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Florence likely to become hurricane; Navy warns of possible deployment of all ships

An enhanced satellite image shows Tropical Storm Florence, center, in the Atlantic Ocean on Saturday, Sept. 8, 2018 at 2:45 p.m. EDT.

NOAA

By GREG PORTER | Special To The Washington Post | Published: September 8, 2018

The odds of a major hurricane making landfall along the U.S. 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 U.S. Southeast coast.

On Saturday, the U.S. Navy's Fleet Forces Command announced that it had ordered all Navy ships in the Hampton Roads, Va., area to set Sortie Condition Charlie, Sept. 7. According to a Navy release, Sortie Condition Charlie sets the stage for preparations for ships getting underway. Condition Charlie indicates the onset of destructive weather conditions to the port within approximately 72 hours.

The setting of Condition Charlie does not mean the actual sortie is inevitable, the Navy said in the release. Should forecasts indicate a decrease in the strength or change in the track of the storm, the sortie condition may be downgraded.

Potential U.S. landfall is still several days away, and Florence's ultimate track and intensity are not yet set in stone, with still a small chance that it meanders just off the East Coast and then curls out to sea.

As of 11 a.m. Saturday morning, Florence bears no resemblance to the beastly storm that it will eventually become. Florence remains a tropical storm with maximum sustained winds of 65 mph and located some 1,500 miles east of east of the U.S. mainland, slowly tracking to the west at less than 10 mph.

Over the last 36 hours, Florence weakened from a hurricane to a tropical storm as the system encountered hostile conditions in the central Atlantic Ocean. Unfortunately, the environment that Florence is about to move into is extremely favorable for rapid strengthening, thanks to warmer-than-average sea surface temperatures and low wind shear (the change in wind direction or speed with height). As a result, the National Hurricane Center expects Florence to regain hurricane status within the next 24 hours and intensify to a major hurricane (Category 3 or higher) by Tuesday.

As Florence enters a region favorable to rapid intensification, the storm will continue to track almost due west, likely passing just south of Bermuda by early next week. Historically speaking, the path that Florence is likely to carve out is a highly unusual one. As tropical weather expert Brian McNoldy pointed out Friday in The Washington Post, 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 U.S. If it verifies, this incredibly strong high pressure system would likely 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.

Most model simulations now show Florence making landfall along the U.S. East Coast as a major hurricane between Wednesday and Friday of the coming week. This kind of model agreement is plenty reason enough to start sounding the alarm for the millions of people along the East Coast who may be impacted by the storm.

However, the exact track, intensity, and landfall location of the storm is impossible to know this far out, 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.

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

Obviously, the worst impacts 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 impacts from Florence could be felt up and down the East Coast and over inland areas as well over several days.

In particular, 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.

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 may bring.

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 the west African coast, was christened late Friday 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 Depression 9 is of greatest concern as it is forecast to head toward the Caribbean over the next several days and attain hurricane strength.
 

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