Nicole’s remnant brings heavy rain and tornado threat to eastern U.S.


Nicole hit eastern Florida early Thursday in the country’s first November hurricane in 37 years, and while it’s now moving away from warmer waters, it’s not over yet. The remnants of the tropical cyclone will bring a stream of heavy rainfall from the southeastern U.S. to Canada, while posing a rare late-season tornado threat to parts of the mid-Atlantic.

Florida’s repeating hurricane path surprises meteorologists

All tropical storm, hurricane and storm surge warnings have been lifted and the system disintegrated into a tropical depression – the remaining vortex of low pressure. Now, concerns have shifted to the risk of tornadoes in the mid-Atlantic. A tornado warning was issued for much of the Carolinas coastal plain and Piedmont, as well as southeastern Virginia, by 3 p.m. ET. More watches may be hung at night.

Nicole made official landfall as a Category 1 hurricane with sustained winds of 75 mph near Vero Beach, Florida, at around 3 a.m. Thursday. As the storm washed ashore, it unleashed gusts of 84 mph and 80 mph near Daytona Beach and Melbourne. An elevated weather station in Cape Canaveral was 120 feet above the ground, and wind gusts reached 100 mph.

As many as 350,000 customers in the Sunshine State were without power Thursday morning, but reported that as of Friday morning, all but 40,000 customers were back in service.

Storm surge, or a rise of 3 to 4 feet above normally dry land, caused light to moderate flooding on Florida’s Atlantic-facing coastline, but erosion from large shock waves proved to be a bigger problem.There are at least a dozen buildings in Daytona Beach become uninhabitable Like the angry sea eroding the cliffs on which they perched.

The storm brought about 3 to 6 inches of rain in eastern and northern Florida.

As of 10 a.m. ET Friday, Nicole was a tropical depression with maximum sustained winds of 30 mph. It is centered 35 miles north of Atlanta and is moving north-northeast at 23 miles per hour.

Nicole’s air pressure is rising as the center of low pressure “fills” with air. This is similar to how a vortex in a morning cup of coffee that gets churned ends up slowing down and flattening the dip in the liquid.

Because of this, there are not as large gradients or changes in air pressure over distance to support strong winds. That’s why all the winds associated with Nicole are below tropical storm strength. It’s like a sled; you’ll accelerate faster if the incline or incline is bigger and the hill is steeper. As Nicole’s gradient is weakening, its winds are weakening.

That being said, it’s still a mass of moisture moving northeast, and an unseasonably warm, moist air mass is heading north ahead of it. Dew points in the mid-to-upper 60s will soar north to the Mason-Dixon line, preparing for several dangerous thunderstorms Friday afternoon.

Dry air is entering Nicole’s circulation from the west, in the same direction as the cold front is approaching. The influx of dry air is both a blessing and a curse: on the one hand, it erodes Nicole’s circulation from the inside out, accelerating the demise of its core. Dry air, on the other hand, helps to whip up warm, moist air ahead of Nicole, creating a powerful thunderstorm.

These thunderstorms will create a highly “sheared” atmosphere. In other words, Nicole is causing a change in wind speed and/or wind height. This will encourage downpours and thunderstorms to spin, and possibly even some tornadoes.

The Storm Prediction Center highlighted a 2 out of 5 severe weather risk to illustrate this possibility. Includes Charlotte, Raleigh, Richmond, Virginia Beach and Wilmington, North Carolina. Level 1 of 5 marginal risk includes Charleston, SC and Columbia

DC, Baltimore and Philadelphia present more uncertainty. They are also in the level 1 risk zone. That’s because they’re dealing with a classic HSLC or high shear low angle setup – notoriously hard to predict by meteorologists. On the one hand, wind dynamics strongly support the threat of rotating thunderstorms and tornadoes. Conversely, fuel for instability or thunderstorms will be fairly limited. Exactly how these ingredients are combined, and in what proportions, remains to be seen.

Nicole plays Friday in Washington area, rain, possible tornadoes

On and off, the storm will continue throughout Friday afternoon and evening. Additional tornado watches may be needed at night to accommodate this potential, especially in Virginia. More targeted warnings will be issued at the local level if meteorologists suspect a tornado is imminent or occurring.

This tornado risk occurs in the “warm zone” of the storm. Temperatures won’t be as warm in the west, but the oncoming cold front will help concentrate Nicole’s moisture and squeeze it out of the air — akin to wringing out a towel.

It appears that most of the heavy rainfall will be on the Acela corridor and west of Interstate 95, walking a tightrope in places like Washington, D.C., Philadelphia, New York and Boston. There will be a fair amount of rain in the west, 2 to 3 inches wide over the Appalachians. In the east, only a quarter to half an inch will fall near the coast.

“Upslope flows,” or places where air is forced uphill, will be accompanied by the largest rainfall totals in western North Carolina. On the eastern slopes south of the Blue Ridge, this would drop 6 inches.

“Today, isolated lightning, urban and creek flooding is possible in the southern and central Appalachians, particularly the Blue Ridge Mountains,” the National Hurricane Center wrote. Isolated flood impacts will extend northward into eastern Ohio, midwestern Pennsylvania, into western New York and northern New England.”

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