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‘Ginormous’ storm Teddy, 1,000 miles wide, puts on powerful display in Canada

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September 23, 2020 at 3:26 p.m. EDT
Satellite imagery of Teddy on Tuesday. (RAMMB/CIRA)
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What was once a powerful Hurricane Teddy blasted ashore in Canada late Tuesday morning after transitioning into a strong extratropical, or mid-latitude, cyclone. Structurally similar to infamous Hurricane Sandy in 2012, Teddy brought strong winds, a soaking rain and a storm surge to the Canadian Maritimes as the system swept northward.

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The textbook-style evolution of the system put on a show for weather satellites. As it morphed from a hurricane to extratropical storm, its zone of tropical-storm force winds ballooned, occupying a zone about 1,000 miles across.

Teddy’s transition also marked a celebrated milestone in the Atlantic — for the first time in more than two weeks, not a single named storm or even tropical depression was present across the ocean basin. And no tropical cyclone formation is expected through the weekend, welcome news for beleaguered meteorologists and coastal residents alike.

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On Wednesday, the GOES East weather satellite revealed the center of circulation associated with former Hurricane Teddy moving inland over eastern Nova Scotia near the town of Ecum Secum. Winds sustained around 60 mph with rain totals approaching six inches in spots were in the forecast. Equally impressive have been the 30-to-40-foot near-shore waves, with a few 50-footers likely well offshore.

Overnight, Buoy 44150, about 100 miles south of western Nova Scotia, observed individual wave heights topping 80 feet, as did a second weather buoy in the vicinity.

Environment Canada, an analogue to the U.S. National Weather Service, issued rainfall, wind, storm surge and tropical storm warnings for much of central and eastern Nova Scotia. Wreckhouse, a wind-prone region in southern Newfoundland and Labrador, gusted to 82 mph Tuesday night into Wednesday.

The week started with major coastal flooding in Charleston. The weather was beautiful.

Former Hurricane Teddy is enormous

Perhaps the most striking element of Teddy’s second life as a post-tropical cyclone is its size. When hurricanes transition, their wind fields expand. The National Hurricane Center reported that Teddy’s zone of tropical storm-force winds reached outward some 520 miles from the center, or roughly 1,000 miles from one end of the storm to the other. In a typical hurricane, tropical storm-force winds typically extend out from the center about 100 or 200 miles.

The National Hurricane Center went as far as to describe Teddy as “ginormous” in an advisory Tuesday evening.

“The best recent comparison is probably Sandy in 2012,” wrote Philip Klotzbach, a hurricane researcher at Colorado State University, in an email.

Mike Brennan, chief of the Hurricane Specialist Unit at the National Hurricane Center, wrote in an email that Teddy’s width was about an eighth smaller than Sandy’s, but that could change depending on what later data becomes available.

“Sandy was an extraordinarily large hurricane,” Brennan wrote.

Powerful storms are fairly common along Canada’s Atlantic coast but not storms Teddy’s size. “Arguably we see the strongest lows anywhere in eastern North America or a regular basis,” wrote Eddie Sheerr, a broadcast meteorologist in Newfoundland. “The surprising thing about Teddy was the sheer size of the storm as it approached.”

A striking transition

On satellite, Teddy’s extratropical transition was as aesthetically striking as it was meteorologically elegant. Last Thursday, Teddy was a powerhouse Category 4 hurricane zeroing in on an eventual track east of Bermuda.

It was still a hurricane on Monday but was showing the first signs of extratropical transition — a more elongated tail of clouds formed on the eastern flank, evocative of a comma-like tail draped back from the storm. Meanwhile, a few slots of clear sky began to emerge southwest of the center as a wedge of cooler, drier air started to work in from the northwest.

In the tropics, there are few horizontal temperature contrasts, so hurricanes and tropical storms should be largely symmetric. They also derive their energy from warm ocean waters.

At the mid-latitudes, extratropical cyclones are powered by horizontal temperature gradients and the clash of air masses. They are often larger, and spread less-intense winds over a broader area.

By Tuesday, Teddy’s transition was firmly underway, the encroaching dry slot wrapping all the way around in an attempt to infiltrate the center. That helped carve out a cold front to the south of Teddy, ahead of which a conveyor belt of warm, tropical air screamed north.

Tuesday’s satellite shot is particularly riveting, because it shows not one but two named storms as Beta churned in the northwest Gulf. The cold front, carrying autumnal air southward, connects the two like a necklace some 2,500 miles long. The trio form an eerie smile.

On the northwest side of Teddy, a razor-sharp edge in the overcast can be seen where dry air abuts the storm. Wildfire smoke from the West Coast crests north over the system.

For a time, Teddy’s core existed as a warm seclusion, meaning that a bubble of warm, moist air had pinched off from the tongue of tropical atmosphere to the south that connected it; that lobe of warmth was eventually swallowed by the dry slot as Teddy’s structure lost virtually all tropical characteristics. At present, it is similar to a typical fall or winter storm — although no snow is falling.

Elsewhere across the Atlantic, the atmosphere is quiet. Last week featured a flurry of activity, with a record-setting three systems named on Friday alone as we dig deeper into the Greek alphabet. Now, aside from Beta’s remnants and the extratropical storm that was once Teddy, the ocean is virtually silent and shows no signs of waking up in the next week.

Afterward, things could become more interesting. October is climatologically a time when we must turn our eyes toward the western Caribbean and Gulf of Mexico, and already there are signs that activity could roar to life once again.

Correction: The headline of this story originally stated the storm was 500 miles across, whereas it is closer to 1,000 miles across. Five hundred miles is the approximate distance from the storm center to its periphery, or its radius. Its diameter, on the other hand, or the size of the storm from end to end (or its width) is closer to 1,000 miles.

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