Northeast Times

Storm surge easily could have hit here

Hur­ricane Sandy spared Phil­adelphia from the worst of its dev­ast­at­ing fury.

But in the af­ter­math of the epic storm that in­flic­ted some $20 bil­lion in dam­age along the East­ern sea­board, the re­gion’s lead­ing gov­ern­ment met­eor­o­lo­gist warns that the Delaware Val­ley is far from im­mune to the type of de­struc­tion seen in coastal cit­ies and towns.

“The strongest winds and strongest push of wa­ters onto the shore were from the Jer­sey shore to New York. But if the track of the storm had been farther south, all of those im­pacts would’ve shif­ted south with it,” said Gary Sz­a­tkowski, the met­eor­o­lo­gist-in-charge for the Na­tion­al Weath­er Ser­vice’s Mount Holly, N.J., of­fice. “Everything you’re see­ing in New York City, you would’ve seen [here]. It would’ve been dis­astrous for Phil­adelphia.”

Not even a 60-mile buf­fer zone between Philly and the At­lantic Ocean might’ve shiel­ded the city from mass flood­ing to go along with hur­ricane-strength winds and even more-wide­spread power out­ages than ex­per­i­enced throughout the re­gion.

Of­fi­cially, Sandy made land­fall at about 8 p.m. on Oct. 29 about five miles south­w­est of At­lantic City. That would place the eye of the storm at Mar­gate. By that time, however, it was no longer a hur­ricane.

One hour earli­er, with the storm still at sea, the NWS re­clas­si­fied it as a post-trop­ic­al cyc­lone, a Nor’east­er. The trans­ition did not di­min­ish its wal­lop.

“This was a ma­jor storm and it transitioned from be­ing a hur­ricane to a very ma­jor Nor’east­er,” Sz­a­tkowski said. “That hap­pens [to oth­er storms], but it doesn’t typ­ic­ally hap­pen just as it’s com­ing to shore. In terms of in­tens­ity, it was one for the re­cord books.”

Both vari­et­ies have sim­il­ar ana­tomy. They fea­ture a cent­ral eye, which is a calm, clear low pres­sure area usu­ally about 20 to 40 miles in dia­met­er; an eye wall com­posed of dense clouds with the highest wind speeds in the storm; and out­er, spiral­ing bands that can fan hun­dreds of miles from the cen­ter.

While hur­ricanes and oth­er trop­ic­al cyc­lones are “warm-core” sys­tems, thriv­ing on warm air, Nor’east­ers are “cold-core” thriv­ing on cold air.

In Sandy’s case, the trans­ition oc­curred as it circled and ul­ti­mately merged with a low-pres­sure cold air mass that had moved over the East­ern U.S. in con­cert with a trough in the jet stream. 

“Tech­nic­ally, [Sandy] was a Nor’east­er when it ar­rived,” Sz­a­tkowski said. “Nor’east­ers nor­mally par­al­lel the coast and go out to sea.”

However, in Sandy’s case, the swirl­ing in­ter­ac­tion between low-pres­sure sys­tems — known as the Fuji­whara Ef­fect — in­flu­enced the storm to make a sharp turn to­ward the north­w­est just be­fore mak­ing land­fall.

“That’s what steered the storm,” Sz­a­tkowski said. “That’s what led to the rather un­usu­al track.”

The storm’s track or path, along with its winds, were the key factors in its dis­astrous out­come.

“The main im­pact you’ve been see­ing on the news was from the storm surge, the high­er-than-nor­mal wa­ter level that Sandy brought to shore,” Sz­a­tkowski said. “That has to do with the strength of winds, the dir­ec­tion of winds and the track of the storm.”

In the North­ern Hemi­sphere, Nor’east­ers cir­cu­late counter-clock­wise, so the strongest winds and tid­al surges are felt in the north­w­est quad­rant of the storm. The winds blow from the north­east.

So, Sz­a­tkowski ex­plained, had the eye of the storm made land­fall along the Delaware coast in­stead of South Jer­sey, the storm surge that struck New York Har­bor in­stead would’ve traveled in­to the Delaware Bay and ul­ti­mately up the Delaware River, which is tid­al as far as Trenton, N.J.

Trib­u­tary wa­ter­ways such as the Schuylkill River, Cobbs Creek, Frank­ford Creek, Pennypack Creek and Poquess­ing Creek would’ve over­flowed their banks.

In­stead, the Delaware en­countered what is con­sidered minor flood­ing along Colum­bus Boulevard, as did Cobbs Creek in South­w­est Phil­adelphia, ac­cord­ing to Joanne Dahme, a spokes­wo­man for the Phil­adelphia Wa­ter De­part­ment.

The Pennypack cres­ted at 6.5 feet near Rhawn Street, about 6 inches be­low minor flood stage. The Frank­ford cres­ted at 5.5 feet, about 18 inches short of minor flood stage. The Poquess­ing cres­ted at 6.5 feet near Grant Av­en­ue and did not flood.

Dahme, the PWD’s gen­er­al man­ager for pub­lic af­fairs, at­trib­uted the lack of flood­ing to the re­l­at­ively low volume of rain dur­ing the storm — it was meas­ured at about 3 inches at Phil­adelphia In­ter­na­tion­al Air­port — as well as the rain’s lack of in­tens­ity.

Also, the wa­ter de­part­ment “pro­act­ively cleaned [storm wa­ter] in­lets days be­fore the storm in pre­par­a­tion,” Dahme said.

PWD crews and cit­izen vo­lun­teers vis­ited 2,954 storm in­lets, cleared 2,616 in­lets and re­moved 155 tons of debris from them.

In the ab­sence of flood­ing, power out­ages and the res­ult­ing traffic snarls were the most wide­spread loc­al prob­lem. Sixty-five thou­sand PECO cus­tom­ers lost power in Phil­adelphia. More than a day after the storm, some 37,000 Phil­adelphia homes and busi­nesses re­mained without power. As of Tues­day, the util­ity com­pany re­por­ted only “scattered” out­ages in the city.

Even with­in that con­text, however, North­east Philly and the city made out well. In the five-county Phil­adelphia re­gion 850,000 lost power in the storm. About 2,000 re­mained power­less on Tues­day, a week after the storm, in­clud­ing about 1,000 in Bucks County and an­oth­er 500 in Mont­gomery County. ••

Re­port­er Wil­li­am Kenny can be reached at 215-354-3031 or wkenny@bsmphilly.com

You can reach at wkenny@bsmphilly.com.

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