Florence is forecast to restrengthen into a hurricane and push close to Bermuda and the United States East Coast next week. Florence is expected to have an indirect impact and may evolve into a serious direct threat.
Florence is a relatively small tropical system, and small tropical systems are very vulnerable to both ideal and poor environmental conditions.
After forming near the Cabo Verde Islands last weekend, Florence became the first Category 4 hurricane of the 2018 Atlantic season as it entered a zone of low wind shear and sufficiently warm waters earlier this week.
Wind shear is the increase in wind speed and change in wind direction with either increasing altitude or over a horizontal distance. High wind shear can prevent a tropical storm from forming and cause a well-developed hurricane to weaken.
A zone of strong wind shear has caused Florence to weaken to a tropical storm. Additional fluctuations in strength are anticipated.
This weekend, wind shear is forecast to diminish, while at the same time Florence moves over much warmer water. As a result, AccuWeather meteorologists expect Florence to gain strength.
The movement of Florence is likely to remain steady in the short term, but a deviation in the path may develop next week.
“An area of high pressure over the central Atlantic will bridge westward and join with an existing high pressure near the U.S. East coast over the next several days,” according to AccuWeather Hurricane Expert Dan Kottlowski.
“This setup will guide Florence on a west to northwesterly course into next week,” Kottlowski said.
If the high pressure area weakens next week, then Florence may be able to curve northward then northeastward out to sea with impacts in the U.S. limited to an indirect nature with rough surf and heavy seas.
However, if the high pressure area remains strong, then Florence may complete a 3,500-mile-long journey over the Atlantic and be guided right into the U.S. East Coast somewhere from the Carolinas to southern New England sometime during Wednesday or Thursday of next week.
Paul Plante says
As of today, according to the Washington Post story “Hurricane Florence could be a lot like Harvey. Here’s why” by Greg Porter on 11 September 2018, the southland on the east coast of the United States is due for a real good soaking.
According to the latest models, a ridge of high pressure, extreme especially for this time of year, will develop just off the coast of New England, shunting the path of Florence toward the southeast coast.
The strength of this ridge will be unprecedented in 30 years, according to forecast models.
With such a strong area of high pressure directly to the north of Florence, the storm has no pathway to curve out to sea as many other tropical systems usually do.
Florence will be forced to the west, passing over an environment that is extremely favorable for intensification and on a collision course with the East Coast.
But that represents only half of the problem because Florence is forecast to stall out after the storm makes landfall, with the stall being the result of the historic high pressure to the north of storm, refusing to budge and trapping Florence in one location for several days.
The bad news is that despite being stuck, Florence won’t die out easily, and while the storm will probably lose its hurricane designation rather quickly once it moves over land, there still will be the problem of all that water the storm was carrying.
According to the Washington Post, even when Florence reaches a post-tropical phase, the storm will still be dumping tons of rain over the same locations for several days, similar to Hurricane Harvey’s impact on Texas and Louisiana in 2017.
The GFS model shows Florence making landfall in North Carolina on Thursday night and then stalling out for the next 48 hours.
The development, position and ultimate strength of the aforementioned high-pressure system will be the ultimate determining factor on where Florence goes and if (and where) the storm stalls out.
Forecast models have generally come into agreement on the strength and placement of the high as Florence approaches the coast — hence, the better agreement on a track forecast.
Regardless of where Florence eventually ends up, it’s safe to say that for the second year in a row, a major hurricane is about to hit an atmospheric roadblock, putting millions of people at risk of what could become a catastrophic flooding situation.
What makes this situation even more tenuous is that several inches of rain have already fallen in the region.
Whatever falls from Hurricane Florence will be hitting saturated soil.
This makes it all the more likely that trees and power lines will come down as winds pick up, and flooding will begin soon after the rain begins.
More than a foot of rain is possible in the Carolinas, and some areas could get much more.
From the higher elevations of the Appalachian Mountains to the coast of the southeast and the Mid-Atlantic, streams, creeks and rivers will rise beyond their banks.
If these forecasts play out, flash flooding will inundate roads and strand motorists and overwhelm homes and businesses.