November 2012
In late October, when a hurricane ventured out of the tropics, into the mid-latitudes, it combined with low-pressure weather processes. The result was Superstorm Sandy – an unusual storm with devastatingly high levels of energy, although with wind speeds that fell below those that would deem it a hurricane (74 mph or more).
Having caused destruction in the Caribbean – killing over 50 people in Haiti – Sandy took a sharp turn for the mainland of the United States. Strong winds, heavy rains and a tidal surge caused widespread flooding, power outages and other storm-related damage. An estimated $30bn-$50bn was caused in the US alone.
‘The combination of tropical and extra-tropical systems into one large system and the storm’s sudden western turn were unusual occurrences,’ Professor Scott Robeson of Indiana University tells Geography in the News. In this article we set out to understand the unusual geographies of Sandy one week after it struck the United States.
When Superstorm Sandy hit the east coast of United States on 29 October 2012, it caused disruption that would dominate the US and global headlines for days.
The human impacts speak for themselves: millions without power, tens of thousands in emergency shelter, the New York Stock Exchange closed for two days, over $30bn worth of damage in the United States alone. However, what about the lesser-known physical attributes of Sandy?
We spoke to Professor Scott Robeson, Chair of Geography at Indiana University. An expert in climatology and spatial data analysis, he helped us to get grips with the formation of the ‘incomparable storm’ (LA Times, 31 October 2012).
Sandy has been defined as a ‘post-tropical superstorm’. What does this actually mean?
The term ‘superstorm’ is a subjective expression that helps to capture the unusual nature of particularly destructive low-pressure systems. The ‘post-tropical’ prefix recognises that Sandy formed from an earlier tropical cyclone, whose energy then entered the mid-latitudes.
Indeed, superstorms are not necessarily tropical in nature – they can occur outside of the tropics, in the mid-latitudes. For instance, the famous ‘Columbus Day Storm’ of 1962 in the northwestern United States and southwestern Canada was among the most powerful storms on record, whilst also being entirely extra-tropical in nature.
So how does a post-tropical superstorm form?
Some superstorms, such as the 1991 ‘Perfect Storm’ and the 2012 ‘Superstorm Sandy’, form when tropical and extra-tropical meteorological features combine. This results in the ‘absorption’ of tropical energy into strong mid-latitude weather systems, which makes them both unusual and dangerous.
Most often, the combination of energy from the systems occurs when a tropical cyclone transitions into an extra-tropical cyclone (or in other words, a ‘post-tropical storm’). As the transition from tropics to mid-latitudes occurs, the primary energy source for the system changes: from the latent heat of condensation, to jet-stream driven dynamics.
How did Sandy develop over time, into a superstorm that caused such disruption in New York City?
Sandy was a post-tropical storm in that it started as a tropical system and then combined with high-energy mid-latitude features that strengthened it as it moved northward. So, its time history was such that it was: a tropical depression, then tropical storm, then hurricane, and finally an extra-tropical cyclone.
Sandy was already a reasonably organised hurricane when it encountered a strong upper-level trough of low pressure off the coast of the southeastern United States. This additional energy from the jet stream acted to ‘blossom’ the hurricane into a much larger and more powerful system.
In addition, a ridge of high pressure near Greenland acted to control Sandy’s path, pushing it directly westward and forcing it to make solid landfall in the northeastern United States – primarily in the states of New Jersey and New York. It was this landfall that resulted in such severe impacts.
The storm’s unusual integration with the southward dip in the jet stream also resulted in very heavy snowfall totals in the mountains of West Virginia and Maryland (over 75cm in some locations).
Is there any evidence that extreme weather hazards such as Sandy are becoming more frequent and involving higher risk?
There is no direct evidence that hybrid storms, such as Sandy, are becoming more frequent. However, there is some evidence that anthropogenic (human-caused) warming will cause hurricanes to be more intense in the future. This is because – in a warmer, wetter world – there is more latent heat available to fuel such storms.
Meanwhile, it is absolutely certain that greater numbers of people are living in coastal areas than ever before. In this sense, (even without the potential changes which may results from climate change) we are becoming more vulnerable to extreme weather hazards than ever before.
What role does technology and advanced forecasting play in increasing preparedness of those at risk from Sandy?
In the past, most of the gains in advanced forecasting of storms, and therefore preparedness, came from satellite-based tracking. Increasingly, sophisticated computer models are providing much more accurate forecasts of large, well-organised weather systems (smaller features such as tornadoes are still poorly forecast). Sandy was over 1,000 miles in diameter, whilst Tornados rarely surpass one mile in diameter.
The National Hurricane Center, using guidance from the model from the European Centre for Medium-Range Weather Forecasts, correctly placed Sandy making landfall in New Jersey over five days prior to that happening. Having accurate model results so far in advance allows for ample preparation and reduces the loss of human life greatly.
Not all storms are as predictable as Sandy, however, and the accuracy of hurricane-intensity forecasts has not kept pace with hurricane-track forecasts. We cannot predict the force at which a hurricane will strike to the same accuracy as we can predict the path that it will follow.
Map to show the course of Superstorm Sandy (image credit Cyclonebiskit)
22 October – Tropical depression forms in the southern Caribbean Sea. Maximum winds of about 40 miles per hour (mph). Tropical Storm Sandy is born. 24 October – Now a category 1 hurricane, Sandy moves northward across the Caribbean (including Jamaica, Dominican Republic and Haiti). More than 50 people die in flooding and mudslides in Haiti. Maximum winds of 80 mph.
Guide to hurricane categories
Category 1 - wind speeds of 74 to 95 mph
Category 2 - 96 to 110 mph
Category 3 - 111 to 130 mph
Category 4 - 131 to 155 mph
Category 5 - more than 155 mph
26 October – Almost a category 3 hurricane, Sandy passes over Cuba. 110 mph winds cause devastation in the history city of Santiago de Cuba. The Bahamas also suffer.
27 October – Having briefly weakened into a tropical depression, Sandy is now a category 1 hurricane. With the Caribbean death tolls in excess of 70, it makes a turn to the northeast off the coast of Florida.
28 October – Continues moving northeast but remains well offshore of the United States’ east coast. Still a category 1 hurricane with winds of 80 mph, but meteorologists warn that an unusual convergence of weather factors will result in a powerful, hybrid superstorm.
29 October – Sandy makes an expected sharp turn northwest towards New Jersey. Having interacted with other weather systems, it gains energy. Running over 300 miles of open water, it builds up a huge storm surge, which is increased slightly by the full moon which brings higher tides.
Brings high winds and heavy rain to Washington, D.C in the afternoon. This topples trees and power lines, cutting off electrical power for millions of people.
By the evening, the post-tropical superstorm hits New Jersey and New York. The 14 foot storm surge arrives at high tide, backed-up with strong winds, and surges the seawall in Lower Manhattan, which results in the flooding of parts of the New York City subway system.
30 October – Sandy has moved away from New York, weakening as it heads inland. The tail of the storm continues to impact the northeast of the United States.
31 October – Sandy dissipates inland over western Pennsylvania.
(Source: National Geographic, 2 November 2012)
Map to show the East coast of the USA. Image credit
Connecticut – Temporary travel ban on state highways. No commuter rail service. Some towns evacuated. Over 600,000 people without power.
Delaware – Some roads and bridges flooded. Some short-term evacuations. 40,000 people without power.
District of Columbia – Subway trains ran a limited schedule for one day. Widespread power failures.
Maryland – Some schools closed. Around 180,000 people without power.
New Jersey – Several people killed. Unprecedented damage along the coast. Two million people without power. More than 2,200 people in emergency shelters. Train services suspended and many roads remained underwater or damaged.
New York – New York Stock Exchange reopened after being closed for two days, despite mains power staying off in Lower Manhattan, part of which remained flooded. Subways not operational and most tunnels closed. Over 375,000 people ordered to evacuate low-lying areas of New York City. 6,400 people in emergency shelter. More than two million people without power.
North Carolina – State Highway closed in some places. No evacuations. Scattered power failures.
Pennsylvania – Trains temporarily suspended. Additional speed restrictions imposed on major highways. Some secondary roads blocked and bridges flooded. Shelter made available for the 10,000 living in flood prone areas. More than 500,000 people without power.
Rhode Island – Mandatory evacuations for those living in low-lying areas. More than 80,000 people without power.
Virginia – Over 100 secondary roads and one major highway closed. Some coastal residents evacuated voluntarily. Widespread power outages.
(Source: New York Times, 31 October 2012)
Protecting New York City in future
New York has 520 miles of coastline and 200,000 people living within just four vertical feet of the high tide mark – second only to New Orleans in the United States. "We are vulnerable," state governor Andrew Cuomo made clear.
So, as New York City suffered flooding, power outages and wind-related damage, state and city officials were left with the question of how to respond. Any decision was made harder by the fact that the flooding caused by Sandy exceeded any disaster scenario expected under future climate change.
"The impacts we saw in the last couple of days were actually impacts we did not think we would see until the 2080s," explains Art DeGaetano, director of the north-east regional climate centre. So how should decision-makers protect a city of 8 million people? Here are some possible options:
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Flood walls and surge protectors: Large sea walls could surround Lower Manhattan to protect against future storm surges. This could be retractable, rising as a threat approaches. This would be costly to implement given the size of the harbor
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Natural defences: Dredged material could be used to build up natural defences along the shoreline. Marshes, wetlands and trees would all help to buffer against storm surges. Not as quick a fix as artificial defences but more environmentally friendly and potentially less costly
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Electricity: Over half of New York’s power plants are in flood-prone areas, which makes them highly vulnerable. Investment could be made to increase the sturdiness of equipment or to encase equipment in flood-safe vaults. Whatever the solution, it is clear that New York needs a back-up plan to safe-guard against widespread blackouts
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Subways: The New York subway train system has been equipped with underground pumps to deal with flooding, however they were not able to deal with the flooding caused by Sandy’s storm surge. With over $30m spent on flood-management since 2007, could more investment be the answer for New York’s subways?
Source: The Guardian (2 November 2012)
Talking point
If you were a decision-maker, which of the above solutions would you give priority to and why? Can you think of any other solutions to reduce the risk and impacts of flooding in the event of future extreme weather events?
Exposing Haiti’s vulnerabilities
Still recovering from the devastating 2010 earthquake, Haiti lay vulnerable to Sandy. 80 mph winds, flooding and landslides impacted heavily on the 350,000 people still living in makeshift shelters.
Hit by only the tail of Sandy, 54 people died and 20 were listed as missing. Prime Minister Laurent Lamothe described the event as a ‘disaster of major proportions.’
Due to high levels of vulnerability and a poor capacity to cope, the long-term consequences for the poorest country in the western hemisphere are arguably far greater than those experienced by the United States.
70% of crops in southern Haiti were damaged due to heavy wind and rain, which has led to fear of food shortages. Aid workers and government officials are also on alert for an expected increase in cholera cases as a result of flooding.
The Caribbean country, which lies to the southeast of the United States, has appealed for international assistance in order to strengthen its capacity to cope. Sources: BBC (5 November 2012) and The Guardian (2 November 2012)
Talking point
How does economic wealth impact on a country’s capacity to cope with such events? Who do you think could help Haiti strengthen its capacity to cope with the impacts of Sandy? How could vulnerability to future extreme weather events be reduced?
Calculating the economic effects
Superstorm Sandy is expected to be one of the United States’ give most costly storms ever. This, it is predicated, will negatively impact on the nation’s economic growth for the months of November and December 2012.
According to consultancy company Eqecat, who analyse the financial cost of disasters, Sandy will cost an estimated to total of $30bn-$50bn. By comparison, Hurricane Katrina – which famously burst the levees to flood New Orleans in 2005 – cost an estimated $100bn worth of damage.
Some of the costs are due to the disruption faced by businesses during the days in which Sandy passed, with some companies losing up to four days of business. Those in the service industry (hotels, for example) will never regain the loss of business that they suffered during those days.
However, it is anticipated that the devastation caused by Sandy will actually boost United States’ economic growth going into 2013, due to widespread investment in reconstruction. For example, construction equipment rental companies are among those expected to benefit financially from the storm. Source: Financial Times (4 November 2012)
Talking point
Who do you think should pay for the cost of reconstruction in the wake of Sandy? Do the government (national, state or city), NGOs, businesses or individuals hold responsibility for reconstruction?
Tackling fuel shortages as winter draws in
The states of New York and New Jersey, which were most severely affected by Superstorm Sandy, have suffered fuel shortages. The storm forced two refineries in the states to close and there were further disruptions to fuel supply networks.
In New York City, queues for some petrol stations weaved around several blocks and stretched back for up to half a mile. At least ten arrests were made in New York and New Jersey in relation to confrontations and line jumping at petrol stations.
New Jersey governor Chris Christie imposed rationing to cope with gas scarcity. Meanwhile, at a national scale, the Homeland Security Department has waived the Jones Act – a law that normally prohibits foreign-flagged vessels from shipping gasoline, diesel and other petroleum products from the Gulf of Mexico to northeastern United States ports.
This emergency waiver, requires shipments to leave the Gulf of Mexico by 13 November and arrive in the north-east of the United States within one week. The Obama administration also ordered the purchase of up to 380,000 barrels of unleaded gasoline and 317,000 barrels of diesel. This is intended to ease fuel-shortages in storm-stricken areas.
Fuel shortages will impact most heavily on those people relying on fuel-powered back-up power generators in the event of ongoing power cuts. With up to 40,000 people (mainly residents of public housing) lacking electricity and heat, New York state governor Andrew Cuomo announced a ‘massive, massive housing problem,’ stating: ‘People are in homes that are uninhabitable.’
Meanwhile, New York City officials agreed that housing was a priority issue and opened warming shelters, especially for elderly people. 25,000 blankets were handed out for those who refused to move from their homes. Sources: The Guardian (3 November 2012) and The Guardian (4 November 2012)
Talking point
Some people were reluctant to move from their homes, even though they may have been deemed uninhabitable by the authorities. Do you think people should be forced to move into safe shelter even if they don’t want to?
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Photo: Then and now: Devastation from Hurricane Sandy (LA Times) Some of the effects of Hurricane Sandy, which struck a wide swath of the East Coast, are shown in these before-and-after photos
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Interactive: Top Ten Most Damaging US Hurricanes (ESRI) What were the worst hurricanes ever? What would happen if they hit today? A NOAA study examined these questions, and came up with this rogue’s gallery of mega-storms
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Map: Wall of water (LA Times) Hurricane Sandy caused major flooding along a large swath of the New Jersey and New York coastline as the storm surge pushed ashore. These graphics go into significant detail
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Map: Google Crisis Map (Google) An up-to-date live tracking with various layers of information that can be toggled on and off. Provides practical information about voting, power outages, precipitation and much more besides
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Map: Assessing the Damage from Hurricane Sandy (New York Times) An assessment of flooded subways, power failures, wastewater, fires and wind
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Video: Anger grows over Sandy response (BBC) Faced with food and fuel shortages, some Americans
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Map: What can Twitter tell us about Hurricane Sandy flooding? Visualised (Guardian) How did Americans use Twitter to talk about flooding on the East Coast? These two maps have the answer! Assessing the Damage From Hurricane Sandy Assessing the Damage From Hurricane Sandy
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Interactive: Sandy: New York devastation mapped (BBC) New York, the country's most populous city, is among the worst-hit, with floodwaters swamping the subway system, flooding low-lying streets and wiping out power. Explore the map to examine the worst of the damage
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Video: Frankenstorm: Why Hurricane Sandy Will Be Historic (Time) A NOAA video shows what’s happening as Sandy collides with the other fronts
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Map: Hurricane Sandy’s path (New York Times) Interactive map and satellite image showing how Sandy developed over time