weather Channel’s hurricane expert, described the danger as “extreme”, tweeting “we must prepare.”

Florence’s potential U.S. landfall is still several days away — probably between Thursday and Friday — and its ultimate track and intensity are not yet set in stone. There is still a small chance that it meanders just off the East Coast and then curls out to sea.

South Carolina, North Carolina, and Virginia have all declared a state of emergency to position money and resources to prepare for the storm.

At 11 p.m. Saturday, Florence was showing signs of becoming better organized but bears little resemblance to the beastly storm that it eventually will become. Florence remains a tropical storm with maximum sustained winds of 70 mph about 1,500 miles east of the U.S. mainland, crawling to the west at 6 mph.


Saturday evening Infrared satellite imagery shows Florence starting to regain a more uniform circular structure, a sign of strengthening.

Florence will probably regain hurricane status shortly

The weakening phase Florence underwent Thursday and Friday is over and the environment that Florence is moving into is extremely favorable for rapid strengthening.

Both warmer-than-average sea surface temperatures and low wind shear (the change in wind direction or speed with height) are present, which will aid the storm’s development. The National Hurricane Center expects Florence to regain hurricane status Saturday night and become a major hurricane (Category 3 or higher) by Monday.


Sea surface temperature anomalies over the Atlantic Ocean. Ocean temperatures are running several degrees warmer than normal at the moment. (NOAA)

In fact, the Hurricane Center predicts that Florence will reach Category 4 strength Tuesday and remain at that intensity through Thursday, leading up to its possible landfall.

The Hurricane Center’s forecast for the storm’s peak winds to reach 145 mph by Wednesday “is indeed the strongest they have ever projected an Atlantic tropical storm in the last two decades” tweeted Sam Lillo, a meteorological researcher at the University of Oklahoma.

Risk of U.S. landfall is rising

As Florence enters a region favorable to rapid intensification, the storm will continue to track almost due west, probably passing just south of Bermuda. Historically speaking, the path that Florence will probably carve out is highly unusual. As Capital Weather Gang’s tropical weather expert Brian McNoldy pointed out Friday, since 1851, 79 tropical systems tracked close to Florence’s current location, and not one of those storms made a U.S. landfall, with the vast majority remaining well offshore.

However, models indicate a historically strong ridge of high pressure will develop in the western Atlantic just as Florence closes in on the United States. If it verifies, this incredibly strong high pressure system would probably prevent Florence from recurving to the north and out to sea. There is still some uncertainty in the strength and position of the high pressure, though, and thus in the ultimate track and intensity of the storm.

Best chance of landfall is in the Carolinas, but entire East Coast still at risk

Most model simulations now show Florence making landfall along the East Coast as a major hurricane between Wednesday and Friday. This model agreement is reason enough to start sounding the alarm for the millions of people living along the coast whom the storm might affect.

However, the exact track, intensity and landfall location of the storm is impossible to know this far in advance, and as shown by some of the blue tracks below, there’s still an outside chance the storm could meander just offshore and then curl back out to sea.


Group of simulations from American (blue) and European (red) computer models from Saturday. Each color strand represents a different model simulation with slight tweaks to initial conditions. Note that the strands are clustered together where the forecast track is most confident, but they diverge where the course of the storm is less certain. The thick bold red line is the average of all of the European model simulations, while the blue is the average of all the American model simulations. The thinner bold (red and blue) lines are the main or operational simulations from each model. (StormVistaWxModels.com)

Even if Florence remains just offshore, dangerous surf, beach erosion and flooding would be likely along portions of the coast, along with wind and rain. Inland effects would be less severe in this scenario, although it is among the least likely.

Based on current information and model guidance, we assign the following landfall likelihoods:

  • 50 percent chance of landfall in the Carolinas
  • 15 percent chance of landfall between Virginia Beach and Delmarva
  • 15 percent chance of  landfall between Central Florida and Georgia
  • 10 percent chance of landfall in the Northeast
  • 10 percent chance that the storm curves out to sea

All of the scenarios anticipate Florence being at hurricane strength at the time of landfall, with a strong chance that the storm is a major hurricane (Category 3 or higher).

Major impact possible up and down the East Coast

Obviously, the worst impact from the storm will occur closest to its ultimate landfall location, with storm surge, wind damage and torrential rain representing the biggest hazards. That said, residual impact from Florence could be felt up and down the East Coast and over inland areas as well over several days.

After a very wet summer, much of the Northeast and Mid-Atlantic regions would face a significant flood threat from Florence, even after the storm moves ashore.


Rainfall totals in the eastern United States (June — August were at or near historic levels in 2018.)

Nearly every location east of the Appalachians has received above normal, and sometimes historic, levels of rainfall this summer. All of that rain amounts to waterlogged terrain and overtaxed water basins unable to take on the potentially drenching rains that Florence could bring.

Some model simulations suggest the Florence could stall after it moves inland, unloading disastrous amounts of rain, but it not possible to determine exactly where this would happen, if it even does, so many days into the future.

In the Richmond, Washington and Baltimore regions, some of the worst damage from tropical storms and hurricanes has come from storms that made landfall in the Carolinas and then tracked west of our region, putting the cities on the eastern side of the counterclockwise rotating system, where most of the rainfall occurs. This is a possible path for Florence — which would potentially affect this region between Friday and the weekend, possibly longer if the storm stalls.

Preparation

It is time to begin thinking about hurricane preparedness if you live along or near the coast.

Do you have a plan if the storm hits your area? Do you know where you would go if evacuations are required? Do you have an emergency kit with at least three days’ worth of critical supplies? Do you have trees that could fall on your house during a windstorm? Trim them now. Declutter drains and gutters.

More threats behind Florence

After nearly no action for from June through August, tropical activity has sprung to life in a hurry in the Atlantic. Tropical Storm Helene, located just off Africa’s west coast, was christened late last night and may reach hurricane status shortly, which would be extremely unusual for a storm situated so far east in the Atlantic. Meanwhile, two other areas of interest are being monitored by the National Hurricane Center for tropical development.

Tropical Storm Isaac, upgraded from a tropical depression on Saturday, is of greatest concern as it is forecast to head toward the Caribbean over the next several days and attain hurricane strength.


Several tropical threats have developed all over the Atlantic basin.

Capital Weather Gang’s Jason Samenow and Dan Stillman contributed to this article.