This weather pattern could complicate your Thanksgiving travel

A Greenland block will bring chilly weather and make storms somewhat likelier.

An area of high pressure over Greenland can cause some bizarre weather events—like Hurricane Sandy’s westward track. A Greenland block formed in the week leading up to Sandy’s landfall in New Jersey that was unusually powerful relative to other years.

Last weekend, a big chunk of the United States got slammed with frigid weather. And there won’t be much of a reprieve. Unseasonably cold temperatures and possible storms will return to the Midwest and eastern states ahead of Thanksgiving.

The weather pattern responsible for this mischief is called a Greenland block. It happens when atmospheric pressure builds over Greenland and forces the jet stream to dip into eastern North America. Greenland blocking conditions will form this weekend and likely stick around into Thanksgiving week, the Weather Channel reports.

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The true cost of a Macy's Thanksgiving Day float
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The true cost of a Macy's Thanksgiving Day float

1. Total costs for the Macy’s Thanksgiving Day Parade average between $11.6 million and $13.4 million.

Annual costs for parade float supplies, float decorations, property taxes and staff salaries total $2.7 million to $4.5 million. The sheer magnitude of the Macy's parade is overwhelming, and so are the assets associated with the event.

Macy's also has its own studio space and a massive supply of costumes to prepare for the parade. Those assets are worth $8.9 million. Combine the parade's total annual expenses with its total assets and the price tag reaches $10.4 million to $12.3 million. 

Photo credit: Reuters

2. Giant balloons rack up at least $510,000 in helium costs.

Inflating balloons that can soar up to five or six stories tall is seriously expensive. Each balloon in the Macy's Thanksgiving parade uses 300,000 to 700,000 cubic feet of helium. Filling every ballon costs a minimum of $510,000.

Each helium-filled giant requires 50 to 90 volunteer handlers, but sometimes that still isn't enough. In 1997, winds up to 43 mph damaged several balloons, including Barney, The Pink Panther, Quik Bunny and the Cat in the Hat, forcing them to exit the parade route early.

Learn: How to Financially Recover From the Holidays 

Photo credit: Reuters

3. New balloons cost sponsors $190,000.

Companies sponsoring brand new balloons pay a seriously pricey construction and parade fee, totaling $190,000. The cost is high, but advertising at the Thanksgiving parade is a huge marketing opportunity — there's certainly not a shortage of businesses willing to shell out the cash.

Some of the new balloons set to debut at the 2017 parade include Chase from the animated Nickelodeon series "PAW Patrol" and Jett from the NBC Sprout animated series "Super Wings." And for the Disney fanatics, take heed — Olaf from Disney's "Frozen" will also be unveiled as a new balloon, according to USA Today.

Photo credit: Reuters

4. Sponsors pay $90,000 for returning balloons.

Backing a balloon in the Macy's parade is a huge investment, so many sponsors opt to participate for several years. Since a new balloon doesn't need to be constructed, the fee to join in this Thanksgiving Day extravaganza drops to $90,000.

Several balloons will be returning for the 2017 parade, including the Pillsbury Doughboy, SpongeBob SquarePants and Sinclair's Dino. One major question mark is the absence of Snoopy — with 39 Macy's Thanksgiving parade appearances, Snoopy has shown up more than any other character. He was replaced by a Charlie Brown balloon in 2016, and his human has been confirmed again for the 2017 parade. 

Photo credit: Reuters 

5. Construction costs for each float average $30,000 to $100,000.

These Turkey Day spectacles are certainly not your average parade float — those on display at the Macy's parade can take four to nine months to get from concept to completion. In 2017, a total of 26 extravagant floats will be in the parade, with average construction costs ranging from $30,000 to $100,000 for each float.

Parade float supply costs add up fast, especially considering one float can contain 100 to 200 pounds of glitter. One of this year's floats includes the three-story Heartwarming Holiday Countdown by the Hallmark Channel featuring a 3-D calendar.

It's Hallmark Movie Season: See How Much the Channel's Stars Are Worth 

Photo credit: Reuters

6. Costumes have a total price tag of $2 million.

The perfect parade float doesn't just boast beautiful construction. Approximately 700 elaborate costumes are designed each year to bring parade float ideas to life. Costumes currently in storage are valued at $2 million. Balloon handlers wear jumpsuits, but those riding on floats are provided with custom-made garments, according to Business Insider.

On Thanksgiving Day, 200 costume fitters are on-site to help participants into their outfits. When the parade is over, costumes are packed into 10 trucks and sent back to the warehouse. 

Photo credit: Reuters

7. Advance ticket sales for participating Broadway shows have climbed $300,000.

Broadway shows vie for the chance to step into the national spotlight and perform in the Macy's parade. The exposure has boosted advance ticket sales by roughly $300,000 in the past. In 2016, the casts of Broadway's "Holiday Inn," "Waitress," "Paramour" and "Cats" entertained the crowd from the 34th Street stage.

Macy's hasn't announced the performers for the 2017 Thanksgiving parade, but Playbill revealed the Broadway casts of "Come From Away" and "Waitress" — including Jason Mraz — will perform on the CBS broadcast. 

Photo credit: Getty

8. Parade floats cost approximately $780,000 to $2.6 million.

The Thanksgiving parade wouldn't be complete without its fancy floats, but these roving works of art add $780,000 to $2.6 million to the parade's bottom line. Beyond float decorations and supplies, considerable manpower is required.

Each parade float must be collapsed to a width of no more than 8.5 feet to get it through the Lincoln Tunnel, which is part of its journey from the studio in New Jersey to New York City. The floats are reconstructed from midnight to 8 a.m the morning of the parade. 

Photo credit: Getty 

9. Macy’s Thanksgiving Day Parade property taxes total $138,573.

Even the Thanksgiving parade can't get away from Uncle Sam. Previously located in Hoboken, N.J., the Macy's Parade Studio completed work on its new Moonachie, N.J., home in 2011.

The 72,000-square-foot, $6.9 million building is nearly double the size of its previous 40,000-square-foot facility. A tremendous amount of space is needed to house each parade float, balloon, costume, accessory and still have room for employees. Large facilities come with considerable expenses, which can explain the sky-high property tax bill of $138,573 — the highest in the entire nation.

Photo credit: Getty 

10. Salaries for Macy’s parade full-time staffers totals $1.3 million.

Despite taking place just once a year on Thanksgiving Day, the Macy's parade is an enormous undertaking that requires a full-time staff of 26 employees. Temporary staffers are hired during the busy fall months, bringing the total employee count to roughly 40. When combined, their salaries total approximately $1.3 million.

The Macy's parade team includes painters, sculptors, carpenters, construction workers, metal workers and more. Employees start working long hours — including weekends — in September to make sure all preparations are in place for the big day.

The Store Behind It All: Find the Best Deals On Your Favorites at Macy's 

Photo credit: Reuters

11. Thanksgiving parade marching bands apply two years in advance.

For marching bands, it's quite an honor to be selected to perform in the Macy's Thanksgiving Day Parade. The application process requires careful planning, as materials must be submitted nearly two years before the desired performance date.

Only 12 supremely talented marching bands are selected each year. Some of the 2017 winners include the NYPD Police Band, The Ohio University Marching 110 and The United States Air Force Band. Groups pay their own way to the parade. 

Photo credit: Reuters

12. More than 50 million people watch the Thanksgiving parade.

A major Thanksgiving tradition, approximately 50 million viewers tune into the parade from home each year. Another 3.5 million revelers head to the streets of New York City to watch the parade in person.

Putting these numbers into perspective, Game 2 of the 2017 World Series attracted 15.5 million viewers. If you're planning to visit Manhattan but don't want to stand in the crowd, several hotels on the route have rooms overlooking the parade. Do note: Travel site Oyster warns hotels might charge up to three times the price of standard rates.

Photo credit: Getty

13. The Macy’s parade is the joint effort of 10,000 people.

Putting on an event as large as the Macy's parade requires a tremendous amount of assistance. A total of 10,000 people work together to make it a success, including Macy's employees who volunteer their time to the parade.

From the artists who create the enormous helium balloons to the people who work all night to assemble the floats after they arrive in Manhattan, this is a major team effort. It's probably safe to assume things get a little hectic at crunch time, but viewers never know it. 

Photo credit: Reuters

14. More than 4,000 Macy’s employees volunteer on Thanksgiving morning.

Many people wouldn't consider offering to work on Thanksgiving morning, but more than 4,000 Macy's employees from across the Northeast volunteer their time to the parade each year. Excited to be part of the tradition, staffers serve in a wide variety of roles, including balloon handler and balloon pilot.

Despite the sheer volume of volunteers, each person is assigned a costume to wear during the parade. Operations are so well organized that each person can get dressed and ready within a two-hour window.

Parade Floats and Sales Flyers: 26 Stores Open on Thanksgiving Day and Black Friday 

Photo credit: Reuters 

15. Thanksgiving Day parade marchers total 10,000.

Considering roughly 10,000 people march in the Macy's parade, it might seem like it's relatively easy to join in, but it's not. Since this Thanksgiving tradition launched in 1924, participation has been limited to Macy's employees, their families and those with relationships to sponsors or others affiliated with the event.

Performing talent is the only exception to the rule. There are no reserved tickets available to purchase for the grandstand seating area, so arrive early if you want to stake out a good spot.

Keep Reading: Save Big by Getting a Head Start on Holiday Travel Deals 

Photo credit: Reuters

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A Greenland block can lead to some wonky weather. In 2012, this weather pattern punted Hurricane Sandy into the coastal Northeast. It’s also contributed to polar vortex intrusions, and record-breaking melting on the Greenland ice sheet.

The good news is we aren’t going to see anything quite that extreme this time. However, it will be bitingly cold—and conditions will be more favorable for storms. Here’s what you need to know about this chill-inducing weather pattern.

Why is this happening?

A block is an area of unusual pressure that forms in the atmosphere and deflects storms and winds. “It’s kind of like if you were to stick a rock in the middle of a river,” says Kyle Mattingly, a graduate student in geography at the University of Georgia in Athens.

Greenland blocks develop in the far Northern Atlantic, in the vicinity of Greenland or Iceland. This can happen when storms pump warm air northward, Mattingly says. As it reaches the jet stream, that warm air circulates in such a way that it piles up above Greenland, increasing air pressure.

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REI

-Closed on Thanksgiving & Black Friday

(Photo by Robert Alexander/Getty Images)

Costco 

-Closed on Thanksgiving

Crate & Barrel

-Closed on Thanksgiving

Home Depot

-Closed on Thanksgiving

IKEA

-Closed on Thanksgiving

Marshalls 

-Closed on Thanksgiving

Lowe's

-Closed on Thanksgiving

Cabela's

-Closed on Thanksgiving

Neiman Marcus

-Closed on Thanksgiving

Petco

-Closed on Thanksgiving

TJ Maxx

-Closed on Thanksgiving

A.C. Moore

-Closed on Thanksgiving

ABT Electronics

-Closed on Thanksgiving

BJ's Wholesale Club

-Closed on Thanksgiving

Burlington Coat Factory

-Closed on Thanksgiving

Cost Plus World Market

-Closed on Thanksgiving

DSW

-Closed on Thanksgiving

Guitar Center

-Closed on Thanksgiving

H&M

-Closed on Thanksgiving

HomeGoods

-Closed on Thanksgiving

Apple

-Closed on Thanksgiving

Half Price Books 

-Closed on Thanksgiving

(Photo by Darren Hauck/Getty Images)

Hobby Lobby

-Closed on Thanksgiving

(Getty)

Jo-Ann Stores

-Closed on Thanksgiving

(Getty)

Nordstrom

-Closed on Thanksgiving

(REUTERS/Rick Wilking)

Nordstrom Rack

-Closed on Thanksgiving

(REUTERS/Brendan McDermid)

Office Depot 

-Closed on Thanksgiving

(REUTERS/Mike Blake)

OfficeMax 

-Closed on Thanksgiving

(Getty)

Pier 1 Imports

-Closed on Thanksgiving

(Luke Sharrett/Bloomberg via Getty Images)

Jos. A. Bank 

-Closed on Thanksgiving

(Photo by Andrew Burton/Getty Images)

P.C. Richard & Son

-Closed on Thanksgiving

(Photo by Jb Reed/Bloomberg via Getty Images)

Party City 

-Closed on Thanksgiving

Patagonia

-Closed on Thanksgiving

(Photo by Robert Alexander/Getty Images)

Publix 

-Closed on Thanksgiving

(Getty)

West Marine

-Closed on Thanksgiving

(Photo by John Patriquin/Portland Press Herald via Getty Images)

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This typically pushes the jet stream south and warps it so it becomes wavier, sending a blast of chilly air to parts of the eastern United States and Western Europe. Meanwhile, the polar lands under the block become warmer. Prevailing winds that flow from west to east across the Atlantic can also slow or change direction. “That typical pattern, where you have cold to the north and warm to the south and strong westerly winds between, reverses,” says Stephen Baxter, a meteorologist at the National Oceanic and Atmospheric Administration’s Climate Prediction Center.

 

Will it ruin my Thanksgiving travel plans?

 

That depends on where you are.

Greenland blocks bring a greater chance of storms and often lay the groundwork for nor’easters, which blow in from the Atlantic Ocean. When a Greenland block is in place, airflow is slow enough that little disturbances in the atmosphere can stick around, link up, and become large storms. A Greenland block also pushes the tracks that storms follow farther south over the Eastern seaboard. Blocking patterns can give a storm time to develop and strengthen off the East Coast instead of moving quickly out to sea.

It’s not very likely that a major snowstorm will take advantage of these conditions in the days leading up to Thanksgiving along the East Coast. “Right now the pattern is not such that we would favor a big storm off the Eastern seaboard, but there is more uncertainty over the East Coast,” Baxter says.

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Severe weather in the US 2017 -- tornadoes, snowstorms, flooding, hail
Abdel Salah, the owner of Sam's Food and Liquor Store surveys damage after a series of tornados tore through in New Orleans, Louisiana, U.S., February 8, 2017. REUTERS/Ben Depp
Heavy thunderstorm clouds fill the sky over Center City Philadelphia, PA, on Feb. 25, 2017. (Photo by Bastiaan Slabbers/NurPhoto via Getty Images)
Residents clear their cars and street of snow in Weehawken, New Jersey, as the One World Trade Center and lower Manhattan are seen after a snowstorm in New York, U.S. March 14, 2017. REUTERS/Eduardo Munoz TPX IMAGES OF THE DAY TPX IMAGES OF THE DAY
PERRYVILLE, MO - MARCH 01: A utility pole was downed during last night's tornado on March 1, 2017 in Perryville, Missouri. At least one person was killed when the tornado crossed interstate 55. (Photo by Jon Durr/Getty Images)
Birds sit on some branches in Central Park in New York on March 14, 2017. Winter Storm Stella dumped sleet and snow across the northeastern United States on Tuesday but spared New York from the worst after authorities cancelled thousands of flights and shut schools. Blizzard warnings were in effect in parts of Connecticut, Massachusetts and upstate New York, but were lifted for New York City, the US financial capital home to 8.4 million residents, where snow turned to sleet, hail and rain. / AFP PHOTO / Eric BARADAT (Photo credit should read ERIC BARADAT/AFP/Getty Images)
PERRYVILLE, MO - MARCH 01: A house along Pcr 906 is destroyed after last night's tornado on March 1, 2017 in Perryville, Missouri. At least one person was killed when the tornado crossed interstate 55. (Photo by Jon Durr/Getty Images)
Heavy thunderstorm clouds fill the sky over Center City Philadelphia, PA, on Feb. 25, 2017. (Photo by Bastiaan Slabbers/NurPhoto via Getty Images)
PERRYVILLE, MO - MARCH 01: A shed for farm equipment on Pcr 906 collapsed and metal sheeting was tangled in trees after last night's tornado, on March 1, 2017 in Perryville, Missouri. At least one person was killed when the tornado crossed interstate 55. (Photo by Jon Durr/Getty Images)
PERRYVILLE, MO - MARCH 01: A house and garage were destroyed on Hwy V after last night's tornado on March 1, 2017 in Perryville, Missouri. At least one person was killed when the tornado crossed interstate 55. (Photo by Jon Durr/Getty Images)
A resident clears the street of snow in Weehawken, New Jersey, as the Empire State Building and Middle Manhattan are seen after a snowstorm in New York, U.S. March 14, 2017. REUTERS/Eduardo Munoz
Debris covers a street in New Orleans East after a series of tornados tore through New Orleans and other parts of Louisiana, leaving trees, power lines and homes and businesses leveled, in New Orleans, Louisiana, U.S., February 8, 2017. REUTERS/Ben Depp
Tien Nguyen cleans up debris in "Q" Nail studio on Chef Menteur highway which he and his wife own, they survived the tornado by sheltering in the bathroom, a tornados tore through New Orleans and other parts of Louisiana, leaving trees, power lines and homes and businesses leveled, in New Orleans, Louisiana, February 8, 2017. REUTERS/Ben Depp
Two snowmen sit in Central Park in New York on March 14, 2017. Winter Storm Stella dumped sleet and snow across the northeastern United States on Tuesday but spared New York from the worst after authorities cancelled thousands of flights and shut schools. Blizzard warnings were in effect in parts of Connecticut, Massachusetts and upstate New York, but were lifted for New York City, the US financial capital home to 8.4 million residents, where snow turned to sleet, hail and rain. / AFP PHOTO / Jewel SAMAD (Photo credit should read JEWEL SAMAD/AFP/Getty Images)
Trailers lie on their sides behind a Procter and Gamble warehouse after a tornado ripped through the area on Sunday in Albany, Georgia, U.S. January 24, 2017. REUTERS/Tami Chappell
A snowplow clears snow in Times Square during a snowstorm in the Manhattan borough of New York, U.S. March 14, 2017. REUTERS/Carlo Allegri
A gas sign from a gas station sits in a tree nearby after a tornado ripped through the area on Sunday in Albany, Georgia, U.S. January 24, 2017. REUTERS/Tami Chappell
Friends used there snow day to go sledding on a hill at 47th street northwest and Massachusetts Avenue in Washington on March 14, 2017. Winter Storm Stella dumped sleet and snow across the northeastern United States on Tuesday but spared New York from the worst after authorities cancelled thousands of flights and shut schools. Blizzard warnings were in effect in parts of Connecticut, Massachusetts and upstate New York, but were lifted for New York City, the US financial capital home to 8.4 million residents, where snow turned to sleet, hail and rain. / AFP PHOTO / Tasos Katopodis (Photo credit should read TASOS KATOPODIS/AFP/Getty Images)
A police car pushes a cab stuck on a snow and sleet-covered street in New York on March 14, 2017. Winter Storm Stella dumped sleet and snow across the northeastern United States on Tuesday but spared New York from the worst after authorities cancelled thousands of flights and shut schools. Blizzard warnings were in effect in parts of Connecticut, Massachusetts and upstate New York, but were lifted for New York City, the US financial capital home to 8.4 million residents, where snow turned to sleet, hail and rain. / AFP PHOTO / Jewel SAMAD (Photo credit should read JEWEL SAMAD/AFP/Getty Images)
The Rustic Barn, an event hall, which suffered major tornado damage, is seen from an unmanned aerial vehicle in Canton, Texas, April 30, 2017. REUTERS/Brandon Wade TPX IMAGES OF THE DAY
Homeowners clean up debris after a tornado hit the town of Emory, Texas, U.S. April 30, 2017. REUTERS/Brandon Wade
Homes are severely damaged after a tornado hit the town of Emory, Texas, U.S. April 30, 2017. REUTERS/Brandon Wade
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“If we were in January or February, meteorologists would be very excited about the potential for some kind of nor’easter type storm," he says. But it’s still a little early in the season to expect that kind of storm.

However, the impending cold front could bring snow to the Great Lakes region, Adirondacks, and Northern New England early next week.

 

What else can we expect?

 

Much of the mid-Atlantic, New England and southeast Canada will be unseasonably cold as we head into Thanksgiving. On average, temperatures will probably be 5 to 10 degrees chillier than normal, but the coldest days are likely to be 8 to 16 degrees below average, Baxter says. Wet, windy weather is also possible. On the other side of the block in central Europe, temperatures will also take a dip.

The Greenland block will probably stick around for at least a week, with lingering impacts possible through the end of the month, Baxter says. “You have colder conditions kind of locked in place from southeast Canada to the eastern U.S.”

It’s common for a Greenland block to persist for one to two weeks, but meteorologists have a hard time predicting how long each one will last. “That can vary pretty dramatically. Sometimes you’ll get blocking conditions that will stay in place for up to a month,” Mattingly says.

Meanwhile, there is a chance that small pieces of the polar vortex will break free and graze the Great Lakes and Northeast with quick blasts of arctic air, AccuWeather forecasts.

The polar vortex is a low-pressure area around the North Pole with high swirling winds. When this maelstrom gets disrupted in winter, a piece of the polar vortex can escape. As it swings southward, temperatures can plunge 20 to 30 degrees below normal.

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Deadliest hailstorm: Moradabad, India, on April 30, 1888, which killed 246 people.

Reportedly there were hailstones the size of "goose eggs and oranges and cricket balls." The WMO report cites an eyewitness who said that roofs collapsed and doors and windows were smashed by the ice. 

"Men caught in the open and without shelter were simply pounded to death by the hail. Fourteen bodies were found in the race-course. More than one marriage party were caught by the storm near the banks of the river, and were annihilated. The police report that 1,600 head of cattle, sheep, and goats were killed,” wrote John Eliot, the first director-general of the India Meteorological Department, according to the WMO report.

(Photo by Shyam Sharma/Hindustan Times via Getty Images)

Deadliest lightning strike: Manical Tribal Trust Lands in Zimbabwe on December 23, 1975, which killed 21 people.

The report says that nearly 90% of sub-Saharan buildings are not lightning safe, often made of mud-brick with thatch or sheet metal roofs. 

(REUTERS/Gene Blevins)

Deadliest indirect lightning strike: Dronka, Egypt on November 2, 1994, when 469 people were killed by a lightning-caused oil fire.

In 1994, a flash of lightning caused a fire that ignited three oil tanks, each holding about 5,000 tons of aircraft or diesel fuel. The railway line holding the tanks collapsed in a flood and floodwaters carried the blazing fuel into Dronka. 

(STR New / Reuters)

Deadliest tornado: Manikganj district, Bangladesh on April 26, 1989, which killed 1,300 people.

The 1989 tornado had a track about a mile wide and destroyed two towns, injuring over 12,000 and leaving about 80,000 people homeless. 

(Photo by David L. Nelson/AFP/Getty Images)

Deadliest tornado: Manikganj district, Bangladesh on April 26, 1989, which killed 1,300 people.

The storm sometimes known as the "Great Bhola Cyclone" caused between 300,000 and 500,000 deaths when the storm surge overwhelmed island and tidal flats along the Bay of Bengal. 

(Photo by Express Newspapers/Getty Images)

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It’s very common for a Greenland block to occur at the same time as a polar vortex disruption. A Greenland block does not cause a polar vortex intrusion per se, Baxter says. But a Greenland block can slow the pattern down so the cold air stays in place longer.

 

Is a Greenland block why last weekend was super cold?

 

The East Coast and Midwest did experience record-low temperatures this past weekend, but that blast of bitter cold was not caused by a Greenland block. Instead, it was fueled by blocking over the North Pacific that allowed a mass of intensely cold air to spill down into the northeastern United States and southeast Canada, Baxter says.

However, a Greenland block sometimes will form repeatedly throughout the winter. “These patterns will pulse in and out,” Baxter says. This makes for a cold, snowy season, as happened during the infamous winters of 1995 to 1996 and 2009 to 2010. For now, it doesn’t look like we're in for that this year.

This weather pattern can occur in summer, too. Mattingly and his team are investigating a Greenland block that formed in July 2012. It brought such toasty temperatures to its immediate vicinity that it caused the most extensive melting of the Greenland ice sheet in recorded history. It appears that summer Greenland block patterns are becoming more extreme.

What about Hurricane Sandy?

Hurricane Sandy’s westward turn in 2012 was a pretty unusual track for a storm to follow. These storms tend to move poleward during October and are pushed east by the prevailing westerlies. “As Sandy moved north from the Caribbean into the Western Atlantic it was following a pretty typical October tropical cyclone path at that point,” Mattingly says.

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A roller coaster is seen in the ocean in the aftermath of Hurricane Sandy in Seaside Heights, New Jersey November 11, 2012. REUTERS/Eric Thayer (UNITED STATES - Tags: DISASTER ENVIRONMENT)
Burnt houses are seen next to those which survived in Breezy Point, a neighborhood located in the New York City borough of Queens, after it was devastated by Hurricane Sandy October 31, 2012. New York City and the sodden U.S. Northeast began an arduous journey back to normal on Wednesday after mammoth storm Sandy killed at least 64 people in a rampage that swamped coastal cities and cut power to millions. REUTERS/Adrees Latif (UNITED STATES - Tags: ENVIRONMENT DISASTER)
Residents stand over vehicles which were submerged in a parking structure in the financial district of Lower Manhattan, New York October 30, 2012. Major U.S. stock exchanges expect to open on Wednesday after a monster storm shut down their trading for two days. The southern tip of Manhattan where Wall Street and the NYSE are located lost power on Monday after being buffetted by Sandy, the worst storm to hit New York since at least 1938. REUTERS/Adrees Latif (UNITES STATES - Tags: ENVIRONMENT DISASTER BUSINESS) FOR BEST QUALITY IMAGE ALSO SEE: GM1E9550Y0K01
A gas station is submerged in floodwaters near the Gowanus Canal in the Brooklyn Borough of New York October 29, 2012. Hurricane Sandy could be the biggest storm to hit the United States mainland when it comes ashore on Monday night, bringing strong winds and dangerous flooding to the East Coast from the mid-Atlantic states to New England, forecasters said on Sunday. REUTERS/Keith Bedford (UNITED STATES - Tags: DISASTER ENVIRONMENT)
An insurance claims adjuster climbs the entrance to a house in the Breezy Point neighborhood which was left devastated by Hurricane Sandy in the New York borough of Queens November 12, 2012. Police raised the storm-related fatality toll in New York City to 43 and at least 121 people have perished in the storm, which caused an estimated $50 billion in property damage and economic losses and ranks as one of the most destructive natural disasters to hit the U.S. Northeast. REUTERS/Adrees Latif (UNITED STATES - Tags: DISASTER ENVIRONMENT)
A view shows boats piled next to a house, where they were washed ashore during Hurricane Sandy, near Monmouth Beach, New Jersey October 31, 2012. The U.S. Northeast began an arduous slog back to normal on Wednesday after historic monster storm Sandy crippled transportation, knocked out power for millions and killed at least 64 people with a massive storm surge that caused epic flooding. REUTERS/Steve Nesius (UNITED STATES - Tags: ENVIRONMENT DISASTER)
Firefighters work to extinguish a fire on a flooded street in the Rockaways section of New York, October 30, 2012. Hurricane Sandy battered the U.S. East Coast on Monday with fierce winds and driving rain, as the monster storm shut down transportation, shuttered businesses and left hundreds of thousands without power. REUTERS/Keith Bedford (UNITED STATES - Tags: ENVIRONMENT DISASTER TPX IMAGES OF THE DAY)
Water pushed up by Hurricane Sandy splashes into the window of a building standing by the shore in Bellport, New York, October 30, 2012. Millions of people across the eastern United States awoke on Tuesday to scenes of destruction wrought by monster storm Sandy, which knocked out power to huge swathes of the nation's most densely populated region, swamped New York's subway system and submerged streets in Manhattan's financial district. REUTERS/Lucas Jackson (UNITED STATES - Tags: ENVIRONMENT DISASTER)
Eddie Liu uses a broom to clean up mud and water from extensive flooding in a laundromat due to superstorm Sandy in the Coney Island neighborhood of New York November 2, 2012. Four days after superstorm Sandy smashed into the U.S. Northeast, rescuers on Friday were still discovering the extent of the death and devastation in New York and the New Jersey shore, and anger mounted over gasoline shortages, power outages and waits for relief supplies. REUTERS/Lucas Jackson (UNITED STATES - Tags: ENVIRONMENT DISASTER TPX IMAGES OF THE DAY)
Residents look over the remains of burned homes in the Rockaways section of New York, October 30, 2012. Hurricane Sandy battered the U.S. East Coast on Monday with fierce winds and driving rain, as the monster storm shut down transportation, shuttered businesses and left hundreds of thousands without power. REUTERS/Keith Bedford (UNITED STATES - Tags: ENVIRONMENT DISASTER TPX IMAGES OF THE DAY)
An NYPD officer jumps over a chasm in the boardwalk caused by the storm surge of Hurricane Sandy in the Brooklyn borough region of Belle Harbor in New York November 14, 2012. REUTERS/Lucas Jackson (UNITED STATES - Tags: DISASTER ENVIRONMENT TPX IMAGES OF THE DAY)
A water slide hangs over the end of an amusement park's pier, partially destroyed from Hurricane Sandy, in Seaside Park, New Jersey October 31, 2012. The U.S. Northeast began an arduous slog back to normal on Wednesday after historic monster storm Sandy crippled transportation, knocked out power for millions and killed at least 64 people with a massive storm surge that caused epic flooding. REUTERS/Steve Nesius (UNITED STATES - Tags: ENVIRONMENT DISASTER)
Burned houses are seen next to those which survived in Breezy Point, a neighborhood located in the New York City borough of Queens, after it was devastated by Hurricane Sandy October 31, 2012. Sandy, the massive story that tore through the U.S. East Coast is being blamed, so far, for the deaths of 64 people, many of whom were killed by falling trees or branches. The storm, at one point extending 1,000 miles in diameter, is making its way north over inland New York, Pennsylvania and into Canada. It knocked out power for millions and crippled transportation systems along the densely populated coastal region. REUTERS/Adrees Latif (UNITED STATES - Tags: ENVIRONMENT DISASTER TPX IMAGES OF THE DAY)
Amy Neukom works to remove sand in her parents house that had been deposited there by the storm surge of Superstorm Sandy in the town of Mantoloking, New Jersey November 16, 2012. REUTERS/Lucas Jackson (UNITED STATES - Tags: DISASTER ENVIRONMENT)
A woman weeps after learning that a neighbor presumed missing is okay while cleaning out her home in a neighborhood heavily damaged by Hurricane Sandy in the New Dorp Beach neighborhood of the Staten Island borough of New York, November 1, 2012. Deaths in the United States and Canada from Sandy, the massive storm that hit the U.S. East Coast this week, rose to at least 95 on Thursday after the number of victims reported by authorities in New York City jumped and deaths in New Jersey and elsewhere also rose. REUTERS/Lucas Jackson (UNITED STATES)
A playground apparatus stands surrounded by water pushed up by Hurricane Sandy in Bellport, New York, October 30, 2012. Millions of people across the eastern United States awoke on Tuesday to scenes of destruction wrought by monster storm Sandy, which knocked out power to huge swathes of the nation's most densely populated region, swamped New York's subway system and submerged streets in Manhattan's financial district. REUTERS/Lucas Jackson (UNITED STATES - Tags: ENVIRONMENT DISASTER)
Jenna Webb (L), 18, and Zoe Jurusik, 20, paddle-board down a flooded city street in the aftermath of Hurricane Sandy in Bethany Beach, Delaware, October 30, 2012. Millions of people were left reeling in the aftermath of monster storm Sandy on Tuesday as New York City and a wide swathe of the eastern United States struggled with epic flooding and massive power outages. REUTERS/Jonathan Ernst (UNITED STATES - Tags: ENVIRONMENT DISASTER)
The boardwalk damaged by Hurricane Sandy is seen in Seaside Heights, New Jersey November 11, 2012. REUTERS/Eric Thayer (UNITED STATES - Tags: DISASTER ENVIRONMENT)
Contractors that have been hired locally work to clean sand, deposited by the storm surge of superstorm Sandy, out of a pool in the Queens borough region of the Rockaways in New York, November 27, 2012. REUTERS/Lucas Jackson (UNITED STATES - Tags: DISASTER ENVIRONMENT TPX IMAGES OF THE DAY)
A sign hangs high on a telephone pole marking the waterline from Superstorm Sandy on Staten Island in New York City October 23, 2013. New York State Governor Andrew Cuomo, who has said that area should be returned to nature, initiated on February 2013 a voluntary $400 million buyback program for some 418 homes in the low-lying neighborhood situated between salt marshes and the Atlantic Ocean that was devastated by surging floodwaters in the historic October 29, 2012 hurricane. As the one year anniversary of the storm approaches and as demolition begins, homes in Oakwood beach now lay mostly vacant and abandoned as the modest ocean-side neighborhood which now resembles a ghost town is set to all but disappear. Picture taken October 23. REUTERS/Mike Segar (UNITED STATES - Tags: DISASTER ENVIRONMENT)
Meg McLoughlin helps sort through the remains of her father's house, which burned to the ground during Hurricane Sandy, in the Breezy Point neighborhood of Queens, New York November 11, 2012. REUTERS/Andrew Burton (UNITED STATES - Tags: ENVIRONMENT DISASTER)
U.S. President Barack Obama hugs North Point Marina owner Donna Vanzant as he tours damage done by Hurricane Sandy in Brigantine, New Jersey, October 31, 2012. Putting aside partisan differences, Obama and Republican Governor Chris Christie toured storm-stricken parts of New Jersey together on Wednesday, taking in scenes of flooded roads and burning homes in the aftermath of superstorm Sandy. REUTERS/Larry Downing (UNITED STATES - Tags: POLITICS DISASTER)
An automobile is seen parked among homes damaged by a fire and the effects of superstorm Sandy in the Belle Harbor section of the Queens borough of New York November 14, 2012. Superstorm Sandy may consign as many as a quarter of a million new and used cars and trucks to the scrap heap, a loss that could eventually lead to a spike in new auto sales, automakers and dealers said. So far, automakers have reported that some 16,000 brand new vehicles will have to be scrapped due to the killer storm that flooded coastal areas in New Jersey and New York. Many of them were stored at the port of Newark when Sandy hit. Picture taken November 14, 2012. REUTERS/Shannon Stapleton (UNITED STATES - Tags: TRANSPORT BUSINESS DISASTER ENVIRONMENT)
Comic books are seen in front of a home that was damaged by Hurricane Sandy in Mantoloking, New Jersey November 12, 2012. REUTERS/Eric Thayer (UNITED STATES - Tags: ENVIRONMENT DISASTER)
A young boy and his mother search through piles of clothes donated for victims of Hurricane Sandy on the South side of Staten Island in New York City, November 12, 2012. Police raised the storm-related fatality toll in New York City to 43 and at least 121 people have perished in the storm, which caused an estimated $50 billion in property damage and economic losses and ranks as one of the most destructive natural disasters to hit the U.S. Northeast. REUTERS/Mike Segar (UNITED STATES - Tags: ENVIRONMENT DISASTER)
Christine Cina poses for a portrait in what is left of her house after Superstorm Sandy in the Staten Island borough of New York, September 20, 2013. A year after Superstorm Sandy wreaked havoc across the eastern United States, only a fraction of the aid money earmarked for recovery has been used, in what some claim is a painfully slow and opaque process. Picture taken September 20, 2013. To match story STORM-SANDY/MONEY REUTERS/Carlo Allegri (UNITED STATES - Tags: SOCIETY DISASTER BUSINESS PORTRAIT TPX IMAGES OF THE DAY)
A resident who lost her home takes pictures while walking through the Breezy Point neighborhood which was left devastated by Hurricane Sandy in the New York borough of Queens November 12, 2012. Police raised the storm-related fatality toll in New York City to 43 and at least 121 people have perished in the storm, which caused an estimated $50 billion in property damage and economic losses and ranks as one of the most destructive natural disasters to hit the U.S. Northeast. REUTERS/Adrees Latif (UNITED STATES - Tags: DISASTER ENVIRONMENT)
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But an intense Greenland block forced it to change direction. “They can’t go through it so they have to go around it, and in this case, Sandy ended up being steered due west into New Jersey,” Mattingly says.

That Greenland block was particularly extreme. Mattingly and his colleagues discovered that it was one of the strongest on record for that time of year. “The fact that this anomalous westward turn of Sandy happened during such an intense, almost unprecedented Greenland blocking episode was definitely something of note,” he says.

The team also examined whether other North Atlantic hurricanes were similarly affected by Greenland blocking conditions. It turns out that when a hurricane did diverge from the normal northeasterly track, there was a better than normal chance that a Greenland block was in place.

Are we going to see more of that in future?

Maybe. It’s not clear how Greenland blocking patterns will evolve in coming years. Climate models have a hard time portraying the North Atlantic jet stream, so they struggle to predict Greenland blocks in the present day, much less the future, Mattingly says.

Some researchers believe that Greenland blocks will happen more frequently because the Arctic is warming faster than the rest of the world. The amplified warming could lead to a more disruptive “wavy” jet stream and feed these high-pressure areas. This, in turn, would thaw ever-greater patches of the Greenland ice sheet.

But others argue that Greenland blocking will decrease in future. If climate change pushes the jet stream further north, there would be less opportunity for Greenland blocks to develop, Mattingly says.

“If there is more blocking in the future, we expect there to be more unusual hurricane tracks,” he says. “But the million dollar question is whether blocking is actually going to increase or decrease with climate change.”

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