Frightful Hurricane Florence aims to devastate coastal Carolinas | Weather Tiger

Remember two weeks ago, when gas was a reasonable $2.79 per gallon, all politicians were honest and noble, and the 2018 hurricane season was a forgettable afterthought?

Me neither.

The Atlantic is currently riding a historic surge of activity through the climatological peak of the season, with four active storms and several additional threats for development. Foremost among these is massive major Hurricane Florence, which is on a course to devastate the coastal Carolinas. But Floridians need to keep watch to the south as well in case Tropical Storm Isaac re-fires next week. More on that later.

STORM TRACKER AND MODEL MIXER: For the latest model runs and path of the storm, click here.

GRIDLOCK GUIDE: Click here to see live traffic views from North Carolina and South Carolina.

For the next five to seven days, all eyes are on historic Florence. As of Wednesday evening, Florence is located about 400 miles southeast of Wilmington, North Carolina, and has sustained winds of around 125 mph. This makes Florence a strong category 3 hurricane on the Saffir-Simpson Hurricane Wind Scale.

Due to eyewall replacement cycles over the past few days, Florence has expanded dramatically even as maximum winds have declined slightly. These changes make the storm on balance more, not less, dangerous. Tropical storm and hurricane force winds extend up to 200 miles and 75 miles north of the center, respectively, similar to the wind radii of Hurricane Irma as it neared Florida one year ago.

Where is Florence headed?

Florence will traverse high ocean heat content waters, including the anomalously warm Gulf Stream, as it moves northwest at 10-15 mph through Thursday evening. Some fluctuations in intensity are possible, but major strengthening or weakening is unlikely as Florence approaches the North Carolina coast between Wilmington and Morehead City overnight Thursday into Friday.

Florence will slow down dramatically on final approach to the N.C. coast as a “blocking” ridge of high pressure develops over the Great Lakes. Trapped between areas of high pressure to its northeast and northwest, the steering currents guiding the storm will weaken to almost nothing by early Friday, at which point increased shear and shallow continental shelf waters mean slow weakening is likely until landfall.

This stall will result in an outcome with few, if any, real precedents in the annals of Atlantic tropical cyclone climatology: the spectacle of a major hurricane grinding to a halt near or just offshore the U.S. coastline.

While a range of outcomes remains possible, in general, I expect a period of slow-motion near Wilmington on Friday and a drift west or southwest into northern South Carolina over the weekend as the high pressure over the northeastern U.S. gradually shifts east.

Given the extent of the blocking, Florence is unlikely to begin moving north or northeast ahead of a trough until Monday, and its remnants may not clear New England until next Wednesday.

Forecasting track in a weak steering current environment is difficult. However, this afternoon’s model guidance has tightened its focus on the southern North Carolina and northern South Carolina coast as the region of greatest impact.

Tuesday night’s European model was an outlier in scraping Florence along the coast all the way southwest to Savannah; Wednesday afternoon’s Euro remains farthest south but has corrected north to a Wilmington-to-Charleston scrape as the model more realistically handles an upper low to Florence’s east.

Overall, the consensus for a slow-motion landfall of Florence in southern North Carolina sometime late Friday or Saturday and subsequent drift westward through Monday is about as strong as could be expected in this environment.

An onslaught of surge, winds and rain

While no hurricane is a point, I would in particular urge you not to focus on exact track in Florence’s case. The hurricane is a true four-quadrant (wind, surge, inland flooding, tornado) threat focused on the Carolinas, with an expected duration of destructive conditions far exceeding that of a typical major hurricane, in which the worst conditions pass in a few minutes to several hours.  

Instead, given Florence’s wind radii and agonizingly slow pace between Friday and Saturday, the coastline between Myrtle Beach, S.C., and Morehead City, N.C., may see 24 hours or more of wind gusts around 100 mph, with maximum gusts even higher.

The massive fetch of easterly winds will drive an enormous storm surge along and to the right of the track as well, with 12-15 feet of rise expected. This will be enhanced by extreme wave action as well as runoff from river flooding.

Frankly, with so many unique factors at play, Florence will test the limits of storm surge predictability. You do not want to be anywhere near the coast or in a known flood plain in the Carolinas this weekend, and all evacuation orders should be heeded immediately.

Please encourage anyone you know still in this situation to leave — you may well be saving their life in doing so.

Significant flooding will extend well inland and away from the coast, as Florence will dump one to two feet of rain across southern North Carolina and eastern South Carolina over the next five days.

Lower totals but flood risks extend west to eastern Georgia and north to central Virginia.

This too is likely to be a major disaster, with the highest impact area to be determined by exactly when and where Florence comes ashore.

However, I am confident that Florence’s rainfall will not reach South Georgia or North Florida, where the most significant “impact” is likely to be breezy conditions and perhaps warmer and drier than normal weather on Sunday and Monday.

Isaac on deck: Will he shear or be something to fear?

Would that the tropical pain train ended there, but the four named systems currently active equal the all-time Atlantic record and that record, in turn, may be broken in the next day.

Going around the Basin in 60 seconds: Hurricane Helene is turning north into the open eastern Atlantic and is not a threat to land. The same goes for newly formed Subtropical Storm Joyce to Helene’s northwest, which will kick around for a few days before merging with a front.

Invest 95L is a cluster of storms in the south-central Gulf of Mexico; the same ridge smooshing Florence west will push that system into South Texas by the weekend, where the potential Tropical Storm Kirk could bring some beneficial rains as it scoots toward Mexico.

That leaves Tropical Storm Isaac to contend with, and it’s one that I’m eyeing warily as a possible threat to Florida or the Gulf Coast in 8-10 days. Currently, Isaac is a modest tropical storm approaching the Lesser Antilles and is struggling mightily under shear induced by Florence’s huge outflow.

Isaac may well succumb to this shear in the next several days and amount to nothing as it continues west across the Caribbean, but a fair number of GFS and Euro ensemble members indicate that Isaac will be put to the test by shear but ultimately survive.

In what I am terming the “Abraham scenario,” Isaac would be spared and could then re-intensify in a more favorable environment in the western Caribbean and potentially follow a steering weakness caused by Florence and turn north into the Gulf of Mexico in 6-8 days. I think there is only a 20-25 percent chance of the Abraham scenario happening at this point, but I do think it is a possibility that needs to be monitored.

Close watchers of this column may also remember I am the dad to a 19-month-old toddler named Isaac, who is currently teething a preposterous number of teeth simultaneously.

That feels like a bad omen, and in this season, I’m not going to err on the side of optimism for the time being.

Until next time, stay safe, and keep watching the skies.

Dr. Ryan Truchelut is co-founder and chief meteorologist at WeatherTiger, which provides weather and climate forecast solutions for government and private enterprise. Get in touch at ryan@weathertiger.com. A more detailed version of WeatherTiger’s hurricane outlook, with additional animated GIFs, is free to read at weathertiger.com.