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Nicole hit East Florida early Thursday as the nation’s first November hurricane in 37 years, and while it’s now far from warm ocean waters, it’s not done yet. The remnants of the tropical cyclone will deliver a swath of heavy rain from the southeastern United States to Canada, while contributing to a rare late-season tornado threat for parts of the Mid-Atlantic.
History-repeating hurricane paths in Florida surprise meteorologists
All tropical storm, hurricane and storm surge warnings have been lifted, the system disintegrated into a tropical depression – a leftover low-pressure vortex. Concern now shifts to the risk of tornadoes in the Mid-Atlantic. A tornado watch was issued for much of the Carolina Coastal Plain and the Piedmont, as well as southeastern Virginia, until 3 pm EST. Additional watches will likely be lifted overnight.
Nicole officially made landfall near Vero Beach, Fla., around 3 a.m. Thursday as a Category 1 hurricane with sustained winds of 75 mph. As the storm made landfall, it unleashed maximum gusts of 84 and 80 mph near Daytona Beach and Melbourne. An elevated weather station at Cape Canaveral, 120 feet above the ground, recorded a gust of 100 mph.
As of Thursday morning, up to 350,000 customers in the Sunshine State had lost power, but PowerOutage.us reports that service had been restored to all but 40,000 customers by Friday morning.
A storm surge, or rise of ocean water above normally dry land, of 3 to 4 feet caused minor to moderate flooding along Florida’s Atlantic coast, but erosion of the big waves turned out to be a bigger problem. At least a dozen structures in Daytona Beach were rendered uninhabitable as angry seas eroded the cliffs they were perched on.
The storm dumped 3 to 6 inches of rain on eastern and northern Florida.
As of 10 a.m. ET Friday morning, Nicole was a tropical depression with maximum sustained winds of 30 mph. Centered 35 miles north of Atlanta, it was moving north-northeast at 23 mph.
Nicole’s air pressure increased as the low pressure center “fills” with air. It’s similar to how a swirling swirl in your morning cup of coffee slows down and the immersion in the liquid flattens out.
Because of this, there is not so much gradient, nor change in air pressure with distance, to withstand strong winds. That’s why all the winds associated with Nicole are below tropical storm strength. It’s like sledding; you will accelerate faster if the gradient, or slope, is greater and the hill is steeper. As Nicole’s gradient is weakening, her winds are diminishing.
That said, it’s still a drop of moisture that’s working its way to the northeast, and an unusually warm, moist air mass is moving north. Dew points in the mid to upper 60s will rise as far north as the Mason-Dixon line, setting the stage for some dangerous thunderstorms Friday afternoon.
Dry air enters Nicole’s circulation from the west, the same direction a cold front was approaching. This intake of dry air is a blessing and a curse: on the one hand, it erodes Nicole’s circulation from the inside out and accelerates the demise of her core. In turn, this dry air helps propel the warm, moist air ahead of Nicole, spawning strong to severe thunderstorms.
These storms will become a very “cut” atmosphere. In other words, Nicole is inducing a change in wind speed and/or directional height. This will encourage the rotation of showers and thunderstorms and maybe even produce a few tornadoes.
The Storm Prediction Center has highlighted a level 2 out of 5 risk of severe weather to account for this potential. These include Charlotte, Raleigh, Richmond, Virginia Beach and Wilmington, North Carolina. A Marginal Risk Level 1 out of 5 includes Charleston and Columbia, SC
DC, Baltimore and Philadelphia present a bit more uncertainty. They are also in the risk zone level 1. This is because they are facing a classic HSLC or High Shear Low Cape configuration, which is infamously difficult for forecasters to forecast. On the one hand, the wind dynamics strongly support rotating storms and a tornado threat. Conversely, instability, or fuel for storms, will be quite limited. Exactly how these ingredients are combined and in what proportion remains to be seen.
Nicole will run through the DC region on Friday, with rain and possible tornadoes
Scattered thunderstorms will continue throughout Friday afternoon and evening. There is a possibility that additional tornado watches will be needed to accommodate this potential, especially in Virginia, overnight. More specific warnings will be issued locally if forecasters suspect a tornado is imminent or occurring.
Isolated, urban and small stream flooding will be possible today in the southern and central Appalachians. Heavy rain and isolated flash flooding will spread northward across parts of Ohio, Pennsylvania, New York and New England this Saturday night. pic.twitter.com/mNpDvtMSTS
— National Weather Service (@NWS) November 11, 2022
This tornado risk occurs in the “warm sector” of the storm. In the west, temperatures won’t be as warm, but the approaching cold front will help concentrate Nicole’s moisture and squeeze it out of the air, similar to wringing out a towel.
It looks like most of the heaviest rain will occur west of the Acela corridor and Interstate 95, leaving places like DC, Philadelphia, New York and Boston walking a tightrope. Considerably higher amounts of rain will fall in the west, with a spread of 2 to 3 inches over the Appalachians. In the east, only a quarter to a half inch will fall near the coast.
The highest rainfall totals will accompany “upflow” over western North Carolina, or where air is forced up the mountains. This will see up to 6 inches fall on the eastern slopes of the southern Blue Ridge.
“Isolated, urban and small stream flooding will be possible today in the southern and central Appalachians, especially in the Blue Ridge Mountains,” the National Hurricane Center wrote. “Heavy rainfall and isolated flooding impacts will extend north across eastern Ohio, west-central Pennsylvania, western New York and northern New England this Saturday night.”