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Category 3 Hurricane Florence rapidly strengthens and may threaten East Coast next week

The Washington Post logo The Washington Post 2018-09-05 Matthew Cappucci
Hurricane Florence on Wednesday midday. © CIRA/CSU/NOAA/ Hurricane Florence on Wednesday midday.

Just like that, hurricane season 2018 is in full swing. And while the remnants of Gordon continue to weaken over the lower Mississippi Valley, the focus shifts to a new threat on the horizon – Hurricane Florence. This storm has a small chance to become a problem for the East Coast next week.

On Wednesday morning, Florence became the first major hurricane, rated Category 3 or higher, to develop during the current Atlantic season. Its peak winds have climbed to 125 mph.

More than 1200 miles from the nearest land mass, Florence isn’t an immediate concern – yet. But the powerful storm does bear watching, boasting a tightly-coiled wall of thunderstorms surrounding its pinhole eye. Florence’s intensity is forecast to fluctuate over the next several days, perhaps modestly weakening to a Category 2 storm.

During this time, Florence will continue to meander northwestwards, possibly inching dangerously close to Bermuda by the latter half of the weekend. After that, the storm’s exact track and strength become major wild cards in the face of compounding uncertainties.

Track forecast for Hurricane Florence through Monday. © National Hurricane Center/ Track forecast for Hurricane Florence through Monday.

Forecasting a storm’s position more than a few days into the future is like playing a game of Plinko or pachinko. At first, it’s pretty easy to analytically figure out where your chip or ball will go. The “cone” of possible outcomes is pretty narrow. But as time goes on that range of possibilities expands to encompass more real estate. The cone grows. The same is true here.

The National Hurricane Center’s average error from 2010 to 2017 in the the predicted position of a storm is 40 to 50 miles but that balloons to about 220 miles five days into the future, and much greater after that. So while awareness and preparation are good, betting on a specific outcome this early has very poor odds.

But there is a chance that Florence could become a big issue in just over a week. A group of model simulations depicting possible tracks have begun to show the possibility of East Coast impacts  – especially near the Southeast and Mid-Atlantic coasts.

Group of simulations from American (blue) and European (red) computer models from Wednesday night. 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 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. © StormVistaWxModels.com/ Group of simulations from American (blue) and European (red) computer models from Wednesday night. 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 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.

It’s important to keep in mind, however, that there is an equal shot of Florence passing far enough offshore that the U.S. sees nothing more than sunshine and rough surf. That enormous variety of end results is the nature of forecasting a week or more into the future. If the United States were to see something, it would be in about 8 days.

A storm in Florence’s current position has never struck the U.S. in recorded history. However, the prevailing weather pattern could provide an exception. A giant ridge of high pressure over the North Atlantic has a chance to steer the storm toward the U.S. mainland unless a trough of low pressure is able to capture the storm late this weekend and turn it more out to sea.

a close up of a map © AccuWeather.com/

Eric Webb, a graduate student in meteorology, pointed out on Twitter that the 1933 Chesapeake-Potomac hurricane took an unusual track over Bermuda into the Mid-Atlantic coast. That storm pushed a massive tidal surge of 11 to 12 feet up to the Potomac River, flooding parts of Washington.  While Florence is positioned somewhat to the north of that 1933 storm, the specter of it taking a similar track needs to be carefully monitored.

It’s far too early to worry about a landfalling storm, but it’s never too soon to be prepared. Have trees that could fall on your house during a windstorm? Trim them now. Declutter drains and gutters. Make sure you have an emergency kit with supplies for at least three days. There are basic things that anyone in the Atlantic Basin should already be doing during hurricane season. This is an excellent opportunity to do them.

All things considered, we’re right on track for where we should be – the average date of the Atlantic’s first major hurricane is September 4. And while the season may not feature as many storms as 2017, it only takes one to change your life.

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

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